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AuthorTitleYearJournal/ProceedingsReftypeDOI/URL
Aalto, T., Hatakka, J., Kouznetsov, R. and Stanislawska, K. Background and anthropogenic influences on atmospheric CO2 concentrations measured at Pallas: comparison of two models for tracing air mass history {2015} BOREAL ENVIRONMENT RESEARCH
Vol. {20}({2}), pp. 213-226 
article  
Abstract: The FLEXTRA and SILAM models were utilized in estimating the influence
regions (TR) for the measured CO2 concentration ([CO2]) at Pallas
together with tracers for anthropogenic emissions. The models produced
similar synoptic features and associated background [CO2] with marine
IR and elevated [CO2] with continental IR, but there were also
differences which affected the interpretation of measurements. The
background, i.e. marine boundary layer (MBL) signal, was compared to the
NOAA MBL reference. Both models performed well, with monthly mean
deviations from the reference usually inside 1 ppm. The FLEXTRA MBL
signal had some seasonality in the difference, however, only very few
cases were associated with anthropogenic emissions. We used [CO] and
fossil fuel [CO2] simulations by the TM5 (CarbonTracker CT2011_oi)
model as emission tracers. The model and [CO] captured well the timing
of high [CO2] in measurements. The anthropogenic influence was more
pronounced in winter than in summer, and it had a large inter-annual
variation.
BibTeX:
@article{aalto15a,
  author = {Aalto, Tuula and Hatakka, Juha and Kouznetsov, Rostislav and Stanislawska, Karolina},
  title = {Background and anthropogenic influences on atmospheric CO2 concentrations measured at Pallas: comparison of two models for tracing air mass history},
  journal = {BOREAL ENVIRONMENT RESEARCH},
  year = {2015},
  volume = {20},
  number = {2},
  pages = {213--226}
}
Agol, E., Jansen, T., Lacy, B., Robinson, T.D. and Meadows, V. THE CENTER OF LIGHT: SPECTROASTROMETRIC DETECTION OF EXOMOONS {2015} ASTROPHYSICAL JOURNAL
Vol. {812}({1}) 
article DOI  
Abstract: Direct imaging of extrasolar planets with future space-based
coronagraphic telescopes may provide a means of detecting companion
moons at wavelengths where the moon outshines the planet. We propose a
detection strategy based on the positional variation of the center of
light with wavelength, ``spectroastrometry.'' This new application of
this technique could be used to detect an exomoon, to determine the
exomoon's orbit and the mass of the host exoplanet, and to disentangle
the spectra of the planet and moon. We consider two model systems, for
which we discuss the requirements for detection of exomoons around
nearby stars. We simulate the characterization of an Earth-Moon analog
system with spectroastrometry, showing that the orbit, the planet mass,
and the spectra of both bodies can be recovered. To enable the detection
and characterization of exomoons we recommend that coronagraphic
telescopes should extend in wavelength coverage to 3 mu m, and should be
designed with spectroastrometric requirements in mind.
BibTeX:
@article{agol15a,
  author = {Agol, Eric and Jansen, Tiffany and Lacy, Brianna and Robinson, Tyler D. and Meadows, Victoria},
  title = {THE CENTER OF LIGHT: SPECTROASTROMETRIC DETECTION OF EXOMOONS},
  journal = {ASTROPHYSICAL JOURNAL},
  year = {2015},
  volume = {812},
  number = {1},
  doi = {https://doi.org/10.1088/0004-637X/812/1/5}
}
Agusti-Panareda, A., Massart, S., Chevallier, F., Balsamo, G., Boussetta, S., Dutra, E. and Beljaars, A. A biogenic CO2 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts {2016} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {16}({16}), pp. 10399-10418 
article DOI  
Abstract: Forecasting atmospheric CO2 daily at the global scale with a good
accuracy like it is done for the weather is a challenging task. However,
it is also one of the key areas of development to bridge the gaps
between weather, air quality and climate models. The challenge stems
from the fact that atmospheric CO2 is largely controlled by the CO2
fluxes at the surface, which are difficult to constrain with
observations. In particular, the biogenic fluxes simulated by land
surface models show skill in detecting synoptic and regional-scale
disturbances up to sub-seasonal time-scales, but they are subject to
large seasonal and annual budget errors at global scale, usually
requiring a posteriori adjustment. This paper presents a scheme to
diagnose and mitigate model errors associated with biogenic fluxes
within an atmospheric CO2 forecasting system. The scheme is an adaptive
scaling procedure referred to as a biogenic flux adjustment scheme
(BFAS), and it can be applied automatically in real time throughout the
forecast. The BFAS method generally improves the continental budget of
CO2 fluxes in the model by combining information from three sources: (1)
retrospective fluxes estimated by a global flux inversion system, (2)
land-use information, (3) simulated fluxes from the model. The method is
shown to produce enhanced skill in the daily CO2 10-day forecasts
without requiring continuous manual intervention. Therefore, it is
particularly suitable for near-real-time CO2 analysis and forecasting
systems.
BibTeX:
@article{agusti-panareda16a,
  author = {Agusti-Panareda, Anna and Massart, Sebastien and Chevallier, Frederic and Balsamo, Gianpaolo and Boussetta, Souhail and Dutra, Emanuel and Beljaars, Anton},
  title = {A biogenic CO2 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2016},
  volume = {16},
  number = {16},
  pages = {10399--10418},
  doi = {https://doi.org/10.5194/acp-16-10399-2016}
}
Ahlstrom, A., Miller, P.A. and Smith, B. Too early to infer a global NPP decline since 2000 {2012} GEOPHYSICAL RESEARCH LETTERS
Vol. {39} 
article DOI  
Abstract: The global terrestrial carbon cycle plays a pivotal role in regulating
the atmospheric composition of greenhouse gases. It has recently been
suggested that the upward trend in net primary production (NPP) seen
during the 1980's and 90's has been replaced by a negative trend since
2000 induced by severe droughts mainly on the southern hemisphere. Here
we compare results from an individual-based global vegetation model to
satellite-based estimates of NPP and top-down reconstructions of net
biome production (NBP) based on inverse modelling of observed CO2
concentrations and CO2 growth rates. We find that simulated NBP exhibits
considerable covariation on a global scale with interannual fluctuations
in atmospheric CO2. Our simulations also suggest that droughts in the
southern hemisphere may have been a major driver of NPP variations
during the past decade. The results, however, do not support conjecture
that global terrestrial NPP has entered a period of drought-induced
decline. Citation: Ahlstrom, A., P. A. Miller, and B. Smith (2012), Too
early to infer a global NPP decline since 2000, Geophys. Res. Lett., 39,
L15403, doi:10.1029/2012GL052336.
BibTeX:
@article{ahlstrom12a,
  author = {Ahlstrom, Anders and Miller, Paul A. and Smith, Benjamin},
  title = {Too early to infer a global NPP decline since 2000},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2012},
  volume = {39},
  doi = {https://doi.org/10.1029/2012GL052336}
}
Ahn, D.Y., Hansford, J.R., Howe, S.T., Ren, X.R., Salawitch, R.J., Zeng, N., Cohen, M.D., Stunder, B., Salmon, O.E., Shepson, P.B., Gurney, K.R., Oda, T., Lopez-Coto, I., Whetstone, J. and Dickerson, R.R. Fluxes of Atmospheric Greenhouse-Gases in Maryland (FLAGG-MD): Emissions of Carbon Dioxide in the Baltimore, MD-Washington, DC Area {2020} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {125}({9}) 
article DOI URL 
Abstract: To study emissions of CO2 in the Baltimore, MD-Washington, D.C. (Balt-Wash) area, an aircraft campaign was conducted in February 2015, as part of the Fluxes of Atmospheric Greenhouse-Gases in Maryland (FLAGG-MD) project. During the campaign, elevated mole fractions of CO2 were observed downwind of the urban center and local power plants. Upwind flight data and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model analyses help account for the impact of emissions outside the Balt-Wash area. The accuracy, precision, and sensitivity of CO2 emissions estimates based on the mass balance approach were assessed for both power plants and cities. Our estimates of CO2 emissions from two local power plants agree well with their Continuous Emissions Monitoring Systems (CEMS) records. For the 16 power plant plumes captured by the aircraft, the mean percentage difference of CO2 emissions was -0.3%. For the Balt-Wash area as a whole, the 1 & x1d70e;& xdf0e; CO2 emission rate uncertainty for any individual aircraft-based mass balance approach experiment was +/- 38%. Treating the mass balance experiments, which were repeated seven times within 9 days, as individual quantifications of the Balt-Wash CO2 emissions, the estimation uncertainty was +/- 16% (standard error of the mean at 95% CL). Our aircraft-based estimate was compared to various bottom-up fossil fuel CO2 (FFCO2) emission inventories. Based on the FLAGG-MD aircraft observations, we estimate 1.9 +/- 0.3 MtC of FFCO2 from the Balt-Wash area during the month of February 2015. The mean estimate of FFCO2 from the four bottom-up models was 2.2 +/- 0.3 MtC.
BibTeX:
@article{ahn20a,
  author = {Ahn, D. Y. and Hansford, J. R. and Howe, S. T. and Ren, X. R. and Salawitch, R. J. and Zeng, N. and Cohen, M. D. and Stunder, B. and Salmon, O. E. and Shepson, P. B. and Gurney, K. R. and Oda, T. and Lopez-Coto, I and Whetstone, J. and Dickerson, R. R.},
  title = {Fluxes of Atmospheric Greenhouse-Gases in Maryland (FLAGG-MD): Emissions of Carbon Dioxide in the Baltimore, MD-Washington, DC Area},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {125},
  number = {9},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD032004},
  doi = {https://doi.org/10.1029/2019JD032004}
}
Ahue, W.K. Regional carbon fluxes and boundary layer heights from the Airborne Carbon in the Mountains Experiment 2007 2010 School: University of Wisconsin--Madison  phdthesis  
BibTeX:
@phdthesis{ahue10a,
  author = {Ahue, William KM},
  title = {Regional carbon fluxes and boundary layer heights from the Airborne Carbon in the Mountains Experiment 2007},
  school = {University of Wisconsin--Madison},
  year = {2010}
}
Alden, C.B., Miller, J.B. and White, J.W.C. Can bottom-up ocean CO2 fluxes be reconciled with atmospheric 13C observations? {2010} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {62}({5, SI}), pp. 369-388 
article DOI  
Abstract: The rare stable carbon isotope, 13C, has been used previously to
partition CO2 fluxes into land and ocean components. Net ocean and land
fluxes impose distinctive and predictable fractionation patterns upon
the stable isotope ratio, making it an excellent tool for distinguishing
between them. Historically, isotope constrained inverse methods for
calculating CO2 surface fluxes-the `double deconvolution'-have disagreed
with bottom-up ocean flux estimates. In this study, we use the double
deconvolution framework, but add, as a constraint, independent estimates
of time histories of ocean fluxes to the atmospheric observations of CO2
and 13CO(2). We calculate timeseries of net land flux, total
disequilibrium flux and terrestrial disequilibrium flux from 1991 to
2008 that are consistent with bottom-up net ocean fluxes. We investigate
possible drivers of interannual variability in terrestrial
disequilibrium flux, including terrestrial discrimination, and test the
sensitivity of our results to those mechanisms. We find that C-3 plant
discrimination and shifts in the global composition of C-3 and C-4
vegetation are likely drivers of interannual variability in terrestrial
disequilibrium flux, while contributions from heterotrophic respiration
and disturbance anomalies are also possible.
BibTeX:
@article{alden10a,
  author = {Alden, Caroline B. and Miller, John B. and White, James W. C.},
  title = {Can bottom-up ocean CO2 fluxes be reconciled with atmospheric 13C observations?},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2010},
  volume = {62},
  number = {5, SI},
  pages = {369--388},
  doi = {https://doi.org/10.1111/j.1600-0889.2010.00481.x}
}
Alden, C.B., Miller, J.B., Gatti, L.V., Gloor, M.M., Guan, K., Michalak, A.M., van der Laan-Luijkx, I.T., Touma, D., Andrews, A., Basso, L.S., Correia, C.S.C., Domingues, L.G., Joiner, J., Krol, M.C., Lyapustin, A.I., Peters, W., Shiga, Y.P., Thoning, K., van der Velde, I.R., van Leeuwen, T.T., Yadav, V. and Diffenbaugh, N.S. Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange {2016} GLOBAL CHANGE BIOLOGY
Vol. {22}({10}), pp. 3427-3443 
article DOI  
Abstract: Understanding tropical rainforest carbon exchange and its response to
heat and drought is critical for quantifying the effects of climate
change on tropical ecosystems, including global climate-carbon
feedbacks. Of particular importance for the global carbon budget is net
biome exchange of CO2 with the atmosphere ( NBE), which represents
nonfire carbon fluxes into and out of biomass and soils. Subannual and
sub-Basin Amazon NBE estimates have relied heavily on process-based
biosphere models, despite lack of model agreement with plot-scale
observations. We present a new analysis of airborne measurements that
reveals monthly, regional-scale (similar to 1-8 x 10(6) km(2)) NBE
variations. We develop a regional atmospheric CO2 inversion that
provides the first analysis of geographic and temporal variability in
Amazon biosphere-atmosphere carbon exchange and that is minimally
influenced by biosphere model-based first guesses of seasonal and annual
mean fluxes. We find little evidence for a clear seasonal cycle in
Amazon NBE but do find NBE sensitivity to aberrations from long-term
mean climate. In particular, we observe increased NBE ( more carbon
emitted to the atmosphere) associated with heat and drought in 2010, and
correlations between wet season NBE and precipitation ( negative
correlation) and temperature ( positive correlation). In the eastern
Amazon, pulses of increased NBE persisted through 2011, suggesting
legacy effects of 2010 heat and drought. We also identify regional
differences in postdrought NBE that appear related to long-term water
availability. We examine satellite proxies and find evidence for higher
gross primary productivity ( GPP) during a pulse of increased carbon
uptake in 2011, and lower GPP during a period of increased NBE in the
2010 dry season drought, but links between GPP and NBE changes are not
conclusive. These results provide novel evidence of NBE sensitivity to
short-term temperature and moisture extremes in the Amazon, where
monthly and sub-Basin estimates have not been previously available.
BibTeX:
@article{alden16a,
  author = {Alden, Caroline B. and Miller, John B. and Gatti, Luciana V. and Gloor, Manuel M. and Guan, Kaiyu and Michalak, Anna M. and van der Laan-Luijkx, Ingrid T. and Touma, Danielle and Andrews, Arlyn and Basso, Luana S. and Correia, Caio S. C. and Domingues, Lucas G. and Joiner, Joanna and Krol, Maarten C. and Lyapustin, Alexei I. and Peters, Wouter and Shiga, Yoichi P. and Thoning, Kirk and van der Velde, Ivar R. and van Leeuwen, Thijs T. and Yadav, Vineet and Diffenbaugh, Noah S.},
  title = {Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange},
  journal = {GLOBAL CHANGE BIOLOGY},
  year = {2016},
  volume = {22},
  number = {10},
  pages = {3427--3443},
  doi = {https://doi.org/10.1111/gcb.13305}
}
Alexandrov, G.A. and Matsunaga, T. Normative productivity of the global vegetation 2008 Carbon balance and management
Vol. 3(1), pp. 8 
article  
BibTeX:
@article{alexandrov08a,
  author = {Alexandrov, Georgii A and Matsunaga, Tsuneo},
  title = {Normative productivity of the global vegetation},
  journal = {Carbon balance and management},
  publisher = {Springer},
  year = {2008},
  volume = {3},
  number = {1},
  pages = {8}
}
Alexe, M., Bergamaschi, P., Segers, A., Detmers, R., Butz, A., Hasekamp, O., Guerlet, S., Parker, R., Boesch, H., Frankenberg, C., Scheepmaker, R.A., Dlugokencky, E., Sweeney, C., Wofsy, S.C. and Kort, E.A. Inverse modelling of CH4 emissions for 2010-2011 using different satellite retrieval products from GOSAT and SCIAMACHY {2015} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {15}({1}), pp. 113-133 
article DOI  
Abstract: At the beginning of 2009 new space-borne observations of dry-air
column-averaged mole fractions of atmospheric methane (XCH4) became
available from the Thermal And Near infrared Sensor for carbon
Observations-Fourier Transform Spectrometer (TANSO-FTS) instrument on
board the Greenhouse Gases Observing SATellite (GOSAT). Until April 2012
concurrent methane (CH4) retrievals were provided by the SCanning
Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY)
instrument on board the ENVironmental SATellite (ENVISAT). The GOSAT and
SCIAMACHY XCH4 retrievals can be compared during the period of overlap.
We estimate monthly average CH4 emissions between January 2010 and
December 2011, using the TM5-4DVAR inverse modelling system. In addition
to satellite data, high-accuracy measurements from the Cooperative Air
Sampling Network of the National Oceanic and Atmospheric Administration
Earth System Research Laboratory (NOAA ESRL) are used, providing strong
constraints on the remote surface atmosphere. We discuss five inversion
scenarios that make use of different GOSAT and SCIAMACHY XCH4 retrieval
products, including two sets of GOSAT proxy retrievals processed
independently by the Netherlands Institute for Space Research
(SRON)/Karlsruhe Institute of Technology (KIT), and the University of
Leicester (UL), and the RemoTeC ``Full-Physics'' (FP) XCH4 retrievals
available from SRON/KIT. The GOSAT-based inversions show significant
reductions in the root mean square (rms) difference between retrieved
and modelled XCH4, and require much smaller bias corrections compared to
the inversion using SCIAMACHY retrievals, reflecting the higher
precision and relative accuracy of the GOSAT XCH4. Despite the large
differences between the GOSAT and SCIAMACHY retrievals, 2-year average
emission maps show overall good agreement among all satellite-based
inversions, with consistent flux adjustment patterns, particularly
across equatorial Africa and North America. Over North America, the
satellite inversions result in a significant redistribution of CH4
emissions from North-East to South-Central United States. This result is
consistent with recent independent studies suggesting a systematic
underestimation of CH4 emissions from North American fossil fuel sources
in bottom-up inventories, likely related to natural gas production
facilities. Furthermore, all four satellite inversions yield lower CH4
fluxes across the Congo basin compared to the NOAA-only scenario, but
higher emissions across tropical East Africa. The GOSAT and SCIAMACHY
inversions show similar performance when validated against independent
shipboard and aircraft observations, and XCH4 retrievals available from
the Total Carbon Column Observing Network (TCCON).
BibTeX:
@article{alexe15a,
  author = {Alexe, M. and Bergamaschi, P. and Segers, A. and Detmers, R. and Butz, A. and Hasekamp, O. and Guerlet, S. and Parker, R. and Boesch, H. and Frankenberg, C. and Scheepmaker, R. A. and Dlugokencky, E. and Sweeney, C. and Wofsy, S. C. and Kort, E. A.},
  title = {Inverse modelling of CH4 emissions for 2010-2011 using different satellite retrieval products from GOSAT and SCIAMACHY},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2015},
  volume = {15},
  number = {1},
  pages = {113--133},
  doi = {https://doi.org/10.5194/acp-15-113-2015}
}
Allen, M., Erickson, D., Kendall, W., Fu, J., Ott, L. and Pawson, S. The influence of internal model variability in GEOS-5 on interhemispheric CO2 exchange {2012} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {117} 
article DOI  
Abstract: An ensemble of eight atmospheric CO2 simulations was completed employing
the National Aeronautics and Space Administration (NASA) Goddard Earth
Observation System, Version 5 (GEOS-5) for the years 2000-2001, each
with initial meteorological conditions corresponding to different days
in January 2000 to examine internal model variability. Globally, the
model runs show similar concentrations of CO2 for the two years, but in
regions of high CO2 concentrations due to fossil fuel emissions, large
differences among different model simulations appear. The phasing and
amplitude of the CO2 cycle at Northern Hemisphere locations in all of
the ensemble members is similar to that of surface observations. In
several southern hemisphere locations, however, some of the GEOS-5 model
CO2 cycles are out of phase by as much as four months, and large
variations occur between the ensemble members. This result indicates
that there is large sensitivity to transport in these regions. The
differences vary by latitude-the most extreme differences in the Tropics
and the least at the South Pole. Examples of these differences among the
ensemble members with regard to CO2 uptake and respiration of the
terrestrial biosphere and CO2 emissions due to fossil fuel emissions are
shown at Cape Grim, Tasmania. Integration-based flow analysis of the
atmospheric circulation in the model runs shows widely varying paths of
flow into the Tasmania region among the models including sources from
North America, South America, South Africa, South Asia and Indonesia.
These results suggest that interhemispheric transport can be strongly
influenced by internal model variability.
BibTeX:
@article{allen12a,
  author = {Allen, Melissa and Erickson, David and Kendall, Wesley and Fu, Joshua and Ott, Lesley and Pawson, Steven},
  title = {The influence of internal model variability in GEOS-5 on interhemispheric CO2 exchange},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2012},
  volume = {117},
  doi = {https://doi.org/10.1029/2011JD017059}
}
Andres, R.J., Boden, T.A., Breon, F.M., Ciais, P., Davis, S., Erickson, D., Gregg, J.S., Jacobson, A., Marland, G., Miller, J., Oda, T., Olivier, J.G.J., Raupach, M.R., Rayner, P. and Treanton, K. A synthesis of carbon dioxide emissions from fossil-fuel combustion {2012} BIOGEOSCIENCES
Vol. {9}({5}), pp. 1845-1871 
article DOI  
Abstract: This synthesis discusses the emissions of carbon dioxide from
fossil-fuel combustion and cement production. While much is known about
these emissions, there is still much that is unknown about the details
surrounding these emissions. This synthesis explores our knowledge of
these emissions in terms of why there is concern about them; how they
are calculated; the major global efforts on inventorying them; their
global, regional, and national totals at different spatial and temporal
scales; how they are distributed on global grids (i.e., maps); how they
are transported in models; and the uncertainties associated with these
different aspects of the emissions. The magnitude of emissions from the
combustion of fossil fuels has been almost continuously increasing with
time since fossil fuels were first used by humans. Despite events in
some nations specifically designed to reduce emissions, or which have
had emissions reduction as a byproduct of other events, global total
emissions continue their general increase with time. Global total
fossil-fuel carbon dioxide emissions are known to within 10%
uncertainty (95% confidence interval). Uncertainty on individ-ual
national total fossil-fuel carbon dioxide emissions range from a few
percent to more than 50 %. This manuscript concludes that carbon
dioxide emissions from fossil-fuel combustion continue to increase with
time and that while much is known about the overall characteristics of
these emissions, much is still to be learned about the detailed
characteristics of these emissions.
BibTeX:
@article{andres12a,
  author = {Andres, R. J. and Boden, T. A. and Breon, F. -M. and Ciais, P. and Davis, S. and Erickson, D. and Gregg, J. S. and Jacobson, A. and Marland, G. and Miller, J. and Oda, T. and Olivier, J. G. J. and Raupach, M. R. and Rayner, P. and Treanton, K.},
  title = {A synthesis of carbon dioxide emissions from fossil-fuel combustion},
  journal = {BIOGEOSCIENCES},
  year = {2012},
  volume = {9},
  number = {5},
  pages = {1845--1871},
  doi = {https://doi.org/10.5194/bg-9-1845-2012}
}
Andrews, A.E., Kofler, J.D., Trudeau, M.E., Williams, J.C., Neff, D.H., Masarie, K.A., Chao, D.Y., Kitzis, D.R., Novelli, P.C., Zhao, C.L., Dlugokencky, E.J., Lang, P.M., Crotwell, M.J., Fischer, M.L., Parker, M.J., Lee, J.T., Baumann, D.D., Desai, A.R., Stanier, C.O., De Wekker, S.F.J., Wolfe, D.E., Munger, J.W. and Tans, P.P. CO2, CO, and CH4 measurements from tall towers in the NOAA Earth System Research Laboratory's Global Greenhouse Gas Reference Network: instrumentation, uncertainty analysis, and recommendations for future high-accuracy greenhouse gas monitoring efforts {2014} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {7}({2}), pp. 647-687 
article DOI  
Abstract: A reliable and precise in situ CO2 and CO analysis system has been
developed and deployed at eight sites in the NOAA Earth System Research
Laboratory's (ESRL) Global Greenhouse Gas Reference Network. The network
uses very tall (> 300 m) television and radio transmitter towers that
provide a convenient platform for mid-boundary-layer trace-gas sampling.
Each analyzer has three sample inlets for profile sampling, and a
complete vertical profile is obtained every 15 min. The instrument suite
at one site has been augmented with a cavity ring-down spectrometer for
measuring CO2 and CH4. The long-term stability of the systems in the
field is typically better than 0.1 ppm for CO2, 6 ppb for CO, and 0.5
ppb for CH4, as determined from repeated standard gas measurements. The
instrumentation is fully automated and includes sensors for measuring a
variety of status parameters, such as temperatures, pressures, and flow
rates, that are inputs for automated alerts and quality control
algorithms. Detailed and time-dependent uncertainty estimates have been
constructed for all of the gases, and the uncertainty framework could be
readily adapted to other species or analysis systems. The design
emphasizes use of off-theshelf parts and modularity to facilitate
network operations and ease of maintenance. The systems report
high-quality data with > 93% uptime. Recurrent problems and limitations
of the current system are discussed along with general recommendations
for high-accuracy trace-gas monitoring. The network is a key component
of the North American Carbon Program and a useful model for future
research-grade operational greenhouse gas monitoring efforts.
BibTeX:
@article{andrews14a,
  author = {Andrews, A. E. and Kofler, J. D. and Trudeau, M. E. and Williams, J. C. and Neff, D. H. and Masarie, K. A. and Chao, D. Y. and Kitzis, D. R. and Novelli, P. C. and Zhao, C. L. and Dlugokencky, E. J. and Lang, P. M. and Crotwell, M. J. and Fischer, M. L. and Parker, M. J. and Lee, J. T. and Baumann, D. D. and Desai, A. R. and Stanier, C. O. and De Wekker, S. F. J. and Wolfe, D. E. and Munger, J. W. and Tans, P. P.},
  title = {CO2, CO, and CH4 measurements from tall towers in the NOAA Earth System Research Laboratory's Global Greenhouse Gas Reference Network: instrumentation, uncertainty analysis, and recommendations for future high-accuracy greenhouse gas monitoring efforts},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2014},
  volume = {7},
  number = {2},
  pages = {647--687},
  doi = {https://doi.org/10.5194/amt-7-647-2014}
}
Babenhauserheide, A., Basu, S., Houweling, S., Peters, W. and Butz, A. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions {2015} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {15}({17}), pp. 9747-9763 
article DOI  
Abstract: Data assimilation systems allow for estimating surface fluxes of
greenhouse gases from atmospheric concentration measurements. Good
knowledge about fluxes is essential to understand how climate change
affects ecosystems and to characterize feedback mechanisms. Based on the
assimilation of more than 1 year of atmospheric in situ concentration
measurements, we compare the performance of two established data
assimilation models, CarbonTracker and TM5-4DVar (Transport Model 5 -
Four-Dimensional Variational model), for CO2 flux estimation.
CarbonTracker uses an ensemble Kalman filter method to optimize fluxes
on ecoregions. TM5-4DVar employs a 4-D variational method and optimizes
fluxes on a 6 degrees x 4 degrees longitude-latitude grid. Harmonizing
the input data allows for analyzing the strengths and weaknesses of the
two approaches by direct comparison of the modeled concentrations and
the estimated fluxes. We further assess the sensitivity of the two
approaches to the density of observations and operational parameters
such as the length of the assimilation time window.
Our results show that both models provide optimized CO2 concentration
fields of similar quality. In Antarctica CarbonTracker underestimates
the wintertime CO2 concentrations, since its 5-week assimilation window
does not allow for adjusting the distant surface fluxes in response to
the detected concentration mismatch. Flux estimates by CarbonTracker and
TM5-4DVar are consistent and robust for regions with good observation
coverage, regions with low observation coverage reveal significant
differences. In South America, the fluxes estimated by TM5-4DVar suffer
from limited representativeness of the few observations. For the North
American continent, mimicking the historical increase of the measurement
network density shows improving agreement between CarbonTracker and
TM5-4DVar flux estimates for increasing observation density.
BibTeX:
@article{babenhauserheide15a,
  author = {Babenhauserheide, A. and Basu, S. and Houweling, S. and Peters, W. and Butz, A.},
  title = {Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2015},
  volume = {15},
  number = {17},
  pages = {9747--9763},
  doi = {https://doi.org/10.5194/acp-15-9747-2015}
}
Badawy, B., Polavarapu, S., Jones, D.B.A., Deng, F., Neish, M., Melton, J.R., Nassar, R. and Arora, V.K. Coupling the Canadian Terrestrial Ecosystem Model (CTEM v. 2.0) to Environment and Climate Change Canada's greenhouse gas forecast model (v.107-glb) 2018 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 11(2), pp. 631-663 
article DOI  
Abstract: The Canadian Land Surface Scheme and the Canadian Terrestrial Ecosystem
Model (CLASS-CTEM) together form the land surface component in the
family of Canadian Earth system models (CanESMs). Here, CLASS-CTEM is
coupled to Environment and Climate Change Canada (ECCC)'s weather and
greenhouse gas forecast model (GEM-MACH-GHG) to consistently model
atmosphere-land exchange of CO2. The coupling between the land and the
atmospheric transport model ensures consistency between meteorological
forcing of CO2 fluxes and CO2 transport. The procedure used to spin up
carbon pools for CLASS-CTEM for multi-decadal simulations needed to be
significantly altered to deal with the limited availability of
consistent meteorological information from a constantly changing
operational environment in the GEM-MACH-GHG model. Despite the
limitations in the spin-up procedure, the simulated fluxes obtained by
driving the CLASS-CTEM model with meteorological forcing from
GEM-MACH-GHG were comparable to those obtained from CLASS-CTEM when it
is driven with standard meteorological forcing from the Climate Research
Unit (CRU) combined with reanalysis fields from the National Centers for
Environmental Prediction (NCEP) to form CRU-NCEP dataset. This is due to
the similarity of the two meteorological datasets in terms of
temperature and radiation. However, notable discrepancies in the
seasonal variation and spatial patterns of precipitation estimates,
especially in the tropics, were reflected in the estimated carbon
fluxes, as they significantly affected the mag-nitude of the vegetation
productivity and, to a lesser extent, the seasonal variations in carbon
fluxes. Nevertheless, the simulated fluxes based on the meteorological
forcing from the GEM-MACH-GHG model are consistent to some extent with
other estimates from bottom-up or top-down approaches. Indeed, when
simulated fluxes obtained by driving the CLASS-CTEM model with
meteorological data from the GEM-MACH-GHG model are used as prior
estimates for an atmospheric CO2 inversion analysis using the adjoint of
the GEOS-Chem model, the retrieved CO2 flux estimates are comparable to
those obtained from other systems in terms of the global budget and the
total flux estimates for the northern extratropical regions, which have
good observational coverage. In data-poor regions, as expected,
differences in the retrieved fluxes due to the prior fluxes become
apparent. Coupling CLASS-CTEM into the Environment Canada Carbon
Assimilation System (EC-CAS) is considered an important step toward
understanding how meteorological uncertainties affect both CO2 flux
estimates and modeled atmospheric transport. Ultimately, such an
approach will provide more direct feedback to the CLASS-CTEM developers
and thus help to improve the performance of CLASS-CTEM by identifying
the model limitations based on atmospheric constraints.
BibTeX:
@article{badawy18a,
  author = {Badawy, Bakr and Polavarapu, Saroja and Jones, Dylan B. A. and Deng, Feng and Neish, Michael and Melton, Joe R. and Nassar, Ray and Arora, Vivek K.},
  title = {Coupling the Canadian Terrestrial Ecosystem Model (CTEM v. 2.0) to Environment and Climate Change Canada's greenhouse gas forecast model (v.107-glb)},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2018},
  volume = {11},
  number = {2},
  pages = {631-663},
  doi = {https://doi.org/10.5194/gmd-11-631-2018}
}
Baier, B.C., Sweeney, C., Choi, Y., Davis, K.J., DiGangi, J.P., Feng, S., Fried, A., Halliday, H., Higgs, J., Lauvaux, T., Miller, B.R., Montzka, S.A., Newberger, T., Nowak, J.B., Patra, P., Richter, D., Walega, J. and Weibring, P. Multispecies Assessment of Factors Influencing Regional CO2 and CH4 Enhancements During the Winter 2017 ACT-America Campaign {2020} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {125}({2}) 
article DOI URL 
Abstract: Diagnosing carbon dioxide (CO2) and methane (CH4) fluxes at subcontinental scales is complicated by sparse observations, limited knowledge of prior fluxes and their uncertainties, and background and transport errors. Multispecies measurements in flasks sampled during the wintertime ACT-America campaign were used for background characterization and source apportionment of regional anthropogenic CO2 and CH4 fluxes when ecosystem CO2 exchange is likely to be least active. Continental background trace gas mole fractions for regional enhancements are defined using samples from the upper troposphere and assessed using model products. Trace gas enhancements taken from flask samples in the lower troposphere with background levels subtracted out are then interpreted to inform CO2 and CH4 enhancement variability in the eastern United States. Strong correlations between CO2 and CH4 enhancements in the Midwestern and Mid-Atlantic United States indicated colocated anthropogenic sources. Oil and natural gas influence was also broadly observed throughout the entire observational domain. In the Midwestern United States, agricultural influence on CO2 and CH4 enhancement variability was evident during above-average wintertime temperatures. Weaker correlations between CO2 and anthropogenic tracer enhancements in the Southeastern United States indicated potentially nonnegligible wintertime ecosystem CO2 exchange, with biogenic tracers indicating more active surface processing than other regions. These whole-air flask samples illuminated significant regional CO2 and CH4 sources or sinks during Atmospheric Carbon and Transport-America (ACT-America) and can provide additional information for informing regional inverse modeling efforts.
BibTeX:
@article{baier20a,
  author = {Baier, Bianca C. and Sweeney, Colm and Choi, Yonghoon and Davis, Kenneth J. and DiGangi, Joshua P. and Feng, Sha and Fried, Alan and Halliday, Hannah and Higgs, Jack and Lauvaux, Thomas and Miller, Benjamin R. and Montzka, Stephen A. and Newberger, Timothy and Nowak, John B. and Patra, Prabir and Richter, Dirk and Walega, James and Weibring, Petter},
  title = {Multispecies Assessment of Factors Influencing Regional CO2 and CH4 Enhancements During the Winter 2017 ACT-America Campaign},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {125},
  number = {2},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031339},
  doi = {https://doi.org/10.1029/2019JD031339}
}
Baker, I.T., Denning, A.S. and Stoeckli, R. North American gross primary productivity: regional characterization and interannual variability {2010} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {62}({5, SI}), pp. 533-549 
article DOI  
Abstract: Seasonality and interannual variability in North American photosynthetic
activity reflect potential patterns of climate variability. We simulate
24 yr (1983-2006) and evaluate regional and seasonal contribution to
annual mean gross primary productivity (GPP) as well as its interannual
variability. The highest productivity occurs in Mexico, the southeast
United States and the Pacific Northwest. Annual variability is largest
in tropical Mexico, the desert Southwest and the Midwestern corridor. We
find that no single region or season consistently determines continental
annual GPP anomaly. GPP variability is dependent upon soil moisture
availability in low- and mid-latitudes, and temperature in the north.
Soil moisture is a better predictor than precipitation as it integrates
precipitation events temporally. The springtime anomaly is the most
frequent seasonal contributor to the annual GPP variability. No climate
mode (i.e. ENSO, NAM) can be associated with annual or seasonal
variability over the entire continent. We define a region extending from
the Northeast United States through the midwest and into the
southwestern United States and northern Mexico that explains a
significant fraction of the variability in springtime GPP. We cannot
correlate this region to a single mechanism (i.e. temperature,
precipitation or soil moisture) or mode of climate variability.
BibTeX:
@article{baker10a,
  author = {Baker, Ian T. and Denning, A. Scott and Stoeckli, Reto},
  title = {North American gross primary productivity: regional characterization and interannual variability},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2010},
  volume = {62},
  number = {5, SI},
  pages = {533--549},
  doi = {https://doi.org/10.1111/j.1600-0889.2010.00492.x}
}
Ballantyne, A.P., Miller, J.B. and Tans, P.P. Apparent seasonal cycle in isotopic discrimination of carbon in the atmosphere and biosphere due to vapor pressure deficit {2010} GLOBAL BIOGEOCHEMICAL CYCLES
Vol. {24} 
article DOI  
Abstract: We explore seasonal variability in isotopic fractionation by analyzing
observational data from the atmosphere and the biosphere, as well as
simulated data from a global model. Using simulated values of
atmospheric CO2 and its carbon isotopic composition, we evaluated
different methods for specifying background concentrations when
calculating the isotopic signature of source CO2 (delta(s)) to the
atmosphere. Based on this evaluation, we determined that free
troposphere measurements should be used when available as a background
reference when calculating delta(s) from boundary layer observations. We
then estimate the seasonal distribution of delta(s) from monthly
climatologies derived from several atmospheric sampling sites. This
approach yields significant seasonal variations in delta(s) with more
enriched values during the summer months that exceed the uncertainty of
delta(s) estimated for any given month. Intra-annual measurements of
delta C-13 in the cellulose of Pinus taeda growing in the southeastern
U.S. also reveal seasonal isotopic variations that are consistent in
phase but not necessarily amplitude with atmospherically derived
estimates of delta(s). Coherent seasonal patterns in delta(s) inferred
from the atmosphere and observed in the biosphere were not consistent
with the seasonal isotopic discrimination simulated by a commonly used
biosphere model. However, delta(s) seasonality consistent with
observations from the atmosphere and biosphere was retrieved with a
revised biosphere model when stomatal conductance, and thus isotopic
discrimination, was allowed to vary in response to vapor pressure
deficit rather than relative humidity. Therefore, in regions where vapor
pressure deficit and relative humidity are positively covariant over the
growth season, such as the sub-tropics, different stomatal conductance
models may yield very different estimates of CO2 and H2O exchange
between the biosphere and atmosphere.
BibTeX:
@article{ballantyne10a,
  author = {Ballantyne, A. P. and Miller, J. B. and Tans, P. P.},
  title = {Apparent seasonal cycle in isotopic discrimination of carbon in the atmosphere and biosphere due to vapor pressure deficit},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  year = {2010},
  volume = {24},
  doi = {https://doi.org/10.1029/2009GB003623}
}
Ballantyne, A.P., Liu, Z., Anderegg, W.R.L., Yu, Z., Stoy, P., Poulter, B., Vanderwall, J., Watts, J., Kelsey, K. and Neff, J. Reconciling carbon-cycle processes from ecosystem to global scales {2021} FRONTIERS IN ECOLOGY AND THE ENVIRONMENT
Vol. {19}({1, SI}), pp. {57-64} 
article DOI URL 
Abstract: Understanding carbon (C) dynamics from ecosystem to global scales remains a challenge. Although expansion of global carbon dioxide (CO2) observatories makes it possible to estimate C-cycle processes from ecosystem to global scales, these estimates do not necessarily agree. At the continental US scale, only 5% of C fixed through photosynthesis remains as net ecosystem exchange (NEE), but ecosystem measurements indicate that only 2% of fixed C remains in grasslands, whereas as much as 30% remains in needleleaf forests. The wet and warm Southeast has the highest gross primary productivity and the relatively wet and cool Midwest has the highest NEE, indicating important spatial mismatches. Newly available satellite and atmospheric data can be combined in innovative ways to identify potential C loss pathways to reconcile these spatial mismatches. Independent datasets compiled from terrestrial and aquatic environments can now be combined to advance C-cycle science across the land-water interface.
BibTeX:
@article{ballantyne21a,
  author = {Ballantyne, Ashley P. and Liu, Zhihua and Anderegg, William R. L. and Yu, Zicheng and Stoy, Paul and Poulter, Ben and Vanderwall, Joseph and Watts, Jennifer and Kelsey, Kathy and Neff, Jason},
  title = {Reconciling carbon-cycle processes from ecosystem to global scales},
  journal = {FRONTIERS IN ECOLOGY AND THE ENVIRONMENT},
  publisher = {WILEY},
  year = {2021},
  volume = {19},
  number = {1, SI},
  pages = {57--64},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/fee.2296},
  doi = {https://doi.org/10.1002/fee.2296}
}
Barichivich, J., Briffa, K.R., Osborn, T.J., Melvin, T.M. and Caesar, J. Thermal growing season and timing of biospheric carbon uptake across the Northern Hemisphere {2012} GLOBAL BIOGEOCHEMICAL CYCLES
Vol. {26} 
article DOI  
Abstract: Gridded daily temperature from 1950 to 2011 and atmospheric CO2
concentration data from high-latitude observing stations and the
CarbonTracker assimilation system are used to examine recent
spatiotemporal variability of the thermal growing season and its
relationship with seasonal biospheric carbon uptake and release in the
Northern Hemisphere. The thermal growing season has lengthened
substantially since 1950 but most of the lengthening has occurred during
the last three decades (2.9 days decade(-1), p < 0.01 for 1980-2011),
with stronger rates of extension in Eurasia (4.0 days decade(-1), p <
0.01) than in North America (1.2 days decade(-1), p > 0.05). Unlike most
previous studies, which had more limited data coverage over the past
decade, we find that strong autumn warming of about 1 degrees C during
the second half of the 2000s has led to a significant shift toward later
termination of the thermal growing season, resulting in the longest
potential growing seasons since 1950. On average, the thermal growing
season has extended symmetrically by about a week during this period,
starting some 4.0 days earlier and ending about 4.3 days later. The
earlier start of the thermal growing season is associated with earlier
onset of the biospheric carbon uptake period at high northern latitudes.
In contrast, later termination of the growing season is associated with
earlier termination of biospheric carbon uptake, but this relationship
appears to have decoupled since the beginning of the period of strong
autumn warming during the second half of the 2000s. Therefore, owing to
these contrasting biospheric responses at the margins of the growing
season, the current extension in the thermal growing season length has
not led to a concomitant extension of the period of biospheric carbon
uptake.
BibTeX:
@article{barichivich12a,
  author = {Barichivich, J. and Briffa, K. R. and Osborn, T. J. and Melvin, T. M. and Caesar, J.},
  title = {Thermal growing season and timing of biospheric carbon uptake across the Northern Hemisphere},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  year = {2012},
  volume = {26},
  doi = {https://doi.org/10.1029/2012GB004312}
}
Detection and attribution of carbon cycle processes from atmospheric O2 and CO2 measurements at Halley Research Station, Antarctica and Weybourne Atmospheric Observatory, U.K. 2018   phdthesis  
BibTeX:
@phdthesis{barningham18a,,
  title = {Detection and attribution of carbon cycle processes from atmospheric O2 and CO2 measurements at Halley Research Station, Antarctica and Weybourne Atmospheric Observatory, U.K.},
  publisher = {UNIVERSITY OF EAST ANGLIA, U.K.},
  year = {2018}
}
Barthlott, S., Schneider, M., Hase, F., Wiegele, A., Christner, E., Gonzalez, Y., Blumenstock, T., Dohe, S., Garcia, O.E., Sepulveda, E., Strong, K., Mendonca, J., Weaver, D., Palm, M., Deutscher, N.M., Warneke, T., Notholt, J., Lejeune, B., Mahieu, E., Jones, N., Griffith, D.W.T., Velazco, V.A., Smale, D., Robinson, J., Kivi, R., Heikkinen, P. and Raffalski, U. Using XCO2 retrievals for assessing the long-term consistency of NDACC/FTIR data sets {2015} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {8}({3}), pp. 1555-1573 
article DOI  
Abstract: Within the NDACC (Network for the Detection of Atmospheric Composition
Change), more than 20 FTIR (Fourier-transform infrared) spectrometers,
spread worldwide, provide long-term data records of many atmospheric
trace gases. We present a method that uses measured and modelled XCO2
for assessing the consistency of these NDACC data records. Our XCO2
retrieval setup is kept simple so that it can easily be adopted for any
NDACC/FTIR-like measurement made since the late 1950s. By a comparison
to coincident TCCON (Total Carbon Column Observing Network)
measurements, we empirically demonstrate the useful quality of this
suggested NDACC XCO2 product (empirically obtained scatter between TCCON
and NDACC is about 4 parts per thousand for daily mean as well as
monthly mean comparisons, and the bias is 25 parts per thousand). Our
XCO2 model is a simple regression model fitted to CarbonTracker results
and the Mauna Loa CO2 in situ records. A comparison to TCCON data
suggests an uncertainty of the model for monthly mean data of below 3
parts per thousand. We apply the method to the NDACC/FTIR spectra that
are used within the project MUSICA (multi-platform remote sensing of
isotopologues for investigating the cycle of atmospheric water) and
demonstrate that there is a good consistency for these globally
representative set of spectra measured since 1996: the scatter between
the modelled and measured XCO2 on a yearly time scale is only 3 parts
per thousand.
BibTeX:
@article{barthlott15a,
  author = {Barthlott, S. and Schneider, M. and Hase, F. and Wiegele, A. and Christner, E. and Gonzalez, Y. and Blumenstock, T. and Dohe, S. and Garcia, O. E. and Sepulveda, E. and Strong, K. and Mendonca, J. and Weaver, D. and Palm, M. and Deutscher, N. M. and Warneke, T. and Notholt, J. and Lejeune, B. and Mahieu, E. and Jones, N. and Griffith, D. W. T. and Velazco, V. A. and Smale, D. and Robinson, J. and Kivi, R. and Heikkinen, P. and Raffalski, U.},
  title = {Using XCO2 retrievals for assessing the long-term consistency of NDACC/FTIR data sets},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2015},
  volume = {8},
  number = {3},
  pages = {1555--1573},
  doi = {https://doi.org/10.5194/amt-8-1555-2015}
}
Basu, S., Houweling, S., Peters, W., Sweeney, C., Machida, T., Maksyutov, S., Patra, P.K., Saito, R., Chevallier, F., Niwa, Y., Matsueda, H. and Sawa, Y. The seasonal cycle amplitude of total column CO2: Factors behind the model-observation mismatch {2011} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {116} 
article DOI  
Abstract: CO2 surface fluxes that are statistically consistent with surface layer
measurements of CO2, when propagated forward in time by atmospheric
transport models, underestimate the seasonal cycle amplitude of total
column CO2 in the northern temperate latitudes by 1-2 ppm. In this paper
we verify the systematic nature of this underestimation at a number of
Total Carbon Column Observation Network (TCCON) stations by comparing
their measurements with a number of transport models. In particular, at
Park Falls, Wisconsin (United States), we estimate this mismatch to be
1.4 ppm and try to attribute portions of this mismatch to different
factors affecting the total column. We find that errors due to (1) the
averaging kernel and prior profile used in forward models, (2) water
vapor in the model atmosphere, (3) incorrect vertical transport by
transport models in the free troposphere, (4) incorrect aging of air in
transport models in the stratosphere, and (5) air mass dependence in
TCCON data can explain up to 1 ppm of this mismatch. The remaining 0.4
ppm mismatch is at the edge of the <= 0.4 ppm accuracy requirement on
satellite measurements to improve on our current estimate of surface
fluxes. Uncertainties in the biosphere fluxes driving the transport
models could explain a part of the remaining 0.4 ppm mismatch, implying
that with corrections to the factors behind the accounted-for 1 ppm
underestimation, present inverse modeling frameworks could effectively
assimilate satellite CO2 measurements.
BibTeX:
@article{basu11a,
  author = {Basu, Sourish and Houweling, Sander and Peters, Wouter and Sweeney, Colm and Machida, Toshinobu and Maksyutov, Shamil and Patra, Prabir K. and Saito, Ryu and Chevallier, Frederic and Niwa, Yosuke and Matsueda, Hidekazu and Sawa, Yousuke},
  title = {The seasonal cycle amplitude of total column CO2: Factors behind the model-observation mismatch},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2011JD016124}
}
Basu, S., Guerlet, S., Butz, A., Houweling, S., Hasekamp, O., Aben, I., Krummel, P., Steele, P., Langenfelds, R., Torn, M., Biraud, S., Stephens, B., Andrews, A. and Worthy, D. Global CO2 fluxes estimated from GOSAT retrievals of total column CO2 {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({17}), pp. 8695-8717 
article DOI  
Abstract: We present one of the first estimates of the global distribution of CO2
surface fluxes using total column CO2 measurements retrieved by the
SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite
(GOSAT). We derive optimized fluxes from June 2009 to December 2010. We
estimate fluxes from surface CO2 measurements to use as baselines for
comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we
can reproduce the observed CO2 time series at surface and TC-CON sites
in the tropics and the northern extra-tropics. In contrast, in the
southern extra-tropics GOSAT X-CO2 leads to enhanced seasonal cycle
amplitudes compared to independent measurements, and we identify it as
the result of a land-sea bias in our GOSAT X-CO2 retrievals. A bias
correction in the form of a global offset between GOSAT land and sea
pixels in a joint inversion of satellite and surface measurements of CO2
yields plausible global flux estimates which are more tightly
constrained than in an inversion using surface CO2 data alone. We show
that assimilating the biascorrected GOSAT data on top of surface CO2
data (a) reduces the estimated global land sink of CO2, and (b) shifts
the terrestrial net uptake of carbon from the tropics to the
extratropics. It is concluded that while GOSAT total column CO2 provide
useful constraints for source-sink inversions, small spatiotemporal
biases -beyond what can be detected using current validation techniques
- have serious consequences for optimized fluxes, even aggregated over
continental scales.
BibTeX:
@article{basu13a,
  author = {Basu, S. and Guerlet, S. and Butz, A. and Houweling, S. and Hasekamp, O. and Aben, I. and Krummel, P. and Steele, P. and Langenfelds, R. and Torn, M. and Biraud, S. and Stephens, B. and Andrews, A. and Worthy, D.},
  title = {Global CO2 fluxes estimated from GOSAT retrievals of total column CO2},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {17},
  pages = {8695--8717},
  doi = {https://doi.org/10.5194/acp-13-8695-2013}
}
Basu, S., Miller, J.B. and Lehman, S. Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and (CO2)-C-14 measurements: Observation System Simulations {2016} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {16}({9}), pp. 5665-5683 
article DOI  
Abstract: National annual total CO2 emissions from combustion of fossil fuels are
likely known to within 5-10aEuro-% for most developed countries.
However, uncertainties are inevitably larger (by unknown amounts) for
emission estimates at regional and monthly scales, or for developing
countries. Given recent international efforts to establish emission
reduction targets, independent determination and verification of
regional and national scale fossil fuel CO2 emissions are likely to
become increasingly important. Here, we take advantage of the fact that
precise measurements of C-14 in CO2 provide a largely unbiased tracer
for recently added fossil-fuel-derived CO2 in the atmosphere and present
an atmospheric inversion technique to jointly assimilate observations of
CO2 and (CO2)-C-14 in order to simultaneously estimate fossil fuel
emissions and biospheric exchange fluxes of CO2. Using this method in a
set of Observation System Simulation Experiments (OSSEs), we show that
given the coverage of (CO2)-C-14 measurements available in 2010 (969
over North America, 1063 globally), we can recover the US national total
fossil fuel emission to better than 1aEuro-% for the year and to within
5aEuro-% for most months. Increasing the number of (CO2)-C-14
observations to similar to 5000 per year over North America, as recently
recommended by the National Academy of Science (NAS) (Pacala et al.,
2010), we recover monthly emissions to within 5aEuro-% for all months
for the US as a whole and also for smaller, highly emissive regions over
which the specified data coverage is relatively dense, such as for the
New England states or the NY-NJ-PA tri-state area. This result suggests
that, given continued improvement in state-of-the art transport models,
a measurement program similar in scale to that recommended by the NAS
can provide for independent verification of bottom-up inventories of
fossil fuel CO2 at the regional and national scale. In addition, we show
that the dual tracer inversion framework can detect and minimize biases
in estimates of the biospheric flux that would otherwise arise in a
traditional CO2-only inversion when prescribing fixed but inaccurate
fossil fuel fluxes.
BibTeX:
@article{basu16a,
  author = {Basu, Sourish and Miller, John Bharat and Lehman, Scott},
  title = {Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and (CO2)-C-14 measurements: Observation System Simulations},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2016},
  volume = {16},
  number = {9},
  pages = {5665--5683},
  doi = {https://doi.org/10.5194/acp-16-5665-2016}
}
Basu, S., Lehman, S.J., Miller, J.B., Andrews, A.E., Sweeney, C., Gurney, K.R., Xu, X., Southon, J. and Tans, P.P. Estimating US fossil fuel CO2 emissions from measurements of C-14 in atmospheric CO2 {2020} PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Vol. {117}({24}), pp. {13300-13307} 
article DOI URL 
Abstract: We report national scale estimates of CO2 emissions from fossilfuel combustion and cement production in the United States based directly on atmospheric observations, using a dual-tracer inverse modeling framework and CO2 and Delta(CO2)-C-14 measurements obtained primarily from the North American portion of the National Oceanic and Atmospheric Administration's Global Greenhouse Gas Reference Network. The derived US national total for 2010 is 1,653 +/- 30 TgC yr(-1) with an uncertainty (1 sigma) that takes into account random errors associated with atmospheric transport, atmospheric measurements, and specified prior CO2 and C-14 fluxes. The atmosphere-derived estimate is significantly larger (> 3 sigma) than US national emissions for 2010 from three global inventories widely used for CO2 accounting, even after adjustments for emissions that might be sensed by the atmospheric network, but which are not included in inventory totals. It is also larger (> 2 sigma) than a similarly adjusted total from the US Environmental Protection Agency (EPA), but overlaps EPA's reported upper 95% confidence limit. In contrast, the atmosphere-derived estimate is within 1 sigma of the adjusted 2010 annual total and nine of 12 adjusted monthly totals aggregated from the latest version of the high-resolution, US-specific ``Vulcan'' emission data product. Derived emissions appear to be robust to a range of assumed prior emissions and other parameters of the inversion framework. While we cannot rule out a possible bias from assumed prior Net Ecosystem Exchange over North America, we show that this can be overcome with additional Delta(CO2)-C-14 measurements. These results indicate the strong potential for quantification of US emissions and their multiyear trends from atmospheric observations.
BibTeX:
@article{basu20a,
  author = {Basu, Sourish and Lehman, Scott J. and Miller, John B. and Andrews, Arlyn E. and Sweeney, Colm and Gurney, Kevin R. and Xu, Xiaomei and Southon, John and Tans, Pieter P.},
  title = {Estimating US fossil fuel CO2 emissions from measurements of C-14 in atmospheric CO2},
  journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA},
  publisher = {NATL ACAD SCIENCES},
  year = {2020},
  volume = {117},
  number = {24},
  pages = {13300--13307},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.pnas.org/content/117/24/13300.short},
  doi = {https://doi.org/10.1073/pnas.1919032117}
}
Bednarsek, N., Naish, K.-A., Feely, R.A., Hauri, C., Kimoto, K., Hermann, A.J., Michel, C., Niemi, A. and Pilcher, D. Integrated Assessment of Ocean Acidification Risks to Pteropods in the Northern High Latitudes: Regional Comparison of Exposure, Sensitivity and Adaptive Capacity 2021 FRONTIERS IN MARINE SCIENCE
Vol. 8 
article DOI  
Abstract: Exposure to the impact of ocean acidification (OA) is increasing in
high-latitudinal productive habitats. Pelagic calcifying snails
(pteropods), a significant component of the diet of economically
important fish, are found in high abundance in these regions. Pteropods
have thin shells that readily dissolve at low aragonite saturation state
(omega(ar)), making them susceptible to OA. Here, we conducted a first
integrated risk assessment for pteropods in the Eastern Pacific subpolar
gyre, the Gulf of Alaska (GoA), Bering Sea, and Amundsen Gulf. We
determined the risk for pteropod populations by integrating measures of
OA exposure, biological sensitivity, and resilience. Exposure was based
on physical-chemical hydrographic observations and regional
biogeochemical model outputs, delineating seasonal and decadal changes
in carbonate chemistry conditions. Biological sensitivity was based on
pteropod morphometrics and shell-building processes, including shell
dissolution, density and thickness. Resilience and adaptive capacity
were based on species diversity and spatial connectivity, derived from
the particle tracking modeling. Extensive shell dissolution was found in
the central and western part of the subpolar gyre, parts of the Bering
Sea, and Amundsen Gulf. We identified two distinct morphotypes: L.
helicina helicina and L. helicina pacifica, with high-spired and flatter
shells, respectively. Despite the presence of different morphotypes,
genetic analyses based on mitochondrial haplotypes identified a single
species, without differentiation between the morphological forms,
coinciding with evidence of widespread spatial connectivity. We found
that shell morphometric characteristics depends on omega saturation
state (omega(ar)); under omega(ar) decline, pteropods build flatter and
thicker shells, which is indicative of a certain level of phenotypic
plasticity. An integrated risk evaluation based on multiple approaches
assumes a high risk for pteropod population persistence with
intensification of OA in the high latitude eastern North Pacific because
of their known vulnerability, along with limited evidence of species
diversity despite their connectivity and our current lack of sufficient
knowledge of their adaptive capacity. Such a comprehensive understanding
would permit improved prediction of ecosystem change relevant to
effective fisheries resource management, as well as a more robust
foundation for monitoring ecosystem health and investigating OA impacts
in high-latitudinal habitats.
BibTeX:
@article{bednarsek21a,
  author = {Bednarsek, Nina and Naish, Kerry-Ann and Feely, Richard A. and Hauri, Claudine and Kimoto, Katsunori and Hermann, Albert J. and Michel, Christine and Niemi, Andrea and Pilcher, Darren},
  title = {Integrated Assessment of Ocean Acidification Risks to Pteropods in the Northern High Latitudes: Regional Comparison of Exposure, Sensitivity and Adaptive Capacity},
  journal = {FRONTIERS IN MARINE SCIENCE},
  year = {2021},
  volume = {8},
  doi = {https://doi.org/10.3389/fmars.2021.671497}
}
Belikov, D.A., Bril, A., Maksyutov, S., Oshchepkov, S., Saeki, T., Takagi, H., Yoshida, Y., Ganshin, A., Zhuravlev, R., Aoki, S. and Yokota, T. Column-averaged CO2 concentrations in the subarctic from GOSAT retrievals and NIES transport model simulations {2014} POLAR SCIENCE
Vol. {8}({2, SI}), pp. 129-145 
article DOI  
Abstract: The distribution of atmospheric carbon dioxide (CO2) in the subarctic
was investigated using the National Institute for Environmental Studies
(NIBS) three-dimensional transport model (TM) and retrievals from the
Greenhouse gases Observing SATellite (GOSAT). Column-averaged dry air
mole fractions of subarctic atmospheric CO2 (XCO2) from the NIES TM for
four flux combinations were analyzed. Two flux datasets were optimized
using only surface observations and two others were optimized using both
surface and GOSAT Level 2 data. Two inverse modeling approaches using
GOSAT data were compared. In the basic approach adopted in the GOSAT
Level 4 product, the GOSAT observations are aggregated into monthly
means over 5 degrees x 5 degrees grids. In the alternative method, the
model observation misfit is estimated for each observation separately.
The XCO2 values simulated with optimized fluxes were validated against
Total Carbon Column Observing Network (TCCON) ground-based
high-resolution Fourier Transform Spectrometer (FTS) measurements.
Optimized fluxes were applied to study XCO2 seasonal variability over
the period 2009-2010 in the Arctic and subarctic regions. The impact on
CO2 levels of emissions from enhancement of biospheric respiration
induced by the high temperature and strong wildfires occurring in the
summer of 2010 was analyzed. Use of GOSAT data has a substantial impact
on estimates of the level of CO2 interanual variability. (C) 2014
Elsevier B.V. and NIPR. All rights reserved.
BibTeX:
@article{belikov14a,
  author = {Belikov, D. A. and Bril, A. and Maksyutov, S. and Oshchepkov, S. and Saeki, T. and Takagi, H. and Yoshida, Y. and Ganshin, A. and Zhuravlev, R. and Aoki, S. and Yokota, T.},
  title = {Column-averaged CO2 concentrations in the subarctic from GOSAT retrievals and NIES transport model simulations},
  journal = {POLAR SCIENCE},
  year = {2014},
  volume = {8},
  number = {2, SI},
  pages = {129--145},
  doi = {https://doi.org/10.1016/j.polar.2014.02.002}
}
Belikov, D.A., Maksyutov, S., Yaremchuk, A., Ganshin, A., Kaminski, T., Blessing, S., Sasakawa, M., Gomez-Pelaez, A.J. and Starchenko, A. Adjoint of the global Eulerian-Lagrangian coupled atmospheric transport model (A-GELCA v1.0): development and validation {2016} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {9}({2}), pp. 749-764 
article DOI  
Abstract: We present the development of the Adjoint of the Global
Eulerian-Lagrangian Coupled Atmospheric (A-GELCA) model that consists of
the National Institute for Environmental Studies (NIES) model as an
Eulerian three-dimensional transport model (TM), and FLEXPART (FLEXible
PARTicle dispersion model) as the Lagrangian Particle Dispersion Model
(LPDM). The forward tangent linear and adjoint components of the
Eulerian model were constructed directly from the original NIES TM code
using an automatic differentiation tool known as TAF (Transformation of
Algorithms in Fortran; http://www.FastOpt.com), with additional manual
pre- and post-processing aimed at improving transparency and clarity of
the code and optimizing the performance of the computing, including MPI
(Message Passing Interface). The Lagrangian component did not require
any code modification, as LPDMs are self-adjoint and track a significant
number of particles backward in time in order to calculate the
sensitivity of the observations to the neighboring emission areas. The
constructed Eulerian adjoint was coupled with the Lagrangian component
at a time boundary in the global domain. The simulations presented in
this work were performed using the A-GELCA model in forward and adjoint
modes. The forward simulation shows that the coupled model improves
reproduction of the seasonal cycle and short-term variability of CO2.
Mean bias and standard deviation for five of the six Siberian sites
considered decrease roughly by 1 ppm when using the coupled model. The
adjoint of the Eulerian model was shown, through several numerical
tests, to be very accurate (within machine epsilon with mismatch around
to +/- 6 e(-14)) compared to direct forward sensitivity calculations.
The developed adjoint of the coupled model combines the flux
conservation and stability of an Eulerian discrete adjoint formulation
with the flexibility, accuracy, and high resolution of a Lagrangian
backward trajectory formulation. A-GELCA will be incorporated into a
variational inversion system designed to optimize surface fluxes of
greenhouse gases.
BibTeX:
@article{belikov16a,
  author = {Belikov, Dmitry A. and Maksyutov, Shamil and Yaremchuk, Alexey and Ganshin, Alexander and Kaminski, Thomas and Blessing, Simon and Sasakawa, Motoki and Gomez-Pelaez, Angel J. and Starchenko, Alexander},
  title = {Adjoint of the global Eulerian-Lagrangian coupled atmospheric transport model (A-GELCA v1.0): development and validation},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2016},
  volume = {9},
  number = {2},
  pages = {749--764},
  doi = {https://doi.org/10.5194/gmd-9-749-2016}
}
Belikov, D., Arshinov, M., Belan, B., Davydov, D., Fofonov, A., Sasakawa, M. and Machida, T. Analysis of the Diurnal, Weekly, and Seasonal Cycles and Annual Trends in Atmospheric CO2 and CH4 at Tower Network in Siberia from 2005 to 2016 {2019} ATMOSPHERE
Vol. {10}({11}) 
article DOI  
Abstract: We analyzed 12 years (20052016) of continuous measurements of atmospheric CO2 and CH4 concentrations made at nine tower observation sites in the JapanRussia Siberian Tall Tower Inland Observation Network (JR-STATION), located in Siberia. Since the data are very noisy and have a low temporal resolution due to gaps in instrument operation, we used the recently developed Prophet model, which was designed to handle the common features of time series (multiple strong seasonalities, trend changes, outliers) and has a robust performance in the presence of missing data and trend shifts. By decomposing each sampled time-series into its major components (i.e., annual trend and seasonal, weekly, and hourly variation), we observed periodically changing patterns of tracer concentrations. Specifically, we detected multi-year variability of tracers and identified high-concentration events. The frequency of such events was found to vary throughout the year, reaching up to 20% of days for some months, while the number of such events was found to be different for CO2 and CH4. An analysis of weather conditions showed that, in most cases, high-concentration events were caused by a temperature inversion and low wind speed. Additionally, wind directions were found to be different for high- and low-concentration events. For some sites, the wind direction indicated the location of strong local sources of CO2 and CH4. As well as elucidating the seasonality of greenhouse gas concentrations, this study confirmed the potential of the Prophet model for detecting periodicity in environmental phenomena.
BibTeX:
@article{belikov19a,
  author = {Belikov, Dmitry and Arshinov, Mikhail and Belan, Boris and Davydov, Denis and Fofonov, Aleksandr and Sasakawa, Motoki and Machida, Toshinobu},
  title = {Analysis of the Diurnal, Weekly, and Seasonal Cycles and Annual Trends in Atmospheric CO2 and CH4 at Tower Network in Siberia from 2005 to 2016},
  journal = {ATMOSPHERE},
  publisher = {MDPI},
  year = {2019},
  volume = {10},
  number = {11},
  doi = {https://doi.org/10.3390/atmos10110689}
}
Bell, E. Evaluation of OCO-2 small-scale XCO2 variability using lidar retrievals from the ACT-America flight campaign 2018 School: Colorado State University  phdthesis URL 
Abstract: With eight 1.25 x 3 kilometer footprints across its swath and nearly 1 million observations of column-mean carbon dioxide concentration (XCO2) per day, the Orbiting Carbon Observatory (OCO-2) presents exciting possibilities for monitoring the global carbon cycle …
BibTeX:
@phdthesis{bell18a,
  author = {Emily Bell},
  title = {Evaluation of OCO-2 small-scale XCO2 variability using lidar retrievals from the ACT-America flight campaign},
  school = {Colorado State University},
  year = {2018},
  url = {https://mountainscholar.org/handle/10217/191457}
}
Berberoglu, H., Gomez, P.S. and Pilon, L. Radiation characteristics of Botryococcus braunii, Chlorococcum littorale, and Chlorella sp. used for CO2 fixation and biofuel production {2009} JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
Vol. {110}({17}), pp. 1879-1893 
article DOI  
Abstract: This paper reports experimental measurements of the radiation
characteristics of green algae Used for carbon dioxide fixation via
photosynthesis. The generated biomass can be used to produce not only
biofuels but also feed for animal and food supplements for human
consumptions. Particular attention was paid to three widely used species
namely Botryococcus braunii, Chlorella sp., and Chlorococcum littorale.
Their extinction and absorption coefficients were obtained from
normal-normal and normal-hemispherical transmittance measurements over
the spectral range from 400 to 800 nm. Moreover, a polar nephelometer
was used to measure the scattering phase function of the microorganisms
at 632.8 nm. It was observed that for all strains, scattering dominates
over absorption. The magnitudes of the extinction and scattering
cross-section are functions of the size, shape, and chlorophyll content
of each strain in a nontrivial manner. Absorption peaks at 435,475, and
676 nm corresponding to chlorophyll a and chlorophyll b. The results can
be used for scaling and optimization of CO2 fixation in ponds or
photobioreactors as well as in the development of controlled ecological
life support systems. (C) 2009 Elsevier Ltd. All rights reserved.
BibTeX:
@article{berberoglu09a,
  author = {Berberoglu, Halil and Gomez, Pedro S. and Pilon, Laurent},
  title = {Radiation characteristics of Botryococcus braunii, Chlorococcum littorale, and Chlorella sp. used for CO2 fixation and biofuel production},
  journal = {JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER},
  year = {2009},
  volume = {110},
  number = {17},
  pages = {1879--1893},
  doi = {https://doi.org/10.1016/j.jqsrt.2009.04.005}
}
Bergamaschi, P., Frankenberg, C., Meirink, J.F., Krol, M., Villani, M.G., Houweling, S., Dentener, F., Dlugokencky, E.J., Miller, J.B., Gatti, L.V., Engel, A. and Levin, I. Inverse modeling of global and regional CH4 emissions using SCIAMACHY satellite retrievals {2009} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {114} 
article DOI  
Abstract: Methane retrievals from the Scanning Imaging Absorption Spectrometer for
Atmospheric Chartography (SCIAMACHY) instrument onboard ENVISAT provide
important information on atmospheric CH4 sources, particularly in
tropical regions which are poorly monitored by in situ surface
observations. Recently, Frankenberg et al. (2008a, 2008b) reported a
major revision of SCIAMACHY retrievals due to an update of spectroscopic
parameters of water vapor and CH4. Here, we analyze the impact of this
revision on global and regional CH4 emissions estimates in 2004, using
the TM5-4DVAR inverse modeling system. Inversions based on the revised
SCIAMACHY retrievals yield similar to 20% lower tropical emissions
compared to the previous retrievals. The new retrievals improve
significantly the consistency between observed and assimilated column
average mixing ratios and the agreement with independent validation
data. Furthermore, the considerable latitudinal and seasonal bias
correction of the previous SCIAMACHY retrievals, derived in the
TM5-4DVAR system by simultaneously assimilating high-accuracy surface
measurements, is reduced by a factor of similar to 3. The inversions
result in significant changes in the spatial patterns of emissions and
their seasonality compared to the bottom-up inventories. Sensitivity
tests were done to analyze the robustness of retrieved emissions,
revealing some dependence on the applied a priori emission inventories
and OH fields. Furthermore, we performed a detailed validation of
simulated CH4 mixing ratios using NOAA ship and aircraft profile
samples, as well as stratospheric balloon samples, showing overall good
agreement. We use the new SCIAMACHY retrievals for a regional analysis
of CH4 emissions from South America, Africa, and Asia, exploiting the
zooming capability of the TM5 model. This allows a more detailed
analysis of spatial emission patterns and better comparison with
aircraft profiles and independent regional emission estimates available
for South America. Large CH4 emissions are attributed to various wetland
regions in tropical South America and Africa, seasonally varying and
opposite in phase with CH4 emissions from biomass burning. India, China
and South East Asia are characterized by pronounced emissions from rice
paddies peaking in the third quarter of the year, in addition to further
anthropogenic emissions throughout the year.
BibTeX:
@article{bergamaschi09a,
  author = {Bergamaschi, Peter and Frankenberg, Christian and Meirink, Jan Fokke and Krol, Maarten and Villani, M. Gabriella and Houweling, Sander and Dentener, Frank and Dlugokencky, Edward J. and Miller, John B. and Gatti, Luciana V. and Engel, Andreas and Levin, Ingeborg},
  title = {Inverse modeling of global and regional CH4 emissions using SCIAMACHY satellite retrievals},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2009},
  volume = {114},
  doi = {https://doi.org/10.1029/2009JD012287}
}
Bergamaschi, P., Houweling, S., Segers, A., Krol, M., Frankenberg, C., Scheepmaker, R.A., Dlugokencky, E., Wofsy, S.C., Kort, E.A., Sweeney, C., Schuck, T., Brenninkmeijer, C., Chen, H., Beck, V. and Gerbig, C. Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements {2013} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {118}({13}), pp. 7350-7369 
article DOI  
Abstract: The causes of renewed growth in the atmospheric CH4 burden since 2007
are still poorly understood and subject of intensive scientific
discussion. We present a reanalysis of global CH4 emissions during the
2000s, based on the TM5-4DVAR inverse modeling system. The model is
optimized using high-accuracy surface observations from NOAA ESRL's
global air sampling network for 2000-2010 combined with retrievals of
column-averaged CH4 mole fractions from SCIAMACHY onboard ENVISAT
(starting 2003). Using climatological OH fields, derived global total
emissions for 2007-2010 are 16-20 Tg CH4/yr higher compared to
2003-2005. Most of the inferred emission increase was located in the
tropics (9-14 Tg CH4/yr) and mid- latitudes of the northern hemisphere
(6-8 Tg CH4/yr), while no significant trend was derived for Arctic
latitudes. The atmospheric increase can be attributed mainly to
increased anthropogenic emissions, but the derived trend is
significantly smaller than estimated in the EDGARv4.2 emission
inventory. Superimposed on the increasing trend in anthropogenic CH4
emissions are significant inter-annual variations (IAV) of emissions
from wetlands (up to +/- 10 Tg CH4/yr), and biomass burning (up to +/- 7
Tg CH4/yr). Sensitivity experiments, which investigated the impact of
the SCIAMACHY observations (versus inversions using only surface
observations), of the OH fields used, and of a priori emission
inventories, resulted in differences in the detailed latitudinal
attribution of CH4 emissions, but the IAV and trends aggregated over
larger latitude bands were reasonably robust. All sensitivity
experiments show similar performance against independent shipboard and
airborne observations used for validation, except over Amazonia where
satellite retrievals improved agreement with observations in the free
troposphere.
BibTeX:
@article{bergamaschi13a,
  author = {Bergamaschi, P. and Houweling, S. and Segers, A. and Krol, M. and Frankenberg, C. and Scheepmaker, R. A. and Dlugokencky, E. and Wofsy, S. C. and Kort, E. A. and Sweeney, C. and Schuck, T. and Brenninkmeijer, C. and Chen, H. and Beck, V. and Gerbig, C.},
  title = {Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2013},
  volume = {118},
  number = {13},
  pages = {7350--7369},
  doi = {https://doi.org/10.1002/jgrd.50480}
}
Bernath, P., Boone, C., Fernando, A. and Jones, S. Low altitude CO2 from the Atmospheric Chemistry Experiment (ACE) satellite {2019} JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
Vol. {238}({SI}) 
article DOI URL 
Abstract: The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) has been measuring atmospheric composition by solar occultation from low Earth orbit since 2004. A new version (4.0) of ACE-FTS processing has added low altitude CO2 as a routine data product. ACE provides a near global data set of altitude profiles of CO(2)( )volume mixing ratios (VMRs) on a 1 km grid from 5 to 18 km. We provide an initial evaluation of these data using occultations from the month of May for 2004-2017 in the 55 degrees-70 degrees S latitude range. Comparisons are made with ground-based measurements at Macquarie Island, the South Pole, the CarbonTracker 2017 model and G. Toon's empirical model. Agreement for trends is good, but ACE FTS VMRs have a low bias at 5.5 and 6.5km in altitude. (C) 2019 Elsevier Ltd. All rights reserved.
BibTeX:
@article{bernath19a,
  author = {Bernath, Peter and Boone, Chris and Fernando, Anton and Jones, Scott},
  title = {Low altitude CO2 from the Atmospheric Chemistry Experiment (ACE) satellite},
  journal = {JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  year = {2019},
  volume = {238},
  number = {SI},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.sciencedirect.com/science/article/pii/S0022407319302778},
  doi = {https://doi.org/10.1016/j.jqsrt.2019.06.007}
}
Berry, J.A. There Ought to Be an Equation for That {2012} Annual Review of Plant Biology
Vol. {63}(1)ANNUAL REVIEW OF PLANT BIOLOGY, VOL 63, pp. 1-17 
article DOI  
Abstract: An overriding interest in photosynthesis has propelled my wanderings
from chemist to biochemist to plant physiologist and on to global
topics. Equations and models have been organizing principles along the
way. This fascination started as a reaction to difficulties with written
communication, but it has proven to be quite useful in moving across
different levels of organization. I conclude with some discussion of the
importance of Earth system models for understanding and predicting how
human activities may influence the climate, environment, and biota in
the future, and some ideas about how disciplinary science might make
larger contributions to this interdisciplinary problem.
BibTeX:
@article{berry12a,
  author = {Berry, Joseph A.},
  title = {There Ought to Be an Equation for That},
  booktitle = {ANNUAL REVIEW OF PLANT BIOLOGY, VOL 63},
  journal = {Annual Review of Plant Biology},
  year = {2012},
  volume = {63},
  number = {1},
  pages = {1--17},
  doi = {https://doi.org/10.1146/annurev-arplant-042811-105547}
}
Bhattacharjee, S. and Chen, J. Prediction of Satellite-Based Column CO2 Concentration by Combining Emission Inventory and LULC Information {2020} IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
Vol. {58}({12}), pp. {8285-8300} 
article DOI URL 
Abstract: In this article, we generate a regional mapping of space-borne carbon dioxide (CO2) concentration through a data fusion approach, including emission estimates and Land Use and Land Cover (LULC) information. NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite measures the column-averaged CO2 dry air mole fraction (XCO2) as contiguous parallelogram footprints. A major hindrance of this data set, specifically with its Level-2 observations, is missing footprints at certain time instants and the sparse sampling density in time. This article aims to generate Level-3 XCO2 maps on a regional scale for different locations worldwide through spatial interpolation of the OCO-2 retrievals. To deal with the sparse OCO-2 sampling, the cokriging-based spatial interpolation methods are suitable, which models auxiliary densely-sampled variables to predict the primary variable. In this article, a cokriging-based approach is applied using auxiliary emission data sets and the principles of the semantic kriging (SemK) method. Two global high-resolution emission data sets, the Open-source Data Inventory for Anthropogenic CO2 (ODIAC) and the Emissions Database for Global Atmospheric Research (EDGAR), are used here. The ontology-based semantic analysis of the SemK method quantifies the interrelationships of LULC classes for analyzing the local XCO2 pattern. Validations have been carried out in different regions worldwide, where the OCO-2 and the Total Carbon Column Observing Network (TCCON) measurements coexist. It is observed that the modeling of auxiliary emission data sets enhances the prediction accuracy of XCO2. This article is one of the initial attempts to generate Level-3 XCO2 mapping of OCO-2 through a data fusion approach using emission data sets.
BibTeX:
@article{bhattacharjee20a,
  author = {Bhattacharjee, Shrutilipi and Chen, Jia},
  title = {Prediction of Satellite-Based Column CO2 Concentration by Combining Emission Inventory and LULC Information},
  journal = {IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING},
  publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC},
  year = {2020},
  volume = {58},
  number = {12},
  pages = {8285--8300},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://ieeexplore.ieee.org/abstract/document/9094001/},
  doi = {https://doi.org/10.1109/TGRS.2020.2985047}
}
Biavati, G., Feist, D.G., Gerbig, C. and Kretschmer, R. Error estimation for localized signal properties: application to atmospheric mixing height retrievals {2015} Atmospheric Measurement Techniques
Vol. {8}({10}), pp. 4215-4230 
article DOI  
Abstract: The mixing height is a key parameter for many applications that relate
surface-atmosphere exchange fluxes to atmospheric mixing ratios, e.g.,
in atmospheric transport modeling of pollutants. The mixing height can
be estimated with various methods: profile measurements from radiosondes
as well as remote sensing (e.g., optical backscatter measurements). For
quantitative applications, it is important to estimate not only the
mixing height itself but also the uncertainty associated with this
estimate. However, classical error propagation typically fails on mixing
height estimates that use thresholds in vertical profiles of some
measured or measurement-derived quantity. Therefore, we propose a method
to estimate the uncertainty of an estimation of the mixing height. The
uncertainty we calculate is related not to the physics of the boundary
layer (e.g., entrainment zone thickness) but to the quality of the
analyzed signals. The method relies on the concept of statistical
confidence and on the knowledge of the measurement errors. It can also
be applied to problems outside atmospheric mixing height retrievals
where properties have to be assigned to a specific position, e.g., the
location of a local extreme.
BibTeX:
@article{biavati15a,
  author = {Biavati, G. and Feist, D. G. and Gerbig, C. and Kretschmer, R.},
  title = {Error estimation for localized signal properties: application to atmospheric mixing height retrievals},
  journal = {Atmospheric Measurement Techniques},
  year = {2015},
  volume = {8},
  number = {10},
  pages = {4215--4230},
  doi = {https://doi.org/10.5194/amt-8-4215-2015}
}
Biraud, S.C., Torn, M.S., Smith, J.R., Sweeney, C., Riley, W.J. and Tans, P.P. A multi-year record of airborne CO2 observations in the US Southern Great Plains {2013} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {6}({3}), pp. 751-763 
article DOI  
Abstract: We report on 10 yr of airborne measurements of atmospheric CO2 mole
fraction from continuous and flask systems, collected between 2002 and
2012 over the Atmospheric Radiation Measurement Program Climate Research
Facility in the US Southern Great Plains (SGP). These observations were
designed to quantify trends and variability in atmospheric mole fraction
of CO2 and other greenhouse gases with the precision and accuracy needed
to evaluate ground-based and satellite-based column CO2 estimates, test
forward and inverse models, and help with the interpretation of
ground-based CO2 mole-fraction measurements. During flights, we measured
CO2 and meteorological data continuously and collected flasks for a rich
suite of additional gases: CO2, CO, CH4, N2O, (CO2)-C-13, carbonyl
sulfide (COS), and trace hydrocarbon species. These measurements were
collected approximately twice per week by small aircraft (Cessna 172
initially, then Cessna 206) on a series of horizontal legs ranging in
altitude from 460 m to 5500 m a.m.s.l. Since the beginning of the
program, more than 400 continuous CO2 vertical profiles have been
collected (2007-2012), along with about 330 profiles from NOAA/ESRL
12-flask (2006-2012) and 284 from NOAA/ESRL 2-flask (2002-2006) packages
for carbon cycle gases and isotopes. Averaged over the entire record,
there were no systematic differences between the continuous and flask
CO2 observations when they were sampling the same air, i.e., over the
one-minute flask-sampling time. Using multiple technologies (a flask
sampler and two continuous analyzers), we documented a mean difference
of < 0.2 ppm between instruments. However, flask data were not
equivalent in all regards; horizontal variability in CO2 mole fraction
within the 5-10 min legs sometimes resulted in significant differences
between flask and continuous measurement values for those legs, and the
information contained in fine-scale variability about atmospheric
transport was not captured by flask-based observations. The CO2 mole
fraction trend at 3000 m a.m.s.l. was 1.91 ppm yr(-1) between 2008 and
2010, very close to the concurrent trend at Mauna Loa of 1.95 ppm
yr(-1). The seasonal amplitude of CO2 mole fraction in the free
troposphere (FT) was half that in the planetary boundary layer (PBL)
(similar to 15 ppm vs. similar to 30 ppm) and twice that at Mauna Loa
(approximately 8 ppm). The CO2 horizontal variability was up to 10 ppm
in the PBL and less than 1 ppm at the top of the vertical profiles in
the FT.
BibTeX:
@article{biraud13a,
  author = {Biraud, S. C. and Torn, M. S. and Smith, J. R. and Sweeney, C. and Riley, W. J. and Tans, P. P.},
  title = {A multi-year record of airborne CO2 observations in the US Southern Great Plains},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2013},
  volume = {6},
  number = {3},
  pages = {751--763},
  doi = {https://doi.org/10.5194/amt-6-751-2013}
}
Bodesheim, P., Jung, M., Gans, F., Mahecha, M.D. and Reichstein, M. Upscaled diurnal cycles of land-atmosphere fluxes: a new global half-hourly data product 2018 Earth System Science Data
Vol. 10(3), pp. 1327-1365 
article DOI  
Abstract: Interactions between the biosphere and the atmosphere can be well
characterized by fluxes between the two. In particular, carbon and
energy fluxes play a major role in understanding biogeochemical
processes on an ecosystem level or global scale. However, the fluxes can
only be measured at individual sites, e.g., by eddy covariance towers,
and an upscaling of these local observations is required to analyze
global patterns. Previous work focused on upscaling monthly, 8-day, or
daily average values, and global maps for each flux have been provided
accordingly. In this paper, we raise the upscaling of carbon and energy
fluxes between land and atmosphere to the next level by increasing the
temporal resolution to subdaily timescales. We provide continuous
half-hourly fluxes for the period from 2001 to 2014 at 0.5 degrees
spatial resolution, which allows for analyzing diurnal cycles globally.
The data set contains four fluxes: gross primary production (GPP), net
ecosystem exchange (NEE), latent heat (LE), and sensible heat (H). We
propose two prediction approaches for the diurnal cycles based on
large-scale regression models and compare them in extensive
cross-validation experiments using different sets of predictor
variables. We analyze the results for a set of FLUXNET tower sites
showing the suitability of our approaches for this upscaling task.
Finally, we have selected one approach to calculate the global
half-hourly data products based on predictor variables from remote
sensing and meteorology at daily resolution as well as half-hourly
potential radiation. In addition, we provide a derived product that only
contains monthly average diurnal cycles, which is a lightweight version
in terms of data storage that still allows studying the important
characteristics of diurnal patterns globally. We recommend to primarily
use these monthly average diurnal cycles, because they are less affected
by the impacts of day-to-day variation, observation noise, and
short-term fluctuations on subdaily timescales compared to the full
half-hourly flux products. The global half-hourly data products are
available at https://doi.org/10.17871/BACI.224.
BibTeX:
@article{bodesheim18a,
  author = {Bodesheim, Paul and Jung, Martin and Gans, Fabian and Mahecha, Miguel D. and Reichstein, Markus},
  title = {Upscaled diurnal cycles of land-atmosphere fluxes: a new global half-hourly data product},
  journal = {Earth System Science Data},
  year = {2018},
  volume = {10},
  number = {3},
  pages = {1327-1365},
  doi = {https://doi.org/10.5194/essd-10-1327-2018}
}
Boland, S., Bösch, H., Brown, L., Burrows, J., Ciais, P., Connor, B., Crisp, D., Denning, S., Doney, S., Engelen, R. and others The need for atmospheric carbon dioxide measurements from space: Contributions from a rapid reflight of the Orbiting Carbon Observatory 2009 White paper to NASA  article  
BibTeX:
@article{boland09a,
  author = {Boland, Stacey and Bösch, Hartmut and Brown, Linda and Burrows, John and Ciais, Philippe and Connor, Brian and Crisp, David and Denning, Scott and Doney, Scott and Engelen, Richard and others},
  title = {The need for atmospheric carbon dioxide measurements from space: Contributions from a rapid reflight of the Orbiting Carbon Observatory},
  journal = {White paper to NASA},
  year = {2009}
}
Boone, C.D. and Bernath, P.F. Tangent height determination from the N-2-continuum for the Atmospheric Chemistry Experiment Fourier transform spectrometer {2019} JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
Vol. {238}({SI}) 
article DOI URL 
Abstract: With inadequate information from sensors onboard the SCISAT satellite to generate accurate pointing information, tangent heights for the solar occultation measurements collected by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) are determined from features in the measured spectra. For version 4.0 processing of the ACE-FTS data, tangent heights below 18 km are generated from the N-2 collision induced absorption continuum near 2500 cm(-1). Because this tangent height determination requires no assumptions on CO2 concentrations in this altitude region (unlike previous processing versions), ACE-FTS version 4.0 includes retrieved CO2 volume mixing ratio profiles below 18 km as a standard product. (C) 2019 Elsevier Ltd. All rights reserved.
BibTeX:
@article{boone19a,
  author = {Boone, C. D. and Bernath, P. F.},
  title = {Tangent height determination from the N-2-continuum for the Atmospheric Chemistry Experiment Fourier transform spectrometer},
  journal = {JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  year = {2019},
  volume = {238},
  number = {SI},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.sciencedirect.com/science/article/pii/S0022407319301918},
  doi = {https://doi.org/10.1016/j.jqsrt.2019.04.033}
}
Borbas, E.E., Adler, D.P., Best, F.A., Knuteson, R.O., L'Ecuyer, T.S., Loveless, M., Olson, E.R., Revercomb, H.E. and Taylor, J.K. Ground-based Far-Infrared Emissivity Measurements with the University of Wisconsin Absolute Radiance Interferometer (ARI) 2021
Vol. 11830INFRARED REMOTE SENSING AND INSTRUMENTATION XXIX 
inproceedings DOI  
Abstract: The infrared Absolute Radiance Interferometer (ARI) instrument -
developed at University of Wisconsin-Madison, Space Science and
Engineering Center (SSEC) - measures absolute spectrally resolved
infrared radiance (200- 2000 cm(-1) or 5-50 mu m at 0.5 cm(-1)
resolution) with ultra-high accuracy (< 0.1 K 3-sigma brightness
temperature at scene temperature). The ARI prototype instrument was
deployed for field measurements of clear-sky far infrared (FIR) surface
emissivity and radiances on the SSEC rooftop. Currently there are very
few measurements available in the FIR spectral region. Our targeted
samples include snow and ice surfaces which are important for radiative
cooling in the polar regions. We will demonstrate the ARI instrument
configuration, capability for ground-based measurements in the FIR
region, and the retrieval of infrared emissivity spectra. The ARI
ground-based FIR measurements would support scientific applications that
involve FIR studies, such as the PREFIRE (Polar Radiant Energy in the
Far InfraRed Experiment) and the European FORUM (Far-infrared-outgoing
Radiation Understating and Monitoring) missions.
BibTeX:
@inproceedings{borbas21a,
  author = {Borbas, E. Eva and Adler, Douglas P. and Best, Fred A. and Knuteson, Robert O. and L'Ecuyer, Tristan S. and Loveless, Michelle and Olson, Erik R. and Revercomb, Henry E. and Taylor, Joseph K.},
  title = {Ground-based Far-Infrared Emissivity Measurements with the University of Wisconsin Absolute Radiance Interferometer (ARI)},
  booktitle = {INFRARED REMOTE SENSING AND INSTRUMENTATION XXIX},
  year = {2021},
  volume = {11830},
  note = {Conference on Infrared Remote Sensing and Instrumentation XXIX, San Diego, CA, AUG 01-05, 2021},
  doi = {https://doi.org/10.1117/12.2594834}
}
Botia, S., Komiya, S., Marshall, J., Koch, T., Galkowski, M., Lavric, J., Gomes-Alves, E., Walter, D., Fisch, G., Pinho, D.M., Nelson, B.W., Martins, G., Luijkx, I.T., Koren, G., Florentie, L., de Araujo, A.C., Sa, M., Andreae, M.O., Heimann, M., Peters, W. and Gerbig, C. The CO2 record at the Amazon Tall Tower Observatory: A new opportunity to study processes on seasonal and inter-annual scales 2022 GLOBAL CHANGE BIOLOGY
Vol. 28(2), pp. 588-611 
article DOI  
Abstract: High-quality atmospheric CO2 measurements are sparse in Amazonia, but
can provide critical insights into the spatial and temporal variability
of sources and sinks of CO2. In this study, we present the first 6 years
(2014-2019) of continuous, high-precision measurements of atmospheric
CO2 at the Amazon Tall Tower Observatory (ATTO, 2.1 degrees S, 58.9
degrees W). After subtracting the simulated background concentrations
from our observational record, we define a CO2 regional signal (Delta
CO2obs) that has a marked seasonal cycle with an amplitude of about 4
ppm. At both seasonal and inter-annual scales, we find differences in
phase between Delta CO2obs and the local eddy covariance net ecosystem
exchange (EC-NEE), which is interpreted as an indicator of a decoupling
between local and non-local drivers of Delta CO2obs. In addition, we
present how the 2015-2016 El Nino-induced drought was captured by our
atmospheric record as a positive 2 sigma anomaly in both the wet and dry
season of 2016. Furthermore, we analyzed the observed seasonal cycle and
inter-annual variability of Delta CO2obs together with net ecosystem
exchange (NEE) using a suite of modeled flux products representing
biospheric and aquatic CO2 exchange. We use both non-optimized and
optimized (i.e., resulting from atmospheric inverse modeling) NEE fluxes
as input in an atmospheric transport model (STILT). The observed shape
and amplitude of the seasonal cycle was captured neither by the
simulations using the optimized fluxes nor by those using the diagnostic
Vegetation and Photosynthesis Respiration Model (VPRM). We show that
including the contribution of CO2 from river evasion improves the
simulated shape (not the magnitude) of the seasonal cycle when using a
data-driven non-optimized NEE product (FLUXCOM). The simulated
contribution from river evasion was found to be 25% of the seasonal
cycle amplitude. Our study demonstrates the importance of the ATTO
record to better understand the Amazon carbon cycle at various spatial
and temporal scales.
BibTeX:
@article{botia22a,
  author = {Botia, Santiago and Komiya, Shujiro and Marshall, Julia and Koch, Thomas and Galkowski, Michal and Lavric, Jost and Gomes-Alves, Eliane and Walter, David and Fisch, Gilberto and Pinho, Davieliton M. and Nelson, Bruce W. and Martins, Giordane and Luijkx, Ingrid T. and Koren, Gerbrand and Florentie, Liesbeth and de Araujo, Alessandro Carioca and Sa, Marta and Andreae, Meinrat O. and Heimann, Martin and Peters, Wouter and Gerbig, Christoph},
  title = {The CO2 record at the Amazon Tall Tower Observatory: A new opportunity to study processes on seasonal and inter-annual scales},
  journal = {GLOBAL CHANGE BIOLOGY},
  year = {2022},
  volume = {28},
  number = {2},
  pages = {588-611},
  doi = {https://doi.org/10.1111/gcb.15905}
}
Bouche, A., Beck-Winchatz, B. and Potosnak, M.J. A high-altitude balloon platform for determining exchange of carbon dioxide over agricultural landscapes {2016} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {9}({12}), pp. 5707-5719 
article DOI  
Abstract: The exchange of carbon dioxide between the terrestrial biosphere and the
atmosphere is a key process in the global carbon cycle. Given emissions
from fossil fuel combustion and the appropriation of net primary
productivity by human activities, understanding the carbon dioxide
exchange of cropland agroecosystems is critical for evaluating future
trajectories of climate change. In addition, human manipulation of
agroecosystems has been proposed as a technique of removing carbon
dioxide from the atmosphere via practices such as no-tillage and cover
crops. We propose a novel method of measuring the exchange of carbon
dioxide over croplands using a high-altitude balloon (HAB) platform. The
HAB methodology measures two sequential vertical profiles of carbon
dioxide mixing ratio, and the surface exchange is calculated using a
fixed-mass column approach. This methodology is relatively inexpensive,
does not rely on any assumptions besides spatial homogeneity (no
horizontal advection) and provides data over a spatial scale between
stationary flux towers and satellite-based inversion calculations. The
HAB methodology was employed during the 2014 and 2015 growing seasons in
central Illinois, and the results are compared to satellite-based NDVI
values and a flux tower located relatively near the launch site in
Bondville, Illinois. These initial favorable results demonstrate the
utility of the methodology for providing carbon dioxide exchange data
over a large (10-100 km) spatial area. One drawback is its relatively
limited temporal coverage. While recruiting citizen scientists to
perform the launches could provide a more extensive dataset, the HAB
methodology is not appropriate for providing estimates of net annual
carbon dioxide exchange. Instead, a HAB dataset could provide an
important check for upscaling flux tower results and verifying
satellite-derived exchange estimates.
BibTeX:
@article{bouche16a,
  author = {Bouche, Angie and Beck-Winchatz, Bernhard and Potosnak, Mark J.},
  title = {A high-altitude balloon platform for determining exchange of carbon dioxide over agricultural landscapes},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2016},
  volume = {9},
  number = {12},
  pages = {5707--5719},
  doi = {https://doi.org/10.5194/amt-9-5707-2016}
}
Bovensmann, H., Buchwitz, M., Burrows, J.P., Reuter, M., Krings, T., Gerilowski, K., Schneising, O., Heymann, J., Tretner, A. and Erzinger, J. A remote sensing technique for global monitoring of power plant CO2 emissions from space and related applications {2010} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {3}({4}), pp. 781-811 
article DOI  
Abstract: Carbon dioxide (CO2) is the most important anthropogenic greenhouse gas
(GHG) causing global warming. The atmospheric CO2 concentration
increased by more than 30% since pre-industrial times - primarily due
to burning of fossil fuels - and still continues to increase. Reporting
of CO2 emissions is required by the Kyoto protocol. Independent
verification of reported emissions, which are typially not directly
measured, by methods such as inverse modeling of measured atmospheric
CO2 concentrations is currently not possible globally due to lack of
appropriate observations. Existing satellite instruments such as
SCIAMACHY/ENVISAT and TANSO/GOSAT focus on advancing our understanding
of natural CO2 sources and sinks. The obvious next step for future
generation satellites is to also constrain anthropogenic CO2 emissions.
Here we present a promising satellite remote sensing concept based on
spectroscopic measurements of reflected solar radiation and show, using
power plants as an example, that strong localized CO2 point sources can
be detected and their emissions quantified. This requires mapping the
atmospheric CO2 column distribution at a spatial resolution of 2x2 km(2)
with a precision of 0.5% (2 ppm) or better. We indicate that this can
be achieved with existing technology. For a single satellite in
sun-synchronous orbit with a swath width of 500 km, each power plant
(PP) is overflown every 6 days or more frequent. Based on the MODIS
cloud mask data product we conservatively estimate that typically 20
sufficiently cloud free overpasses per PP can be achieved every year. We
found that for typical wind speeds in the range of 2-6 m/s the
statistical uncertainty of the retrieved PP CO2 emission due to
instrument noise is in the range 1.6-4.8MtCO(2)/yr for single
overpasses. This corresponds to 12-36% of the emission of a mid-size PP
(13 MtCO(2)/yr). We have also determined the sensitivity to parameters
which may result in systematic errors such as atmospheric transport and
aerosol related parameters. We found that the emission error depends
linearly on wind speed, i.e., a 10% wind speed error results in a 10%
emission error, and that neglecting enhanced aerosol concentrations in
the PP plume may result in errors in the range 0.2-2.5 MtCO(2)/yr,
depending on PP aerosol emission. The discussed concept has the
potential to contribute to an independent verification of reported
anthropogenic CO2 emissions and therefore could be an important
component of a future global anthropogenic GHG emission monitoring
system. This is of relevance in the context of Kyoto protocol follow-on
agreements but also allows detection and monitoring of a variety of
other strong natural and anthropogenic CO2 and CH4 emitters. The
investigated instrument is not limited to these applications as it has
been specified to also deliver the data needed for global regional-scale
CO2 and CH4 surface flux inverse modeling.
BibTeX:
@article{bovensmann10a,
  author = {Bovensmann, H. and Buchwitz, M. and Burrows, J. P. and Reuter, M. and Krings, T. and Gerilowski, K. and Schneising, O. and Heymann, J. and Tretner, A. and Erzinger, J.},
  title = {A remote sensing technique for global monitoring of power plant CO2 emissions from space and related applications},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2010},
  volume = {3},
  number = {4},
  pages = {781--811},
  doi = {https://doi.org/10.5194/amt-3-781-2010}
}
Bowman, K., Liu, J., Bloom, A., Parazoo, N., Lee, M., Jiang, Z., Menemenlis, D., Gierach, M., Collatz, G., Gurney, K. and others Global and Brazilian carbon response to El Niño Modoki 2011--2010 2017 Earth and Space Science
Vol. 4(10), pp. 637-660 
article  
BibTeX:
@article{bowman17a,
  author = {Bowman, KW and Liu, J and Bloom, AA and Parazoo, NC and Lee, M and Jiang, Z and Menemenlis, D and Gierach, MM and Collatz, GJ and Gurney, KR and others},
  title = {Global and Brazilian carbon response to El Niño Modoki 2011--2010},
  journal = {Earth and Space Science},
  year = {2017},
  volume = {4},
  number = {10},
  pages = {637--660}
}
Bozhinova, D.N. Interpreting plant-sampled?` 14CO2 to study regional anthropogenic CO2 signals in Europe 2015   book  
BibTeX:
@book{bozhinova15a,
  author = {Bozhinova, Denica Nikolaeva},
  title = {Interpreting plant-sampled?` 14CO2 to study regional anthropogenic CO2 signals in Europe},
  publisher = {Wageningen University},
  year = {2015}
}
Bril, A., Oshchepkov, S. and Yokota, T. Retrieval of atmospheric methane from high spectral resolution satellite measurements: a correction for cirrus cloud effects {2009} APPLIED OPTICS
Vol. {48}({11}), pp. 2139-2148 
article DOI  
Abstract: We assessed the accuracy of methane (CH4) retrievals from synthetic
radiance spectra particular to Greenhouse Gases Observing Satellite
observations. We focused on estimating the CH4 vertical column amount
from an atmosphere that includes thin cirrus clouds, taking into account
uncertain meteorological conditions. A photon path-length probability
density function (PPDF)-based method was adapted to correct for
atmospheric scattering effects in CH4 retrievals. This method was shown
to provide similar retrieval accuracy as compared to a carbon dioxide
(CO2)-proxy-based correction approach. It infers some advantages of
PPDF-based method for methane retrievals under high variability of CO2
abundance. (C) 2009 Optical Society of America
BibTeX:
@article{bril09a,
  author = {Bril, Andrey and Oshchepkov, Sergey and Yokota, Tatsuya},
  title = {Retrieval of atmospheric methane from high spectral resolution satellite measurements: a correction for cirrus cloud effects},
  journal = {APPLIED OPTICS},
  year = {2009},
  volume = {48},
  number = {11},
  pages = {2139--2148},
  doi = {https://doi.org/10.1364/AO.48.002139}
}
Brioude, J., Petron, G., Frost, G.J., Ahmadov, R., Angevine, W.M., Hsie, E.Y., Kim, S.W., Lee, S.H., McKeen, S.A., Trainer, M., Fehsenfeld, F.C., Holloway, J.S., Peischl, J., Ryerson, T.B. and Gurney, K.R. A new inversion method to calculate emission inventories without a prior at mesoscale: Application to the anthropogenic CO2 emission from Houston, Texas {2012} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {117} 
article DOI  
Abstract: We developed a new inversion method to calculate an emission inventory
for an anthropogenic pollutant without a prior emission estimate at
mesoscale. This method employs slopes between mixing ratio enhancements
of a given pollutant (CO2, for instance) with other co-emitted tracers
in conjunction with the emission inventories of those tracers (CO, NOy,
and SO2 are used in this example). The current application of this
method employed in situ measurements onboard the NOAA WP-3 research
aircraft during the 2006 Texas Air Quality Study (TexAQS 2006). We used
3 different transport models to estimate the uncertainties introduced by
the transport models in the inversion. We demonstrated the validity of
the new inversion method by calculating a 4 x 4 km(2) emission inventory
of anthropogenic CO2 in the Houston area in Texas, and comparing it to
the 10 x 10 km(2) Vulcan emission inventory for the same region. The
calculated anthropogenic CO2 inventory for the Houston Ship Channel,
home to numerous major industrial and port emission sources, showed
excellent agreement with Vulcan. The daytime CO2 average flux from the
Ship Channel is the largest urban CO2 flux reported in the literature.
Compared to Vulcan, the daytime urban area CO2 emissions were higher by
37% +/- 6%. Those differences can be explained by uncertainties in
emission factors in Vulcan and by increased emissions from point sources
and on-road emitters between 2002, the reference year in Vulcan, and
2006, the year that the TexAQS observations were made.
BibTeX:
@article{brioude12a,
  author = {Brioude, J. and Petron, G. and Frost, G. J. and Ahmadov, R. and Angevine, W. M. and Hsie, E. -Y. and Kim, S. -W. and Lee, S. -H. and McKeen, S. A. and Trainer, M. and Fehsenfeld, F. C. and Holloway, J. S. and Peischl, J. and Ryerson, T. B. and Gurney, K. R.},
  title = {A new inversion method to calculate emission inventories without a prior at mesoscale: Application to the anthropogenic CO2 emission from Houston, Texas},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2012},
  volume = {117},
  doi = {https://doi.org/10.1029/2011JD016918}
}
Brioude, J., Angevine, W.M., Ahmadov, R., Kim, S.W., Evan, S., McKeen, S.A., Hsie, E.Y., Frost, G.J., Neuman, J.A., Pollack, I.B., Peischl, J., Ryerson, T.B., Holloway, J., Brown, S.S., Nowak, J.B., Roberts, J.M., Wofsy, S.C., Santoni, G.W., Oda, T. and Trainer, M. Top-down estimate of surface flux in the Los Angeles Basin using a mesoscale inverse modeling technique: assessing anthropogenic emissions of CO, NOx and CO2 and their impacts {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({7}), pp. 3661-3677 
article DOI  
Abstract: We present top-down estimates of anthropogenic CO, NOx and CO2 surface
fluxes at mesoscale using a Lagrangian model in combination with three
different WRF model configurations, driven by data from aircraft flights
during the CALNEX campaign in southern California in May-June 2010. The
US EPA National Emission Inventory 2005 (NEI 2005) was the prior in the
CO and NOx inversion calculations. The flux ratio inversion method,
based on linear relationships between chemical species, was used to
calculate the CO2 inventory without prior knowledge of CO2 surface
fluxes. The inversion was applied to each flight to estimate the
variability of single-flight-based flux estimates. In Los Angeles (LA)
County, the uncertainties on CO and NOx fluxes were 10% and 15 %,
respectively. Compared with NEI 2005, the CO posterior emissions were
lower by 43% in LA County and by 37% in the South Coast Air Basin
(SoCAB). NOx posterior emissions were lower by 32% in LA County and by
27% in the SoCAB. NOx posterior emissions were 40% lower on weekends
relative to weekdays. The CO2 posterior estimates were 183 Tgyr(-1) in
SoCAB. A flight during ITCT (Intercontinental Transport and Chemical
Transformation) in 2002 was used to estimate emissions in the LA Basin
in 2002. From 2002 to 2010, the CO and NOx posterior emissions decreased
by 41% and 37%, respectively, in agreement with previous studies. Over
the same time period, CO2 emissions increased by 10% in LA County but
decreased by 4% in the SoCAB, a statistically insignificant change.
Overall, the posterior estimates were in good agreement with the
California Air Resources Board (CARB) inventory, with differences of
15% or less. However, the posterior spatial distribution in the basin
was significantly different from CARB for NOx emissions. WRF-Chem
mesoscale chemical-transport model simulations allowed an evaluation of
differences in chemistry using different inventory assumptions,
including NEI 2005, a gridded CARB inventory and the posterior
inventories derived in this study. The biases in WRF-Chem ozone were
reduced and correlations were increased using the posterior from this
study compared with simulations with the two bottom-up inventories,
suggesting that improving the spatial distribution of ozone precursor
surface emissions is also important in mesoscale chemistry simulations.
BibTeX:
@article{brioude13a,
  author = {Brioude, J. and Angevine, W. M. and Ahmadov, R. and Kim, S. -W. and Evan, S. and McKeen, S. A. and Hsie, E. -Y. and Frost, G. J. and Neuman, J. A. and Pollack, I. B. and Peischl, J. and Ryerson, T. B. and Holloway, J. and Brown, S. S. and Nowak, J. B. and Roberts, J. M. and Wofsy, S. C. and Santoni, G. W. and Oda, T. and Trainer, M.},
  title = {Top-down estimate of surface flux in the Los Angeles Basin using a mesoscale inverse modeling technique: assessing anthropogenic emissions of CO, NOx and CO2 and their impacts},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {7},
  pages = {3661--3677},
  doi = {https://doi.org/10.5194/acp-13-3661-2013}
}
Brondfield, M.N., Hutyra, L.R., Gately, C.K., Raciti, S.M. and Peterson, S.A. Modeling and validation of on-road CO2 emissions inventories at the urban regional scale {2012} ENVIRONMENTAL POLLUTION
Vol. {170}, pp. 113-123 
article DOI  
Abstract: On-road emissions are a major contributor to rising concentrations of
atmospheric greenhouse gases. In this study, we applied a downscaling
methodology based on commonly available spatial parameters to model
on-road CO2 emissions at the 1 x 1 km scale for the Boston. MA region
and tested our approach with surface-level CO2 observations. Using two
previously constructed emissions inventories with differing spatial
patterns and underlying data sources, we developed regression models
based on impervious surface area and volume-weighted road density that
could be scaled to any resolution. We found that the models accurately
reflected the inventories at their original scales (R-2 = 0.63 for both
models) and exhibited a strong relationship with observed CO2 mixing
ratios when downscaled across the region. Moreover, the improved spatial
agreement of the models over the original inventories confirmed that
either product represents a viable basis for downscaling in other
metropolitan regions, even with limited data. (c) 2012 Elsevier Ltd. All
rights reserved.
BibTeX:
@article{brondfield12a,
  author = {Brondfield, Max N. and Hutyra, Lucy R. and Gately, Conor K. and Raciti, Steve M. and Peterson, Scott A.},
  title = {Modeling and validation of on-road CO2 emissions inventories at the urban regional scale},
  journal = {ENVIRONMENTAL POLLUTION},
  year = {2012},
  volume = {170},
  pages = {113--123},
  doi = {https://doi.org/10.1016/j.envpol.2012.06.003}
}
Brooks, B.G.J., Desai, A.R., Stephens, B.B., Bowling, D.R., Burns, S.P., Watt, A.S., Heck, S.L. and Sweeney, C. Assessing filtering of mountaintop CO2 mole fractions for application to inverse models of biosphere-atmosphere carbon exchange {2012} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {12}({4}), pp. 2099-2115 
article DOI  
Abstract: There is a widely recognized need to improve our understanding of
biosphere-atmosphere carbon exchanges in areas of complex terrain
including the United States Mountain West. CO2 fluxes over mountainous
terrain are often difficult to measure due to unusual and complicated
influences associated with atmospheric transport. Consequently, deriving
regional fluxes in mountain regions with carbon cycle inversion of
atmospheric CO2 mole fraction is sensitive to filtering of observations
to those that can be represented at the transport model resolution.
Using five years of CO2 mole fraction observations from the Regional
Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky
RACCOON), five statistical filters are used to investigate a range of
approaches for identifying regionally representative CO2 mole fractions.
Test results from three filters indicate that subsets based on
short-term variance and local CO2 gradients across tower inlet heights
retain nine-tenths of the total observations and are able to define
representative diel variability and seasonal cycles even for
difficult-to-model sites where the influence of local fluxes is much
larger than regional mole fraction variations. Test results from two
other filters that consider measurements from previous and following
days using spline fitting or sliding windows are overly selective. Case
study examples showed that these windowing-filters rejected measurements
representing synoptic changes in CO2, which suggests that they are not
well suited to filtering continental CO2 measurements. We present a
novel CO2 lapse rate filter that uses CO2 differences between levels in
the model atmosphere to select subsets of site measurements that are
representative on model scales. Our new filtering techniques provide
guidance for novel approaches to assimilating mountain-top CO2 mole
fractions in carbon cycle inverse models.
BibTeX:
@article{brooks12a,
  author = {Brooks, B. -G. J. and Desai, A. R. and Stephens, B. B. and Bowling, D. R. and Burns, S. P. and Watt, A. S. and Heck, S. L. and Sweeney, C.},
  title = {Assessing filtering of mountaintop CO2 mole fractions for application to inverse models of biosphere-atmosphere carbon exchange},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2012},
  volume = {12},
  number = {4},
  pages = {2099--2115},
  doi = {https://doi.org/10.5194/acp-12-2099-2012}
}
Brophy, K. Development of atmospheric inversions to evaluate fossil fuel CO2 emissions in California 2018 School: Imperial College London  phdthesis URL 
Abstract: The aim of this thesis is to explore the use of atmospheric inversions to quantify emissions of fossil fuel CO2 (ffCO2) for the US state of California and assess its implications for the monitoring and verification of emissions. California is of particular interest to atmospheric …
BibTeX:
@phdthesis{brophy18a,
  author = {Kieran Brophy},
  title = {Development of atmospheric inversions to evaluate fossil fuel CO2 emissions in California},
  school = {Imperial College London},
  year = {2018},
  url = {https://spiral.imperial.ac.uk/handle/10044/1/64778}
}
Bruhwiler, L., Dlugokencky, E., Masarie, K., Ishizawa, M., Andrews, A., Miller, J., Sweeney, C., Tans, P. and Worthy, D. CarbonTracker-CH4: an assimilation system for estimating emissions of atmospheric methane {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({16}), pp. 8269-8293 
article DOI  
Abstract: We describe an assimilation system for atmospheric methane (CH4),
CarbonTracker-CH4, and demonstrate the diagnostic value of global or
zonally averaged CH4 abundances for evaluating the results. We show that
CarbonTracker-CH4 is able to simulate the observed zonal average mole
fractions and capture inter-annual variability in emissions quite well
at high northern latitudes (53-90 degrees N). In contrast,
CarbonTracker-CH4 is less successful in the tropics where there are few
observations and therefore misses significant variability and is more
influenced by prior flux estimates. CarbonTracker-CH4 estimates of total
fluxes at high northern latitudes are about 81+/- 7 TgCH(4) yr-1, about
12 TgCH(4) yr-1 (13 %) lower than prior estimates, a result that is
consistent with other atmospheric inversions. Emissions from European
wetlands are decreased by 30 %, a result consistent with previous work
by Bergamaschi et al. (2005); however, unlike their results, emissions
from wetlands in boreal Eurasia are increased relative to the prior
estimate. Although CarbonTracker-CH4 does not estimate an increasing
trend in emissions from high northern latitudes for 2000 through 2010,
significant inter-annual variability in high northern latitude fluxes is
recovered. Exceptionally warm growing season temperatures in the Arctic
occurred in 2007, a year that was also anonymously wet. Estimated
emissions from natural sources were greater than the decadal average by
4.4+/- 3.8 TgCH(4) yr(-1) in 2007.
CarbonTracker-CH4 estimates for temperate latitudes are only slightly
increased over prior estimates, but about 10 TgCH(4) yr(-1) is
redistributed from Asia to North America. This difference exceeds the
estimated uncertainty for North America (+/- 3.5 TgCH(4) yr(-1)). We
used time invariant prior flux estimates, so for the period from 2000 to
2006, when the growth rate of global atmospheric CH4 was very small, the
assimilation does not produce increases in natural or anthropogenic
emissions in contrast to bottom-up emission data sets. After 2006, when
atmospheric CH4 began its recent increases, CarbonTracker-CH4 allocates
some of the increases to anthropogenic emissions at temperate latitudes,
and some to tropical wetland emissions. For temperate North America the
prior flux increases by about 4 TgCH(4) yr(-1) during winter when
biogenic emissions are small. Examination of the residuals at some North
American observation sites suggests that increased gas and oil
exploration may play a role since sites near fossil fuel production are
particularly hard for the inversion to fit and the prior flux estimates
at these sites are apparently lower and lower over time than what the
atmospheric measurements imply.
The tropics are not currently well resolved by CarbonTracker-CH4 due to
sparse observational coverage and a short assimilation window. However,
there is a small uncertainty reduction and posterior emissions are about
18% higher than prior estimates. Most of this increase is allocated to
tropical South America rather than being distributed among the global
tropics. Our estimates for this source region are about 32+/- 4 TgCH(4)
yr(-1), in good agreement with the analysis of Melack et al. (2004) who
obtained 29 TgCH(4) yr(-1) for the most productive region, the Amazon
Basin.
BibTeX:
@article{bruhwiler14a,
  author = {Bruhwiler, L. and Dlugokencky, E. and Masarie, K. and Ishizawa, M. and Andrews, A. and Miller, J. and Sweeney, C. and Tans, P. and Worthy, D.},
  title = {CarbonTracker-CH4: an assimilation system for estimating emissions of atmospheric methane},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {16},
  pages = {8269--8293},
  doi = {https://doi.org/10.5194/acp-14-8269-2014}
}
Bruhwiler, L., Parmentier, F.-J.W., Cril, P., Leonard, M. and Palmer, P.I. The Arctic Carbon Cycle and Its Response to Changing Climate 2021 Current Climate Change Reports
Vol. 7(14-34) 
article URL 
Abstract: Long-term observations using both bottom-up (eg, flux) and top-down (atmospheric abundance) approaches are essential for understanding changing carbon cycle budgets. Consideration of atmospheric transport is critical for interpretation of top-down observations …
BibTeX:
@article{bruhwiler21a,
  author = {Lori Bruhwiler and Frans-Jan W. Parmentier and Patrick Cril and Mark Leonard and Paul I. Palmer},
  title = {The Arctic Carbon Cycle and Its Response to Changing Climate},
  journal = {Current Climate Change Reports},
  year = {2021},
  volume = {7},
  number = {14-34},
  url = {https://link.springer.com/article/10.1007/s40641-020-00169-5}
}
Buchwitz, M., Schneising, O., Burrows, J.P., Bovensmann, H., Reuter, M. and Notholt, J. First direct observation of the atmospheric CO2 year-to-year increase from space {2007} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {7}({16}), pp. 4249-4256 
article  
BibTeX:
@article{buchwitz07a,
  author = {Buchwitz, M. and Schneising, O. and Burrows, J. P. and Bovensmann, H. and Reuter, M. and Notholt, J.},
  title = {First direct observation of the atmospheric CO2 year-to-year increase from space},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2007},
  volume = {7},
  number = {16},
  pages = {4249--4256}
}
Buchwitz, M., Reuter, M., Schneising, O., Heymann, J., Bovensmann, H. and Burrows, J. Towards an improved CO2 retrieval algorithm for SCIAMACHY on ENVISAT 2009 Proceedings Atmospheric Science Conference, Barcelona, Spain, pp. 7-11  inproceedings  
BibTeX:
@inproceedings{buchwitz09a,
  author = {Buchwitz, M and Reuter, M and Schneising, O and Heymann, J and Bovensmann, H and Burrows, JP},
  title = {Towards an improved CO2 retrieval algorithm for SCIAMACHY on ENVISAT},
  booktitle = {Proceedings Atmospheric Science Conference, Barcelona, Spain},
  year = {2009},
  pages = {7--11}
}
Buchwitz, M., Bovensmann, H., Burrows, J., Schneising, O. and Reuter, M. Global mapping of methane and carbon dioxide: from SCIAMACHY to CarbonSat 2010 Proceedings ESA-iLEAPS-EGU conference on earth observation for land-atmosphere interaction science, ESA Special Publications SP-688, ESRIN, Italy, pp. 3-5  inproceedings URL 
BibTeX:
@inproceedings{buchwitz10a,
  author = {Buchwitz, M and Bovensmann, H and Burrows, JP and Schneising, O and Reuter, M},
  title = {Global mapping of methane and carbon dioxide: from SCIAMACHY to CarbonSat},
  booktitle = {Proceedings ESA-iLEAPS-EGU conference on earth observation for land-atmosphere interaction science, ESA Special Publications SP-688, ESRIN, Italy},
  year = {2010},
  pages = {3--5},
  url = {http://tratin.cinvestav.mx/Portals/0/PapersADM/B/Buchwitz%20et%20al%202011%20global%20mapping%20sciamachy%20carbonsat.pdf}
}
Buchwitz, M., Reuter, M., Schneising, O., Boesch, H., Aben, I., Alexe, M., Armante, R., Bergamaschi, P., Bovensmann, H., Brunner, D., Buchmann, B., Burrows, J.P., Butz, A., Chevallier, F., Chedin, A., Crevoisier, C.D., Gonzi, S., De Maziere, M., De Wachter, E., Detmers, R., Dils, B., Frankenberg, C., Hahne, P., Hasekamp, O.P., Hewson, W., Heymann, J., Houweling, S., Hilker, M., Kaminski, T., Kuhlmann, G., Laeng, A., v Leeuwen, T.T., Lichtenberg, G., Marshall, J., Noel, S., Notholt, J., Palmer, P., Parker, R., Scholze, M., Stiller, G.P., Warneke, T. and Zehner, C. THE GREENHOUSE GAS PROJECT OF ESA'S CLIMATE CHANGE INITIATIVE (GHG-CCI): OVERVIEW, ACHIEVEMENTS AND FUTURE PLANS {2015}
Vol. {47}({W3})36TH INTERNATIONAL SYMPOSIUM ON REMOTE SENSING OF ENVIRONMENT, pp. 165-172 
inproceedings DOI  
Abstract: The GHG-CCI project (http://www.esa-ghg-cci.org/) is one of several
projects of the European Space Agency's (ESA) Climate Change Initiative
(CCI). The goal of the CCI is to generate and deliver data sets of
various satellite-derived Essential Climate Variables (ECVs) in line
with GCOS (Global Climate Observing System) requirements. The ``ECV
Greenhouse Gases'' (ECV GHG) is the global distribution of important
climate relevant gases - namely atmospheric CO2 and CH4 - with a quality
sufficient to obtain information on regional CO2 and CH4 sources and
sinks. The main goal of GHG-CCI is to generate long-term highly accurate
and precise time series of global near-surface-sensitive satellite
observations of CO2 and CH4, i.e., XCO2 and XCH4, starting with the
launch of ESA's ENVISAT satellite. These products are currently
retrieved from SCIAMACHY/ENVISAT (2002-2012) and TANSO-FTS/GOSAT
(2009-today) nadir mode observations in the
near-infrared/shortwave-infrared spectral region. In addition, other
sensors (e.g., IASI and MIPAS) and viewing modes (e.g., SCIAMACHY solar
occultation) are also considered and in the future also data from other
satellites. The GHG-CCI data products and related documentation are
freely available via the GHG-CCI website and yearly updates are
foreseen. Here we present an overview about the latest data set (Climate
Research Data Package No. 2 (CRDP#2)) and summarize key findings from
using satellite CO2 and CH4 retrievals to improve our understanding of
the natural and anthropogenic sources and sinks of these important
atmospheric greenhouse gases. We also shortly mention ongoing activities
related to validation and initial user assessment of CRDP#2 and future
plans.
BibTeX:
@inproceedings{buchwitz15a,
  author = {Buchwitz, M. and Reuter, M. and Schneising, O. and Boesch, H. and Aben, I. and Alexe, M. and Armante, R. and Bergamaschi, P. and Bovensmann, H. and Brunner, D. and Buchmann, B. and Burrows, J. P. and Butz, A. and Chevallier, F. and Chedin, A. and Crevoisier, C. D. and Gonzi, S. and De Maziere, M. and De Wachter, E. and Detmers, R. and Dils, B. and Frankenberg, C. and Hahne, P. and Hasekamp, O. P. and Hewson, W. and Heymann, J. and Houweling, S. and Hilker, M. and Kaminski, T. and Kuhlmann, G. and Laeng, A. and v Leeuwen, T. T. and Lichtenberg, G. and Marshall, J. and Noel, S. and Notholt, J. and Palmer, P. and Parker, R. and Scholze, M. and Stiller, G. P. and Warneke, T. and Zehner, C.},
  title = {THE GREENHOUSE GAS PROJECT OF ESA'S CLIMATE CHANGE INITIATIVE (GHG-CCI): OVERVIEW, ACHIEVEMENTS AND FUTURE PLANS},
  booktitle = {36TH INTERNATIONAL SYMPOSIUM ON REMOTE SENSING OF ENVIRONMENT},
  year = {2015},
  volume = {47},
  number = {W3},
  pages = {165--172},
  note = {36th International Symposium on Remote Sensing of the Environment (ISRSE), Berlin, GERMANY, MAY 11-15, 2015},
  doi = {https://doi.org/10.5194/isprsarchives-XL-7-W3-165-2015}
}
Buchwitz, M., Reuter, M., Schneising, O., Hewson, W., Detmers, R.G., Boesch, H., Hasekamp, O.P., Aben, I., Bovensmann, H., Burrows, J.P., Butz, A., Chevallier, F., Dils, B., Frankenberg, C., Heymann, J., Lichtenberg, G., De Maziere, M., Notholt, J., Parker, R., Warneke, T., Zehner, C., Griffith, D.W.T., Deutscher, N.M., Kuze, A., Suto, H. and Wunch, D. Global satellite observations of column-averaged carbon dioxide and methane: The GHG-CCI XCO2 and XCH4 CRDP3 data set {2017} REMOTE SENSING OF ENVIRONMENT
Vol. {203}, pp. 276-295 
article DOI  
Abstract: Carbon dioxide (CO2) and methane (CH4) are the two most important
greenhouse gases emitted by mankind. Better knowledge of the surface
sources and sinks of these Essential Climate Variables (ECVs) and
related carbon uptake and release processes is needed for important
climate change related applications such as improved climate modelling
and prediction. Some satellites provide near-surface-sensitive
atmospheric CO2 and CH4 observations that can be used to obtain
information on CQ(2) and CH4 surface fluxes. The goal of the GHG-CCI
project of the European Space Agency's (ESA) Climate Change Initiative
(CCI) is to use satellite data to generate atmospheric CO2 and CH4 data
products meeting demanding GCOS (Global Climate Observing System)
greenhouse gas (GHG) ECV requirements. To achieve this, retrieval
algorithms are regularly being improved followed by annual data
reprocessing and analysis cycles to generate better products in terms of
extended time series and continuously improved data quality. Here we
present an overview about the latest GHG-CCI data set called Climate
Research Data Package No.3 (CRDP3) focusing on the GHG-CCI core data
products, which are column-averaged dry air mole fractions of CO2 and
CH4, i.e., XCO2 and XCH4, as retrieved from SCIAMACHY/ENVISAT and
TANSO/GOSAT satellite radiances covering the time period end of 2002 to
end of 2014. We present global maps and time series including initial
validation results obtained by comparisons with Total Carbon Column
Observing Network (TCCON) ground-based observations. We show that the
GCOS requirements for systematic error (<1 ppm for XCO2, <10 ppb for
XCH4) and long-term stability (<0.2 ppm/year for XCO2, <2 ppb/year for
XCH4) are met for nearly all products (an exception is SCIAMACHY methane
especially since 2010). For XCO2 we present comparisons with global
models using the output of two CO2 assimilation systems (MACC version
14r2 and CarbonTracker version CT2013B). We show that overall there is
reasonable consistency and agreement between all data sets (within-1-2
ppm) but we also found significant differences depending on region and
time period. (C) 2017 Elsevier Inc. All rights reserved.
BibTeX:
@article{buchwitz17a,
  author = {Buchwitz, M. and Reuter, M. and Schneising, O. and Hewson, W. and Detmers, R. G. and Boesch, H. and Hasekamp, O. P. and Aben, I. and Bovensmann, H. and Burrows, J. P. and Butz, A. and Chevallier, F. and Dils, B. and Frankenberg, C. and Heymann, J. and Lichtenberg, G. and De Maziere, M. and Notholt, J. and Parker, R. and Warneke, T. and Zehner, C. and Griffith, D. W. T. and Deutscher, N. M. and Kuze, A. and Suto, H. and Wunch, D.},
  title = {Global satellite observations of column-averaged carbon dioxide and methane: The GHG-CCI XCO2 and XCH4 CRDP3 data set},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2017},
  volume = {203},
  pages = {276--295},
  doi = {https://doi.org/10.1016/j.rse.2016.12.027}
}
Buchwitz, M., Reuter, M., Schneising, O., Noel, S., Gier, B., Bovensmann, H., Burrows, J.P., Boesch, H., Anand, J., Parker, R.J., Somkuti, P., Detmers, R.G., Hasekamp, O.P., Aben, I., Butz, A., Kuze, A., Suto, H., Yoshida, Y., Crisp, D. and O'Dell, C. Computation and analysis of atmospheric carbon dioxide annual mean growth rates from satellite observations during 2003-2016 {2018} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {18}({23}), pp. 17355-17370 
article DOI  
Abstract: The growth rate of atmospheric carbon dioxide (CO2) reflects the net
effect of emissions and uptake resulting from anthropogenic and natural
carbon sources and sinks. Annual mean CO2 growth rates have been
determined from satellite retrievals of column-averaged dry-air mole
fractions of CO2, i.e. XCO2, for the years 2003 to 2016. The XCO2 growth
rates agree with National Oceanic and Atmospheric Administration (NOAA)
growth rates from CO2 surface observations within the uncertainty of the
satellite-derived growth rates (mean difference +/- standard deviation:
0.0 +/- 0.3 ppm year(-1); R: 0.82). This new and independent data set
confirms record-large growth rates of around 3 ppm year(-1) in 2015 and
2016, which are attributed to the 2015-2016 El Nino. Based on a
comparison of the satellite-derived growth rates with human CO2
emissions from fossil fuel combustion and with El Nino Southern
Oscillation (ENSO) indices, we estimate by how much the impact of ENSO
dominates the impact of fossil-fuel-burning-related emissions in
explaining the variance of the atmospheric CO2 growth rate. Our analysis
shows that the ENSO impact on CO2 growth rate variations dominates that
of human emissions throughout the period 2003-2016 but in particular
during the period 2010-2016 due to strong La Nina and El Nino events.
Using the derived growth rates and their uncertainties, we estimate the
probability that the impact of ENSO on the variability is larger than
the impact of human emissions to be 63 % for the time period 2003-2016.
If the time period is restricted to 2010-2016, this probability
increases to 94%.
BibTeX:
@article{buchwitz18a,
  author = {Buchwitz, Michael and Reuter, Maximilian and Schneising, Oliver and Noel, Stefan and Gier, Bettina and Bovensmann, Heinrich and Burrows, John P. and Boesch, Hartmut and Anand, Jasdeep and Parker, Robert J. and Somkuti, Peter and Detmers, Rob G. and Hasekamp, Otto P. and Aben, Ilse and Butz, Andre and Kuze, Akihiko and Suto, Hiroshi and Yoshida, Yukio and Crisp, David and O'Dell, Christopher},
  title = {Computation and analysis of atmospheric carbon dioxide annual mean growth rates from satellite observations during 2003-2016},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2018},
  volume = {18},
  number = {23},
  pages = {17355--17370},
  doi = {https://doi.org/10.5194/acp-18-17355-2018}
}
Buchwitz, M., Reuter, M., Noël, S., Bramstedt, K., Schneising, O., Hilker, M., Andrade, B.F., Bovensmann, H., Burrows, J.P., Noia, A.D., Boesch, H., Wu, L., Landgraf, J., Aben, I., Retscher, C., O'Dell, C.W. and Crisp, D. Can a regional-scale reduction of atmospheric CO2 during the COVID-19 pandemic be detected from space? A case study for East China using satellite XCO2 retrievals 2021 Atmospheric Measurement Techniques  article URL 
Abstract: The COVID-19 pandemic resulted in reduced anthropogenic carbon dioxide (CO 2) emissions during 2020 in large parts of the world. To investigate whether a regional-scale reduction of anthropogenic CO 2 emissions during the COVID-19 pandemic can be detected …
BibTeX:
@article{buchwitz21a,
  author = {Michael Buchwitz and Maximilian Reuter and Stefan Noël and Klaus Bramstedt and Oliver Schneising and Michael Hilker and Blanca Fuentes Andrade and Heinrich Bovensmann and John P. Burrows and Antonio Di Noia and Hartmut Boesch and Lianghai Wu and Jochen Landgraf and Ilse Aben and Christian Retscher and Christopher W. O'Dell and David Crisp},
  title = {Can a regional-scale reduction of atmospheric CO2 during the COVID-19 pandemic be detected from space? A case study for East China using satellite XCO2 retrievals},
  journal = {Atmospheric Measurement Techniques},
  year = {2021},
  url = {https://amt.copernicus.org/articles/14/2141/2021/}
}
Burgin, M.S. Physics-based modeling for high-fidelity radar retrievals 2014 School: University of Michigan  phdthesis  
BibTeX:
@phdthesis{burgin14a,
  author = {Burgin, Mariko Sofie},
  title = {Physics-based modeling for high-fidelity radar retrievals},
  school = {University of Michigan},
  year = {2014}
}
Burman, P.K.D. Estimation of Net Primary Productivity: An Introduction to Different Approaches 2020 Spatial Modeling in Forest Resources Management  article URL 
Abstract: The net primary productivity (NPP) is defined as the net carbon gain by plants in natural and agricultural ecosystems, which is computed by subtracting the autotrophic respiration from the gross photosynthetic carbon uptake by the ecosystems. It acts as the indicators of carbon …
BibTeX:
@article{burman20a,
  author = {Pramit Kumar Deb Burman},
  title = {Estimation of Net Primary Productivity: An Introduction to Different Approaches},
  journal = {Spatial Modeling in Forest Resources Management},
  publisher = {Springer},
  year = {2020},
  url = {https://link.springer.com/chapter/10.1007/978-3-030-56542-8_2}
}
Buschmann, M., Deutscher, N.M., Sherlock, V., Palm, M., Warneke, T. and Notholt, J. Retrieval of xCO(2) from ground-based mid-infrared (NDACC) solar absorption spectra and comparison to TCCON {2016} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {9}({2}), pp. 577-585 
article DOI  
Abstract: High-resolution solar absorption spectra, taken within the Network for
the Detection of Atmospheric Composition Change Infrared Working Group
(NDACC-IRWG) in the mid-infrared spectral region, are used to infer
partial or total column abundances of many gases. In this paper we
present the retrieval of a column-averaged mole fraction of carbon
dioxide from NDACC-IRWG spectra taken with a Fourier transform infrared
(FTIR) spectrometer at the site in Ny-Alesund, Spitsbergen. The
retrieved time series is compared to colocated standard TCCON (Total
Carbon Column Observing Network) measurements of column-averaged dry-air
mole fractions of CO2 (denoted by xCO(2)). Comparing the NDACC and TCCON
retrievals, we find that the sensitivity of the NDACC retrieval is lower
in the troposphere (by a factor of 2) and higher in the stratosphere,
compared to TCCON. Thus, the NDACC retrieval is less sensitive to
tropospheric changes (e.g., the seasonal cycle) in the column average.
BibTeX:
@article{buschmann16a,
  author = {Buschmann, Matthias and Deutscher, Nicholas M. and Sherlock, Vanessa and Palm, Mathias and Warneke, Thorsten and Notholt, Justus},
  title = {Retrieval of xCO(2) from ground-based mid-infrared (NDACC) solar absorption spectra and comparison to TCCON},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2016},
  volume = {9},
  number = {2},
  pages = {577--585},
  doi = {https://doi.org/10.5194/amt-9-577-2016}
}
Butler, M.P., Davis, K.J., Denning, A.S. and Kawa, S.R. Using continental observations in global atmospheric inversions of CO2: North American carbon sources and sinks {2010} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {62}({5, SI}), pp. 550-572 
article DOI  
Abstract: We evaluate North American carbon fluxes using a monthly global Bayesian
synthesis inversion that includes well-calibrated carbon dioxide
concentrations measured at continental flux towers. We employ the NASA
Parametrized Chemistry Tracer Model (PCTM) for atmospheric transport and
a TransCom-style inversion with subcontinental resolution. We subsample
carbon dioxide time series at four North American flux tower sites for
mid-day hours to ensure sampling of a deep, well-mixed atmospheric
boundary layer. The addition of these flux tower sites to a global
network reduces North America mean annual flux uncertainty for 2001-2003
by 20% to 0.4 Pg C yr-1 compared to a network without the tower sites.
North American flux is estimated to be a net sink of 1.2 +/- 0.4 Pg C
yr-1 which is within the uncertainty bounds of the result without the
towers. Uncertainty reduction is found to be local to the regions within
North America where the flux towers are located, and including the
towers reduces covariances between regions within North America. Mid-day
carbon dioxide observations from flux towers provide a viable means of
increasing continental observation density and reducing the uncertainty
of regional carbon flux estimates in atmospheric inversions.
BibTeX:
@article{butler10a,
  author = {Butler, M. P. and Davis, K. J. and Denning, A. S. and Kawa, S. R.},
  title = {Using continental observations in global atmospheric inversions of CO2: North American carbon sources and sinks},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2010},
  volume = {62},
  number = {5, SI},
  pages = {550--572},
  doi = {https://doi.org/10.1111/j.1600-0889.2010.00501.x}
}
Butler, M.P., Lauvaux, T., Feng, S., Liu, J., Bowman, K.W. and Davis, K.J. Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework {2020} ATMOSPHERE
Vol. {11}({8}) 
article DOI  
Abstract: Quantifying the uncertainty of inversion-derived CO2 surface fluxes and attributing the uncertainty to errors in either flux or atmospheric transport simulations continue to be challenges in the characterization of surface sources and sinks of carbon dioxide (CO2). Despite recent studies inferring fluxes while using higher-resolution modeling systems, the utility of regional-scale models remains unclear when compared to existing coarse-resolution global systems. Here, we present an off-line coupling of the mesoscale Weather Research and Forecasting (WRF) model to optimized biogenic CO2 fluxes and mole fractions from the global Carbon Monitoring System inversion system (CMS-Flux). The coupling framework consists of methods to constrain the mass of CO2 introduced into WRF, effectively nesting our regional domain covering most of North America (except the northern half of Canada) within the CMS global model. We test the coupling by simulating Greenhouse gases Observing SATellite (GOSAT) column-averaged dry-air mole fractions (XCO2) over North America for 2010. We find mean model-model differences in summer of similar to 0.12 ppm, significantly lower than the original coupling scheme (from 0.5 to 1.5 ppm, depending on the boundary). While 85% of the XCO2 values are due to long-range transport from outside our North American domain, most of the model-model differences appear to be due to transport differences in the fraction of the troposphere below 850 hPa. Satellite data from GOSAT and tower and aircraft data are used to show that vertical transport above the Planetary Boundary Layer is responsible for significant model-model differences in the horizontal distribution of column XCO2 across North America.
BibTeX:
@article{butler20a,
  author = {Butler, Martha P. and Lauvaux, Thomas and Feng, Sha and Liu, Junjie and Bowman, Kevin W. and Davis, Kenneth J.},
  title = {Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework},
  journal = {ATMOSPHERE},
  publisher = {MDPI},
  year = {2020},
  volume = {11},
  number = {8},
  doi = {https://doi.org/10.3390/atmos11080787}
}
Butz, A., Hasekamp, O.P., Frankenberg, C., Vidot, J. and Aben, I. CH4 retrievals from space-based solar backscatter measurements: Performance evaluation against simulated aerosol and cirrus loaded scenes {2010} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {115} 
article DOI  
Abstract: Monitoring of atmospheric methane (CH4) concentrations from space-based
instruments such as the Scanning Imaging Absorption Spectrometer for
Atmospheric Chartography (SCIAMACHY) and the Greenhouse Gases Observing
Satellite (GOSAT) relies on observations of sunlight backscattered to
space by the Earth's surface and atmosphere. Retrieval biases occur due
to unaccounted scattering effects by aerosols and thin cirrus that
modify the lightpath. Here, we evaluate the accuracy of two retrieval
methods that aim at minimizing such scattering induced errors. The
lightpath ``proxy'' method, applicable to SCIAMACHY and GOSAT,
retrieves CH4 and carbon dioxide (CO2) simultaneously and uses CO2 as a
proxy for lightpath modification. The ``physics-based'' method, which
we propose for GOSAT, aims at simultaneously retrieving CH4
concentrations and scattering properties of the atmosphere. We evaluate
performance of the methods against a trial ensemble of simulated aerosol
and cirrus loaded scenes. More than 80% of the trials yield residual
scattering induced CH4 errors below 0.6% and 0.8% for the proxy and
the physics-based approach, respectively. Very few cases result in
errors greater than 2% for both methods. Advantages of the proxy
approach are efficient and robust performance yielding more useful
retrievals than the physics-based method which reveals some
nonconvergent cases. The major disadvantage of the proxy method is the
uncertainty of the proxy CO2 concentration contributing to the overall
error budget. Residual errors generally correlate with particle and
surface properties and thus might impact inverse modeling of CH4 sources
and sinks.
BibTeX:
@article{butz10a,
  author = {Butz, A. and Hasekamp, O. P. and Frankenberg, C. and Vidot, J. and Aben, I.},
  title = {CH4 retrievals from space-based solar backscatter measurements: Performance evaluation against simulated aerosol and cirrus loaded scenes},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2010},
  volume = {115},
  doi = {https://doi.org/10.1029/2010JD014514}
}
Butz, A., Guerlet, S., Hasekamp, O., Schepers, D., Galli, A., Aben, I., Frankenberg, C., Hartmann, J.M., Tran, H., Kuze, A., Keppel-Aleks, G., Toon, G., Wunch, D., Wennberg, P., Deutscher, N., Griffith, D., Macatangay, R., Messerschmidt, J., Notholt, J. and Warneke, T. Toward accurate CO2 and CH4 observations from GOSAT {2011} GEOPHYSICAL RESEARCH LETTERS
Vol. {38} 
article DOI  
Abstract: The column-average dry air mole fractions of atmospheric carbon dioxide
and methane (X-CO2 and X-CH4) are inferred from observations of
backscattered sunlight conducted by the Greenhouse gases Observing
SATellite (GOSAT). Comparing the first year of GOSAT retrievals over
land with colocated ground-based observations of the Total Carbon Column
Observing Network (TCCON), we find an average difference (bias) of
-0.05% and -0.30% for X-CO2 and X-CH4 with a station-to-station
variability (standard deviation of the bias) of 0.37% and 0.26% among
the 6 considered TCCON sites. The root-mean square deviation of the
bias-corrected satellite retrievals from colocated TCCON observations
amounts to 2.8 ppm for X-CO2 and 0.015 ppm for X-CH4. Without any data
averaging, the GOSAT records reproduce general source/sink patterns such
as the seasonal cycle of X-CO2 suggesting the use of the satellite
retrievals for constraining surface fluxes. Citation: Butz, A., et al.
(2011), Toward accurate CO2 and CH4 observations from GOSAT, Geophys.
Res. Lett., 38, L14812, doi:10.1029/2011GL047888.
BibTeX:
@article{butz11a,
  author = {Butz, A. and Guerlet, S. and Hasekamp, O. and Schepers, D. and Galli, A. and Aben, I. and Frankenberg, C. and Hartmann, J. -M. and Tran, H. and Kuze, A. and Keppel-Aleks, G. and Toon, G. and Wunch, D. and Wennberg, P. and Deutscher, N. and Griffith, D. and Macatangay, R. and Messerschmidt, J. and Notholt, J. and Warneke, T.},
  title = {Toward accurate CO2 and CH4 observations from GOSAT},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2011},
  volume = {38},
  doi = {https://doi.org/10.1029/2011GL047888}
}
Butz, A., Guerlet, S., Hasekamp, O.P., Kuze, A. and Suto, H. Using ocean-glint scattered sunlight as a diagnostic tool for satellite remote sensing of greenhouse gases {2013} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {6}({9}), pp. 2509-2520 
article DOI  
Abstract: Spectroscopic measurements of sunlight backscattered by the Earth's
surface is a technique widely used for remote sensing of atmospheric
constituent concentrations from space. Thereby, remote sensing of
greenhouse gases poses particularly challenging accuracy requirements
for instrumentation and retrieval algorithms which, in general, suffer
from various error sources. Here, we investigate a method that helps
disentangle sources of error for observations of sunlight backscattered
from the glint spot on the ocean surface. The method exploits the
backscattering characteristics of the ocean surface, which is bright for
glint geometry but dark for off-glint angles. This property allows for
identifying a set of clean scenes where light scattering due to
particles in the atmosphere is negligible such that uncertain knowledge
of the lightpath can be excluded as a source of error. We apply the
method to more than 3 yr of ocean-glint measurements by the Thermal And
Near infrared Sensor for carbon Observation (TANSO) Fourier Transform
Spectrometer (FTS) onboard the Greenhouse Gases Observing Satellite
(GOSAT), which aims at measuring carbon dioxide (CO2) and methane (CH4)
concentrations. The proposed method is able to clearly monitor recent
improvements in the instrument calibration of the oxygen (O-2) A-band
channel and suggests some residual uncertainty in our knowledge about
the instrument. We further assess the consistency of CO2 retrievals from
several absorption bands between 6400 cm(-1) (1565 nm) and 4800 cm(-1)
(2100 nm) and find that the absorption bands commonly used for
monitoring of CO2 dry air mole fractions from GOSAT allow for
consistency better than 1.5 ppm. Usage of other bands reveals
significant inconsistency among retrieved CO2 concentrations pointing at
inconsistency of spectroscopic parameters.
BibTeX:
@article{butz13a,
  author = {Butz, A. and Guerlet, S. and Hasekamp, O. P. and Kuze, A. and Suto, H.},
  title = {Using ocean-glint scattered sunlight as a diagnostic tool for satellite remote sensing of greenhouse gases},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2013},
  volume = {6},
  number = {9},
  pages = {2509--2520},
  doi = {https://doi.org/10.5194/amt-6-2509-2013}
}
Butz, A., Orphal, J., Checa-Garcia, R., Friedl-Vallon, F., von Clarmann, T., Bovensmann, H., Hasekamp, O., Landgraf, J., Knigge, T., Weise, D., Sqalli-Houssini, O. and Kemper, D. Geostationary Emission Explorer for Europe (G3E): mission concept and initial performance assessment {2015} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {8}({11}), pp. 4719-4734 
article DOI  
Abstract: The Geostationary Emission Explorer for Europe (G3E) is a concept for a
geostationary satellite sounder that aims to constrain the sources and
sinks of greenhouse gases carbon dioxide (CO2) and methane (CH4) for
continental-scale regions. Its primary focus is on central Europe. G3E
carries a spectrometer system that collects sunlight backscattered from
the Earth's surface and atmosphere in the near-infrared (NIR) and
shortwave-infrared (SWIR) spectral range. Solar absorption spectra allow
for spatiotemporally dense observations of the column-average
concentrations of carbon dioxide (XCO2), methane (XCH4), and carbon
monoxide (XCO). The mission concept in particular facilitates sampling
of the diurnal variation with several measurements per day during
summer.
Here, we present the mission concept and carry out an initial
performance assessment of the retrieval capabilities. The radiometric
performance of the 4 grating spectrometers is tuned to reconcile small
ground-pixel sizes (similar to 2 km x 3 km at 50 degrees latitude) with
short single-shot exposures (similar to 2.9 s) that allow for sampling
continental regions such as central Europe within 2 h while providing a
sufficient signal-to-noise ratio. The noise errors to be expected for
XCO2, XCH4, and XCO are assessed through retrieval simulations for a
European trial ensemble. Generally, single-shot precision for the
targeted XCO2 and XCH4 is better than 0.5% with some exception for
scenes with low infrared surface albedo observed under low sun
conditions in winter. For XCO, precision is generally better than 10 %.
Performance for aerosol and cirrus loaded atmospheres is assessed by
mimicking G3E's slant view on Europe for an ensemble of atmospheric
scattering properties used previously for evaluating nadir-viewing
low-Earth-orbit (LEO) satellites. While retrieval concepts developed for
LEO configurations generally succeed in mitigating aerosol- and
cirrus-induced retrieval errors for G3E's setup, residual errors are
somewhat greater in geostationary orbit (GEO) than in LEO. G3E's
deployment in the vicinity of the Meteosat Third Generation (MTG)
satellites has the potential to make synergistic use of MTG's sounding
capabilities e.g. with respect to characterization of aerosol and cloud
properties or with respect to enhancing carbon monoxide retrievals by
combining G3E's solar and MTG's thermal infrared spectra.
BibTeX:
@article{butz15a,
  author = {Butz, A. and Orphal, J. and Checa-Garcia, R. and Friedl-Vallon, F. and von Clarmann, T. and Bovensmann, H. and Hasekamp, O. and Landgraf, J. and Knigge, T. and Weise, D. and Sqalli-Houssini, O. and Kemper, D.},
  title = {Geostationary Emission Explorer for Europe (G3E): mission concept and initial performance assessment},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2015},
  volume = {8},
  number = {11},
  pages = {4719--4734},
  doi = {https://doi.org/10.5194/amt-8-4719-2015}
}
Byrne, B., Jones, D.B.A., Strong, K., Zeng, Z.C., Deng, F. and Liu, J. Sensitivity of CO2 surface flux constraints to observational coverage {2017} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {122}({12}), pp. 6672-6694 
article DOI  
Abstract: Inverse modeling of regional CO2 fluxes using atmospheric CO2 data is
sensitive to the observational coverage of the observing network. Here
we use the GEOS-Chem adjoint model to examine the sensitivity to CO2
fluxes of observations from the in situ surface network, the Total
Carbon Column Observing Network (TCCON), the Greenhouse Gases Observing
Satellite (GOSAT), and the Orbiting Carbon Observatory (OCO-2). We find
that OCO-2 has high sensitivity to fluxes throughout the tropics and
Southern Hemisphere, while surface observations have high sensitivity to
fluxes in the northern extratropics throughout the year. For GOSAT
viewing modes, ocean glint data provide the strongest constraints on
fluxes in the tropics and Southern Hemisphere during Northern Hemisphere
fall and winter relative to other viewing modes. In contrast, GOSAT
nadir land data offer the greater sensitivity to fluxes in these regions
during Northern Hemisphere spring and summer. For OCO-2 viewing modes,
ocean glint data provided the dominant sensitivity to the surface fluxes
in the northern subtropics, tropics, and Southern Hemisphere. We
performed a series of inversion analyses using pseudodata and found that
the varying sensitivities can result in large differences in regional
flux estimates. However, combining measurements from different observing
systems to exploit their complementarity may lead to a posteriori flux
estimates with improved accuracy.
BibTeX:
@article{byrne17a,
  author = {Byrne, B. and Jones, D. B. A. and Strong, K. and Zeng, Z. -C. and Deng, F. and Liu, J.},
  title = {Sensitivity of CO2 surface flux constraints to observational coverage},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2017},
  volume = {122},
  number = {12},
  pages = {6672--6694},
  doi = {https://doi.org/10.1002/2016JD026164}
}
Byrne, B., Wunch, D., Jones, D.B.A., Strong, K., Deng, F., Baker, I., Kohler, P., Frankenberg, C., Joiner, J., Arora, V.K., Badawy, B., Harper, A.B., Warneke, T., Petri, C., Kivi, R. and Roehl, C.M. Evaluating GPP and Respiration Estimates Over Northern Midlatitude Ecosystems Using Solar-Induced Fluorescence and Atmospheric CO2 Measurements {2018} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {123}({9}), pp. {2976-2997} 
article DOI  
Abstract: On regional to global scales, few constraints exist on gross primary
productivity (GPP) and ecosystem respiration (R-e) fluxes. Yet
constraints on these fluxes are critical for evaluating and improving
terrestrial biosphere models. In this study, we evaluate the seasonal
cycle of GPP, R-e, and net ecosystem exchange (NEE) produced by four
terrestrial biosphere models and FLUXCOM, a data-driven model, over
northern midlatitude ecosystems. We evaluate the seasonal cycle of GPP
and NEE using solar-induced fluorescence retrieved from the Global Ozone
Monitoring Experiment-2 and column-averaged dry-air mole fractions of
CO2 (X-CO2) from the Total Carbon Column Observing Network,
respectively. We then infer R-e by combining constraints on GPP with
constraints on NEE from two flux inversions. An ensemble of optimized
R-e seasonal cycles is generated using five GPP estimates and two NEE
estimates. The optimized R-e curves generally show high consistency with
each other, with the largest differences due to the magnitude of GPP. We
find optimized R-e exhibits a systematically broader summer maximum than
modeled R-e, with values lower during June-July and higher during the
fall than R-e. Further analysis suggests that the differences could be
due to seasonal variations in the carbon use efficiency (possibly due to
an ecosystem-scale Kok effect) and to seasonal variations in the leaf
litter and fine root carbon pool. The results suggest that the inclusion
of variable carbon use efficiency for autotrophic respiration and carbon
pool dependence for heterotrophic respiration is important for
accurately simulating R-e.
BibTeX:
@article{byrne18a,
  author = {Byrne, B. and Wunch, D. and Jones, D. B. A. and Strong, K. and Deng, F. and Baker, I. and Kohler, P. and Frankenberg, C. and Joiner, J. and Arora, V. K. and Badawy, B. and Harper, A. B. and Warneke, T. and Petri, C. and Kivi, R. and Roehl, C. M.},
  title = {Evaluating GPP and Respiration Estimates Over Northern Midlatitude Ecosystems Using Solar-Induced Fluorescence and Atmospheric CO2 Measurements},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2018},
  volume = {123},
  number = {9},
  pages = {2976-2997},
  doi = {https://doi.org/10.1029/2018JG004472}
}
Byrne, B. Monitoring the carbon cycle: Evaluation of terrestrial biosphere models and anthropogenic greenhouse gas emissions with atmospheric observations 2018 School: University of Toronto  phdthesis URL 
Abstract: Reliable projections of climate change will require terrestrial biosphere models (TBMs) that produce robust projections of changes in the exchange of CO2 between the atmosphere and terrestrial biosphere. In this thesis, atmospheric CO2 observations are used to evaluate …
BibTeX:
@phdthesis{byrne18b,
  author = {Brendan Byrne},
  title = {Monitoring the carbon cycle: Evaluation of terrestrial biosphere models and anthropogenic greenhouse gas emissions with atmospheric observations},
  school = {University of Toronto},
  year = {2018},
  url = {https://tspace.library.utoronto.ca/handle/1807/91885}
}
Byrne, B., Jones, D.B.A., Strong, K., Polavarapu, S.M., Harper, A.B., Baker, D.F. and Maksyutov, S. On what scales can GOSAT flux inversions constrain anomalies in terrestrial ecosystems? {2019} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {19}({20}), pp. {13017-13035} 
article DOI URL 
Abstract: Interannual variations in temperature and precipitation impact the carbon balance of terrestrial ecosystems, leaving an imprint in atmospheric CO2. Quantifying the impact of climate anomalies on the net ecosystem exchange (NEE) of terrestrial ecosystems can provide a constraint to evaluate terrestrial biosphere models against and may provide an emergent constraint on the response of terrestrial ecosystems to climate change. We investigate the spatial scales over which interannual variability in NEE can be constrained using atmospheric CO2 observations from the Greenhouse Gases Observing Satellite (GOSAT). NEE anomalies are calculated by performing a series of inversion analyses using the GEOS-Chem adjoint model to assimilate GOSAT observations. Monthly NEE anomalies are compared to ``proxies'', variables that are associated with anomalies in the terrestrial carbon cycle, and to upscaled NEE estimates from FLUXCOM. Statistically significant correlations (P < 0.05) are obtained between posterior NEE anomalies and anomalies in soil temperature and FLUXCOM NEE on continental and larger scales in the tropics, as well as in the northern extratropics on subcontinental scales during the summer (R-2 >= 0.49), suggesting that GOSAT measurements provide a constraint on NEE interannual variability (IAV) on these spatial scales. Furthermore, we show that GOSAT flux inversions are generally better correlated with the environmental proxies and FLUXCOM NEE than NEE anomalies produced by a set of terrestrial biosphere models (TBMs), suggesting that GOSAT flux inversions could be used to evaluate TBM NEE fluxes.
BibTeX:
@article{byrne19a,
  author = {Byrne, Brendan and Jones, Dylan B. A. and Strong, Kimberly and Polavarapu, Saroja M. and Harper, Anna B. and Baker, David F. and Maksyutov, Shamil},
  title = {On what scales can GOSAT flux inversions constrain anomalies in terrestrial ecosystems?},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {19},
  number = {20},
  pages = {13017--13035},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://acp.copernicus.org/articles/19/13017/2019/},
  doi = {https://doi.org/10.5194/acp-19-13017-2019}
}
Byrne, B., Liu, J., Bloom, A.A., Bowman, K.W., Butterfield, Z., Joiner, J., Keenan, T.F., Keppel-Aleks, G., Parazoo, N.C. and Yin, Y. Contrasting Regional Carbon Cycle Responses to Seasonal Climate Anomalies Across the East-West Divide of Temperate North America {2020} GLOBAL BIOGEOCHEMICAL CYCLES
Vol. {34}({11}) 
article DOI URL 
Abstract: Across temperate North America, interannual variability (IAV) in gross primary production (GPP) and net ecosystem exchange (NEE) and their relationship with environmental drivers are poorly understood. Here, we examine IAV in GPP and NEE and their relationship to environmental drivers using two state-of-the-science flux products: NEE constrained by surface and space-based atmospheric CO2 measurements over 2010-2015 and satellite up-scaled GPP from FluxSat over 2001-2017. We show that the arid western half of temperate North America provides a larger contribution to IAV in GPP (104% of east) and NEE (127% of east) than the eastern half, in spite of smaller magnitude of annual mean GPP and NEE. This occurs because anomalies in western ecosystems are temporally coherent across the growing season leading to an amplification of GPP and NEE. In contrast, IAV in GPP and NEE in eastern ecosystems is dominated by seasonal compensation effects, associated with opposite responses to temperature anomalies in spring and summer. Terrestrial biosphere models in the MsTMIP ensemble generally capture these differences between eastern and western temperate North America, although there is considerable spread between models.
BibTeX:
@article{byrne20a,
  author = {Byrne, B. and Liu, J. and Bloom, A. A. and Bowman, K. W. and Butterfield, Z. and Joiner, J. and Keenan, T. F. and Keppel-Aleks, G. and Parazoo, N. C. and Yin, Y.},
  title = {Contrasting Regional Carbon Cycle Responses to Seasonal Climate Anomalies Across the East-West Divide of Temperate North America},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {34},
  number = {11},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GB006598},
  doi = {https://doi.org/10.1029/2020GB006598}
}
Carels, N. The Challenge of Bioenergies: An Overview {2011} BIOFUEL'S ENGINEERING PROCESS TECHNOLOGY, pp. 23-64  incollection  
BibTeX:
@incollection{carels11a,
  author = {Carels, Nicolas},
  title = {The Challenge of Bioenergies: An Overview},
  booktitle = {BIOFUEL'S ENGINEERING PROCESS TECHNOLOGY},
  publisher = {InTech},
  year = {2011},
  pages = {23--64}
}
Carouge, C., Rayner, P.J., Peylin, P., Bousquet, P., Chevallier, F. and Ciais, P. What can we learn from European continuous atmospheric CO2 measurements to quantify regional fluxes - Part 2: Sensitivity of flux accuracy to inverse setup {2010} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {10}({6}), pp. 3119-3129 
article DOI  
Abstract: An inverse model using atmospheric CO2 observations from a European
network of stations to reconstruct daily CO2 fluxes and their
uncertainties over Europe at 50 km resolution has been developed within
a Bayesian framework. We use the pseudo-data approach in which we try to
recover known fluxes using a range of perturbations to the input. In
this study, the focus is put on the sensitivity of flux accuracy to the
inverse setup, varying the prior flux errors, the pseudo-data errors and
the network of stations. We show that, under a range of assumptions
about prior error and data error we can recover fluxes reliably at the
scale of 1000 km and 10 days. At smaller scales the performance is
highly sensitive to details of the inverse set-up. The use of temporal
correlations in the flux domain appears to be of the same importance as
the spatial correlations. We also note that the use of simple, isotropic
correlations on the prior flux errors is more reliable than the use of
apparently physically-based errors. Finally, increasing the European
atmospheric network density improves the area with significant error
reduction in the flux retrieval.
BibTeX:
@article{carouge10a,
  author = {Carouge, C. and Rayner, P. J. and Peylin, P. and Bousquet, P. and Chevallier, F. and Ciais, P.},
  title = {What can we learn from European continuous atmospheric CO2 measurements to quantify regional fluxes - Part 2: Sensitivity of flux accuracy to inverse setup},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2010},
  volume = {10},
  number = {6},
  pages = {3119--3129},
  doi = {https://doi.org/10.5194/acp-10-3119-2010}
}
Cassol, H.L.G., Domingues, L.G., Sanchez, A.H., Basso, L.S., Marani, L., Tejada, G., Arai, E., Correia, C., Alden, C.B., Miller, J.B., Gloor, M., Anderson, L.O., Aragao, L.E.O.C. and Gatti, L.V. Determination of Region of Influence Obtained by Aircraft Vertical Profiles Using the Density of Trajectories from the HYSPLIT Model {2020} ATMOSPHERE
Vol. {11}({10}) 
article DOI URL 
Abstract: Aircraft atmospheric profiling is a valuable technique for determining greenhouse gas fluxes at regional scales (10(4)-10(6) km(2)). Here, we describe a new, simple method for estimating the surface influence of air samples that uses backward trajectories based on the Lagrangian model Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT). We determined ``regions of influence'' on a quarterly basis between 2010 and 2018 for four aircraft vertical profile sites: SAN and ALF in the eastern Amazon, and RBA and TAB or TEF in the western Amazon. We evaluated regions of influence in terms of their relative sensitivity to areas inside and outside the Amazon and their total area inside the Amazon. Regions of influence varied by quarter and less so by year. In the first and fourth quarters, the contribution of the region of influence inside the Amazon was 83-93% for all sites, while in the second and third quarters, it was 57-75%. The interquarter differences are more evident in the eastern than in the western Amazon. Our analysis indicates that atmospheric profiles from the western sites are sensitive to 42-52.2% of the Amazon. In contrast, eastern Amazon sites are sensitive to only 10.9-25.3%. These results may help to spatially resolve the response of greenhouse gas emissions to climate variability over Amazon.
BibTeX:
@article{cassol20a,
  author = {Cassol, Henrique L. G. and Domingues, Lucas G. and Sanchez, Alber H. and Basso, Luana S. and Marani, Luciano and Tejada, Graciela and Arai, Egidio and Correia, Caio and Alden, Caroline B. and Miller, John B. and Gloor, Manuel and Anderson, Liana O. and Aragao, Luiz E. O. C. and Gatti, Luciana V.},
  title = {Determination of Region of Influence Obtained by Aircraft Vertical Profiles Using the Density of Trajectories from the HYSPLIT Model},
  journal = {ATMOSPHERE},
  publisher = {MDPI},
  year = {2020},
  volume = {11},
  number = {10},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.mdpi.com/2073-4433/11/10/1073},
  doi = {https://doi.org/10.3390/atmos11101073}
}
Cervarich, M., Shu, S., Jain, A.K., Arneth, A., Canadell, J., Friedlingstein, P., Houghton, R.A., Kato, E., Koven, C., Patra, P., Poulter, B., Sitch, S., Stocker, B., Viovy, N., Wiltshire, A. and Zeng, N. The terrestrial carbon budget of South and Southeast Asia {2016} ENVIRONMENTAL RESEARCH LETTERS
Vol. {11}({10}) 
article DOI  
Abstract: Accomplishing the objective of the current climate policies will require
establishing carbon budget and flux estimates in each region and county
of the globe by comparing and reconciling multiple estimates including
the observations and the results of top-down atmospheric carbon dioxide
(CO2) inversions and bottom-up dynamic global vegetation models. With
this in view, this study synthesizes the carbon source/sink due to net
ecosystem productivity (NEP), land cover land use change (E-LUC), fires
and fossil burning (E-FIRE) for the South Asia (SA), Southeast Asia
(SEA) and South and Southeast Asia (SSEA = SA + SEA) and each country in
these regions using the multiple top-down and bottom-up modeling
results. The terrestrial net biome productivity (NBP = NEP - E-LUC -
E-FIRE) calculated based on bottom-up models in combination with E-FIRE
based on GFED4s data show net carbon sinks of 217 +/- 147, 10 +/- 55,
and 227 +/- 279 TgC yr(-1) for SA, SEA, and SSEA. The top-down models
estimated NBP net carbon sinks were 20 +/- 170, 4 +/- 90 and 24 +/- 180
TgC yr(-1). In comparison, regional emissions from the combustion of
fossil fuels were 495, 275, and 770 TgC yr(-1), which are many times
higher than the NBP sink estimates, suggesting that the contribution of
the fossil fuel emissions to the carbon budget of SSEA results in a
significant net carbon source during the 2000s. When considering both
NBP and fossil fuel emissions for the individual countries within the
regions, Bhutan and Laos were net carbon sinks and rest of the countries
were net carbon source during the 2000s. The relative contributions of
each of the fluxes (NBP, NEP, ELUC, and EFIRE, fossil fuel emissions) to
a nation's net carbon flux varied greatly from country to country,
suggesting a heterogeneous dominant carbon fluxes on the country-level
throughout SSEA.
BibTeX:
@article{cervarich16a,
  author = {Cervarich, Matthew and Shu, Shijie and Jain, Atul K. and Arneth, Almut and Canadell, Josep and Friedlingstein, Pierre and Houghton, Richard A. and Kato, Etsushi and Koven, Charles and Patra, Prabir and Poulter, Ben and Sitch, Stephen and Stocker, Beni and Viovy, Nicolas and Wiltshire, Andy and Zeng, Ning},
  title = {The terrestrial carbon budget of South and Southeast Asia},
  journal = {ENVIRONMENTAL RESEARCH LETTERS},
  year = {2016},
  volume = {11},
  number = {10},
  doi = {https://doi.org/10.1088/1748-9326/11/10/105006}
}
Chatterjee, A., Michalak, A.M., Anderson, J.L., Mueller, K.L. and Yadav, V. Toward reliable ensemble Kalman filter estimates of CO2 fluxes {2012} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {117} 
article DOI  
Abstract: The use of ensemble filters for estimating sources and sinks of carbon
dioxide (CO2) is becoming increasingly common, because they provide a
relatively computationally efficient framework for assimilating
high-density observations of CO2. Their applicability for estimating
fluxes at high-resolutions and the equivalence of their estimates to
those from more traditional ``batch'' inversion methods have not been
demonstrated, however. In this study, we introduce a Geostatistical
Ensemble Square Root Filter (GEnSRF) as a prototypical filter and
examine its performance using a synthetic data study over North America
at a high spatial (1 degrees x 1 degrees) and temporal (3-hourly)
resolution. The ensemble performance, both in terms of estimates and
associated uncertainties, is benchmarked against a batch inverse
modeling setup in order to isolate and quantify the degradation in the
estimates due to the numerical approximations and parameter choices in
the ensemble filter. The examined case studies demonstrate that adopting
state-of-the-art covariance inflation and localization schemes is a
necessary but not sufficient condition for ensuring good filter
performance, as defined by its ability to yield reliable flux estimates
and uncertainties across a range of resolutions. Observational density
is found to be another critical factor for stabilizing the ensemble
performance, which is attributed to the lack of a dynamical model for
evolving the ensemble between assimilation times. This and other results
point to key differences between the applicability of ensemble
approaches to carbon cycle science relative to its use in meteorological
applications where these tools were originally developed.
BibTeX:
@article{chatterjee12a,
  author = {Chatterjee, Abhishek and Michalak, Anna M. and Anderson, Jeffrey L. and Mueller, Kim L. and Yadav, Vineet},
  title = {Toward reliable ensemble Kalman filter estimates of CO2 fluxes},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2012},
  volume = {117},
  doi = {https://doi.org/10.1029/2012JD018176}
}
Chatterjee, A. Data Assimilation for Atmospheric CO2: Towards Improved Estimates of CO2 Concentrations and Fluxes. 2012 School: University of Michigan  phdthesis URL 
BibTeX:
@phdthesis{chatterjee12b,
  author = {A Chatterjee},
  title = {Data Assimilation for Atmospheric CO2: Towards Improved Estimates of CO2 Concentrations and Fluxes.},
  school = {University of Michigan},
  year = {2012},
  url = {https://deepblue.lib.umich.edu/handle/2027.42/96172}
}
Checa-Garcia, R., Landgraf, J., Galli, A., Hase, F., Velazco, V.A., Tran, H., Boudon, V., Alkemade, F. and Butz, A. Mapping spectroscopic uncertainties into prospective methane retrieval errors from Sentinel-5 and its precursor {2015} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {8}({9}), pp. 3617-3629 
article DOI  
Abstract: Sentinel-5 (S5) and its precursor (S5P) are future European satellite
missions aiming at global monitoring of methane (CH4) column-average dry
air mole fractions (XCH4). The spectrometers to be deployed onboard the
satellites record spectra of sunlight backscattered from the Earth's
surface and atmosphere. In particular, they exploit CH4 absorption in
the shortwave infrared spectral range around 1.65 mu m (S5 only) and
2.35 mu m (both S5 and S5P) wavelength. Given an accuracy goal of better
than 2% for XCH4 to be delivered on regional scales, assessment and
reduction of potential sources of systematic error such as spectroscopic
uncertainties is crucial. Here, we investigate how spectroscopic errors
propagate into retrieval errors on the global scale. To this end,
absorption spectra of a ground-based Fourier transform spectrometer
(FTS) operating at very high spectral resolution serve as estimate for
the quality of the spectroscopic parameters. Feeding the FTS fitting
residuals as a perturbation into a global ensemble of simulated S5- and
S5P-like spectra at relatively low spectral resolution, XCH4 retrieval
errors exceed 0.6% in large parts of the world and show systematic
correlations on regional scales, calling for improved spectroscopic
parameters.
BibTeX:
@article{checa-garcia15a,
  author = {Checa-Garcia, R. and Landgraf, J. and Galli, A. and Hase, F. and Velazco, V. A. and Tran, H. and Boudon, V. and Alkemade, F. and Butz, A.},
  title = {Mapping spectroscopic uncertainties into prospective methane retrieval errors from Sentinel-5 and its precursor},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2015},
  volume = {8},
  number = {9},
  pages = {3617--3629},
  doi = {https://doi.org/10.5194/amt-8-3617-2015}
}
Chen, B. and Coops, N.C. Understanding of Coupled Terrestrial Carbon, Nitrogen and Water Dynamics-An Overview {2009} SENSORS
Vol. {9}({11}), pp. 8624-8657 
article DOI  
Abstract: Coupled terrestrial carbon (C), nitrogen (N) and hydrological processes
play a crucial role in the climate system, providing both positive and
negative feedbacks to climate change. In this review we summarize
published research results to gain an increased understanding of the
dynamics between vegetation and atmosphere processes. A variety of
methods, including monitoring (e. g., eddy covariance flux tower, remote
sensing, etc.) and modeling (i.e., ecosystem, hydrology and atmospheric
inversion modeling) the terrestrial carbon and water budgeting, are
evaluated and compared. We highlight two major research areas where
additional research could be focused: (i) Conceptually, the hydrological
and biogeochemical processes are closely linked, however, the coupling
processes between terrestrial C, N and hydrological processes are far
from well understood; and (ii) there are significant uncertainties in
estimates of the components of the C balance, especially at landscape
and regional scales. To address these two questions, a synthetic
research framework is needed which includes both bottom-up and top-down
approaches integrating scalable (footprint and ecosystem) models and a
spatially nested hierarchy of observations which include multispectral
remote sensing, inventories, existing regional clusters of
eddy-covariance flux towers and CO2 mixing ratio towers and chambers.
BibTeX:
@article{chen09a,
  author = {Chen, Baozhang and Coops, Nicholas C.},
  title = {Understanding of Coupled Terrestrial Carbon, Nitrogen and Water Dynamics-An Overview},
  journal = {SENSORS},
  year = {2009},
  volume = {9},
  number = {11},
  pages = {8624--8657},
  doi = {https://doi.org/10.3390/s91108624}
}
Chen, H., Winderlich, J., Gerbig, C., Katrynski, K., Jordan, A. and Heimann, M. Validation of routine continuous airborne CO2 observations near the Bialystok Tall Tower {2012} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {5}({4}), pp. 873-889 
article DOI  
Abstract: Since 2002 in situ airborne measurements of atmospheric CO2 mixing
ratios have been performed regularly aboard a rental aircraft near
Bialystok (53A degrees 08A ` N, 23A degrees 09A ` E), a city in
northeastern Poland. Since August 2008, the in situ CO2 measurements
have been made by a modified commercially available and fully automated
non-dispersive infrared (NDIR) analyzer system. The response of the
analyzer has been characterized and the CO2 mixing ratio stability of
the associated calibration system has been fully tested, which results
in an optimal calibration strategy and allows for an accuracy of the CO2
measurements within 0.2 ppm. Besides the in situ measurements, air
samples have been collected in glass flasks and analyzed in the
laboratory for CO2 and other trace gases. To validate the in situ CO2
measurements against reliable discrete flask measurements, we developed
weighting functions that mimic the temporal averaging of the flask
sampling process. Comparisons between in situ and flask CO2 measurements
demonstrate that these weighting functions can compensate for
atmospheric variability, and provide an effective method for validating
airborne in situ CO2 measurements. In addition, we show the nine-year
records of flask CO2 measurements. The new system, automated since
August 2008, has eliminated the need for manual in-flight calibrations,
and thus enables an additional vertical profile, 20 km away, to be
sampled at no additional cost in terms of flight hours. This sampling
strategy provides an opportunity to investigate both temporal and
spatial variability on a regular basis.
BibTeX:
@article{chen12a,
  author = {Chen, H. and Winderlich, J. and Gerbig, C. and Katrynski, K. and Jordan, A. and Heimann, M.},
  title = {Validation of routine continuous airborne CO2 observations near the Bialystok Tall Tower},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2012},
  volume = {5},
  number = {4},
  pages = {873--889},
  doi = {https://doi.org/10.5194/amt-5-873-2012}
}
Chen, B. Towards an understanding of coupled carbon, water and nitrogen dynamics at sand, landscape and regional scales 2012 School: THE UNIVERSITY OF BRITISH COLUMBIA  phdthesis URL 
BibTeX:
@phdthesis{chen12b,
  author = {B Chen},
  title = {Towards an understanding of coupled carbon, water and nitrogen dynamics at sand, landscape and regional scales},
  school = {THE UNIVERSITY OF BRITISH COLUMBIA},
  year = {2012},
  url = {https://open.library.ubc.ca/collections/ubctheses/24/items/1.0103459}
}
Chen, B., Zhang, H., Coops, N.C., Fu, D., Worthy, D.E.J., Xu, G. and Black, T.A. Assessing scalar concentration footprint climatology and land surface impacts on tall-tower CO2 concentration measurements in the boreal forest of central Saskatchewan, Canada {2014} THEORETICAL AND APPLIED CLIMATOLOGY
Vol. {118}({1-2}), pp. 115-132 
article DOI  
Abstract: Reducing the large uncertainties in current estimates of CO2 sources and
sinks at regional scales (10(2)-10(5) km(2)) is fundamental to improving
our understanding of the terrestrial carbon cycle. Continuous
high-precision CO2 concentration measurements on a tower within the
planetary boundary layer contain information on regional carbon fluxes;
however, its spatial representativeness is generally unknown. In this
study, we developed a footprint model (Simple Analytical Footprint model
based on Eulerian coordinates for scalar Concentration [SAFE-C]) and
applied it to two CO2 concentration towers in central Canada: the East
Trout Lake 106-m-tall tower (54A degrees 21'N, 104A degrees 59'W) and
the Candle Lake 28-m-high tower (53A degrees 59'N, 105A degrees 07'W).
Results show that the ETL tower's annual concentration footprints were
around 10(3)-10(5) km(2). The monthly footprint climatologies in summer
were 1.5-2 times larger than in winter. The impacts of land surface
carbon flux associated with heterogeneous distribution of vegetation
types on the CO2 concentration measurements were different for the
different heights, varied with a range of +/- 5 % to +/- 10 % among
four heights. This study indicates that concentration footprint
climatology analysis is important in interpreting the seasonal, annual
and inter-annual variations of tower measured CO2 concentration data and
is essential for comparing and scaling regional carbon flux estimates
using top-down or bottom-up approaches.
BibTeX:
@article{chen14a,
  author = {Chen, Baozhang and Zhang, Huifang and Coops, Nicholas C. and Fu, Dongjie and Worthy, Douglas E. J. and Xu, Guang and Black, T. Andy},
  title = {Assessing scalar concentration footprint climatology and land surface impacts on tall-tower CO2 concentration measurements in the boreal forest of central Saskatchewan, Canada},
  journal = {THEORETICAL AND APPLIED CLIMATOLOGY},
  year = {2014},
  volume = {118},
  number = {1-2},
  pages = {115--132},
  doi = {https://doi.org/10.1007/s00704-013-1038-2}
}
Chen, J.M., Fung, J.W., Mo, G., Deng, F. and West, T.O. Atmospheric inversion of surface carbon flux with consideration of the spatial distribution of US crop production and consumption {2015} BIOGEOSCIENCES
Vol. {12}({2}), pp. 323-343 
article DOI  
Abstract: In order to improve quantification of the spatial distribution of carbon
sinks and sources in the conterminous US, we conduct a nested global
atmospheric inversion with detailed spatial information on crop
production and consumption. County-level cropland net primary
productivity, harvested biomass, soil carbon change, and human and
livestock consumption data over the conterminous US are used for this
purpose. Time-dependent Bayesian synthesis inversions are conducted
based on CO2 observations at 210 stations to infer CO2 fluxes globally
at monthly time steps with a nested focus on 30 regions in North
America. Prior land surface carbon fluxes are first generated using a
bio-spheric model, and the inversions are constrained using prior fluxes
with and without adjustments for crop production and consumption over
the 2002-2007 period. After these adjustments, the inverted regional
carbon sink in the US Midwest increases from 0.25 +/- 0.03 to 0.42 +/-
0.13 PgC yr(-1), whereas the large sink in the US southeast forest
region is weakened from 0.41 +/- 0.12 to 0.29 +/- 0.12 PgC yr(-1). These
adjustments also reduce the inverted sink in the west region from 0.066
+/- 0.04 to 0.040 +/- 0.02 PgC yr(-1) because of high crop consumption
and respiration by humans and livestock. The general pattern of sink
increases in crop production areas and sink decreases (or source
increases) in crop consumption areas highlights the importance of
considering the lateral carbon transfer in crop products in atmospheric
inverse modeling, which provides a reliable atmospheric perspective of
the overall carbon balance at the continental scale but is unreliable
for separating fluxes from different ecosystems.
BibTeX:
@article{chen15a,
  author = {Chen, J. M. and Fung, J. W. and Mo, G. and Deng, F. and West, T. O.},
  title = {Atmospheric inversion of surface carbon flux with consideration of the spatial distribution of US crop production and consumption},
  journal = {BIOGEOSCIENCES},
  year = {2015},
  volume = {12},
  number = {2},
  pages = {323--343},
  doi = {https://doi.org/10.5194/bg-12-323-2015}
}
Chen, M. Evaluation and Application of the Community Land Model for Simulating Energy and Carbon Exchange in Agricultural Ecosystems 2016 School: UNIVERSITY OF MINNESOTA  phdthesis URL 
BibTeX:
@phdthesis{chen16a,
  author = {M Chen},
  title = {Evaluation and Application of the Community Land Model for Simulating Energy and Carbon Exchange in Agricultural Ecosystems},
  school = {UNIVERSITY OF MINNESOTA},
  year = {2016},
  url = {http://search.proquest.com/openview/4e5113263c4ca244a5b38a8271693056/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Chen, Z., Chen, J.M., Zhang, S., Zheng, X., Ju, W., Mo, G. and Lu, X. Optimization of terrestrial ecosystem model parameters using atmospheric CO2 concentration data with the Global Carbon Assimilation System (GCAS) 2016 Journal of Geophysical Research: Biogeosciences
Vol. 122(12), pp. 3218-3237 
article DOI  
BibTeX:
@article{chen16b,
  author = {Chen, Zhuoqi and Chen, Jing M and Zhang, Shupeng and Zheng, Xiaogu and Ju, Weiming and Mo, Gang and Lu, Xiaoliang},
  title = {Optimization of terrestrial ecosystem model parameters using atmospheric CO2 concentration data with the Global Carbon Assimilation System (GCAS)},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {Wiley Online Library},
  year = {2016},
  volume = {122},
  number = {12},
  pages = {3218--3237},
  doi = {https://doi.org/10.1002/2016JG003716/full}
}
Chen, J.M., Mo, G. and Deng, F. A joint global carbon inversion system using both CO2 and (CO2)-C-13 atmospheric concentration data {2017} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {10}({3}), pp. 1131-1156 
article DOI  
Abstract: Observations of (CO2)-C-13 at 73 sites compiled in the GLOBALVIEW
database are used for an additional constraint in a global atmospheric
inversion of the surface CO2 flux using CO2 observations at 210 sites
(62 collocated with (CO2)-C-13 sites) for the 2002-2004 period for 39
land regions and 11 ocean regions. This constraint is implemented using
prior CO2 fluxes estimated with a terrestrial ecosystem model and an
ocean model. These models simulate (CO2)-C-13 discrimination rates of
terrestrial photosynthesis and oceanatmosphere diffusion processes. In
both models, the (CO2)-C-13 disequilibrium between fluxes to and from
the atmosphere is considered due to the historical change in atmospheric
(CO2)-C-13 concentration. This joint inversion system using
both(13)CO(2) and CO2 observations is effectively a double deconvolution
system with consideration of the spatial variations of isotopic
discrimination and disequilibrium. Compared to the CO2-only inversion,
this (CO2)-C-13 constraint on the inversion considerably reduces the
total land carbon sink from 3.40 +/- 0.84 to 2.53 +/- 0.93 Pg Cyear 1
but increases the total oceanic carbon sink from 1.48 +/- 0.40 to 2.36
+/- 0.49 Pg C year 1. This constraint also changes the spatial
distribution of the carbon sink. The largest sink increase occurs in the
Amazon, while the largest source increases are in southern Africa, and
Asia, where CO2 data are sparse. Through a case study, in which the
spatial distribution of the annual (CO2)-C-13 discrimination rate over
land is ignored by treating it as a constant at the global average of 14
: 1 %, the spatial distribution of the inverted CO2 flux over land was
found to be significantly modified (up to 15% for some regions). The
uncertainties in our disequilibrium flux estimation are 8.0 and 12.7 Pg
C year 1% for land and ocean, respectively. These uncertainties induced
the unpredictability of 0.47 and 0.54 Pg Cyear(-1) in the inverted CO2
fluxes for land and ocean, respectively. Our joint inversion system is
therefore useful for improving the partitioning between ocean and land
sinks and the spatial distribution of the inverted carbon flux.
BibTeX:
@article{chen17a,
  author = {Chen, Jing M. and Mo, Gang and Deng, Feng},
  title = {A joint global carbon inversion system using both CO2 and (CO2)-C-13 atmospheric concentration data},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2017},
  volume = {10},
  number = {3},
  pages = {1131--1156},
  doi = {https://doi.org/10.5194/gmd-10-1131-2017}
}
Chen, X., Liu, Y., Yang, D., Cai, Z., Chen, H. and Wang, M. A Theoretical Analysis for Improving Aerosol-Induced CO2 Retrieval Uncertainties Over Land Based on TanSat Nadir Observations Under Clear Sky Conditions {2019} REMOTE SENSING
Vol. {11}({9}) 
article DOI  
Abstract: Aerosols significantly affect carbon dioxide (CO2) retrieval accuracy and precision by modifying the light path. Hyperspectral measurements in the near infrared and shortwave infrared (NIR/SWIR) bands from the generation of new greenhouse gas satellites (e.g., the Chinese Global Carbon Dioxide Monitoring Scientific Experimental Satellite, TanSat) contain aerosol information for correction of scattering effects in the retrieval. Herein, a new approach is proposed for optimizing the aerosol model used in the TanSat CO2 retrieval algorithm to reduce CO2 uncertainties associated with aerosols. The weighting functions of hyperspectral observations with respect to elements in the state vector are simulated by a forward radiative transfer model. Using the optimal estimation method (OEM), the information content and each component of the CO2 column-averaged dry-air mole fraction (XCO2) retrieval errors from the TanSat simulations are calculated for typical aerosols which are described by Aerosol Robotic Network (AERONET) inversion products at selected sites based on the a priori and measurement assumptions. The results indicate that the size distribution parameters (r(eff), v(eff)), real refractive index coefficient of fine mode (a(r)(f)) and fine mode fraction (fmf) dominate the interference errors, with each causing 0.2-0.8 ppm of XCO2 errors. Given that only 4-7 degrees of freedom for signal (DFS) of aerosols can be obtained simultaneously and CO2 information decreases as more aerosol parameters are retrieved, four to seven aerosol parameters are suggested as the most appropriate for inclusion in CO2 retrieval. Focusing on only aerosol-induced XCO2 errors, forward model parameter errors, rather than interference errors, are dominant. A comparison of these errors across different aerosol parameter combination groups reveals that fewer aerosol-induced XCO2 errors are found when retrieving seven aerosol parameters. Therefore, the model selected as the optimal aerosol model includes aerosol optical depth (AOD), peak height of aerosol profile (H-p), width of aerosol profile (H-w), effective variance of fine mode aerosol (v(eff)(f)), effective radius of coarse mode aerosol (r(eff)(c)), coefficient a of the real part of the refractive index for the fine mode and coarse mode (a(r)(f) and a(r)(c)), with the lowest error of less than 1.7 ppm for all aerosol and surface types. For marine aerosols, only five parameters (AOD, H-p, H-w, r(eff)(c) and a(r)(c)) are recommended for the low aerosol information. This optimal aerosol model therefore offers a theoretical foundation for improving CO2 retrieval precision from real TanSat observations in the future.
BibTeX:
@article{chen19a,
  author = {Chen, Xi and Liu, Yi and Yang, Dongxu and Cai, Zhaonan and Chen, Hongbin and Wang, Maohua},
  title = {A Theoretical Analysis for Improving Aerosol-Induced CO2 Retrieval Uncertainties Over Land Based on TanSat Nadir Observations Under Clear Sky Conditions},
  journal = {REMOTE SENSING},
  publisher = {MDPI},
  year = {2019},
  volume = {11},
  number = {9},
  doi = {https://doi.org/10.3390/rs11091061}
}
Chen, H.W., Zhang, F., Lauvaux, T., Davis, K.J., Feng, S., Butler, M.P. and Alley, R.B. Characterization of Regional-Scale CO2 Transport Uncertainties in an Ensemble with Flow-Dependent Transport Errors {2019} GEOPHYSICAL RESEARCH LETTERS
Vol. {46}({7}), pp. {4049-4058} 
article DOI URL 
Abstract: Inference of CO2 surface fluxes using atmospheric CO2 observations in atmospheric inversions depends critically on accurate representation of atmospheric transport. Here we characterize regional-scale CO2 transport uncertainties due to uncertainties in meteorological fields using a mesoscale atmospheric model and an ensemble of simulations with flow-dependent transport errors. During a 1-month summer period over North America, transport uncertainties yield an ensemble spread in instantaneous CO2 at 100 m above ground level comparable to the CO2 uncertainties resulting from 48% relative uncertainty in 3-hourly natural CO2 fluxes. Temporal averaging reduces transport uncertainties but increases the influence of CO2 uncertainties from the lateral boundaries. The influence of CO2 background uncertainties is especially large for column-averaged CO2. These results suggest that transport errors and CO2 background errors limit regional atmospheric inversions at two distinct timescales and that the error characteristics of transport and background errors should guide the design of regional inversion systems.
BibTeX:
@article{chen19b,
  author = {Chen, Hans W. and Zhang, Fuqing and Lauvaux, Thomas and Davis, Kenneth J. and Feng, Sha and Butler, Martha P. and Alley, Richard B.},
  title = {Characterization of Regional-Scale CO2 Transport Uncertainties in an Ensemble with Flow-Dependent Transport Errors},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2019},
  volume = {46},
  number = {7},
  pages = {4049--4058},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081341},
  doi = {https://doi.org/10.1029/2018GL081341}
}
Chen, H.W., Zhang, L.N., Zhang, F., Davis, K.J., Lauvaux, T., Pal, S., Gaudet, B. and DiGangi, J.P. Evaluation of Regional CO2 Mole Fractions in the ECMWF CAMS Real-Time Atmospheric Analysis and NOAA CarbonTracker Near-Real-Time Reanalysis With Airborne Observations From ACT-America Field Campaigns {2019} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {124}({14}), pp. {8119-8133} 
article DOI URL 
Abstract: This study systematically examines the regional uncertainties and biases in carbon dioxide (CO2) mole fractions from two of the state-of-the-art global CO2 analysis products, namely, the Copernicus Atmosphere Monitoring Service (CAMS) real-time atmospheric analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the CarbonTracker Near-Real-Time (CT-NRT) reanalysis from the National Oceanic and Atmospheric Administration (NOAA), by evaluation against hundreds of hours of airborne in situ measurements from the summer 2016 and winter 2017 Atmospheric Carbon and Transport (ACT)-America field campaigns. Both the CAMS and CT-NRT analyses agree reasonably well with the independent ACT-America airborne CO2 measurements in the free troposphere, with root-mean-square deviations (RMSDs) between analyses and observations generally between 1 and 2 ppm but show considerably larger uncertainties in the atmospheric boundary layer where the RMSDs exceed 8 ppm in the lowermost 1 km of the troposphere in summer. There are strong variations in accuracy and bias between seasons, and across three different subregions in the United States (Mid-Atlantic, Midwest, and South), with the largest uncertainties in the Mid-Atlantic region in summer. Overall, the RMSDs of the CAMS and CT-NRT analyses against airborne data are comparable to each other and largely consistent with the differences between the two analyses. The current study provides uncertainty estimates for both analysis products over North America and suggests that these two independent estimates can be used to approximate regional CO2 analysis uncertainties. Both statistics are important in future studies in quantifying the uncertainties in regional CO2 mole fraction and flux estimates.
BibTeX:
@article{chen19c,
  author = {Chen, Hans W. and Zhang, Lily N. and Zhang, Fuqing and Davis, Kenneth J. and Lauvaux, Thomas and Pal, Sandip and Gaudet, Brian and DiGangi, Joshua P.},
  title = {Evaluation of Regional CO2 Mole Fractions in the ECMWF CAMS Real-Time Atmospheric Analysis and NOAA CarbonTracker Near-Real-Time Reanalysis With Airborne Observations From ACT-America Field Campaigns},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2019},
  volume = {124},
  number = {14},
  pages = {8119--8133},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD029992},
  doi = {https://doi.org/10.1029/2018JD029992}
}
Chen, Z., Liu, J., Henze, D.K., Huntzinger, D.N., Wells, K.C. and Miller, S.M. Linking global terrestrial CO2 fluxes and environmental drivers using OCO-2 and a geostatistical inverse model 2020 ATMOSPHERIC CHEMISTRY AND PHYSICS  article URL 
Abstract: Observations from the OCO-2 satellite, launched in July 2014, have been used to estimate CO 2 fluxes in many regions of the globe and provide new insight on the global carbon cycle. A challenge now is to not only estimate fluxes using satellite observations but also to …
BibTeX:
@article{chen20a,
  author = {Zichong Chen and Junjie Liu and Daven K. Henze and Deborah N. Huntzinger and Kelley C. Wells and Scot M. Miller},
  title = {Linking global terrestrial CO2 fluxes and environmental drivers using OCO-2 and a geostatistical inverse model},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2020},
  url = {https://acp.copernicus.org/preprints/acp-2020-285/}
}
Chen, B., Zhang, H., Wang, T. and Zhang, X. An atmospheric perspective on the carbon budgets of terrestrial ecosystems in China: progress and challenges 2021 SCIENCE BULLETIN
Vol. 66(17), pp. 1713-1718 
article DOI  
BibTeX:
@article{chen21a,
  author = {Chen, Baozhang and Zhang, Huifang and Wang, Tao and Zhang, Xiaoye},
  title = {An atmospheric perspective on the carbon budgets of terrestrial ecosystems in China: progress and challenges},
  journal = {SCIENCE BULLETIN},
  year = {2021},
  volume = {66},
  number = {17},
  pages = {1713-1718},
  doi = {https://doi.org/10.1016/j.scib.2021.05.017}
}
Cheng, Y., An, X., Yun, F., Zhou, L., Liu, L., Fang, S. and Xu, L. Simulation of CO2 variations at Chinese background atmospheric monitoring stations between 2000 and 2009: Applying a CarbonTracker model 2013 Chin. Sci. Bull
Vol. 58(32), pp. 3986-3993 
article  
BibTeX:
@article{cheng13a,
  author = {Cheng, Y and An, X and Yun, F and Zhou, L and Liu, L and Fang, S and Xu, Lin},
  title = {Simulation of CO2 variations at Chinese background atmospheric monitoring stations between 2000 and 2009: Applying a CarbonTracker model},
  journal = {Chin. Sci. Bull},
  year = {2013},
  volume = {58},
  number = {32},
  pages = {3986--3993}
}
Cheng, S., An, X., Zhou, L., Liu, L., Fang, S., Yao, B. and Liu, Z. CO2 concentration representation of source and sink area at Shangdianzi atmospheric background station in Beijing 2015 China Environmental Science  article URL 
BibTeX:
@article{cheng15a,
  author = {Cheng, Siyang and An, Xingqin and Zhou, Lingxi and Liu, LiXin and Fang, Shuangxi and Yao, Bo and Liu, Zhao},
  title = {CO2 concentration representation of source and sink area at Shangdianzi atmospheric background station in Beijing},
  journal = {China Environmental Science},
  year = {2015},
  url = {http://or.nsfc.gov.cn/bitstream/00001903-5/261235/1/1000014841151.pdf}
}
Cheng, S., An, X., Zhou, L., Tans, P.P. and Jacobson, A. Atmospheric CO2 at Waliguan station in China: Transport climatology, temporal patterns and source-sink region representativeness {2017} ATMOSPHERIC ENVIRONMENT
Vol. {159}, pp. 107-116 
article DOI  
Abstract: In order to explore where the source and sink have the greatest impact
on CO2 background concentration at Waliguan (WLG) station, a statistical
method is here proposed to calculate the representative source sink
region. The key to this method is to find the best footprint threshold,
and the study is carried out in four parts. Firstly, transport
climatology, expressed by total monthly footprint, was simulated by FLEX
PART on a 7-day time scale. Surface CO2 emissions in Eurasia frequently
transported to WLG station. WLG station was mainly influenced by the
westerlies in winter and partly controlled by the Southeast Asian
monsoon in summer. Secondly, CO2 concentrations, simulated by CT2015,
were processed and analyzed through data quality control, screening,
fitting and comparing. CO2 concentrations displayed obvious seasonal
variation, with the maximum and minimum concentration appearing in April
and August, respectively. The correlation of CO2 fitting background
concentrations was R-2 = 0.91 between simulation and observation. The
temporal patterns were mainly correlated with CO2 exchange of biosphere
atmosphere, human activities and air transport. Thirdly, for the monthly
CO2 fitting background concentrations from CT2015, a best footprint
threshold was found based on correlation analysis and numerical
iteration using the data of footprints and emissions. The grid cells
where monthly footprints were greater than the best footprint threshold
were the best threshold area corresponding to representative source-sink
region. The representative source-sink region of maximum CO2
concentration in April was primarily located in Qinghai province, but
the minimum CO2 concentration in August was mainly influenced by
emissions in a wider region. Finally, we briefly presented the CO2
source-sink characteristics in the best threshold area. Generally, the
best threshold area was a carbon sink. The major source and sink were
relatively weak owing to less human activities and vegetation types in
this high altitude area. CO2 concentrations were more influenced by
human activities when air mass passed through many urban areas in
summer. Therefore, the combination of footprints and emissions is an
effective approach for assessing the source-sink region
representativeness of CO2 background concentration. (C) 2017 Elsevier
Ltd. All rights reserved.
BibTeX:
@article{cheng17a,
  author = {Cheng, Siyang and An, Xingqin and Zhou, Lingxi and Tans, Pieter P. and Jacobson, Andy},
  title = {Atmospheric CO2 at Waliguan station in China: Transport climatology, temporal patterns and source-sink region representativeness},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2017},
  volume = {159},
  pages = {107--116},
  doi = {https://doi.org/10.1016/j.atmosenv.2017.03.055}
}
Cheng, H., Mi, Z., Wei, X., Yong-wei, W., Wei, W., Griffis, T., Shou-dong, L. and Xu-hui, L. Effect of Flux and its Uncertainty on Tall Tower CO2 Concentration Simulation in the Agricultural Domain 2017 中国农业气象 (Chinese Journal of Agrometeorology)  article URL 
BibTeX:
@article{cheng17b,
  author = {Hu Cheng and Zhang Mi and Xiao Wei and Wang Yong-wei and Wang Wei and Tim Griffis and Liu Shou-dong and Li Xu-hui},
  title = {Effect of Flux and its Uncertainty on Tall Tower CO2 Concentration Simulation in the Agricultural Domain},
  journal = {中国农业气象 (Chinese Journal of Agrometeorology)},
  year = {2017},
  url = {https://yncenter.sites.yale.edu/sites/default/files/files/hu_cheng_2017-2.pdf}
}
Cheng, H., Mi, Z., Wei, X., Yong-wei, W., Wei, W., Griffis, T., Shou-dong, L. and Xu-hui, L. Tall tower CO2 concentration simulation using the WRF-STILT model 2017 China Environmental Science
Vol. 37(7), pp. 2424-24-37 
article URL 
BibTeX:
@article{cheng17c,
  author = {Hu Cheng and Zhang Mi and Xiao Wei and Wang Yong-wei and Wang Wei and Tim Griffis and Liu Shou-dong and Li Xu-hui},
  title = {Tall tower CO2 concentration simulation using the WRF-STILT model},
  journal = {China Environmental Science},
  year = {2017},
  volume = {37},
  number = {7},
  pages = {2424-24-37},
  url = {http://manu36.magtech.com.cn/Jweb_zghjkx/CN/article/downloadArticleFile.do?attachType=PDF&id=15218}
}
Cheng, H., Shoudong, L., Chang, C., Jingzheng, X., Zhengda, C., Wengian, L., Jiaping, X., mi , Z., Wei, X. and Xuhui, L. Simulation of atmospheric CO2 concentration and source apportionment analysis in Nanjing City 2017 Acta Scientiae Circumstantiae
Vol. 37(10), pp. 3862-3875 
article URL 
BibTeX:
@article{cheng17d,
  author = {Hu Cheng and Liu Shoudong and Cao Chang and Xu Jingzheng and Cao Zhengda and Li Wengian and Xu Jiaping and Zhang mi and Xiao Wei and Li Xuhui},
  title = {Simulation of atmospheric CO2 concentration and source apportionment analysis in Nanjing City},
  journal = {Acta Scientiae Circumstantiae},
  year = {2017},
  volume = {37},
  number = {10},
  pages = {3862-3875},
  url = {http://html.rhhz.net/hjkxxb/html/20170224004.htm}
}
Cheng, S., Zhou, L., Tans, P.P., An, X. and Liu, Y. Comparison of atmospheric CO2 mole fractions and source sink characteristics at four WMO/GAW stations in China {2018} ATMOSPHERIC ENVIRONMENT
Vol. {180}, pp. {216-225} 
article DOI  
Abstract: As CO2 is a primary driving factor of climate change, the mole fraction
and source-sink characteristics of atmospheric CO2 over China are
constantly inferred from multi-source and multi-site data. In this
paper, we compared ground-based CO2 measurements with satellite
retrievals and investigated the source-sink regional representativeness
at China's four WMO/GAW stations. The results indicate that, firstly,
atmospheric CO2 mole fractions from ground-based sampling measurement
and Greenhouse Gases Observing Satellite (GOSAT) products reveal similar
seasonal variation. The seasonal amplitude of the column-averaged CO2
mole fractions is smaller than that of the ground-based CO2 at all
stations. The extrema of the seasonal cycle of ground-based and column
CO2 mole fractions are basically synchronous except a slight phase delay
at Lin'an (LAN) station. For the two-year average, the column CO2 is
lower than ground-based CO2, and both of them reveal the lowest CO2 mole
fraction at Waliguan (WLG) station. The lowest (similar to 4 ppm) and
largest (similar to 8 ppm) differences between the column and
ground-based CO2 appear at WLG and Longfengshan (LFS) stations,
respectively. The CO2 mole fraction and its difference between GOSAT and
ground-based measurement are smaller in summer than in winter. The
differences of summer column CO2 among these stations are also much
smaller than their ground-based counterparts. In winter, the maximum of
ground-based CO2 mole fractions and the greatest difference between the
two (ground-based and column) datasets appear at the LFS station.
Secondly, the representative areas of the monthly CO2 background mole
fractions at each station were found by employing footprints and
emissions. Smaller representative areas appeared at Shangdianzi (SDZ)
and LFS, whereas larger ones were seen at WLG and LAN. The
representative areas in summer are larger than those in winter at WLG
and SDZ, but the situation is opposite at LAN and LFS. The
representative areas for the stations are different in summer and
winter, distributed in four typical regions. The CO2 net fluxes in these
representative areas show obvious seasonal cycles with similar trends
but different varying ranges and different time of the strongest sink.
The intensities and uncertainties of the CO2 fluxes are different at
different stations in different months and source-sink sectors. Overall,
the WLG station is almost a carbon sink, but the other three stations
present stronger carbon sources for most of the year. These findings
could be conducive to the application of multi-source CO2 data and the
understanding of regional CO2 source-sink characteristics and patterns
over China.
BibTeX:
@article{cheng18a,
  author = {Cheng, Siyang and Zhou, Lingxi and Tans, Pieter P. and An, Xingqin and Liu, Yunsong},
  title = {Comparison of atmospheric CO2 mole fractions and source sink characteristics at four WMO/GAW stations in China},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2018},
  volume = {180},
  pages = {216-225},
  doi = {https://doi.org/10.1016/j.atmosenv.2018.03.010}
}
Chevallier, F., Engelen, R.J., Carouge, C., Conway, T.J., Peylin, P., Pickett-Heaps, C., Ramonet, M., Rayner, P.J. and Xueref-Remy, I. AIRS-based versus flask-based estimation of carbon surface fluxes {2009} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {114} 
article DOI  
Abstract: This paper demonstrates an inversion of surface CO2 fluxes using
concentrations derived from assimilation of satellite radiances.
Radiances come from the Atmospheric Infrared Sounder (AIRS) and are
assimilated within the system of the European Centre for Medium-Range
Weather Forecasts. We evaluate the quality of the inverted fluxes by
comparing simulated concentrations with independent airborne
measurements. As a benchmark we use an inversion based on surface flask
measurements and another using only the global concentration trend. We
show that the AIRS-based inversion is able to improve the match to the
independent data compared to the prior estimate but that it usually
performs worse than either the flask-based or trend-based inversion.
BibTeX:
@article{chevallier09a,
  author = {Chevallier, Frederic and Engelen, Richard J. and Carouge, Claire and Conway, Thomas J. and Peylin, Philippe and Pickett-Heaps, Christopher and Ramonet, Michel and Rayner, Peter J. and Xueref-Remy, Irene},
  title = {AIRS-based versus flask-based estimation of carbon surface fluxes},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2009},
  volume = {114},
  doi = {https://doi.org/10.1029/2009JD012311}
}
Chevallier, F., Ciais, P., Conway, T.J., Aalto, T., Anderson, B.E., Bousquet, P., Brunke, E.G., Ciattaglia, L., Esaki, Y., Froehlich, M., Gomez, A., Gomez-Pelaez, A.J., Haszpra, L., Krummel, P.B., Langenfelds, R.L., Leuenberger, M., Machida, T., Maignan, F., Matsueda, H., Morgui, J.A., Mukai, H., Nakazawa, T., Peylin, P., Ramonet, M., Rivier, L., Sawa, Y., Schmidt, M., Steele, L.P., Vay, S.A., Vermeulen, A.T., Wofsy, S. and Worthy, D. CO2 surface fluxes at grid point scale estimated from a global 21 year reanalysis of atmospheric measurements {2010} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {115} 
article DOI  
Abstract: This paper documents a global Bayesian variational inversion of CO2
surface fluxes during the period 1988-2008. Weekly fluxes are estimated
on a 3.75 degrees x 2.5 degrees (longitude-latitude) grid throughout the
21 years. The assimilated observations include 128 station records from
three large data sets of surface CO2 mixing ratio measurements. A Monte
Carlo approach rigorously quantifies the theoretical uncertainty of the
inverted fluxes at various space and time scales, which is particularly
important for proper interpretation of the inverted fluxes. Fluxes are
evaluated indirectly against two independent CO2 vertical profile data
sets constructed from aircraft measurements in the boundary layer and in
the free troposphere. The skill of the inversion is evaluated by the
improvement brought over a simple benchmark flux estimation based on the
observed atmospheric growth rate. Our error analysis indicates that the
carbon budget from the inversion should be more accurate than the a
priori carbon budget by 20% to 60% for terrestrial fluxes aggregated
at the scale of subcontinental regions in the Northern Hemisphere and
over a year, but the inversion cannot clearly distinguish between the
regional carbon budgets within a continent. On the basis of the
independent observations, the inversion is seen to improve the fluxes
compared to the benchmark: the atmospheric simulation of CO2 with the
Bayesian inversion method is better by about 1 ppm than the benchmark in
the free troposphere, despite possible systematic transport errors. The
inversion achieves this improvement by changing the regional fluxes over
land at the seasonal and at the interannual time scales.
BibTeX:
@article{chevallier10a,
  author = {Chevallier, F. and Ciais, P. and Conway, T. J. and Aalto, T. and Anderson, B. E. and Bousquet, P. and Brunke, E. G. and Ciattaglia, L. and Esaki, Y. and Froehlich, M. and Gomez, A. and Gomez-Pelaez, A. J. and Haszpra, L. and Krummel, P. B. and Langenfelds, R. L. and Leuenberger, M. and Machida, T. and Maignan, F. and Matsueda, H. and Morgui, J. A. and Mukai, H. and Nakazawa, T. and Peylin, P. and Ramonet, M. and Rivier, L. and Sawa, Y. and Schmidt, M. and Steele, L. P. and Vay, S. A. and Vermeulen, A. T. and Wofsy, S. and Worthy, D.},
  title = {CO2 surface fluxes at grid point scale estimated from a global 21 year reanalysis of atmospheric measurements},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2010},
  volume = {115},
  doi = {https://doi.org/10.1029/2010JD013887}
}
Chevallier, F., Wang, T., Ciais, P., Maignan, F., Bocquet, M., Arain, M.A., Cescatti, A., Chen, J., Dolman, A.J., Law, B.E., Margolis, H.A., Montagnani, L. and Moors, E.J. What eddy-covariance measurements tell us about prior land flux errors in CO2-flux inversion schemes {2012} GLOBAL BIOGEOCHEMICAL CYCLES
Vol. {26} 
article DOI  
Abstract: To guide the future development of CO2-atmospheric inversion modeling
systems, we analyzed the errors arising from prior information about
terrestrial ecosystem fluxes. We compared the surface fluxes calculated
by a process-based terrestrial ecosystem model with daily averages of
CO2 flux measurements at 156 sites across the world in the FLUXNET
network. At the daily scale, the standard deviation of the model-data
fit was 2.5 gC.m(2).d(-1); temporal autocorrelations were significant at
the weekly scale (>0.3 for lags less than four weeks), while spatial
correlations were confined to within the first few hundred kilometers
(<0.2 after 200 km). Separating out the plant functional types did not
increase the spatial correlations, except for the deciduous broad-leaved
forests. Using the statistics of the flux measurements as a proxy for
the statistics of the prior flux errors was shown not to be a viable
approach. A statistical model allowed us to upscale the site-level flux
error statistics to the coarser spatial and temporal resolutions used in
regional or global models. This approach allowed us to quantify how
aggregation reduces error variances, while increasing correlations. As
an example, for a typical inversion of grid point (300 km x 300 km)
monthly fluxes, we found that the prior flux error follows an
approximate e-folding correlation length of 500 km only, with
correlations from one month to the next as large as 0.6.
BibTeX:
@article{chevallier12a,
  author = {Chevallier, Frederic and Wang, Tao and Ciais, Philippe and Maignan, Fabienne and Bocquet, Marc and Arain, M. Altaf and Cescatti, Alessandro and Chen, Jiquan and Dolman, A. Johannes and Law, Beverly E. and Margolis, Hank A. and Montagnani, Leonardo and Moors, Eddy J.},
  title = {What eddy-covariance measurements tell us about prior land flux errors in CO2-flux inversion schemes},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  year = {2012},
  volume = {26},
  doi = {https://doi.org/10.1029/2010GB003974}
}
Chevallier, F. and O'Dell, C.W. Error statistics of Bayesian CO2 flux inversion schemes as seen from GOSAT {2013} GEOPHYSICAL RESEARCH LETTERS
Vol. {40}({6}), pp. 1252-1256 
article DOI  
Abstract: Statistical modeling is at the root of CO2 atmospheric inversion
systems, but few studies have focused on the quality of their assigned
probability distributions. In this paper, we assess the reliability of
the error models that are in input and in output of a specific CO2
atmospheric inversion system when it assimilates surface air sample
measurements. We confront these error models with the mismatch between
4D simulations of CO2 and independent satellite retrievals of the total
CO2 column. Taking all sources of uncertainties into account, it is
shown that both prior and posterior errors are consistent with the
actual departures, to the point that the theoretical error reduction
brought by the surface measurements on the simulation of the Greenhouse
gases Observing SATellite (GOSAT) total column measurements (15%)
corresponds to the actual reduction seen over the midlatitude and
tropical lands and over the tropical oceans.
BibTeX:
@article{chevallier13a,
  author = {Chevallier, Frederic and O'Dell, Christopher W.},
  title = {Error statistics of Bayesian CO2 flux inversion schemes as seen from GOSAT},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2013},
  volume = {40},
  number = {6},
  pages = {1252--1256},
  doi = {https://doi.org/10.1002/grl.50228}
}
Chevallier, F. On the parallelization of atmospheric inversions of CO2 surface fluxes within a variational framework {2013} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {6}({3}), pp. 783-790 
article DOI  
Abstract: The variational formulation of Bayes' theorem allows inferring CO2
sources and sinks from atmospheric concentrations at much higher
time-space resolution than the ensemble or analytical approaches.
However, it usually exhibits limited scalable parallelism. This
limitation hinders global atmospheric inversions operated on decadal
time scales and regional ones with kilometric spatial scales because of
the computational cost of the underlying transport model that has to be
run at each iteration of the variational minimization. Here, we
introduce a physical parallelization (PP) of variational atmospheric
inversions. In the PP, the inversion still manages a single physically
and statistically consistent window, but the transport model is run in
parallel overlapping sub-segments in order to massively reduce the
computation wall-clock time of the inversion. For global inversions, a
simplification of transport modelling is described to connect the output
of all segments. We demonstrate the performance of the approach on a
global inversion for CO2 with a 32 yr inversion window (1979-2010) with
atmospheric measurements from 81 sites of the NOAA global cooperative
air sampling network. In this case, we show that the duration of the
inversion is reduced by a seven-fold factor (from months to days), while
still processing the three decades consistently and with improved
numerical stability.
BibTeX:
@article{chevallier13b,
  author = {Chevallier, F.},
  title = {On the parallelization of atmospheric inversions of CO2 surface fluxes within a variational framework},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2013},
  volume = {6},
  number = {3},
  pages = {783--790},
  doi = {https://doi.org/10.5194/gmd-6-783-2013}
}
Chevallier, F. Report on the quality of the inverted CO2 fluxes 2013 MACC-II delivrable D
Vol. 43 
article URL 
BibTeX:
@article{chevallier13c,
  author = {F Chevallier},
  title = {Report on the quality of the inverted CO2 fluxes},
  journal = {MACC-II delivrable D},
  year = {2013},
  volume = {43},
  url = {https://www-gmes-atmosphere-eu.ecmwf.int/documents/maccii/deliverables/ghg/MACCII_GHG_DEL_D43.4_20120430_Chevallier.pdf}
}
Cho, M. and Kim, H.M. Effect of assimilating CO2 observations in the Korean Peninsula on the inverse modeling to estimate surface CO2 flux over Asia 2022 PLOS ONE
Vol. 17(2) 
article DOI  
Abstract: To investigate the impact of two CO2 observation datasets obtained from
the Korean Peninsula on the surface CO2 flux estimation over Asia, the
two datasets are assimilated into the CarbonTracker (CT) inverse
modeling system and the estimated surface CO2 fluxes are analyzed.
Anmyeon-do (AMY) and Gosan (GSN) sites in the Korean Peninsula have
observed surface CO2 mole fraction since the late 1990s. To investigate
the effect of assimilating the additional Korean observations on the
surface CO2 flux estimation over Asia, two experiments are conducted.
The reference experiment (CNTL) only assimilates observations provided
by National Oceanic and Atmospheric Administration (NOAA), while the
other experiment (EXP1) assimilates both NOAA observations and two
Korean observation datasets. The results are analyzed for 9 years from
2003 to 2011 in Asia region because both AMY and GSN datasets exist
almost completely for this period. The annual average of estimated
biosphere CO2 flux of EXP1 shows more flux absorption in summer and less
flux emission from fall to spring compared to CNTL, mainly on Eurasia
Temperate and Eurasia Boreal regions. When comparing model results to
independent CO2 concentration data from surface stations and aircraft,
the root mean square error is smaller for EXP1 than CNTL. The EXP1
yields more reduction on uncertainty of estimated biosphere CO2 flux
over Asia, and the observation impact of AMY, GSN sites on flux
estimation is approximately 11%, which is greater than other
observation sites around the world. Therefore, the two CO2 observation
sets in the Korean Peninsula are useful in reducing uncertainties for
regional as well as global scale CO2 flux estimation.
BibTeX:
@article{cho22a,
  author = {Cho, Minkwang and Kim, Hyun Mee},
  title = {Effect of assimilating CO2 observations in the Korean Peninsula on the inverse modeling to estimate surface CO2 flux over Asia},
  journal = {PLOS ONE},
  year = {2022},
  volume = {17},
  number = {2},
  doi = {https://doi.org/10.1371/journal.pone.0263925}
}
Ciais, P., Canadell, J.G., Luyssaert, S., Chevallier, F., Shvidenko, A., Poussi, Z., Jonas, M., Peylin, P., King, A.W., Schulze, E.-D., Piao, S., Roedenbeck, C., Peters, W. and Breon, F.-M. Can we reconcile atmospheric estimates of the Northern terrestrial carbon sink with land-based accounting? {2010} CURRENT OPINION IN ENVIRONMENTAL SUSTAINABILITY
Vol. {2}({4}), pp. 225-230 
article DOI  
Abstract: We estimate the northern hemisphere (NH) terrestrial carbon sink by
comparing four recent atmospheric inversions with land-based C
accounting data for six large northern regions. The mean NH terrestrial
CO2 sink from the inversion models is 1.7 Pg C year(-1) over the period
2000-2004. The uncertainty of this estimate is based on the typical
individual (1-sigma) precision of one inversion (0.9 Pg C year(-1)) and
is consistent with the min-max range of the four inversion mean
estimates (0.8 Pg C year(-1)). Inversions agree within their uncertainty
for the distribution of the NH sink of CO2 in longitude, with Russia
being the largest sink. The land-based accounting estimate of NH carbon
sink is 1.7 Pg C year(-1) for the sum of the six regions studied. The
1-sigma uncertainty of the land-based estimate (0.3 Pg C year(-1)) is
smaller than that of atmospheric inversions, but no independent
land-based flux estimate is available to derive a `between accounting
model' uncertainty. Encouragingly, the top-down atmospheric and the
bottom-up land-based methods converge to consistent mean estimates
within their respective errors, increasing the confidence in the overall
budget. These results also confirm the continued critical role of NH
terrestrial ecosystems in slowing down the atmospheric accumulation of
anthropogenic CO2.
BibTeX:
@article{ciais10a,
  author = {Ciais, Philippe and Canadell, Josep G. and Luyssaert, Sebastiaan and Chevallier, Frederic and Shvidenko, Anatoly and Poussi, Zegbeu and Jonas, Matthias and Peylin, Philippe and King, Anthony Wayne and Schulze, Ernest-Detlef and Piao, Shilong and Roedenbeck, Christian and Peters, Wouter and Breon, Francois-Marie},
  title = {Can we reconcile atmospheric estimates of the Northern terrestrial carbon sink with land-based accounting?},
  journal = {CURRENT OPINION IN ENVIRONMENTAL SUSTAINABILITY},
  year = {2010},
  volume = {2},
  number = {4},
  pages = {225--230},
  doi = {https://doi.org/10.1016/j.cosust.2010.06.008}
}
Ciais, P., Dolman, A.J., Bombelli, A., Duren, R., Peregon, A., Rayner, P.J., Miller, C., Gobron, N., Kinderman, G., Marland, G., Gruber, N., Chevallier, F., Andres, R.J., Balsamo, G., Bopp, L., Breon, F.M., Broquet, G., Dargaville, R., Battin, T.J., Borges, A., Bovensmann, H., Buchwitz, M., Butler, J., Canadell, J.G., Cook, R.B., DeFries, R., Engelen, R., Gurney, K.R., Heinze, C., Heimann, M., Held, A., Henry, M., Law, B., Luyssaert, S., Miller, J., Moriyama, T., Moulin, C., Myneni, R.B., Nussli, C., Obersteiner, M., Ojima, D., Pan, Y., Paris, J.D., Piao, S.L., Poulter, B., Plummer, S., Quegan, S., Raymond, P., Reichstein, M., Rivier, L., Sabine, C., Schimel, D., Tarasova, O., Valentini, R., Wang, R., van der Werf, G., Wickland, D., Williams, M. and Zehner, C. Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system {2014} BIOGEOSCIENCES
Vol. {11}({13}), pp. 3547-3602 
article DOI  
Abstract: A globally integrated carbon observation and analysis system is needed
to improve the fundamental understanding of the global carbon cycle, to
improve our ability to project future changes, and to verify the
effectiveness of policies aiming to reduce greenhouse gas emissions and
increase carbon sequestration. Building an integrated carbon observation
system requires transformational advances from the existing sparse,
exploratory framework towards a dense, robust, and sustained system in
all components: anthropogenic emissions, the atmosphere, the ocean, and
the terrestrial biosphere. The paper is addressed to scientists,
policymakers, and funding agencies who need to have a global picture of
the current state of the (diverse) carbon observations. We identify the
current state of carbon observations, and the needs and notional
requirements for a global integrated carbon observation system that can
be built in the next decade. A key conclusion is the substantial
expansion of the ground-based observation networks required to reach the
high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks
for addressing policy-relevant objectives, and attributing flux changes
to underlying processes in each region. In order to establish flux and
stock diagnostics over areas such as the southern oceans, tropical
forests, and the Arctic, in situ observations will have to be
complemented with remote-sensing measurements. Remote sensing offers the
advantage of dense spatial coverage and frequent revisit. A key
challenge is to bring remote-sensing measurements to a level of
long-term consistency and accuracy so that they can be efficiently
combined in models to reduce uncertainties, in synergy with ground-based
data. Bringing tight observational constraints on fossil fuel and land
use change emissions will be the biggest challenge for deployment of a
policy-relevant integrated carbon observation system. This will require
in situ and remotely sensed data at much higher resolution and density
than currently achieved for natural fluxes, although over a small land
area (cities, industrial sites, power plants), as well as the inclusion
of fossil fuel CO2 proxy measurements such as radiocarbon in CO2 and
carbon-fuel combustion tracers. Additionally, a policy-relevant carbon
monitoring system should also provide mechanisms for reconciling
regional top-down (atmosphere-based) and bottom-up (surface-based) flux
estimates across the range of spatial and temporal scales relevant to
mitigation policies. In addition, uncertainties for each observation
data-stream should be assessed. The success of the system will rely on
long-term commitments to monitoring, on improved international
collaboration to fill gaps in the current observations, on sustained
efforts to improve access to the different data streams and make
databases interoperable, and on the calibration of each component of the
system to agreed-upon international scales.
BibTeX:
@article{ciais14a,
  author = {Ciais, P. and Dolman, A. J. and Bombelli, A. and Duren, R. and Peregon, A. and Rayner, P. J. and Miller, C. and Gobron, N. and Kinderman, G. and Marland, G. and Gruber, N. and Chevallier, F. and Andres, R. J. and Balsamo, G. and Bopp, L. and Breon, F. -M. and Broquet, G. and Dargaville, R. and Battin, T. J. and Borges, A. and Bovensmann, H. and Buchwitz, M. and Butler, J. and Canadell, J. G. and Cook, R. B. and DeFries, R. and Engelen, R. and Gurney, K. R. and Heinze, C. and Heimann, M. and Held, A. and Henry, M. and Law, B. and Luyssaert, S. and Miller, J. and Moriyama, T. and Moulin, C. and Myneni, R. B. and Nussli, C. and Obersteiner, M. and Ojima, D. and Pan, Y. and Paris, J. -D. and Piao, S. L. and Poulter, B. and Plummer, S. and Quegan, S. and Raymond, P. and Reichstein, M. and Rivier, L. and Sabine, C. and Schimel, D. and Tarasova, O. and Valentini, R. and Wang, R. and van der Werf, G. and Wickland, D. and Williams, M. and Zehner, C.},
  title = {Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system},
  journal = {BIOGEOSCIENCES},
  year = {2014},
  volume = {11},
  number = {13},
  pages = {3547--3602},
  doi = {https://doi.org/10.5194/bg-11-3547-2014}
}
Cochran, F.V. and Brunsell, N.A. Temporal scales of tropospheric CO2, precipitation, and ecosystem responses in the central Great Plains {2012} REMOTE SENSING OF ENVIRONMENT
Vol. {127}, pp. 316-328 
article DOI  
Abstract: Natural and anthropogenic sources of CO2 around the globe contribute to
mid-tropospheric concentrations, yet it remains unknown how measurements
of mid-tropospheric CO2 relate to regional ecosystem dynamics. NASA
Atmospheric Infrared Sounder (AIRS) measurements of CO2 concentrations
in the mid-troposphere from 2002 to 2010 were examined in relation to
precipitation and vegetation phenology across the US Great Plains.
Wavelet multi-resolution analysis and the information theory metric of
relative entropy were applied to assess regional relationships between
mid-tropospheric CO2, Normalized Difference Vegetation Index (NDVI), and
precipitation (PPT). Results show that AIRS observations of
mid-tropospheric CO2 exchange greater amounts of information with
regional PPT and NDVI at seasonal, annual, and longer time scales
compared to shorter time scales. PPT and NDVI contribute to
mid-tropospheric CO2 at the 18-month time scale, while spatial patterns
seen at this time scale for PIT and mid-tropospheric CO2 are reflective
of the influence of PPT on NDVI at the annual scale. Identification of
these dominant temporal scales may facilitate utilization of AIRS CO2
for monitoring regional source/sink dynamics related to climate and
land-use/cover change. (c) 2012 Elsevier Inc. All rights reserved.
BibTeX:
@article{cochran12a,
  author = {Cochran, Ferdouz V. and Brunsell, Nathaniel A.},
  title = {Temporal scales of tropospheric CO2, precipitation, and ecosystem responses in the central Great Plains},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2012},
  volume = {127},
  pages = {316--328},
  doi = {https://doi.org/10.1016/j.rse.2012.09.012}
}
Collalti, A., Marconi, S., Ibrom, A., Trotta, C., Anav, A., D'Andrea, E., Matteucci, G., Montagnani, L., Gielen, B., Mammarella, I., Gruenwald, T., Knohl, A., Berninger, F., Zhao, Y., Valentini, R. and Santini, M. Validation of 3D-CMCC Forest Ecosystem Model (v.5.1) against eddy covariance data for 10 European forest sites {2016} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {9}({2}), pp. 479-504 
article DOI  
Abstract: This study evaluates the performances of the new version (v.5.1) of
3D-CMCC Forest Ecosystem Model (FEM) in simulating gross primary
productivity (GPP), against eddy covariance GPP data for 10 FLUXNET
forest sites across Europe. A new carbon allocation module, coupled with
new both phenological and autotrophic respiration schemes, was
implemented in this new daily version. Model ability in reproducing
timing and magnitude of daily and monthly GPP fluctuations is validated
at intra-annual and inter-annual scale, including extreme anomalous
seasons. With the purpose to test the 3D-CMCC FEM applicability over
Europe without a site-related calibration, the model has been
deliberately parametrized with a single set of species-specific
parametrizations for each forest ecosystem. The model consistently
reproduces both in timing and in magnitude daily and monthly GPP
variability across all sites, with the exception of the two
Mediterranean sites. We find that 3D-CMCC FEM tends to better simulate
the timing of inter-annual anomalies than their magnitude within
measurements' uncertainty. In six of eight sites where data are
available, the model well reproduces the 2003 summer drought event.
Finally, for three sites we evaluate whether a more accurate
representation of forest structural characteristics (i.e. cohorts,
forest layers) and species composition can improve model results. In two
of the three sites results reveal that model slightly increases its
performances although, statistically speaking, not in a relevant way.
BibTeX:
@article{collalti16a,
  author = {Collalti, A. and Marconi, S. and Ibrom, A. and Trotta, C. and Anav, A. and D'Andrea, E. and Matteucci, G. and Montagnani, L. and Gielen, B. and Mammarella, I. and Gruenwald, T. and Knohl, A. and Berninger, F. and Zhao, Y. and Valentini, R. and Santini, M.},
  title = {Validation of 3D-CMCC Forest Ecosystem Model (v.5.1) against eddy covariance data for 10 European forest sites},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2016},
  volume = {9},
  number = {2},
  pages = {479--504},
  doi = {https://doi.org/10.5194/gmd-9-479-2016}
}
Combe, M., de wit , A.J.W., de Arellano, J.V.-G., van der Molen, M.K., Magliulo, V. and Peters, W. Grain Yield Observations Constrain Cropland CO2 Fluxes Over Europe {2017} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {122}({12}), pp. {3238-3259} 
article DOI  
Abstract: Carbon exchange over croplands plays an important role in the European
carbon cycle over daily to seasonal time scales. A better description of
this exchange in terrestrial biosphere models-most of which currently
treat crops as unmanaged grasslands-is needed to improve atmospheric CO2
simulations. In the framework we present here, we model gross European
cropland CO2 fluxes with a crop growth model constrained by grain yield
observations. Our approach follows a two-step procedure. In the first
step, we calculate day-to-day crop carbon fluxes and pools with the
WOrld FOod STudies (WOFOST) model. A scaling factor of crop growth is
optimized regionally by minimizing the final grain carbon pool
difference to crop yield observations from the Statistical Office of the
European Union. In a second step, we re-run our WOFOST model for the
full European 25 x 25 km gridded domain using the optimized scaling
factors. We combine our optimized crop CO2 fluxes with a simple soil
respiration model to obtain the net cropland CO2 exchange. We assess our
model's ability to represent cropland CO2 exchange using 40 years of
observations at seven European FluxNet sites and compare it with carbon
fluxes produced by a typical terrestrial biosphere model. We conclude
that our new model framework provides a more realistic and strongly
observation-driven estimate of carbon exchange over European croplands.
Its products will be made available to the scientific community through
the ICOS Carbon Portal and serve as a new cropland component in the
CarbonTracker Europe inverse model.
BibTeX:
@article{combe17a,
  author = {Combe, M. and de wit, A. J. W. and de Arellano, J. Vila-Guerau and van der Molen, M. K. and Magliulo, V. and Peters, W.},
  title = {Grain Yield Observations Constrain Cropland CO2 Fluxes Over Europe},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2017},
  volume = {122},
  number = {12},
  pages = {3238-3259},
  doi = {https://doi.org/10.1002/2017JG003937}
}
Cooley, D., Breidt, F.J., Ogle, S.M., Schuh, A.E. and Lauvaux, T. A constrained least-squares approach to combine bottom-up and top-down CO2 flux estimates {2013} ENVIRONMENTAL AND ECOLOGICAL STATISTICS
Vol. {20}({1}), pp. 129-146 
article DOI  
Abstract: Terrestrial CO2 flux estimates are obtained from two fundamentally
different methods generally termed bottom-up and top-down approaches.
Inventory methods are one type of bottom-up approach which uses various
sources of information such as crop production surveys and forest
monitoring data to estimate the annual CO2 flux at locations covering a
study region. Top-down approaches are various types of atmospheric
inversion methods which use CO2 concentration measurements from
monitoring towers and atmospheric transport models to estimate CO2 flux
over a study region. Both methods can also quantify the uncertainty
associated with their estimates. Historically, these two approaches have
produced estimates that differ considerably. The goal of this work is to
construct a statistical model which sensibly combines estimates from the
two approaches to produce a new estimate of CO2 flux for our study
region. The two approaches have complementary strengths and weaknesses,
and our results show that certain aspects of the uncertainty associated
with each of the approaches are greatly reduced by combining the
methods. Our model is purposefully simple and designed to take the two
approaches' estimates and measures of uncertainty at `face value'.
Specifically, we use a constrained least-squares approach to
appropriately weigh the estimates by the inverse of their variance, and
the constraint imposes agreement between the two sources. Our
application involves nearly 18,000 flux estimates for the upper midwest
United States. The constrained dependencies result in a non-sparse
covariance matrix, but computation requires only minutes due to the
structure of the model.
BibTeX:
@article{cooley13a,
  author = {Cooley, Daniel and Breidt, F. Jay and Ogle, Stephen M. and Schuh, Andrew E. and Lauvaux, Thomas},
  title = {A constrained least-squares approach to combine bottom-up and top-down CO2 flux estimates},
  journal = {ENVIRONMENTAL AND ECOLOGICAL STATISTICS},
  year = {2013},
  volume = {20},
  number = {1},
  pages = {129--146},
  doi = {https://doi.org/10.1007/s10651-012-0211-6}
}
Corbin, K.D. Investigating causes of regional variations in atmospheric carbon dioxide concentrations 2008 School: Colorado State University  phdthesis  
BibTeX:
@phdthesis{corbin08a,
  author = {Corbin, Katherine D},
  title = {Investigating causes of regional variations in atmospheric carbon dioxide concentrations},
  school = {Colorado State University},
  year = {2008}
}
Crevoisier, C., Sweeney, C., Gloor, M., Sarmiento, J.L. and Tans, P.P. Regional US carbon sinks from three-dimensional atmospheric CO2 sampling {2010} PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Vol. {107}({43}), pp. 18348-18353 
article DOI  
Abstract: Studies diverge substantially on the actual magnitude of the North
American carbon budget. This is due to the lack of appropriate data and
also stems from the difficulty to properly model all the details of the
flux distribution and transport inside the region of interest. To
sidestep these difficulties, we use here a simple budgeting approach to
estimate land-atmosphere fluxes across North America by balancing the
inflow and outflow of CO2 from the troposphere. We base our study on the
unique sampling strategy of atmospheric CO2 vertical profiles over North
America from the National Oceanic and Atmospheric Administration/Earth
System Research Laboratory aircraft network, from which we infer the
three-dimensional CO2 distribution over the continent. We find a
moderate sink of 0.5 +/- 0.4 PgCy(-1) for the period 2004-2006 for the
coterminous United States, in good agreement with the
forest-inventory-based estimate of the first North American State of the
Carbon Cycle Report, and averaged climate conditions. We find that the
highest uptake occurs in the Midwest and in the Southeast. This
partitioning agrees with independent estimates of crop uptake in the
Midwest, which proves to be a significant part of the US atmospheric
sink, and of secondary forest regrowth in the Southeast. Provided that
vertical profile measurements are continued, our study offers an
independent means to link regional carbon uptake to climate drivers.
BibTeX:
@article{crevoisier10a,
  author = {Crevoisier, Cyril and Sweeney, Colm and Gloor, Manuel and Sarmiento, Jorge L. and Tans, Pieter P.},
  title = {Regional US carbon sinks from three-dimensional atmospheric CO2 sampling},
  journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA},
  year = {2010},
  volume = {107},
  number = {43},
  pages = {18348--18353},
  doi = {https://doi.org/10.1073/pnas.0900062107}
}
Crowell, S.M.R., Kawa, S.R., Browell, E.V., Hammerling, D.M., Moore, B., Schaefer, K. and Doney, S.C. On the Ability of Space-Based Passive and Active Remote Sensing Observations of CO2 to Detect Flux Perturbations to the Carbon Cycle {2018} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {123}({2}), pp. {1460-1477} 
article DOI  
Abstract: Space-borne observations of CO2 are vital to gaining understanding of
the carbon cycle in regions of the world that are difficult to measure
directly, such as the tropical terrestrial biosphere, the high northern
and southern latitudes, and in developing nations such as China.
Measurements from passive instruments such as GOSAT and OCO-2, however,
are constrained by solar zenith angle limitations as well as sensitivity
to the presence of clouds and aerosols. Active measurements such as
those in development for the Active Sensing of CO2 Emissions over
Nights, Days and Seasons (ASCENDS) mission show strong potential for
making measurements in the high-latitude winter and in cloudy regions.
In this work we examine the enhanced flux constraint provided by the
improved coverage from an active measurement such as ASCENDS. The
simulation studies presented here show that with sufficient precision,
ASCENDS will detect permafrost thaw and fossil fuel emissions shifts at
annual and seasonal time scales, even in the presence of transport
errors, representativeness errors, and biogenic flux errors. While OCO-2
can detect some of these perturbations at the annual scale, the seasonal
sampling provided by ASCENDS provides the stronger constraint.
Plain Language Summary Active and passive remote sensors show the
potential to provide unprecedented information on the carbon cycle. With
the all-season sampling, active remote sensors are more capable of
constraining high-latitude emissions. The reduced sensitivity to cloud
and aerosol also makes active sensors more capable of providing
information in cloudy and polluted scenes with sufficient accuracy.
These experiments account for errors that are fundamental to the
top-down approach for constraining emissions, and even including these
sources of error, we show that satellite remote sensors are critical for
understanding the carbon cycle.
BibTeX:
@article{crowell18a,
  author = {Crowell, Sean M. R. and Kawa, S. Randolph and Browell, Edward V. and Hammerling, Dorit M. and Moore, Berrien and Schaefer, Kevin and Doney, Scott C.},
  title = {On the Ability of Space-Based Passive and Active Remote Sensing Observations of CO2 to Detect Flux Perturbations to the Carbon Cycle},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2018},
  volume = {123},
  number = {2},
  pages = {1460-1477},
  doi = {https://doi.org/10.1002/2017JD027836}
}
Crowell, S., Baker, D., Schuh, A., Basu, S., Jacobson, A.R., Chevallier, F., Liu, J., Deng, F., Feng, L., McKain, K., Chatterjee, A., Miller, J.B., Stephens, B.B., Eldering, A., Crisp, D., Schimel, D., Nassar, R., O'Dell, C., Oda, T., Sweeney, C., Palmer, P.I. and Jones, D.B.A. The 2015-2016 carbon cycle as seen from OCO-2 and the global in situ network {2019} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {19}({15}), pp. {9797-9831} 
article DOI URL 
Abstract: The Orbiting Carbon Observatory-2 has been on orbit since 2014, and its global coverage holds the potential to reveal new information about the carbon cycle through the use of top-down atmospheric inversion methods combined with column average CO2 retrievals. We employ a large ensemble of atmospheric inversions utilizing different transport models, data assimilation techniques, and prior flux distributions in order to quantify the satellite-informed fluxes from OCO-2 Version 7r land observations and their uncertainties at continental scales. Additionally, we use in situ measurements to provide a baseline against which to compare the satellite-constrained results. We find that within the ensemble spread, in situ observations, and satellite retrievals constrain a similar global total carbon sink of 3.7 +/- 0.5 PgC yr(-1), and 1.5 +/- 0.6 PgC yr(-1) for global land, for the 2015-2016 annual mean. This agreement breaks down in smaller regions, and we discuss the differences between the experiments. Of particular interest is the difference between the different assimilation constraints in the tropics, with the largest differences occurring in tropical Africa, which could be an indication of the global perturbation from the 2015-2016 El Nino. Evaluation of posterior concentrations using TCCON and aircraft observations gives some limited insight into the quality of the different assimilation constraints, but the lack of such data in the tropics inhibits our ability to make strong conclusions there.
BibTeX:
@article{crowell19a,
  author = {Crowell, Sean and Baker, David and Schuh, Andrew and Basu, Sourish and Jacobson, Andrew R. and Chevallier, Frederic and Liu, Junjie and Deng, Feng and Feng, Liang and McKain, Kathryn and Chatterjee, Abhishek and Miller, John B. and Stephens, Britton B. and Eldering, Annmarie and Crisp, David and Schimel, David and Nassar, Ray and O'Dell, ChristopherW. and Oda, Tomohiro and Sweeney, Colm and Palmer, Paul I. and Jones, Dylan B. A.},
  title = {The 2015-2016 carbon cycle as seen from OCO-2 and the global in situ network},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {19},
  number = {15},
  pages = {9797--9831},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://acp.copernicus.org/articles/19/9797/2019/},
  doi = {https://doi.org/10.5194/acp-19-9797-2019}
}
Cui, Y.Y., Jacobson, A.R., Feng, S., Wesloh, D., Barkley, Z.R., Zhang, L., Gerken, T., Keller, K., Baker, D. and Davis, K.J. Evaluation of CarbonTracker's Inverse Estimates of North American Net Ecosystem Exchange of CO2 From Different Observing Systems Using ACT-America Airborne Observations 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(12) 
article DOI  
Abstract: Quantification of regional terrestrial carbon dioxide (CO2) fluxes is
critical to our understanding of the carbon cycle. We evaluate inverse
estimates of net ecosystem exchange (NEE) of CO2 fluxes in temperate
North America, and their sensitivity to the observational data used to
drive the inversions. Specifically, we consider the state-of-the-science
CarbonTracker global inversion system, which assimilates (a) in situ
measurements (IS), (b) the Orbiting Carbon Observatory-2 (OCO-2) v9
column CO2 (XCO2) retrievals over land (LNLG), (c) OCO-2 v9 XCO2
retrievals ocean-glint (OG), and (d) a combination of all these
observational constraints (LNLGOGIS). We use independent CO2
observations from the Atmospheric Carbon and Transport (ACT)-America
aircraft mission to evaluate the inversions. We diagnose errors in the
flux estimates using the differences between modeled and observed
biogenic CO2 mole fractions, influence functions from a Lagrangian
transport model, Bayesian inference, and root-mean-square error (RMSE)
and bias metrics. The IS fluxes have the smallest RMSE among the four
products, followed by LNLG. Both IS and LNLG outperform the OG and
LNLGOGIS inversions with regard to RMSE. Regional errors do not differ
markedly across the four sets of posterior fluxes. The CarbonTracker
inversions appear to overestimate the seasonal cycle of NEE in the
Midwest and Western Canada, and overestimate dormant season NEE across
the Central and Eastern US. The CarbonTracker inversions may
overestimate annual NEE in the Central and Eastern US. The success of
the LNLG inversion with respect to independent observations bodes well
for satellite-based inversions in regions with more limited in situ
observing networks.
BibTeX:
@article{cui21a,
  author = {Cui, Yu Yan and Jacobson, Andrew R. and Feng, Sha and Wesloh, Daniel and Barkley, Zachary R. and Zhang, Li and Gerken, Tobias and Keller, Klaus and Baker, David and Davis, Kenneth J.},
  title = {Evaluation of CarbonTracker's Inverse Estimates of North American Net Ecosystem Exchange of CO2 From Different Observing Systems Using ACT-America Airborne Observations},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {12},
  doi = {https://doi.org/10.1029/2020JD034406}
}
Cui, Y., Li, N., Fu, Y. and Chen, L. Carbon neutrality and mitigating contribution of terrestrial carbon sink on anthropogenic climate warming in China, the United States, Russia and Canada 2021 JOURNAL OF GEOGRAPHICAL SCIENCES
Vol. 31(7), pp. 925-937 
article DOI  
Abstract: Carbon dioxide (CO2) is a major climate forcing factor, closely related
to human activities. Quantifying the contribution of CO2 emissions to
the global radiative forcing (RF) is therefore important to evaluate
climate effects caused by anthropogenic and natural factors. China, the
United States (USA), Russia and Canada are the largest countries by land
area, at different levels of socio-economic development. In this study,
we used data from the CarbonTracker CO2 assimilation model (CT2017 data
set) to analyze anthropogenic CO2 emissions and terrestrial ecosystem
carbon sinks from 2000 to 2016. We derived net RF contributions and
showed that anthropogenic CO2 emissions had increased significantly from
2000 to 2016, at a rate of 0.125 PgC yr(-1). Over the same period,
carbon uptake by terrestrial ecosystems increased at a rate of 0.003 PgC
yr(-1). Anthropogenic CO2 emissions in China and USA accounted for
87.19% of the total, while Russian terrestrial ecosystems were the
largest carbon sink and absorbed 14.69 PgC. The resulting cooling effect
was -0.013 W m(-2) in 2016, representing an offset of -45.06% on
climate warming induced by anthropogenic CO2. This indicates that net
climate warming would be significantly overestimated if terrestrial
ecosystems were not included in RF budget analyses. In terms of
cumulative effects, we analyzed RFs using reference atmospheres of 1750,
at the start of the Industrial Revolution, and 2000, the initial year of
this study. Anthropogenic CO2 emissions in the study area contributed by
+ 0.42 W m(-2) and +0.32 W m(-2) to the global RF, relative to CO2
levels of 1750 and 2000, respectively. We also evaluated correlations
between global mean atmospheric temperature and net, anthropogenic and
natural RFs. We found that the combined (net) RF caused by CO2 emissions
accounted for 30.3% of global mean temperature variations in 2000-2016.
BibTeX:
@article{cui21b,
  author = {Cui, Yaoping and Li, Nan and Fu, Yiming and Chen, Liangyu},
  title = {Carbon neutrality and mitigating contribution of terrestrial carbon sink on anthropogenic climate warming in China, the United States, Russia and Canada},
  journal = {JOURNAL OF GEOGRAPHICAL SCIENCES},
  year = {2021},
  volume = {31},
  number = {7},
  pages = {925-937},
  doi = {https://doi.org/10.1007/s11442-021-1878-0}
}
Dang, X., Lai, C.-T., Hollinger, D.Y., Schauer, A.J., Xiao, J., Munger, J.W., Owensby, C. and Ehleringer, J.R. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over four flux towers in the United States {2011} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {116} 
article DOI  
Abstract: We evaluated an idealized boundary layer (BL) model with simple
parameterizations using vertical transport information from community
model outputs (NCAR/NCEP Reanalysis and ECMWF Interim Analysis) to
estimate regional-scale net CO2 fluxes from 2002 to 2007 at three forest
and one grassland flux sites in the United States. The BL modeling
approach builds on a mixed-layer model to infer monthly average net CO2
fluxes using high-precision mixing ratio measurements taken on flux
towers. We compared BL model net ecosystem exchange (NEE) with estimates
from two independent approaches. First, we compared modeled NEE with
tower eddy covariance measurements. The second approach (EC-MOD) was a
data-driven method that upscaled EC fluxes from towers to regions using
MODIS data streams. Comparisons between modeled CO2 and tower NEE fluxes
showed that modeled regional CO2 fluxes displayed interannual and
intra-annual variations similar to the tower NEE fluxes at the Rannells
Prairie and Wind River Forest sites, but model predictions were
frequently different from NEE observations at the Harvard Forest and
Howland Forest sites. At the Howland Forest site, modeled CO2 fluxes
showed a lag in the onset of growing season uptake by 2 months behind
that of tower measurements. At the Harvard Forest site, modeled CO2
fluxes agreed with the timing of growing season uptake but
underestimated the magnitude of observed NEE seasonal fluctuation. This
modeling inconsistency among sites can be partially attributed to the
likely misrepresentation of atmospheric transport and/or CO2 gradients
between ABL and the free troposphere in the idealized BL model. EC-MOD
fluxes showed that spatial heterogeneity in land use and cover very
likely explained the majority of the data-model inconsistency. We show a
site-dependent atmospheric rectifier effect that appears to have had the
largest impact on ABL CO2 inversion in the North American Great Plains.
We conclude that a systematic BL modeling approach provided new insights
when employed in multiyear, cross-site synthesis studies. These results
can be used to develop diagnostic upscaling tools, improving our
understanding of the seasonal and interannual variability of surface CO2
fluxes.
BibTeX:
@article{dang11a,
  author = {Dang, Xuerui and Lai, Chun-Ta and Hollinger, David Y. and Schauer, Andrew J. and Xiao, Jingfeng and Munger, J. William and Owensby, Clenton and Ehleringer, James R.},
  title = {Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over four flux towers in the United States},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2010JG001554}
}
Dang, Y., Ren, W., Tao, B., Chen, G., Lu, C., Yang, J., Pan, S., Wang, G., Li, S. and Tian, H. Climate and Land Use Controls on Soil Organic Carbon in the Loess Plateau Region of China {2014} PLOS ONE
Vol. {9}({5}) 
article DOI  
Abstract: The Loess Plateau of China has the highest soil erosion rate in the
world where billion tons of soil is annually washed into Yellow River.
In recent decades this region has experienced significant climate change
and policy-driven land conversion. However, it has not yet been well
investigated how these changes in climate and land use have affected
soil organic carbon (SOC) storage on the Loess Plateau. By using the
Dynamic Land Ecosystem Model (DLEM), we quantified the effects of
climate and land use on SOC storage on the Loess Plateau in the context
of multiple environmental factors during the period of 1961-2005. Our
results show that SOC storage increased by 0.27 Pg C on the Loess
Plateau as a result of multiple environmental factors during the study
period. About 55% (0.14 Pg C) of the SOC increase was caused by land
conversion from cropland to grassland/forest owing to the government
efforts to reduce soil erosion and improve the ecological conditions in
the region. Historical climate change reduced SOC by 0.05 Pg C
(approximately 19% of the total change) primarily due to a significant
climate warming and a slight reduction in precipitation. Our results
imply that the implementation of ``Grain for Green'' policy may
effectively enhance regional soil carbon storage and hence starve off
further soil erosion on the Loess Plateau.
BibTeX:
@article{dang14a,
  author = {Dang, Yaai and Ren, Wei and Tao, Bo and Chen, Guangsheng and Lu, Chaoqun and Yang, Jia and Pan, Shufen and Wang, Guodong and Li, Shiqing and Tian, Hanqin},
  title = {Climate and Land Use Controls on Soil Organic Carbon in the Loess Plateau Region of China},
  journal = {PLOS ONE},
  year = {2014},
  volume = {9},
  number = {5},
  doi = {https://doi.org/10.1371/journal.pone.0095548}
}
Davidson, G.R., Phillips-Housley, A. and Stevens, M.T. Soil-zone adsorption of atmospheric CO2 as a terrestrial carbon sink {2013} GEOCHIMICA ET COSMOCHIMICA ACTA
Vol. {106}, pp. 44-50 
article DOI  
Abstract: Identifying and quantifying sources and sinks of CO2 is integral to
developing global carbon budgets and effectively modeling climate
change. Adsorption of CO2 onto mineral and soil surfaces has generally
been regarded as an insignificant sink, though few studies have
investigated adsorption on natural materials at temperatures and CO2
concentrations relevant to atmospheric or soil zone conditions. In this
study, annual adsorption at the scale of North America was modeled for
the upper 3 m of the Earth's surface (the root zone) based on our own
and published adsorption data, and results compared with reported
estimates for the North American terrestrial carbon sink during
2000-2005. Our results suggest that adsorption can account for 1-3% of
the average annual sink during these years. At smaller regional scales
where more adsorptive deposits are present, such as volcanic ash or
high-organic soils, the sink may be significantly larger. (C) 2013
Elsevier Ltd. All rights reserved.
BibTeX:
@article{davidson13a,
  author = {Davidson, Gregg R. and Phillips-Housley, Ashley and Stevens, Maria T.},
  title = {Soil-zone adsorption of atmospheric CO2 as a terrestrial carbon sink},
  journal = {GEOCHIMICA ET COSMOCHIMICA ACTA},
  year = {2013},
  volume = {106},
  pages = {44--50},
  doi = {https://doi.org/10.1016/j.gca.2012.12.015}
}
Davis, K.J., Browell V, E., Feng, S., Lauvaux, T., Obland, M.D., Pal, S., Baier, B.C., Baker, D.F., Baker, I.T., Barkley, Z.R., Bowman, K.W., Cui, Y.Y., Denning, A.S., DiGangi, J.P., Dobler, J.T., Fried, A., Gerken, T., Keller, K., Lin, B., Nehrir, A.R., Normile, C.P., O'Dell, C.W., Ott, L.E., Roiger, A., Schuh, A.E., Sweeney, C., Wei, Y., Weir, B., Xue, M. and Williams, C.A. The Atmospheric Carbon and Transport (ACT)-America Mission 2021 BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
Vol. 102(9), pp. E1714-E1734 
article DOI  
Abstract: The Atmospheric Carbon and Transport (ACT)-America NASA Earth Venture
Suborbital Mission set out to improve regional atmospheric greenhouse
gas (GHG) inversions by exploring the intersection of the strong GHG
fluxes and vigorous atmospheric transport that occurs within the
midlatitudes. Two research aircraft instrumented with remote and in situ
sensors to measure GHG mole fractions, associated trace gases, and
atmospheric state variables collected 1,140.7 flight hours of research
data, distributed across 305 individual aircraft sorties, coordinated
within 121 research flight days, and spanning five 6-week seasonal
flight campaigns in the central and eastern United States. Flights
sampled 31 synoptic sequences, including fair-weather and frontal
conditions, at altitudes ranging from the atmospheric boundary layer to
the upper free troposphere. The observations were complemented with
global and regional GHG flux and transport model ensembles. We found
that midlatitude weather systems contain large spatial gradients in GHG
mole fractions, in patterns that were consistent as a function of season
and altitude. We attribute these patterns to a combination of regional
terrestrial fluxes and inflow from the continental boundaries. These
observations, when segregated according to altitude and air mass,
provide a variety of quantitative insights into the realism of regional
CO 2 and CH 4 fluxes and atmospheric GHG transport realizations. The
ACT-America dataset and ensemble modeling methods provide benchmarks for
the development of atmospheric inversion systems. As global and regional
atmospheric inversions incorporate ACT-America's findings and methods,
we anticipate these systems will produce increasingly accurate and
precise subcontinental GHG flux estimates.
BibTeX:
@article{davis21a,
  author = {Davis, Kenneth J. and Browell, V, Edward and Feng, Sha and Lauvaux, Thomas and Obland, Michael D. and Pal, Sandip and Baier, Bianca C. and Baker, David F. and Baker, Ian T. and Barkley, Zachary R. and Bowman, Kevin W. and Cui, Yu Yan and Denning, A. Scott and DiGangi, Joshua P. and Dobler, Jeremy T. and Fried, Alan and Gerken, Tobias and Keller, Klaus and Lin, Bing and Nehrir, Amin R. and Normile, Caroline P. and O'Dell, Christopher W. and Ott, Lesley E. and Roiger, Anke and Schuh, Andrew E. and Sweeney, Colm and Wei, Yaxing and Weir, Brad and Xue, Ming and Williams, Christopher A.},
  title = {The Atmospheric Carbon and Transport (ACT)-America Mission},
  journal = {BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY},
  year = {2021},
  volume = {102},
  number = {9},
  pages = {E1714-E1734},
  doi = {https://doi.org/10.1175/BAMS-D-20-0300.1}
}
Deng, F. and Chen, J.M. Recent global CO2 flux inferred from atmospheric CO2 observations and its regional analyses {2011} BIOGEOSCIENCES
Vol. {8}({11}), pp. 3263-3281 
article DOI  
Abstract: The net surface exchange of CO2 for the years 2002-2007 is inferred from
12 181 atmospheric CO2 concentration data with a time-dependent Bayesian
synthesis inversion scheme. Monthly CO2 fluxes are optimized for 30
regions of the North America and 20 regions for the rest of the globe.
Although there have been many previous multiyear inversion studies, the
reliability of atmospheric inversion techniques has not yet been
systematically evaluated for quantifying regional interannual
variability in the carbon cycle. In this study, the global interannual
variability of the CO2 flux is found to be dominated by terrestrial
ecosystems, particularly by tropical land, and the variations of
regional terrestrial carbon fluxes are closely related to climate
variations. These interannual variations are mostly caused by abnormal
meteorological conditions in a few months in the year or part of a
growing season and cannot be well represented using annual means,
suggesting that we should pay attention to finer temporal climate
variations in ecosystem modeling. We find that, excluding fossil fuel
and biomass burning emissions, terrestrial ecosystems and oceans absorb
an average of 3.63 +/- 0.49 and 1.94 +/- 0.41 PgC yr(-1), respectively.
The terrestrial uptake is mainly in northern land while the tropical and
southern lands contribute 0.62 +/- 0.47, and 0.67 +/- 0.34 PgC yr(-1) to
the sink, respectively. In North America, terrestrial ecosystems absorb
0.89 +/- 0.18 PgC yr(-1) on average with a strong flux density found in
the south-east of the continent.
BibTeX:
@article{deng11a,
  author = {Deng, F. and Chen, J. M.},
  title = {Recent global CO2 flux inferred from atmospheric CO2 observations and its regional analyses},
  journal = {BIOGEOSCIENCES},
  year = {2011},
  volume = {8},
  number = {11},
  pages = {3263--3281},
  doi = {https://doi.org/10.5194/bg-8-3263-2011}
}
Deng, F., Chen, J.M., Pan, Y., Peters, W., Birdsey, R., McCullough, K. and Xiao, J. The use of forest stand age information in an atmospheric CO2 inversion applied to North America {2013} BIOGEOSCIENCES
Vol. {10}({8}), pp. 5335-5348 
article DOI  
Abstract: Atmospheric inversions have become an important tool in quantifying
carbon dioxide (CO2) sinks and sources at a variety of spatiotemporal
scales, but associated large uncertainties restrain the inversion
research community from reaching agreement on many important subjects.
We enhanced an atmospheric inversion of the CO2 flux for North America
by introducing spatially explicit information on forest stand age for US
and Canada as an additional constraint, since forest carbon dynamics are
closely related to time since disturbance. To use stand age information
in the inversion, we converted stand age into an age factor, and
included the covariances between subcontinental regions in the inversion
based on the similarity of the age factors. Our inversion results show
that, considering age factors, regions with recently disturbed or old
forests are often nudged towards carbon sources, while regions with
middle-aged productive forests are shifted towards sinks. This conforms
to stand age effects observed in flux networks. At the subcontinental
level, our inverted carbon fluxes agree well with continuous estimates
of net ecosystem carbon exchange (NEE) upscaled from eddy covariance
flux data based on MODIS data. Inverted fluxes with the age constraint
exhibit stronger correlation to these upscaled NEE estimates than those
inverted without the age constraint. While the carbon flux at the
continental and subcontinental scales is predominantly determined by
atmospheric CO2 observations, the age constraint is shown to have
potential to improve the inversion of the carbon flux distribution among
subcontinental regions, especially for regions lacking atmospheric CO2
observations.
BibTeX:
@article{deng13a,
  author = {Deng, F. and Chen, J. M. and Pan, Y. and Peters, W. and Birdsey, R. and McCullough, K. and Xiao, J.},
  title = {The use of forest stand age information in an atmospheric CO2 inversion applied to North America},
  journal = {BIOGEOSCIENCES},
  year = {2013},
  volume = {10},
  number = {8},
  pages = {5335--5348},
  doi = {https://doi.org/10.5194/bg-10-5335-2013}
}
Deng, F., Jones, D.B.A., Henze, D.K., Bousserez, N., Bowman, K.W., Fisher, J.B., Nassar, R., O'Dell, C., Wunch, D., Wennberg, P.O., Kort, E.A., Wofsy, S.C., Blumenstock, T., Deutscher, N.M., Griffith, D.W.T., Hase, F., Heikkinen, P., Sherlock, V., Strong, K., Sussmann, R. and Warneke, T. Inferring regional sources and sinks of atmospheric CO2 from GOSAT XCO2 data {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({7}), pp. 3703-3727 
article DOI  
Abstract: We have examined the utility of retrieved column-averaged, dry-air mole
fractions of CO2 (XCO2) from the Greenhouse Gases Observing Satellite
(GOSAT) for quantifying monthly, regional flux estimates of CO2, using
the GEOS-Chem four-dimensional variational (4D-Var) data assimilation
system. We focused on assessing the potential impact of biases in the
GOSAT CO2 data on the regional flux estimates. Using different screening
and bias correction approaches, we selected three different subsets of
the GOSAT XCO2 data for the 4D-Var inversion analyses, and found that
the inferred global fluxes were consistent across the three XCO2
inversions. However, the GOSAT observational coverage was a challenge
for the regional flux estimates. In the northern extratropics, the
inversions were more sensitive to North American fluxes than to European
and Asian fluxes due to the lack of observations over Eurasia in winter
and over eastern and southern Asia in summer. The regional flux
estimates were also sensitive to the treatment of the residual bias in
the GOSAT XCO2 data. The largest differences obtained were for temperate
North America and temperate South America, for which the largest spread
between the inversions was 1.02 and 0.96 Pg C, respectively. In the case
of temperate North America, one inversion suggested a strong source,
whereas the second and third XCO2 inversions produced a weak and strong
sink, respectively. Despite the discrepancies in the regional flux
estimates between the three XCO2 inversions, the a posteriori CO2
distributions were in good agreement (with a mean difference between the
three inversions of typically less than 0.5 ppm) with independent data
from the Total Carbon Column Observing Network (TCCON), the surface
flask network, and from the HIAPER Pole-to-Pole Observations (HIPPO)
aircraft campaign. The discrepancy in the regional flux estimates from
the different inversions, despite the agreement of the global flux
estimates suggests the need for additional work to determine the minimum
spatial scales at which we can reliably quantify the fluxes using GOSAT
XCO2. The fact that the a posteriori CO2 from the different inversions
were in good agreement with the independent data although the regional
flux estimates differed significantly, suggests that innovative ways of
exploiting existing data sets, and possibly additional observations, are
needed to better evaluate the inferred regional flux estimates.
BibTeX:
@article{deng14a,
  author = {Deng, F. and Jones, D. B. A. and Henze, D. K. and Bousserez, N. and Bowman, K. W. and Fisher, J. B. and Nassar, R. and O'Dell, C. and Wunch, D. and Wennberg, P. O. and Kort, E. A. and Wofsy, S. C. and Blumenstock, T. and Deutscher, N. M. and Griffith, D. W. T. and Hase, F. and Heikkinen, P. and Sherlock, V. and Strong, K. and Sussmann, R. and Warneke, T.},
  title = {Inferring regional sources and sinks of atmospheric CO2 from GOSAT XCO2 data},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {7},
  pages = {3703--3727},
  doi = {https://doi.org/10.5194/acp-14-3703-2014}
}
Deng, F., Jones, D.B.A., O'Dell, C.W., Nassar, R. and Parazoo, N.C. Combining GOSAT XCO2 observations over land and ocean to improve regional CO2 flux estimates {2016} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {121}({4}), pp. 1896-1913 
article DOI  
Abstract: We used the GEOS-Chem data assimilation system to examine the impact of
combining Greenhouse Gases Observing Satellite (GOSAT) XCO2 data over
land and ocean on regional CO2 flux estimates for 2010-2012. We found
that compared to assimilating only land data, combining land and ocean
data produced an a posteriori CO2 distribution that is in better
agreement with independent data and fluxes that are in closer agreement
with existing top-down and bottom-up estimates. Adding XCO2 data over
oceans changed the tropical land regions from a source of 0.64PgC/yr to
a sink of -0.60PgC/yr and produced a corresponding reduction in the
estimated sink in northern and southern land regions by 0.49PgC/yr and
0.80PgC/yr, respectively. This highlights the importance of improved
observational coverage in the tropics to better quantify the latitudinal
distribution of the terrestrial fluxes. Based only on land XCO2 data, we
estimated a strong source in northern tropical South America, which
experienced wet conditions in 2010-2012. In contrast, with the land and
ocean data, we estimated a sink for this wet region in the north, and a
source for the seasonally dry regions in the south and east, which is
consistent with our understanding of the impact of moisture availability
on the carbon balance of the region. Our results suggest that using
satellite data with a more zonally balanced observational coverage could
help mitigate discrepancies in CO2 flux estimates; further improvement
could be expected with the greater observational coverage provided by
the Orbiting Carbon Observatory-2.
BibTeX:
@article{deng16a,
  author = {Deng, Feng and Jones, Dylan B. A. and O'Dell, Christopher W. and Nassar, Ray and Parazoo, Nicholas C.},
  title = {Combining GOSAT XCO2 observations over land and ocean to improve regional CO2 flux estimates},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2016},
  volume = {121},
  number = {4},
  pages = {1896--1913},
  doi = {https://doi.org/10.1002/2015JD024157}
}
Deng, A., Lauvaux, T., Davis, K.J., Gaudet, B.J., Miles, N., Richardson, S.J., Wu, K., Sarmiento, D.P., Hardesty, R.M. and Bonin, T.A. Toward reduced transport errors in a high resolution urban CO2 inversion system 2017 Elem Sci Anth  article DOI  
BibTeX:
@article{deng17a,
  author = {Deng, Aijun and Lauvaux, Thomas and Davis, Kenneth J and Gaudet, Brian J and Miles, Natasha and Richardson, Scott J and Wu, Kai and Sarmiento, Daniel P and Hardesty, R Michael and Bonin, Timothy A},
  title = {Toward reduced transport errors in a high resolution urban CO2 inversion system},
  journal = {Elem Sci Anth},
  year = {2017},
  doi = {https://doi.org/10.1525/elementa.133/}
}
Deng, Z., Ciais, P., Tzompa-Sosa, Z.A., Saunois, M., Qiu, C., Tan, C., Sun, T., Ke, P., Cui, Y., Tanaka, K., Lin, X., Thompson, R.L., Tian, H., Yao, Y., Huang, Y., Lauerwald, R., Jain, A.K., Xu, X., Bastos, A., Sitch, S., Palmer, P.I., Lauvaux, T., d'Aspremont , A., Giron, C., Benoit, A., Poulter, B., Chang, J., Petrescu, A.M.R., Davis, S.J., Liu, Z., Grassi, G., Albergel, C., Tubiello, F.N., Perugini, L., Peters, W. and Chevallier, F. Comparing national greenhouse gas budgets reported in UNFCCC inventories against atmospheric inversions 2022 EARTH SYSTEM SCIENCE DATA
Vol. 14(4), pp. 1639-1675 
article DOI  
Abstract: In support of the global stocktake of the Paris Agreement on climate
change, this study presents a comprehensive framework to process the
results of an ensemble of atmospheric inversions in order to make their
net ecosystem exchange (NEE) carbon dioxide (CO2) flux suitable for
evaluating national greenhouse gas inventories (NGHGIs) submitted by
countries to the United Nations Framework Convention on Climate Change
(UNFCCC). From inversions we also deduced anthropogenic methane (CH4)
emissions regrouped into fossil and agriculture and waste emissions, as
well as anthropogenic nitrous oxide (N2O) emissions. To compare
inversion results with national reports, we compiled a new global
harmonized database of emissions and removals from periodical UNFCCC
inventories by Annex I countries, and from sporadic and less detailed
emissions reports by non-Annex I countries, given by national
communications and biennial update reports. No gap filling was applied.
The method to reconcile inversions with inventories is applied to
selected large countries covering similar to 90% of the global land
carbon uptake for CO2 and top emitters of CH4 and N2O. Our method uses
results from an ensemble of global inversions produced by the Global
Carbon Project for the three greenhouse gases, with ancillary data. We
examine the role of CO2 fluxes caused by lateral transfer processes from
rivers and from trade in crop and wood products and the role of carbon
uptake in unmanaged lands, both not accounted for by NGHGIs. Here we
show that, despite a large spread across the inversions, the median of
available inversion models points to a larger terrestrial carbon sink
than inventories over temperate countries or groups of countries of the
Northern Hemisphere like Russia, Canada and the European Union. For CH4,
we find good consistency between the inversions assimilating only data
from the global in situ network and those using satellite CH4 retrievals
and a tendency for inversions to diagnose higher CH4 emission estimates
than reported by NGHGIs. In particular, oil- and gas-extracting
countries in central Asia and the Persian Gulf region tend to
systematically report lower emissions compared to those estimated by
inversions. For N2O, inversions tend to produce higher anthropogenic
emissions than inventories for tropical countries, even when attempting
to consider only managed land emissions. In the inventories of many
non-Annex I countries, this can be tentatively attributed to a lack of
reporting indirect N2O emissions from atmospheric deposition and from
leaching to rivers, to the existence of natural sources intertwined with
managed lands, or to an underestimation of N2O emission factors for
direct agricultural soil emissions. Inversions provide insights into
seasonal and interannual greenhouse gas fluxes anomalies, e.g., during
extreme events such as drought or abnormal fire episodes, whereas
inventory methods are established to estimate trends and multi-annual
changes. As a much denser sampling of atmospheric CO2 and CH4
concentrations by different satellites coordinated into a global
constellation is expected in the coming years, the methodology proposed
here to compare inversion results with inventory reports (e.g., NGHGIs)
could be applied regularly for monitoring the effectiveness of
mitigation policy and progress by countries to meet the objective of
their pledges.
The dataset constructed by this study is publicly available at
https://doi.org/10.5281/zenodo.5089799 (Deng et al., 2021).
BibTeX:
@article{deng22a,
  author = {Deng, Zhu and Ciais, Philippe and Tzompa-Sosa, Zitely A. and Saunois, Marielle and Qiu, Chunjing and Tan, Chang and Sun, Taochun and Ke, Piyu and Cui, Yanan and Tanaka, Katsumasa and Lin, Xin and Thompson, Rona L. and Tian, Hanqin and Yao, Yuanzhi and Huang, Yuanyuan and Lauerwald, Ronny and Jain, Atul K. and Xu, Xiaoming and Bastos, Ana and Sitch, Stephen and Palmer, Paul I. and Lauvaux, Thomas and d'Aspremont, Alexandre and Giron, Clement and Benoit, Antoine and Poulter, Benjamin and Chang, Jinfeng and Petrescu, Ana Maria Roxana and Davis, Steven J. and Liu, Zhu and Grassi, Giacomo and Albergel, Clement and Tubiello, Francesco N. and Perugini, Lucia and Peters, Wouter and Chevallier, Frederic},
  title = {Comparing national greenhouse gas budgets reported in UNFCCC inventories against atmospheric inversions},
  journal = {EARTH SYSTEM SCIENCE DATA},
  year = {2022},
  volume = {14},
  number = {4},
  pages = {1639-1675},
  doi = {https://doi.org/10.5194/essd-14-1639-2022}
}
Desai, A.R., Helliker, B.R., Moorcroft, P.R., Andrews, A.E. and Berry, J.A. Climatic controls of interannual variability in regional carbon fluxes from top-down and bottom-up perspectives {2010} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {115} 
article DOI  
Abstract: Observations of regional net ecosystem exchange (NEE) of CO(2) for
1997-2007 were analyzed for climatic controls on interannual variability
(IAV). Quantifying IAV of regional (10(4)-10(6) km(2)) NEE over long
time periods is key to understanding potential feedbacks between climate
and the carbon cycle. Four independent techniques estimated monthly
regional NEE for 10(4) km(2) in a spatially heterogeneous
temperate-boreal transition region of the north central United States,
centered on the Park Falls, Wisconsin, United States, National Oceanic
and Atmospheric Administration tall tower site. These techniques
included two bottom-up methods, based on flux tower upscaling and forest
inventory based demographic modeling, respectively, and two top-down
methods, based on tall tower equilibrium boundary layer budgets and
tracer-transport inversion, respectively. While all four methods
revealed a moderate carbon sink, they diverged significantly in
magnitude. Coherence of relative magnitude and variability of NEE
anomalies was strong across the methods. The strongest coherence was a
trend of declining carbon sink since 2002. Most climatic controls were
not strongly correlated with IAV. Significant controls on IAV were those
related to hydrology, such as water table depth, and atmospheric CO(2).
Weaker relationships were found with phenological controls such as
autumn soil temperature. Hydrologic relationships were strongest with a
1 year lag, potentially highlighting a previously unrecognized predictor
of IAV in this region. These results highlight a need for continued
development of techniques to estimate regional IAV and incorporation of
hydrologic cycling into couple carbon-climate models.
BibTeX:
@article{desai10a,
  author = {Desai, Ankur R. and Helliker, Brent R. and Moorcroft, Paul R. and Andrews, Arlyn E. and Berry, Joseph A.},
  title = {Climatic controls of interannual variability in regional carbon fluxes from top-down and bottom-up perspectives},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2010},
  volume = {115},
  doi = {https://doi.org/10.1029/2009JG001122}
}
Desai, A.R., Moore, D.J.P., Ahue, W.K.M., Wilkes, P.T.V., De Wekker, S.F.J., Brooks, B.G., Campos, T.L., Stephens, B.B., Monson, R.K., Burns, S.P., Quaife, T., Aulenbach, S.M. and Schimel, D.S. Seasonal pattern of regional carbon balance in the central Rocky Mountains from surface and airborne measurements {2011} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {116} 
article DOI  
Abstract: High-elevation forests represent a large fraction of potential carbon
uptake in North America, but this uptake is not well constrained by
observations. Additionally, forests in the Rocky Mountains have recently
been severely damaged by drought, fire, and insect outbreaks, which have
been quantified at local scales but not assessed in terms of carbon
uptake at regional scales. The Airborne Carbon in the Mountains
Experiment was carried out in 2007 partly to assess carbon uptake in
western U. S. mountain ecosystems. The magnitude and seasonal change of
carbon uptake were quantified by (1) paired upwind-downwind airborne CO2
observations applied in a boundary layer budget, (2) a spatially
explicit ecosystem model constrained using remote sensing and flux tower
observations, and (3) a downscaled global tracer transport inversion.
Top-down approaches had mean carbon uptake equivalent to flux tower
observations at a subalpine forest, while the ecosystem model showed
less. The techniques disagreed on temporal evolution. Regional carbon
uptake was greatest in the early summer immediately following snowmelt
and tended to lessen as the region experienced dry summer conditions.
This reduction was more pronounced in the airborne budget and inversion
than in flux tower or upscaling, possibly related to lower snow water
availability in forests sampled by the aircraft, which were lower in
elevation than the tower site. Changes in vegetative greenness
associated with insect outbreaks were detected using satellite
reflectance observations, but impacts on regional carbon cycling were
unclear, highlighting the need to better quantify this emerging
disturbance effect on montane forest carbon cycling.
BibTeX:
@article{desai11a,
  author = {Desai, Ankur R. and Moore, David J. P. and Ahue, William K. M. and Wilkes, Phillip T. V. and De Wekker, Stephan F. J. and Brooks, Bjorn G. and Campos, Teresa L. and Stephens, Britton B. and Monson, Russell K. and Burns, Sean P. and Quaife, Tristan and Aulenbach, Steven M. and Schimel, David S.},
  title = {Seasonal pattern of regional carbon balance in the central Rocky Mountains from surface and airborne measurements},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2011JG001655}
}
Deutscher, N.M., Sherlock, V., Fletcher, S.E.M., Griffith, D.W.T., Notholt, J., Macatangay, R., Connor, B.J., Robinson, J., Shiona, H., Velazco, V.A., Wang, Y., Wennberg, P.O. and Wunch, D. Drivers of column-average CO2 variability at Southern Hemispheric Total Carbon Column Observing Network sites {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({18}), pp. 9883-9901 
article DOI  
Abstract: We investigate factors that drive the variability in total column CO2 at
the Total Carbon Column Observing Network sites in the Southern
Hemisphere using fluxes tagged by process and by source region from the
Carbon-Tracker analysed product as well as the Simple Biosphere model.
We show that the terrestrial biosphere is the largest driver of
variability in the Southern Hemisphere column CO2. However, it does not
dominate in the same fashion as in the Northern Hemisphere. Local-and
hemispheric-scale biomass burning can also play an important role,
particularly at the tropical site, Darwin. The magnitude of seasonal
variability in the column-average dry-air mole fraction of CO2, XCO2, is
also much smaller in the Southern Hemisphere and comparable in magnitude
to the annual increase. Comparison of measurements to the model
simulations highlights that there is some discrepancy between the two
time series, especially in the early part of the Darwin data record. We
show that this mismatch is most likely due to erroneously estimated
local fluxes in the Australian tropical region, which are associated
with enhanced photosynthesis caused by early rainfall during the
tropical monsoon season.
BibTeX:
@article{deutscher14a,
  author = {Deutscher, N. M. and Sherlock, V. and Fletcher, S. E. Mikaloff and Griffith, D. W. T. and Notholt, J. and Macatangay, R. and Connor, B. J. and Robinson, J. and Shiona, H. and Velazco, V. A. and Wang, Y. and Wennberg, P. O. and Wunch, D.},
  title = {Drivers of column-average CO2 variability at Southern Hemispheric Total Carbon Column Observing Network sites},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {18},
  pages = {9883--9901},
  doi = {https://doi.org/10.5194/acp-14-9883-2014}
}
Diallo, M., Legras, B., Ray, E., Engel, A. and Anel, J.A. Global distribution of CO2 in the upper troposphere and stratosphere {2017} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {17}({6}), pp. 3861-3878 
article DOI  
Abstract: In this study, we construct a new monthly zonal mean carbon dioxide
(CO2) distribution from the upper troposphere to the stratosphere over
the 2000-2010 time period. This reconstructed CO2 product is based on a
Lagrangian backward trajectory model driven by ERA-Interim reanalysis
meteorology and tropospheric CO2 measurements. Comparisons of our CO2
product to extratropical in situ measurements from aircraft transects
and balloon profiles show remarkably good agreement. The main features
of the CO2 distribution include (1) relatively large mixing ratios in
the tropical stratosphere; (2) seasonal variability in the extratropics,
with relatively high mixing ratios in the summer and autumn hemisphere
in the 15-20 km altitude layer; and (3) decreasing mixing ratios with
increasing altitude from the upper troposphere to the middle
stratosphere (similar to 35 km). These features are consistent with
expected variability due to the transport of long-lived trace gases by
the stratospheric Brewer-Dobson circulation. The method used here to
construct this CO2 product is unique from other modelling efforts and
should be useful for model and satellite validation in the upper
troposphere and stratosphere as a prior for inversion modelling and to
analyse features of stratosphere-troposphere exchange as well as the
stratospheric circulation and its variability.
BibTeX:
@article{diallo17a,
  author = {Diallo, Mohamadou and Legras, Bernard and Ray, Eric and Engel, Andreas and Anel, Juan A.},
  title = {Global distribution of CO2 in the upper troposphere and stratosphere},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2017},
  volume = {17},
  number = {6},
  pages = {3861--3878},
  doi = {https://doi.org/10.5194/acp-17-3861-2017}
}
D\iaz-Isaac, L.I., Lauvaux, T. and Davis, K.J. Impact of physical parameterizations and initial conditions on simulated atmospheric transport and CO2 mole fractions in the US Midwest 2018 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 18, pp. 14813 
article URL 
BibTeX:
@article{diaz-isaac18a,
  author = {Liza I. D\iaz-Isaac and Thomas Lauvaux and Kenneth J. Davis},
  title = {Impact of physical parameterizations and initial conditions on simulated atmospheric transport and CO2 mole fractions in the US Midwest},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2018},
  volume = {18},
  pages = {14813},
  url = {https://www.atmos-chem-phys.net/18/14813/2018/acp-18-14813-2018.pdf}
}
Diaz-Isaac, L.I., Lauvaux, T., Bocquet, M. and Davis, K.J. Calibration of a multi-physics ensemble for estimating the uncertainty of a greenhouse gas atmospheric transport model {2019} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {19}({8}), pp. {5695-5718} 
article DOI URL 
Abstract: Atmospheric inversions have been used to assess biosphere-atmosphere CO2 surface exchanges at various scales, but variability among inverse flux estimates remains significant, especially at continental scales. Atmospheric transport errors are one of the main contributors to this variability. To characterize transport errors and their spatiotemporal structures, we present an objective method to generate a calibrated ensemble adjusted with meteorological measurements collected across a region, here the upper US Midwest in midsummer. Using multiple model configurations of the Weather Research and Forecasting (WRF) model, we show that a reduced number of simulations (less than 10 members) reproduces the transport error characteristics of a 45-member ensemble while minimizing the size of the ensemble. The large ensemble of 45 members was constructed using different physics parameterization (i.e., land surface models (LSMs), planetary boundary layer (PBL) schemes, cumulus parameterizations and microphysics parameterizations) and meteorological initial/boundary conditions. All the different models were coupled to CO2 fluxes and lateral boundary conditions from CarbonTracker to simulate CO2 mole fractions. Observed meteorological variables critical to inverse flux estimates, PBL wind speed, PBL wind direction and PBL height are used to calibrate our ensemble over the region. Two optimization techniques (i.e., simulated annealing and a genetic algorithm) are used for the selection of the optimal ensemble using the flatness of the rank histograms as the main criterion. We also choose model configurations that minimize the systematic errors (i.e., monthly biases) in the ensemble. We evaluate the impact of transport errors on atmospheric CO2 mole fraction to represent up to 40% of the model-data mismatch (fraction of the total variance). We conclude that a carefully chosen subset of the physics ensemble can represent the uncertainties in the full ensemble, and that transport ensembles calibrated with relevant meteorological variables provide a promising path forward for improving the treatment of transport uncertainties in atmospheric inverse flux estimates.
BibTeX:
@article{diaz-isaac19a,
  author = {Diaz-Isaac, Liza I. and Lauvaux, Thomas and Bocquet, Marc and Davis, Kenneth J.},
  title = {Calibration of a multi-physics ensemble for estimating the uncertainty of a greenhouse gas atmospheric transport model},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {19},
  number = {8},
  pages = {5695--5718},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://acp.copernicus.org/articles/19/5695/2019/},
  doi = {https://doi.org/10.5194/acp-19-5695-2019}
}
DiGangi, J.P., Choi, Y., Nowak, J.B., Halliday, H.S., Diskin, G.S., Feng, S., Barkley, Z.R., Lauvaux, T., Pal, S., Davis, K.J., Baier, B.C. and Sweeney, C. Seasonal Variability in Local Carbon Dioxide Biomass Burning Sources Over Central and Eastern US Using Airborne In Situ Enhancement Ratios 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(24) 
article DOI  
Abstract: We present observations of local enhancements in carbon dioxide (CO2)
from local emissions sources over three eastern US regions during four
deployments of the Atmospheric Carbon Transport-America (ACT-America)
campaign between summer 2016 and spring 2018. Local CO2 emissions were
characterized by carbon monoxide (CO) to CO2 enhancement ratios (i.e.,
Delta CO/Delta CO2) in air mass mixing observed during aircraft
transects within the planetary boundary layer. By analyzing
regional-scale variability of CO2 enhancements as a function of Delta
CO/Delta CO2 enhancement ratios, observed relative contributions to CO2
emissions were separated into fossil fuel and biomass burning (BB)
regimes across regions and seasons. CO2 emission contributions
attributed to biomass burning (Delta CO/Delta CO2 > 4%) were negligible
during summer and fall in all regions but climbed to similar to 9%-11%
of observed combustion contributions in the South during winter and
spring. Relative CO2 fire emission trends matched observed winter and
spring BB contributions, but conflictingly predicted similar levels of
BB during the fall. Satellite fire data from MODIS and VIIRS suggested
the use of higher spatial resolution fire data that might improve
modeled BB emissions but were not able to explain the bulk of the
discrepancy.
BibTeX:
@article{digangi21a,
  author = {DiGangi, Joshua P. and Choi, Yonghoon and Nowak, John B. and Halliday, Hannah S. and Diskin, Glenn S. and Feng, Sha and Barkley, Zachary R. and Lauvaux, Thomas and Pal, Sandip and Davis, Kenneth J. and Baier, Bianca C. and Sweeney, Colm},
  title = {Seasonal Variability in Local Carbon Dioxide Biomass Burning Sources Over Central and Eastern US Using Airborne In Situ Enhancement Ratios},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {24},
  doi = {https://doi.org/10.1029/2020JD034525}
}
Dils, B., Buchwitz, M., Reuter, M., Schneising, O., Boesch, H., Parker, R., Guerlet, S., Aben, I., Blumenstock, T., Burrows, J.P., Butz, A., Deutscher, N.M., Frankenberg, C., Hase, F., Hasekamp, O.P., Heymann, J., De Maziere, M., Notholt, J., Sussmann, R., Warneke, T., Griffith, D., Sherlock, V. and Wunch, D. The Greenhouse Gas Climate Change Initiative (GHG-CCI): comparative validation of GHG-CCI SCIAMACHY/ENVISAT and TANSO-FTS/GOSAT CO2 and CH4 retrieval algorithm products with measurements from the TCCON {2014} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {7}({6}), pp. 1723-1744 
article DOI  
Abstract: Column-averaged dry-air mole fractions of carbon dioxide and methane
have been retrieved from spectra acquired by the TANSO-FTS (Thermal And
Near-infrared Sensor for carbon Observations-Fourier Transform
Spectrometer) and SCIAMACHY (Scanning Imaging Absorption Spectrometer
for Atmospheric Cartography) instruments on board GOSAT (Greenhouse
gases Observing SATellite) and ENVISAT (ENVIronmental SATellite),
respectively, using a range of European retrieval algorithms. These
retrievals have been compared with data from ground-based
high-resolution Fourier transform spectrometers (FTSs) from the Total
Carbon Column Observing Network (TCCON). The participating algorithms
are the weighting function modified differential optical absorption
spectroscopy (DOAS) algorithm (WFMD, University of Bremen), the Bremen
optimal estimation DOAS algorithm (BESD, University of Bremen), the
iterative maximum a posteriori DOAS (IMAP, Jet Propulsion Laboratory
(JPL) and Netherlands Institute for Space Research algorithm (SRON)),
the proxy and full-physics versions of SRON's RemoTeC algorithm (SRPR
and SRFP, respectively) and the proxy and full-physics versions of the
University of Leicester's adaptation of the OCO (Orbiting Carbon
Observatory) algorithm (OCPR and OCFP, respectively). The goal of this
algorithm inter-comparison was to identify strengths and weaknesses of
the various so-called round-robin data sets generated with the various
algorithms so as to determine which of the competing algorithms would
proceed to the next round of the European Space Agency's (ESA)
Greenhouse Gas Climate Change Initiative (GHG-CCI) project, which is the
generation of the so-called Climate Research Data Package (CRDP), which
is the first version of the Essential Climate Variable (ECV)
``greenhouse gases'' (GHGs).
For XCO2, all algorithms reach the precision requirements for inverse
modelling (< 8 ppm), with only WFMD having a lower precision (4.7 ppm)
than the other algorithm products (2.4-2.5 ppm). When looking at the
seasonal relative accuracy (SRA, variability of the bias in space and
time), none of the algorithms have reached the demanding < 0.5 ppm
threshold.
For XCH4, the precision for both SCIAMACHY products (50.2 ppb for IMAP
and 76.4 ppb for WFMD) fails to meet the < 34 ppb threshold for inverse
modelling, but note that this work focusses on the period after the 2005
SCIAMACHY detector degradation. The GOSAT XCH4 precision ranges between
18.1 and 14.0 ppb. Looking at the SRA, all GOSAT algorithm products
reach the < 10 ppm threshold (values ranging between 5.4 and 6.2 ppb).
For SCIAMACHY, IMAP and WFMD have a SRA of 17.2 and 10.5 ppb,
respectively.
BibTeX:
@article{dils14a,
  author = {Dils, B. and Buchwitz, M. and Reuter, M. and Schneising, O. and Boesch, H. and Parker, R. and Guerlet, S. and Aben, I. and Blumenstock, T. and Burrows, J. P. and Butz, A. and Deutscher, N. M. and Frankenberg, C. and Hase, F. and Hasekamp, O. P. and Heymann, J. and De Maziere, M. and Notholt, J. and Sussmann, R. and Warneke, T. and Griffith, D. and Sherlock, V. and Wunch, D.},
  title = {The Greenhouse Gas Climate Change Initiative (GHG-CCI): comparative validation of GHG-CCI SCIAMACHY/ENVISAT and TANSO-FTS/GOSAT CO2 and CH4 retrieval algorithm products with measurements from the TCCON},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2014},
  volume = {7},
  number = {6},
  pages = {1723--1744},
  doi = {https://doi.org/10.5194/amt-7-1723-2014}
}
Doherty, S.J., Bojinski, S., Henderson-Sellers, A., Noone, K., Goodrich, D., Bindoff, N.L., Church, J.A., Hibbard, K.A., Karl, T.R., Kajefez-Bogataj, L., Lynch, A.H., Parker, D.E., Prentice, I.C., Ramaswamy, V., Saunders, R.W., Smith, M.S., Steffen, K., Stocker, T.F., Thorne, P.W., Trenberth, K.E., Verstraete, M.M. and Zwiers, F.W. LESSONS LEARNED FROM IPCC AR4 Scientific Developments Needed To Understand, Predict, And Respond To Climate Change {2009} BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
Vol. {90}({4}), pp. 497-513 
article DOI  
Abstract: The Fourth Assessment Report (AR4) of the Intergovernmental Panel on
Climate Change (IPCC) concluded that global warming is ``unequivocal''
and that most of the observed increase since the mid-twentieth century
is very likely due to the increase in anthropogenic greenhouse gas
concentrations, with discernible human influences on ocean warming,
continental-average temperatures, temperature extremes, wind patterns,
and other physical and biological indicators, impacting both
socioeconomic and ecological systems. It is now clear that we are
committed to some level of global climate change, and it is imperative
that this be considered when planning future climate research and
observational strategies. The Global Climate Observing System program
(GCOS), the World Climate Research Programme (WCRP), and the
International Geosphere-Biosphere Programme (IGBP) therefore initiated a
process to summarize the lessons learned through AR4 Working Groups I
and II and to identify a set of high-priority modeling and observational
needs. Two classes of recommendations emerged. First is the need to
improve climate models, observational and climate monitoring systems,
and our understanding of key processes. Second, the framework for
climate research and observations must be extended to document impacts
and to guide adaptation and mitigation efforts. Research and
observational strategies specifically aimed at improving our ability to
predict and understand impacts, adaptive capacity, and societal and
ecosystem vulnerabilities will serve both purposes and are the subject
of the specific recommendations made in this paper.
BibTeX:
@article{doherty09a,
  author = {Doherty, Sarah J. and Bojinski, Stephan and Henderson-Sellers, Ann and Noone, Kevin and Goodrich, David and Bindoff, Nathaniel L. and Church, John A. and Hibbard, Kathy A. and Karl, Thomas R. and Kajefez-Bogataj, Lucka and Lynch, Amanda H. and Parker, David E. and Prentice, I. Colin and Ramaswamy, Venkatachalam and Saunders, Roger W. and Smith, Mark Stafford and Steffen, Konrad and Stocker, Thomas F. and Thorne, Peter W. and Trenberth, Kevin E. and Verstraete, Michel M. and Zwiers, Francis W.},
  title = {LESSONS LEARNED FROM IPCC AR4 Scientific Developments Needed To Understand, Predict, And Respond To Climate Change},
  journal = {BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY},
  year = {2009},
  volume = {90},
  number = {4},
  pages = {497--513},
  doi = {https://doi.org/10.1175/2008BAMS2643.1}
}
Dolman, A.J., Gerbig, C., Noilhan, J., Sarrat, C. and Miglietta, F. Detecting regional variability in sources and sinks of carbon dioxide: a synthesis {2009} BIOGEOSCIENCES
Vol. {6}({6}), pp. 1015-1026 
article DOI  
Abstract: The current paper reviews the experimental setup of the CarboEurope
Experimental Strategy (CERES) campaigns with the aim of providing an
overview of the instrumentation used, the data-set and associated
modelling. It then assesses progress in the field of regional
observation and modelling of carbon fluxes, bringing the papers of this
special issue into a somewhat broader context of analysis.
Instrumental progress has been obtained in the field of remotely
monitoring from tall towers and the experimental planning. Flux
measurements from aircraft are now capable, within some constraints, to
provide regular regional observations of fluxes of CO(2), latent and
sensible heat.
Considerable effort still needs to be put into calibrating the surface
schemes of models, as they have direct impact on the input of energy,
moisture and carbon fluxes in the boundary layer. Overall, the mesoscale
models appear to be capable of simulating the large scale dynamics of
the region, but in the fine detail, like the precise horizontal and
vertical CO(2) field differences between the models still exist. These
errors translate directly into transport uncertainty, when the forward
simulations are used in inverse mode. Quantification of this
uncertainty, including that of inadequate boundary layer height
modelling, still remains a major challenge for state of the art
mesoscale models. Progress in inverse models has been slow, but has
shown that it is possible to estimate some of the errors involved, and
that using the combination of observations. Overall, the capability to
produce regional, high-resolution estimates of carbon exchange, exist in
potential, but the routine application will require considerable effort,
both in the experimental as in the modelling domain.
BibTeX:
@article{dolman09a,
  author = {Dolman, A. J. and Gerbig, C. and Noilhan, J. and Sarrat, C. and Miglietta, F.},
  title = {Detecting regional variability in sources and sinks of carbon dioxide: a synthesis},
  journal = {BIOGEOSCIENCES},
  year = {2009},
  volume = {6},
  number = {6},
  pages = {1015--1026},
  doi = {https://doi.org/10.5194/bg-6-1015-2009}
}
Dolman, A.J., van der Werf, G.R., van der Molen, M.K., Ganssen, G., Erisman, J.W. and Strengers, B. A Carbon Cycle Science Update Since IPCC AR-4 {2010} AMBIO
Vol. {39}({5-6}), pp. 402-412 
article DOI  
Abstract: We review important advances in our understanding of the global carbon
cycle since the publication of the IPCC AR4. We conclude that: the
anthropogenic emissions of CO2 due to fossil fuel burning have increased
up through 2008 at a rate near to the high end of the IPCC emission
scenarios; there are contradictory analyses whether an increase in
atmospheric fraction, that might indicate a declining sink strength of
ocean and/or land, exists; methane emissions are increasing, possibly
through enhanced natural emission from northern wetland, methane
emissions from dry plants are negligible; old-growth forest take up more
carbon than expected from ecological equilibrium reasoning; tropical
forest also take up more carbon than previously thought, however, for
the global budget to balance, this would imply a smaller uptake in the
northern forest; the exchange fluxes between the atmosphere and ocean
are increasingly better understood and bottom up and observation-based
top down estimates are getting closer to each other; the North Atlantic
and Southern ocean take up less CO2, but it is unclear whether this is
part of the `natural' decadal scale variability; large-scale fires and
droughts, for instance in Amazonia, but also at Northern latitudes, have
lead to significant decreases in carbon uptake on annual timescales; the
extra uptake of CO2 stimulated by increased N-deposition is, from a
greenhouse gas forcing perspective, counterbalanced by the related
additional N2O emissions; the amount of carbon stored in permafrost
areas appears much (two times) larger than previously thought;
preservation of existing marine ecosystems could require a CO2
stabilization as low as 450 ppm; Dynamic Vegetation Models show a wide
divergence for future carbon trajectories, uncertainty in the process
description, lack of understanding of the CO2 fertilization effect and
nitrogen-carbon interaction are major uncertainties.
BibTeX:
@article{dolman10a,
  author = {Dolman, A. J. and van der Werf, G. R. and van der Molen, M. K. and Ganssen, G. and Erisman, J. -W. and Strengers, B.},
  title = {A Carbon Cycle Science Update Since IPCC AR-4},
  journal = {AMBIO},
  year = {2010},
  volume = {39},
  number = {5-6},
  pages = {402--412},
  doi = {https://doi.org/10.1007/s13280-010-0083-7}
}
Dong, J. Impedance Matching Readouts-A New Family of Ultrasensitive Cavity Enhanced Spectroscopy Techniques 2020 School: The Australian National University  phdthesis URL 
Abstract: Optical cavity enhanced spectroscopy (CES) is a well-established analytical research area, providing powerful and ultra-sensitive tools for the detection and quantification of trace gas concentrations by using optical cavities to effectively enhance the optical absorption. In this …
BibTeX:
@phdthesis{dong20a,
  author = {Jiahao Dong},
  title = {Impedance Matching Readouts-A New Family of Ultrasensitive Cavity Enhanced Spectroscopy Techniques},
  school = {The Australian National University},
  year = {2020},
  url = {https://search.proquest.com/openview/13e8bf53ff391312db4a6248f16bafe4/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Dong, X., Yue, M., Jiang, Y., Hu, X.-M., Ma, Q., Pu, J. and Zhou, G. Analysis of CO2 spatio-temporal variations in China using a weather-biosphere online coupled model 2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(9), pp. 7217-7233 
article DOI  
Abstract: The dynamics of atmospheric CO2 has received considerable attention in
the literature, yet significant uncertainties remain within the
estimates of contribution from the terrestrial flux and the influence of
atmospheric mixing. In this study we apply the WRF-Chem model configured
with the Vegetation Photosynthesis and Respiration Model (VPRM) option
for biomass fluxes in China to characterize the dynamics of CO2 in the
atmosphere. The online coupled WRF-Chem model is able to simulate
biosphere processes (photosynthetic uptake and ecosystem respiration)
and meteorology in one coordinate system. We apply WRF-Chem for a
multi-year simulation (2016-2018) with integrated data from a satellite
product, flask samplings, and tower measurements to diagnose the
spatio-temporal variations of CO2 fluxes and concentrations in China. We
find that the spatial distribution of CO2 was dominated by anthropogenic
emissions, while its seasonality (with maxima in April 15 ppmv higher
than minima in August) was dominated by the terrestrial flux and
background CO2. Observations and simulations revealed a consistent
increasing trend in column-averaged CO2 (XCO2) of 2.46 ppmv (0.6%
yr(-1)) resulting from anthropogenic emission growth and biosphere
uptake. WRF-Chem successfully reproduced ground-based measurements of
surface CO2 concentration with a mean bias of -0.79 ppmv and
satellite-derived XCO2 with a mean bias of 0.76 ppmv. The
model-simulated seasonality was also consistent with observations, with
correlation coefficients of 0.90 and 0.89 for ground-based measurements
and satellite data, respectively. Tower observations from a background
site at Lin'an (30.30 degrees N, 119.75 degrees E) revealed a strong
correlation (-0.98) between vertical CO2 and temperature gradients,
suggesting a significant influence of boundary layer thermal structure
on the accumulation and depletion of atmospheric CO2.
BibTeX:
@article{dong21a,
  author = {Dong, Xinyi and Yue, Man and Jiang, Yujun and Hu, Xiao-Ming and Ma, Qianli and Pu, Jingjiao and Zhou, Guangqiang},
  title = {Analysis of CO2 spatio-temporal variations in China using a weather-biosphere online coupled model},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2021},
  volume = {21},
  number = {9},
  pages = {7217-7233},
  doi = {https://doi.org/10.5194/acp-21-7217-2021}
}
Eldering, A., Taylor, T.E., O'Dell, C.W. and Pavlick, R. The OCO-3 mission: measurement objectives and expected performance based on 1 year of simulated data {2019} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {12}({4}), pp. {2341-2370} 
article DOI URL 
Abstract: The Orbiting Carbon Observatory-3 (OCO-3) is NASA's next instrument dedicated to extending the record of the dry-air mole fraction of column carbon dioxide (XCO2) and solar-induced fluorescence (SIF) measurements from space. The current schedule calls for a launch from the Kennedy Space Center no earlier than April 2019 via a Space-X Falcon 9 and Dragon capsule. The instrument will be installed as an external payload on the Japanese Experimental Module Exposed Facility (JEM-EF) of the International Space Station (ISS) with a nominal mission lifetime of 3 years. The precessing orbit of the ISS will allow for viewing of the Earth at all latitudes less than approximately 52 degrees, with a ground repeat cycle that is much more complicated than the polar-orbiting satellites that so far have carried all of the instruments capable of measuring carbon dioxide from space. The grating spectrometer at the core of OCO-3 is a direct copy of the OCO-2 spectrometer, which was launched into a polar orbit in July 2014. As such, OCO-3 is expected to have similar instrument sensitivity and performance characteristics to OCO-2, which provides measurements of XCO2 with precision better than 1 ppm at 3 Hz, with each viewing frame containing eight footprints approximately 1.6 km by 2.2 km in size. However, the physical configuration of the instrument aboard the ISS, as well as the use of a new pointing mirror assembly (PMA), will alter some of the characteristics of the OCO-3 data compared to OCO-2. Specifically, there will be significant differences from day to day in the sampling locations and time of day. In addition, the flexible PMA system allows for a much more dynamic observation-mode schedule. This paper outlines the science objectives of the OCO-3 mission and, using a simulation of 1 year of global observations, characterizes the spatial sampling, time-of-day coverage, and anticipated data quality of the simulated L1b. After application of cloud and aerosol prescreening, the L1b radiances are run through the operational L2 full physics retrieval algorithm, as well as post-retrieval filtering and bias correction, to examine the expected coverage and quality of the retrieved XCO2 and to show how the measurement objectives are met. In addition, results of the SIF from the IMAP-DOAS algorithm are analyzed. This paper focuses only on the nominal nadir-land and glint-water observation modes, although on-orbit measurements will also be made in transition and target modes, similar to OCO-2, as well as the new snapshot area mapping (SAM) mode.
BibTeX:
@article{eldering19a,
  author = {Eldering, Annmarie and Taylor, Thomas E. and O'Dell, Christopher W. and Pavlick, Ryan},
  title = {The OCO-3 mission: measurement objectives and expected performance based on 1 year of simulated data},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {12},
  number = {4},
  pages = {2341--2370},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://amt.copernicus.org/articles/12/2341/2019/},
  doi = {https://doi.org/10.5194/amt-12-2341-2019}
}
Elias, E., Dougherty, M., Srivastava, P. and Laband, D. The impact of forest to urban land conversion on streamflow, total nitrogen, total phosphorus, and total organic carbon inputs to the converse reservoir, Southern Alabama, USA {2013} URBAN ECOSYSTEMS
Vol. {16}({1, SI}), pp. 79-107 
article DOI  
Abstract: High total organic carbon (TOC) concentrations in Converse Reservoir, a
water source for Mobile, Alabama, have concerned water treatment
officials due to the potential for disinfection byproduct (DBP)
formation. TOC reacts with chlorine during drinking water treatment to
form DBPs. This study evaluated how increased urbanization can alter
watershed-derived total nitrogen (TN), total phosphorus (TP) and TOC
inputs to the Converse Reservoir. Converse Watershed, on the urban
fringe of Mobile, is projected to undergo urbanization increasing
watershed urban land from 3% in 1992 to 22% urban land by 2020. A
pre-urbanization scenario using 1992 land cover was coupled with 2020
projections of land use. The Loading Simulation Program C++ watershed
model was used to evaluate changes in nutrient concentrations (mg L-1)
and loads (kg) to Converse Reservoir. Urban and suburban growth of 52
km(2) simulated from 1991 to 2005 (15 year) caused overall TN and TP
loads to increase by 109 and 62%, respectively. Simulated urban growth
generally increased monthly flows by 15%, but resulted in lower
streamflows (2.9%) during drought months. Results indicate that
post-urbanization median TN and TP concentrations were 59 and 66%
higher than corresponding pre-urbanization concentrations, whereas TOC
concentrations were 16% lower. An increase in urban flow caused TOC
loads to increase by 26%, despite lower post-urbanization TOC
concentrations.
BibTeX:
@article{elias13a,
  author = {Elias, Emile and Dougherty, Mark and Srivastava, Puneet and Laband, David},
  title = {The impact of forest to urban land conversion on streamflow, total nitrogen, total phosphorus, and total organic carbon inputs to the converse reservoir, Southern Alabama, USA},
  journal = {URBAN ECOSYSTEMS},
  year = {2013},
  volume = {16},
  number = {1, SI},
  pages = {79--107},
  doi = {https://doi.org/10.1007/s11252-011-0198-z}
}
Elshall, A.S., Ye, M., Niu, G.-Y. and Barron-Gafford, G.A. Bayesian inference and predictive performance of soil respiration models in the presence of model discrepancy {2019} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {12}({5}), pp. {2009-2032} 
article DOI URL 
Abstract: Bayesian inference of microbial soil respiration models is often based on the assumptions that the residuals are independent (i.e., no temporal or spatial correlation), identically distributed (i.e., Gaussian noise), and have constant variance (i.e., homoscedastic). In the presence of model discrepancy, as no model is perfect, this study shows that these assumptions are generally invalid in soil respiration modeling such that residuals have high temporal correlation, an increasing variance with increasing magnitude of CO2 efflux, and non-Gaussian distribution. Relaxing these three assumptions stepwise results in eight data models. Data models are the basis of formulating likelihood functions of Bayesian inference. This study presents a systematic and comprehensive investigation of the impacts of data model selection on Bayesian inference and predictive performance. We use three mechanistic soil respiration models with different levels of model fidelity (i.e., model discrepancy) with respect to the number of carbon pools and the explicit representations of soil moisture controls on carbon degradation; therefore, we have different levels of model complexity with respect to the number of model parameters. The study shows that data models have substantial impacts on Bayesian inference and predictive performance of the soil respiration models such that the following points are true: (i) the level of complexity of the best model is generally justified by the cross-validation results for different data models; (ii) not accounting for heteroscedasticity and autocorrelation might not necessarily result in biased parameter estimates or predictions, but will definitely underestimate uncertainty; (iii) using a non-Gaussian data model improves the parameter estimates and the predictive performance; and (iv) accounting for autocorrelation only or joint inversion of correlation and heteroscedasticity can be problematic and requires special treatment. Although the conclusions of this study are empirical, the analysis may provide insights for selecting appropriate data models for soil respiration modeling.
BibTeX:
@article{elshall19a,
  author = {Elshall, Ahmed S. and Ye, Ming and Niu, Guo-Yue and Barron-Gafford, Greg A.},
  title = {Bayesian inference and predictive performance of soil respiration models in the presence of model discrepancy},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {12},
  number = {5},
  pages = {2009--2032},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://gmd.copernicus.org/articles/12/2009/2019/},
  doi = {https://doi.org/10.5194/gmd-12-2009-2019}
}
Fadnavis, S., Kumar, K.R., Tiwari, Y.K. and Pozzoli, L. Atmospheric CO2 source and sink patterns over the Indian region {2016} ANNALES GEOPHYSICAE
Vol. {34}({2}), pp. 279-291 
article DOI  
Abstract: In this paper we examine CO2 emission hot spots and sink regions over
India as identified from global model simulations during the period
2000-2009. CO2 emission hot spots overlap with locations of densely
clustered thermal power plants, coal mines and other industrial and
urban centres; CO2 sink regions coincide with the locations of dense
forest. Fossil fuel CO2 emissions are compared with two bottom-up
inventories: the Regional Emission inventories in ASia (REAS v1.11;
2000-2009) and the Emission Database for Global Atmospheric Research
(EDGAR v4.2) (2000-2009). Estimated fossil fuel emissions over the hot
spot region are similar to 500-950 gCm(-2) yr(-1) as obtained from the
global model simulation, EDGAR v4.2 and REAS v1.11 emission inventory.
Simulated total fluxes show increasing trends, from 1.39 +/- 1.01%
yr(-1) (19.8 +/- 1.9 TgC yr(-1)) to 6.7 +/- 0.54% yr(-1) (97 +/- 12 TgC
yr(-1)) over the hot spot regions and decreasing trends of -0.95 +/-
1.51% yr(-1) (-1 +/- 2 TgC yr(-1)) to 5.7 +/- 2.89% yr(-1) (-2.3 +/- 2
TgC yr(-1)) over the sink regions. Model-simulated terrestrial ecosystem
fluxes show decreasing trends (increasing CO2 uptake) over the sink
regions. Decreasing trends in terrestrial ecosystem fluxes imply that
forest cover is increasing, which is consistent with India State of
Forest Report (2009). Fossil fuel emissions show statistically
significant increasing trends in all the data sets considered in this
study. Estimated trend in simulated total fluxes over the Indian region
is similar to 4.72 +/- 2.25% yr(-1) (25.6 TgC yr(-1)) which is slightly
higher than global growth rate similar to 3.1%yr(-1) during 2000-2010.
BibTeX:
@article{fadnavis16a,
  author = {Fadnavis, Suvarna and Kumar, K. Ravi and Tiwari, Yogesh K. and Pozzoli, Luca},
  title = {Atmospheric CO2 source and sink patterns over the Indian region},
  journal = {ANNALES GEOPHYSICAE},
  year = {2016},
  volume = {34},
  number = {2},
  pages = {279--291},
  doi = {https://doi.org/10.5194/angeo-34-279-2016}
}
Fang, S.X., Zhou, L.X., Tans, P.P., Ciais, P., Steinbacher, M., Xu, L. and Luan, T. In situ measurement of atmospheric CO2 at the four WMO/GAW stations in China {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({5}), pp. 2541-2554 
article DOI  
Abstract: Atmospheric carbon dioxide (CO2) mole fractions were continuously
measured from January 2009 to December 2011 at four atmospheric
observatories in China using cavity ring-down spectroscopy instruments.
The stations are Lin'an (LAN), Longfengshan (LFS), Shangdianzi (SDZ),
and Waliguan (WLG), which are regional (LAN, LFS, SDZ) or global (WLG)
measurement stations of the World Meteorological Organization's Global
Atmosphere Watch program (WMO/ GAW). LAN is located near the megacity of
Shanghai, in China's economically most developed region. LFS is in a
forest and rice production area, close to the city of Harbin in
northeastern China. SDZ is located 150 km northeast of Beijing. WLG,
hosting the longest record of measured CO2 mole fractions in China, is a
high-altitude site in northwestern China recording background CO2
concentration. The CO2 growth rates are 3.7 +/- 1.2 ppm yr(-1) for LAN,
2.7 +/- 0.8 ppm yr(-1) for LFS, 3.5 +/- 1.6 ppm yr(-1) for SDZ, and 2.2
+/- 0.8 ppm yr(-1) (1 sigma ) for WLG during the period of 2009 to 2011.
The highest annual mean CO2 mole fraction of 404.2 +/- 3.9 ppm was
observed at LAN in 2011. A comprehensive analysis of CO2 variations,
their diurnal and seasonal cycles as well as the analysis of the
influence of local sources on the CO2 mole fractions allows a
characterization of the sampling sites and of the key processes driving
the CO2 mole fractions. These data form a basis to improve our
understanding of atmospheric CO2 variations in China and the underlying
fluxes using atmospheric inversion models.
BibTeX:
@article{fang14a,
  author = {Fang, S. X. and Zhou, L. X. and Tans, P. P. and Ciais, P. and Steinbacher, M. and Xu, L. and Luan, T.},
  title = {In situ measurement of atmospheric CO2 at the four WMO/GAW stations in China},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {5},
  pages = {2541--2554},
  doi = {https://doi.org/10.5194/acp-14-2541-2014}
}
Fang, Y., Michalak, A.M., Shiga, Y.P. and Yadav, V. Using atmospheric observations to evaluate the spatiotemporal variability of CO2 fluxes simulated by terrestrial biospheric models {2014} BIOGEOSCIENCES
Vol. {11}({23}), pp. 6985-6997 
article DOI  
Abstract: Terrestrial biospheric models (TBMs) are used to extrapolate local
observations and process-level understanding of land-atmosphere carbon
exchange to larger regions, and serve as predictive tools for examining
carbon-climate interactions. Understanding the performance of TBMs is
thus crucial to the carbon cycle and climate science communities. In
this study, we present and assess an approach to evaluating the
spatiotemporal patterns, rather than aggregated magnitudes, of net
ecosystem exchange (NEE) simulated by TBMs using atmospheric CO2
measurements. The approach is based on statistical model selection
implemented within a high-resolution atmospheric inverse model. Using
synthetic data experiments, we find that current atmospheric
observations are sensitive to the underlying spatiotemporal flux
variability at sub-biome scales for a large portion of North America,
and that atmospheric observations can therefore be used to evaluate
simulated spatiotemporal flux patterns as well as to differentiate
between multiple competing TBMs. Experiments using real atmospheric
observations and four prototypical TBMs further confirm the
applicability of the method, and demonstrate that the performance of
TBMs in simulating the spatiotemporal patterns of NEE varies
substantially across seasons, with best performance during the growing
season and more limited skill during transition seasons. This result is
consistent with previous work showing that the ability of TBMs to model
flux magnitudes is also seasonally-dependent. Overall, the proposed
approach provides a new avenue for evaluating TBM performance based on
sub-biome-scale flux patterns, presenting an opportunity for assessing
and informing model development using atmospheric observations.
BibTeX:
@article{fang14b,
  author = {Fang, Y. and Michalak, A. M. and Shiga, Y. P. and Yadav, V.},
  title = {Using atmospheric observations to evaluate the spatiotemporal variability of CO2 fluxes simulated by terrestrial biospheric models},
  journal = {BIOGEOSCIENCES},
  year = {2014},
  volume = {11},
  number = {23},
  pages = {6985--6997},
  doi = {https://doi.org/10.5194/bg-11-6985-2014}
}
Fang, Y. and Michalak, A.M. Atmospheric observations inform CO2 flux responses to enviroclimatic drivers {2015} GLOBAL BIOGEOCHEMICAL CYCLES
Vol. {29}({5}), pp. 555-566 
article DOI  
Abstract: Understanding the response of the terrestrial biospheric carbon cycle to
variability in enviroclimatic drivers is critical for predicting
climate-carbon interactions. Here we apply an
atmospheric-inversion-based framework to assess the relationships
between the spatiotemporal patterns of net ecosystem CO2 exchange (NEE)
and those of enviroclimatic drivers. We show that those relationships
can be directly observed at 1 degrees x1 degrees 3-hourly resolution
from atmospheric CO2 measurements for four of seven large biomes in
North America, namely, (i) boreal forests and taiga; (ii) temperate
coniferous forests; (iii) temperate grasslands, savannas, and
shrublands; and (iv) temperate broadleaf and mixed forests. We find that
shortwave radiation plays a dominant role during the growing season over
all four biomes. Specific humidity and precipitation also play key roles
and are associated with decreased CO2 uptake (or increased release). The
explanatory power of specific humidity is especially strong during
transition seasons, while that of precipitation appears during both the
growing and dormant seasons. We further find that the ability of four
prototypical terrestrial biospheric models (TBMs) to represent the
spatiotemporal variability of NEE improves as the influence of radiation
becomes more dominant, implying that TBMs have a better skill in
representing the impact of radiation relative to other drivers. Even so,
we show that TBMs underestimate the strength of the relationship to
radiation and do not fully capture its seasonality. Furthermore, the
TBMs appear to misrepresent the relationship to precipitation and
specific humidity at the examined scales, with relationships that are
not consistent in terms of sign, seasonality, or significance relative
to observations. More broadly, we demonstrate the feasibility of
directly probing relationships between NEE and enviroclimatic drivers at
scales with no direct measurements of NEE, opening the door to the study
of emergent processes across scales and to the evaluation of their
scaling within TBMs.
BibTeX:
@article{fang15a,
  author = {Fang, Yuanyuan and Michalak, Anna M.},
  title = {Atmospheric observations inform CO2 flux responses to enviroclimatic drivers},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  year = {2015},
  volume = {29},
  number = {5},
  pages = {555--566},
  doi = {https://doi.org/10.1002/2014GB005034}
}
Feldman, D.R., Collins, W.D., Gero, P.J., Torn, M.S., Mlawer, E.J. and Shippert, T.R. Observational determination of surface radiative forcing by CO2 from 2000 to 2010 {2015} NATURE
Vol. {519}({7543}), pp. {339+} 
article DOI  
Abstract: The climatic impact of CO2 and other greenhouse gases is usually
quantified in terms of radiative forcing', calculated as the difference
between estimates of the Earth's radiation field from pre-industrial and
presentday concentrations of these gases. Radiative transfer models
calculate that the increase in CO2 since 1750 corresponds to a global
annualmean radiative forcing at the tropopause of 1.82 +/- 0.19W m(-2)
(ref. 2). However, despite widespread scientific discussion and
modelling of the climate impacts of well-mixed greenhouse gases, there
is little direct observational evidence of the radiative impact of
increasing atmospheric CO2. Here we present observationally based
evidence of clear-sky CO2 surface radiative forcing that is directly
attributable to the increase, between 2000 and 2010, of 22 parts per
million atmospheric CO2. The time series of this forcing at the two
locations the Southern Great Plains and the North Slope of Alaska are
derived from Atmospheric Emitted Radiance Interferometer spectra'
together with ancillary measurements and thoroughly corroborated
radiative transfer calculations'. The time series both show
statistically significant trends of 0.2 W m(-2) per decade (with
respective uncertainties of +/- 0.06 W m(-2) per decade and 0.07 W m(-2)
per decade) and have seasonal ranges of 0.1-0.2W m(-2). This is
approximately ten per cent of the trend in downwelling longwave
radiation'''. These results confirm theoretical predictions of the
atmospheric greenhouse effect due to anthropogenic emissions, and
provide empirical evidence of how rising CO2 levels, mediated by
temporal variations due to photosynthesis and respiration, are affecting
the surface energy balance.
BibTeX:
@article{feldman15a,
  author = {Feldman, D. R. and Collins, W. D. and Gero, P. J. and Torn, M. S. and Mlawer, E. J. and Shippert, T. R.},
  title = {Observational determination of surface radiative forcing by CO2 from 2000 to 2010},
  journal = {NATURE},
  year = {2015},
  volume = {519},
  number = {7543},
  pages = {339+},
  doi = {https://doi.org/10.1038/nature14240}
}
Feldman, D.R., Collins, W.D., Biraud, S.C., Risser, M.D., Turner, D.D., Gero, P.J., Tadic, J., Helmig, D., Xie, S., Mlawer, E.J., Shippert, T.R. and Torn, M.S. Observationally derived rise in methane surface forcing mediated by water vapour trends {2018} NATURE GEOSCIENCE
Vol. {11}({4}), pp. {238+} 
article DOI  
Abstract: Atmospheric methane (CH4) mixing ratios exhibited a plateau between 1995
and 2006 and have subsequently been increasing. While there are a number
of competing explanations for the temporal evolution of this greenhouse
gas, these prominent features in the temporal trajectory of atmospheric
CH4 are expected to perturb the surface energy balance through radiative
forcing, largely due to the infrared radiative absorption features of
CH4. However, to date this has been determined strictly through
radiative transfer calculations. Here, we present a quantified
observation of the time series of clear-sky radiative forcing by CH4 at
the surface from 2002 to 2012 at a single site derived from
spectroscopic measurements along with line-by-line calculations using
ancillary data. There was no significant trend in CH4 forcing between
2002 and 2006, but since then, the trend in forcing was 0.026 +/- 0.006
(99.7% CI) W m(2) yr(-1). The seasonal-cycle amplitude and secular
trends in observed forcing are influenced by a corresponding seasonal
cycle and trend in atmospheric CH4. However, we find that we must
account for the overlapping absorption effects of atmospheric water
vapour (H2O) and CH4 to explain the observations fully. Thus, the
determination of CH4 radiative forcing requires accurate observations of
both the spatiotemporal distribution of CH4 and the vertically resolved
trends in H2O.
BibTeX:
@article{feldman18a,
  author = {Feldman, D. R. and Collins, W. D. and Biraud, S. C. and Risser, M. D. and Turner, D. D. and Gero, P. J. and Tadic, J. and Helmig, D. and Xie, S. and Mlawer, E. J. and Shippert, T. R. and Torn, M. S.},
  title = {Observationally derived rise in methane surface forcing mediated by water vapour trends},
  journal = {NATURE GEOSCIENCE},
  year = {2018},
  volume = {11},
  number = {4},
  pages = {238+},
  doi = {https://doi.org/10.1038/s41561-018-0085-9}
}
Feltz, M.L., Knuteson, R.O. and Revercomb, H.E. Assessment of COSMIC radio occultation and AIRS hyperspectral IR sounder temperature products in the stratosphere using observed radiances {2017} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {122}({16}), pp. 8593-8616 
article DOI  
Abstract: Upper air temperature is defined as an essential climate variable by the
World Meteorological Organization. Two remote sensing technologies being
promoted for monitoring stratospheric temperatures are GPS radio
occultation (RO) and spectrally resolved IR radiances. This study
assesses RO and hyperspectral IR sounder derived temperature products
within the stratosphere by comparing IR spectra calculated from GPS RO
and IR sounder products to coincident IR observed radiances, which are
used as a reference standard. RO dry temperatures from the University
Corporation for Atmospheric Research (UCAR) Constellation Observing
System for Meteorology, Ionosphere, and Climate (COSMIC) mission are
compared to NASA Atmospheric Infrared Sounder (AIRS) retrievals using a
previously developed profile-to-profile collocation method and vertical
temperature averaging kernels. Brightness temperatures (BTs) are
calculated for both COSMIC and AIRS temperature products and are then
compared to coincident AIRS measurements. The COSMIC calculated minus
AIRS measured BTs exceed the estimated 0.5 K measurement uncertainty for
the winter time extratropics around 35 hPa. These differences are
attributed to seasonal UCAR COSMIC biases. Unphysical vertical
oscillations are seen in the AIRS L2 temperature product in austral
winter Antarctic regions, and results imply a small AIRS tropical warm
bias around similar to 35 hPa in the middle stratosphere.
BibTeX:
@article{feltz17a,
  author = {Feltz, M. L. and Knuteson, R. O. and Revercomb, H. E.},
  title = {Assessment of COSMIC radio occultation and AIRS hyperspectral IR sounder temperature products in the stratosphere using observed radiances},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2017},
  volume = {122},
  number = {16},
  pages = {8593--8616},
  doi = {https://doi.org/10.1002/2017JD026704}
}
Feng, S., Lauvaux, T., Davis, K., Keller, K. and ... Seasonal Characteristics of Model Uncertainties From Biogenic Fluxes, Transport, and Large‐Scale Boundary Inflow in Atmospheric CO2 Simulations Over North … 2019 Journal of Geophysical Research: Atmospheres  article URL 
Abstract: Regional estimates of biogenic carbon fluxes over North America from both atmospheric inversions (``top‐down'' approach) and terrestrial biosphere models (``bottom‐up'') remain highly uncertain. We merge these approaches with an ensemble‐based, regional modeling …
BibTeX:
@article{feng19a,
  author = {S Feng and T Lauvaux and KJ Davis and K Keller and ...},
  title = {Seasonal Characteristics of Model Uncertainties From Biogenic Fluxes, Transport, and Large‐Scale Boundary Inflow in Atmospheric CO2 Simulations Over North …},
  journal = {Journal of Geophysical Research: Atmospheres},
  publisher = {Wiley Online Library},
  year = {2019},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031165}
}
Feng, S., Lauvaux, T., Keller, K., Davis, K. and ... A road map for improving the treatment of uncertainties in high‐resolution regional carbon flux inverse estimates 2019 Geophysical Research Letters  article URL 
Abstract: Atmospheric inversions allow us to estimate the terrestrial carbon sink by combining atmospheric observations with atmospheric transport models. However, these inverse estimates remain highly uncertain. Here we quantify uncertainties in simulations of North …
BibTeX:
@article{feng19b,
  author = {S Feng and T Lauvaux and K Keller and KJ Davis and ...},
  title = {A road map for improving the treatment of uncertainties in high‐resolution regional carbon flux inverse estimates},
  journal = {Geophysical Research Letters},
  year = {2019},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082987}
}
Feng, S., Jiang, F., Wu, Z., Wang, H., Ju, W. and Wang, H. CO Emissions Inferred From Surface CO Observations Over China in December 2013 and 2017 {2020} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {125}({7}) 
article DOI URL 
Abstract: China has implemented active clean air policies in recent years, and the spatiotemporal patterns of major pollutant emissions have changed substantially. In this study, we construct a regional air pollution data assimilation system based on the WRF/CMAQ model and ensemble Kalman filter algorithm to quantitatively optimize gridded CO emissions using hourly surface CO measurements over China. The Multi-resolution Emission Inventory of China CO emission inventories in December 2012 and 2016 are treated as prior emissions, and the CO emissions in December 2013 and 2017 are optimized using the CO observations of December of 2013 and 2017, respectively. The results show that in both periods, assimilation of CO observations significantly improves the CO simulations and emission estimates. Assimilation increases the CO emissions in most areas of mainland China, especially in northern China, and the spatial patterns of the increases in the two periods are similar. Overall, the posterior CO emissions in December 2017 are 17% lower than those in December 2013. Large emission decreases are mainly found in most key urban areas and developed regions, and emission increases are mainly located in their surrounding areas and certain central and western regions, which might reflect the emission migration from developed regions or urban areas to developing regions or surrounding areas. These changes are not found in the prior emissions but are basically consistent with the emission control strategies and industrial transformation and upgrade phenomena in recent years, indicating that our CO assimilation system could successfully capture the temporal and spatial variations.
BibTeX:
@article{feng20a,
  author = {Feng, Shuzhuang and Jiang, Fei and Wu, Zheng and Wang, Hengmao and Ju, Weimin and Wang, Haikun},
  title = {CO Emissions Inferred From Surface CO Observations Over China in December 2013 and 2017},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {125},
  number = {7},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031808},
  doi = {https://doi.org/10.1029/2019JD031808}
}
Feng, S., Lauvaux, T., Williams, C.A., Davis, K.J., Zhou, Y., Baker, I., Barkley, Z.R. and Wesloh, D. Joint CO2 Mole Fraction and Flux Analysis Confirms Missing Processes in CASA Terrestrial Carbon Uptake Over North America 2021 GLOBAL BIOGEOCHEMICAL CYCLES
Vol. 35(7) 
article DOI  
Abstract: Terrestrial biosphere models (TBMs) play a key role in the detection and
attribution of carbon cycle processes at local to global scales and in
projections of the coupled carbon-climate system. TBM evaluation
commonly involves direct comparison to eddy-covariance flux
measurements. We use atmospheric CO2 mole fraction ([CO2]) measured in
situ from aircraft and tower, in addition to flux-measurements from
summer 2016 to evaluate the Carnegie-Ames-Stanford-Approach (CASA) TBM.
WRF-Chem is used to simulate [CO2] using biogenic CO2 fluxes from a
CASA parameter-based ensemble and CarbonTracker version 2017 (CT2017) in
addition to transport and CO2 boundary condition ensembles. The
resulting ``super ensemble'' of modeled [CO2] demonstrates that the
biosphere introduces the majority of uncertainty to the simulations.
Both aircraft and tower [CO2] data show that the CASA ensemble net
ecosystem exchange (NEE) of CO2 is biased high (NEE too positive) and
identify the maximum light use efficiency E-max a key parameter that
drives the spread of the CASA ensemble in summer 2016. These findings
are verified with flux-measurements. The direct comparison of the CASA
flux ensemble with flux-measurements confirms missing sink processes in
CASA. Separating the daytime and nighttime flux, we discover that the
underestimated net uptake results from missing sink processes that
result in overestimation of respiration. NEE biases are smaller in the
CT2017 posterior biogenic fluxes, which assimilate observed [CO2].
Flux tower analyses reveal an unrealistic overestimation of nighttime
respiration in CT2017 which we attribute to limited flexibility in the
inversion strategy.
BibTeX:
@article{feng21a,
  author = {Feng, Sha and Lauvaux, Thomas and Williams, Christopher A. and Davis, Kenneth J. and Zhou, Yu and Baker, Ian and Barkley, Zachary R. and Wesloh, Daniel},
  title = {Joint CO2 Mole Fraction and Flux Analysis Confirms Missing Processes in CASA Terrestrial Carbon Uptake Over North America},
  journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
  year = {2021},
  volume = {35},
  number = {7},
  doi = {https://doi.org/10.1029/2020GB006914}
}
Feng, S., Jiang, F., Wang, H., Shen, Y., Zheng, Y., Zhang, L., Lou, C. and Ju, W. Anthropogenic emissions estimated using surface observations and their impacts on PM2.5 source apportionment over the Yangtze River Delta, China 2022 SCIENCE OF THE TOTAL ENVIRONMENT
Vol. 828 
article DOI  
Abstract: Source-tagged source apportionment (SA) has advantages for quantifying
the contribution of various source regions and categories to PM2.5;
however, it is highly affected by uncertainty in the emission inventory.
In this study, we used a Regional multi-Air Pollutant Assimilation
System (RAPAS) to optimize daily SO2, NOx and primary PM2.5 (PPM2.5)
emissions in the Yangtze River Delta (YRD) in December 2016 by
assimilating hourly in-situ measurements. The CMAQ-ISAM model was
implemented with prior and posterior emissions respectively to
investigate the impacts of optimizing emissions on PM2.5 SA in the YRD
megalopolis (YRDM) and three megacities of Shanghai, Nanjing, and I
langzhou in the YRDM. The results showed that RAPAS significantly
improved the simulations and reduced the emission uncertainties of the
different pollutants. Compared with prior emissions, the posterior
emissions in the YRD decreased by 13% and 11% for SO2 and NOx
respectively, and increased by 24% for PPM2.5. Compared with SA using
prior emissions, the contributions from Hangzhou, northern Zhejiang, and
areas outside of the YRD to the YRDM increased. The local contributions
from the YRDM, Nanjing and Shanghai decreased by L8%, 9.7%, and 2.3%,
respectively, whereas that of Hangzhou increased by 5.6%. The changes
in the daily local contributions caused by optimizing emissions ranged
from - 18.0% to 23.6%. Generally, under stable weather conditions, the
local contribution changed the most, whereas under unstable weather
conditions, the contribution from upwind areas changed significantly.
Overall, with optimized emissions, we found in Nanjing, Shanghai, and
Hangzhou, local emissions contributed 18.2%, 39.6% and 36.8% of their
PM2.5 concentrations, respectively; long-range transport from outside
the YRDM contributed 59.2%, 48.1%, and 48.2%, respectively. This
study emphasizes the importance of improving emission estimations for
source-tagged SA and provides more reliable SA results for the main
cities in the YRD, which will contribute to pollution control in these
regions.
BibTeX:
@article{feng22a,
  author = {Feng, Shuzhuang and Jiang, Fei and Wang, Hengmao and Shen, Yang and Zheng, Yanhua and Zhang, Lingyu and Lou, Chenxi and Ju, Weimin},
  title = {Anthropogenic emissions estimated using surface observations and their impacts on PM2.5 source apportionment over the Yangtze River Delta, China},
  journal = {SCIENCE OF THE TOTAL ENVIRONMENT},
  year = {2022},
  volume = {828},
  doi = {https://doi.org/10.1016/j.scitotenv.2022.154522}
}
Fernando, A.M. Trend Analyses of the Abundances of Atmospheric Molecules 2020 School: OLD DOMINION UNIVERSITY  phdthesis URL 
Abstract: A new line list for the A 3 Π-X 3 Σ-electronic transition of NH has been prepared using line positions from the literature and calculated line intensities. High level ab initio calculations were performed with the MOLPRO program to obtain the AX transition dipole moment …
BibTeX:
@phdthesis{fernando20a,
  author = {Anton M. Fernando},
  title = {Trend Analyses of the Abundances of Atmospheric Molecules},
  school = {OLD DOMINION UNIVERSITY},
  year = {2020},
  url = {https://digitalcommons.odu.edu/physics_etds/125/}
}
Flower, C.E. and Gonzalez-Meler, M.A. Responses of Temperate Forest Productivity to Insect and Pathogen Disturbances {2015}
Vol. {66}ANNUAL REVIEW OF PLANT BIOLOGY, VOL 66, pp. 547-569 
incollection DOI  
Abstract: Pest and pathogen disturbances are ubiquitous across forest ecosystems,
impacting their species composition, structure, and function. Whereas
severe abiotic disturbances (e.g., clear-cutting and fire) largely reset
successional trajectories, pest and pathogen disturbances cause diffuse
mortality, driving forests into nonanalogous system states. Biotic
perturbations that disrupt forest carbon dynamics either reduce or
enhance net primary production (NPP) and carbon storage, depending on
pathogen type. Relative to defoliators, wood borers and invasive pests
have the largest negative impact on NPP and the longest recovery time.
Forest diversity is an important contributing factor to productivity:
NPP is neutral, marginally enhanced, or reduced in high-diversity stands
in which a small portion of the canopy is affected (temperate deciduous
or mixed forests) but very negative in low-diversity stands in which a
large portion of the canopy is affected (western US forests). Pests and
pathogens reduce forest structural and functional redundancy, affecting
their resilience to future climate change or new outbreaks. Therefore,
pests and pathogens can be considered biotic forcing agents capable of
causing consequences of similar magnitude to climate forcing factors.
BibTeX:
@incollection{flower15a,
  author = {Flower, Charles E. and Gonzalez-Meler, Miquel A.},
  title = {Responses of Temperate Forest Productivity to Insect and Pathogen Disturbances},
  booktitle = {ANNUAL REVIEW OF PLANT BIOLOGY, VOL 66},
  publisher = {Annual Reviews},
  year = {2015},
  volume = {66},
  pages = {547--569},
  doi = {https://doi.org/10.1146/annurev-arplant-043014-115540}
}
Font, A., Morgui, J.A., Curcoll, R., Pouchet, I., Casals, I. and Rodo, X. Daily carbon surface fluxes in the West Ebre (Ebro) watershed from aircraft profiling on late June 2007 {2010} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {62}({5, SI}), pp. 427-440 
article DOI  
Abstract: An intensive aircraft campaign measuring atmospheric CO(2) mixing ratios
was carried out in the central part of the Ebre watershed on late June
2007 to characterize the CO(2) dynamics in the Ebre basin and to
calculate the regional cumulative carbon surface flux. CO(2)
concentrations were obtained from vertical profiles over La Muela (LMU;
41.60 degrees N, 1.1 degrees W) from 900 to 4000 m above the sea level
(masl), horizontal transects at similar to 2000 m 100 km west from LMU,
and continuous measurements at similar to 650 masl. Different estimates
of surface flux from changes in the convective boundary layer (CBL)
CO(2) concentration were obtained following the Integral CBL budgeting
equation (ICBL) and the carbon content integration (CCI) method. Values
of the mean surface flux calculated from the different approaches range
from -2.4 to -7.9 mu molCO(2)/m2s. Regional surface flux calculated from
vertical profiling appears to be consistent in a distance of 70 km away
from the measurement site. The ICBL method is very sensitive to the
accurate determination of the concentration in the entrainment zone. The
overall uncertainty from fluxes calculated from the ICBL method rises to
a value of 70%, whereas the uncertainty linked to the CCI method is
55%.
BibTeX:
@article{font10a,
  author = {Font, A. and Morgui, J. -A. and Curcoll, R. and Pouchet, I. and Casals, I. and Rodo, X.},
  title = {Daily carbon surface fluxes in the West Ebre (Ebro) watershed from aircraft profiling on late June 2007},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2010},
  volume = {62},
  number = {5, SI},
  pages = {427--440},
  doi = {https://doi.org/10.1111/j.1600-0889.2010.00469.x}
}
Font, A., Morgui, J.A. and Rodo, X. Assessing the regional surface influence through Backward Lagrangian Dispersion Models for aircraft CO2 vertical profiles observations in NE Spain {2011} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {11}({4}), pp. 1659-1670 
article DOI  
Abstract: In this study the differences in the measured atmospheric CO2 mixing
ratio at three aircraft profiling sites in NE Spain separated by 60 km
are analyzed in regard to the variability of the surface fluxes in the
regional surface influence area. First, the Regional Potential Surface
Influence (RPSI) for fifty-one days in 2006 is calculated to assess the
vertical, horizontal and temporal extent of the surface influence for
the three sites at the regional scale (10(4) km(2)) at different
altitudes of the profile (600, 1200, 2500 and 4000 meters above the sea
level, ma.s.l.). Second, three flights carried out in 2006 (7 February,
24 August and 29 November) following the Crown Atmospheric Sampling
(CAS) design are presented to study the relation between the measured
CO2 variability and the Potential Surface Influence (PSI) and RPSI
concepts. At 600 and 1200 ma.s.l. the regional signal is confined up to
50 h before the measurements whereas at higher altitudes (2500 and 4000
ma.s.l.) the regional surface influence is only recovered during spring
and summer months. The RPSI from sites separated by similar to 60 km
overlap by up to 70% of the regional surface influence at 600 and 1200
ma.s.l., while the overlap decreases to 10-40% at higher altitudes
(2500 and 4000 ma.s.l.). The scale of the RPSI area is suitable to
understand the differences in the measured CO2 concentration in the
three vertices of the CAS, as CO2 differences are attributed to local
surrounding fluxes (February) or to the variability of regional surface
influence as for the August and November flights. For these two flights,
the variability in the regional scale influences the variability
measured in the local scale. The CAS sampling design for aircraft
measurements appears to be a suitable method to cope with the
variability of a typical grid for inversion models as measurements are
intensified within the PBL and the background concentration is measured
every similar to 10(2) km.
BibTeX:
@article{font11a,
  author = {Font, A. and Morgui, J. -A. and Rodo, X.},
  title = {Assessing the regional surface influence through Backward Lagrangian Dispersion Models for aircraft CO2 vertical profiles observations in NE Spain},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2011},
  volume = {11},
  number = {4},
  pages = {1659--1670},
  doi = {https://doi.org/10.5194/acp-11-1659-2011}
}
Forbes, S.J., Cernusak, L.A., Northfield, T.D., Gleadow, R.M., Lambert, S. and Cheesman, A.W. Elevated temperature and carbon dioxide alter resource allocation to growth, storage and defence in cassava (Manihot esculenta) {2020} ENVIRONMENTAL AND EXPERIMENTAL BOTANY
Vol. {173} 
article DOI URL 
Abstract: Rising atmospheric CO2 concentrations and global warming can alter how plants partition their resources. This is important for food crops through changes in resource allocation to edible tissues and toxic defence compounds. While research suggests elevated temperature and [CO2] independently drive changes in plant metabolism and stress levels, and photosynthetic rates, respectively, it is less clear how these environmental changes impact plants when combined. Cassava is an important dietary staple for many developing nations. However, the safety of cassava depends on cyanogenic glucoside concentrations. In a climate-controlled greenhouse, the effects of elevated temperature in the presence and absence of elevated [CO2] on the growth, physiology and chemical defence of cassava at two growth stages were examined. Growth in cassava was initially increased by elevated temperature. However, across time, simultaneous elevated [CO2] led to an increasing biomass advantage over plants grown at ambient [CO2] and temperature. Elevated temperature and [CO2] also significantly increased tuber initiation and early tuber expansion. Tuber and leaf cyanide concentrations were significantly reduced under elevated temperature, while elevated temperature and [CO2] produced tuber cyanide concentrations similar to the higher levels found in plants grown at ambient conditions. The findings highlight how future climate change may impact both cassava production and quality.
BibTeX:
@article{forbes20a,
  author = {Forbes, Samantha J. and Cernusak, Lucas A. and Northfield, Tobin D. and Gleadow, Roslyn M. and Lambert, Smilja and Cheesman, Alexander W.},
  title = {Elevated temperature and carbon dioxide alter resource allocation to growth, storage and defence in cassava (Manihot esculenta)},
  journal = {ENVIRONMENTAL AND EXPERIMENTAL BOTANY},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  year = {2020},
  volume = {173},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.sciencedirect.com/science/article/pii/S009884722030023X},
  doi = {https://doi.org/10.1016/j.envexpbot.2020.103997}
}
Forster, F. Verfahren zur hochgenauen Ableitung von Methan-Säü̈r die Satellitenvalidierung und Trendanalyse 2019 School: Universität Augsburg  phdthesis URL 
Abstract: Page 1. Frank Forster Verfahren zur hochgenauen Ableitung von Methan-Säulengehalten mit der solaren FTIR-Spektrometrie im mittleren Infrarotbereich: Nutzung für die Satellitenvalidierung und Trendanalyse 96 98 00 02 04 06 08 10 12 Garmisch b) X C H 4 (ppb) X C H 4 (ppb) a) …
BibTeX:
@phdthesis{forster19a,
  author = {Frank Forster},
  title = {Verfahren zur hochgenauen Ableitung von Methan-Säü̈r die Satellitenvalidierung und Trendanalyse},
  school = {Universität Augsburg},
  year = {2019},
  url = {https://opus.bibliothek.uni-augsburg.de/opus4/files/47800/Forster_Diss.pdf}
}
Foucher, P.Y., Chedin, A., Armante, R., Boone, C., Crevoisier, C. and Bernath, P. Carbon dioxide atmospheric vertical profiles retrieved from space observation using ACE-FTS solar occultation instrument {2011} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {11}({6}), pp. 2455-2470 
article DOI  
Abstract: Major limitations of our present knowledge of the global distribution of
CO2 in the atmosphere are the uncertainty in atmospheric transport and
the sparseness of in situ concentration measurements. Limb viewing
spaceborne sounders such as the Atmospheric Chemistry Experiment Fourier
transform spectrometer (ACE-FTS) offer a vertical resolution of a few
kilometres for profiles, which is much better than currently flying or
planned nadir sounding instruments can achieve. After having
demonstrated the feasibility of obtaining CO2 vertical profiles in the
5-25 km altitude range with an accuracy of about 2 ppm in a previous
study, we present here the results of five years of ACE-FTS observations
in terms of monthly mean profiles of CO2 averaged over 10 degrees
latitude bands for northern mid-latitudes. These results are compared
with in-situ aircraft measurements and with simulations from two
different air transport models. Key features of the measured altitude
distribution of CO2 are shown to be accurately reproduced by the ACE-FTS
retrievals: variation in altitude of the seasonal cycle amplitude and
extrema, seasonal change of the vertical gradient, and mean growth rate.
We show that small but significant differences from model simulations
could result from an over estimation of the model circulation strength
during the northern hemisphere spring. Coupled with column measurements
from a nadir viewing instrument, it is expected that occultation
measurements will bring useful constraints to the surface carbon flux
determination.
BibTeX:
@article{foucher11a,
  author = {Foucher, P. Y. and Chedin, A. and Armante, R. and Boone, C. and Crevoisier, C. and Bernath, P.},
  title = {Carbon dioxide atmospheric vertical profiles retrieved from space observation using ACE-FTS solar occultation instrument},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2011},
  volume = {11},
  number = {6},
  pages = {2455--2470},
  doi = {https://doi.org/10.5194/acp-11-2455-2011}
}
Frankenberg, C., Bergamaschi, P., Butz, A., Houweling, S., Meirink, J.F., Notholt, J., Petersen, A.K., Schrijver, H., Warneke, T. and Aben, I. Tropical methane emissions: A revised view from SCIAMACHY onboard ENVISAT {2008} GEOPHYSICAL RESEARCH LETTERS
Vol. {35}({15}) 
article DOI  
Abstract: Methane retrievals from near-infrared spectra recorded by the SCIAMACHY
instrument onboard ENVISAT hitherto suggested unexpectedly large
tropical emissions. Even though recent studies confirm substantial
tropical emissions, there were indications for an unresolved error in
the satellite retrievals. Here we identify a retrieval error related to
inaccuracies in water vapor spectroscopic parameters, causing a
substantial overestimation of methane correlated with high water vapor
abundances. We report on the overall implications of an update in water
spectroscopy on methane retrievals with special focus on the tropics
where the impact is largest. The new retrievals are applied in a
four-dimensional variational (4D-VAR) data assimilation system to derive
a first estimate of the impact on tropical CH(4) sources. Compared to
inversions based on previous SCIAMACHY retrievals, annual tropical
emission estimates are reduced from 260 to about 201 Tg CH(4) but still
remain higher than previously anticipated.
BibTeX:
@article{frankenberg08a,
  author = {Frankenberg, Christian and Bergamaschi, Peter and Butz, Andre and Houweling, Sander and Meirink, Jan Fokke and Notholt, Justus and Petersen, Anna Katinka and Schrijver, Hans and Warneke, Thorsten and Aben, Ilse},
  title = {Tropical methane emissions: A revised view from SCIAMACHY onboard ENVISAT},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2008},
  volume = {35},
  number = {15},
  doi = {https://doi.org/10.1029/2008GL034300}
}
Frankenberg, C., Aben, I., Bergamaschi, P., Dlugokencky, E.J., van Hees, R., Houweling, S., van der Meer, P., Snel, R. and Tol, P. Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability {2011} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {116} 
article DOI  
Abstract: After a decade of stable or slightly decreasing global methane
concentrations, ground-based in situ data show that CH4 began increasing
again in 2007 and that this increase continued through 2009. So far,
space-based retrievals sensitive to the lower troposphere in the time
period under consideration have not been available. Here we report a
long-term data set of column-averaged methane mixing ratios retrieved
from spectra of the Scanning Imaging Absorption Spectrometer for
Atmospheric Cartography (SCIAMACHY) instrument onboard Envisat. The
retrieval quality after 2005 was severely affected by degrading detector
pixels within the methane 2v(3) absorption band. We identified the most
crucial problems in SCIAMACHY detector degradation and overcame the
problem by applying a strict pixel mask as well as a new dark current
characterization. Even though retrieval precision after the end of 2005
is invariably degraded, consistent methane retrievals from 2003 through
2009 are now possible. Regional time series in the Sahara, Australia,
tropical Africa, South America, and Asia show the methane increase in
2007-2009, but we cannot yet draw a firm conclusion concerning the
origin of the increase. Tropical Africa even seems to exhibit a negative
anomaly in 2006, but an impact from changes in SCIAMACHY detector
degradation cannot be excluded yet. Over Assakrem, Algeria, we observed
strong similarities between SCIAMACHY measurements and ground-based data
in deseasonalized time series. We further show long-term SCIAMACHY
xCH(4) averages at high spatial resolution that provide further insight
into methane variations on regional scales. The Red Basin in China
exhibits, on average, the highest methane abundance worldwide, while
other localized features such as the Sudd wetlands in southern Sudan can
also be identified in SCIAMACHY xCH(4) averages.
BibTeX:
@article{frankenberg11a,
  author = {Frankenberg, C. and Aben, I. and Bergamaschi, P. and Dlugokencky, E. J. and van Hees, R. and Houweling, S. and van der Meer, P. and Snel, R. and Tol, P.},
  title = {Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2010JD014849}
}
Frankenberg, C., Kulawik, S.S., Wofsy, S.C., Chevallier, F., Daube, B., Kort, E.A., O'Dell, C., Olsen, E.T. and Osterman, G. Using airborne HIAPER Pole-to-Pole Observations (HIPPO) to evaluate model and remote sensing estimates of atmospheric carbon dioxide {2016} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {16}({12}), pp. 7867-7878 
article DOI  
Abstract: In recent years, space-borne observations of atmospheric carbon dioxide
(CO2) have been increasingly used in global carbon-cycle studies. In
order to obtain added value from space-borne measurements, they have to
suffice stringent accuracy and precision requirements, with the latter
being less crucial as it can be reduced by just enhanced sample size.
Validation of CO2 column-averaged dry air mole fractions (XCO2) heavily
relies on measurements of the Total Carbon Column Observing Network
(TCCON). Owing to the sparseness of the network and the requirements
imposed on space-based measurements, independent additional validation
is highly valuable. Here, we use observations from the High-Performance
Instrumented Airborne Platform for Environmental Research (HIAPER)
Pole-to-Pole Observations (HIPPO) flights from 01/2009 through 09/2011
to validate CO2 measurements from satellites (Greenhouse Gases Observing
Satellite - GOSAT, Thermal Emission Sounder - TES, Atmospheric Infrared
Sounder - AIRS) and atmospheric inversion models (CarbonTracker CT2013B,
Monitoring Atmospheric Composition and Climate (MACC) v13r1). We find
that the atmospheric models capture the XCO2 variability observed in
HIPPO flights very well, with correlation coefficients (r(2)) of 0.93
and 0.95 for CT2013B and MACC, respectively. Some larger discrepancies
can be observed in profile comparisons at higher latitudes, in
particular at 300aEuro-hPa during the peaks of either carbon uptake or
release. These deviations can be up to 4aEuro-ppm and hint at
misrepresentation of vertical transport.
Comparisons with the GOSAT satellite are of comparable quality, with an
r(2) of 0.85, a mean bias mu of -0.06aEuro-ppm, and a standard deviation
sigma of 0.45aEuro-ppm. TES exhibits an r(2) of 0.75, mu of
0.34aEuro-ppm, and sigma of 1.13aEuro-ppm. For AIRS, we find an r(2) of
0.37, mu of 1.11aEuro-ppm, and sigma of 1.46aEuro-ppm, with
latitude-dependent biases. For these comparisons at least 6, 20, and 50
atmospheric soundings have been averaged for GOSAT, TES, and AIRS,
respectively. Overall, we find that GOSAT soundings over the remote
Pacific Ocean mostly meet the stringent accuracy requirements of about
0.5aEuro-ppm for space-based CO2 observations.
BibTeX:
@article{frankenberg16a,
  author = {Frankenberg, Christian and Kulawik, Susan S. and Wofsy, Steven C. and Chevallier, Frederic and Daube, Bruce and Kort, Eric A. and O'Dell, Christopher and Olsen, Edward T. and Osterman, Gregory},
  title = {Using airborne HIAPER Pole-to-Pole Observations (HIPPO) to evaluate model and remote sensing estimates of atmospheric carbon dioxide},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2016},
  volume = {16},
  number = {12},
  pages = {7867--7878},
  doi = {https://doi.org/10.5194/acp-16-7867-2016}
}
Fraser, A., Palmer, P.I., Feng, L., Boesch, H., Cogan, A., Parker, R., Dlugokencky, E.J., Fraser, P.J., Krummel, P.B., Langenfelds, R.L., O'Doherty, S., Prinn, R.G., Steele, L.P., van der Schoot, M. and Weiss, R.F. Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({11}), pp. 5697-5713 
article DOI  
Abstract: We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem
chemistry transport model, to estimate regional monthly methane (CH4)
fluxes for the period June 2009-December 2010 using proxy dry-air
column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse
gases Observing SATellite) and/or NOAA ESRL (Earth System Research
Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory)
CH4 surface mole fraction measurements. Global posterior estimates using
GOSAT and/or surface measurements are between 510-516 Tg yr(-1), which
is less than, though within the uncertainty of, the prior global flux of
529 +/- 25 Tg yr(-1). We find larger differences between regional prior
and posterior fluxes, with the largest changes in monthly emissions (75
Tg yr(-1)) occurring in Temperate Eurasia. In non-boreal regions the
error reductions for inversions using the GOSAT data are at least three
times larger (up to 45 %) than if only surface data are assimilated, a
reflection of the greater spatial coverage of GOSAT, with the two
exceptions of latitudes >60 degrees associated with a data filter and
over Europe where the surface network adequately describes fluxes on our
model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2
model output to investigate model error on quantifying proxy GOSAT XCH4
(involving model XCO2) and inferring methane flux estimates from surface
mole fraction data and show similar resulting fluxes, with differences
reflecting initial differences in the proxy value. Using a series of
observing system simulation experiments (OSSEs) we characterize the
posterior flux error introduced by non-uniform atmospheric sampling by
GOSAT. We show that clear-sky measurements can theoretically reproduce
fluxes within 10% of true values, with the exception of tropical
regions where, due to a large seasonal cycle in the number of
measurements because of clouds and aerosols, fluxes are within 15% of
true fluxes. We evaluate our posterior methane fluxes by incorporating
them into GEOS-Chem and sampling the model at the location and time of
surface CH4 measurements from the AGAGE (Advanced Global Atmospheric
Gases Experiment) network and column XCH4 measurements from TCCON (Total
Carbon Column Observing Network). The posterior fluxes modestly improve
the model agreement with AGAGE and TCCON data relative to prior fluxes,
with the correlation coefficients (r(2)) increasing by a mean of 0.04
(range: -0.17 to 0.23) and the biases decreasing by a mean of 0.4 ppb
(range: -8.9 to 8.4 ppb).
BibTeX:
@article{fraser13a,
  author = {Fraser, A. and Palmer, P. I. and Feng, L. and Boesch, H. and Cogan, A. and Parker, R. and Dlugokencky, E. J. and Fraser, P. J. and Krummel, P. B. and Langenfelds, R. L. and O'Doherty, S. and Prinn, R. G. and Steele, L. P. and van der Schoot, M. and Weiss, R. F.},
  title = {Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {11},
  pages = {5697--5713},
  doi = {https://doi.org/10.5194/acp-13-5697-2013}
}
Freeman, N.M., Munro, D.R., Sprintall, J., Mazloff, M.R., Purkey, S., Rosso, I., DeRanek, C.A. and Sweeney, C. The Observed Seasonal Cycle of Macronutrients in Drake Passage: Relationship to Fronts and Utility as a Model Metric {2019} JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
Vol. {124}({7}), pp. {4763-4783} 
article DOI URL 
Abstract: The Drake Passage Time-series (DPT) is used to quantify the spatial and seasonal variability of historically undersampled, biogeochemically relevant properties across the Drake Passage. From 2004-2017, discrete ship-based observations of surface macronutrients (silicate, nitrate, and phosphate), temperature, and salinity have been collected 5-8 times per year as part of the DPT program. Using the DPT and Antarctic Circumpolar Current (ACC) front locations derived from concurrent expendable bathythermograph data, the distinct physical and biogeochemical characteristics of ACC frontal zones are characterized. Biogeochemical-Argo floats in the region confirm that the near-surface sampling scheme of the DPT robustly captures mixed-layer biogeochemistry. While macronutrient concentrations consistently increase toward the Antarctic continent, their meridional distribution, variability, and biogeochemical gradients are unique across physical ACC fronts, suggesting a combination of physical and biological processes controlling nutrient availability and nutrient front location. The Polar Front is associated with the northern expression of the Silicate Front, marking the biogeographically relevant location between silicate-poor and silicate-rich waters. South of the northern Silicate Front, the silicate-to-nitrate ratio increases, with the sharpest gradient in silicate associated with the Southern ACC Front (i.e., the southern expression of the Silicate Front). Nutrient cycling is an important control on variability in the surface ocean partial pressure of carbon dioxide (pCO(2)). The robust characterization of the spatiotemporal variability of nutrients presented here highlights the utility of biogeochemical time series for diagnosing and potentially reducing biases in modeling Southern Ocean pCO(2) variability, and by inference, air-sea CO2 flux. Plain Language Summary Nutrients fuel phytoplankton communities that are important in the marine food web and global carbon cycling. Understanding modern-day nutrient availability and its physical and biological drivers is critical to accurately predict future climate with models. The Southern Ocean helps regulate climate and is vulnerable to future change, but as one of the least sampled oceans, physical and biogeochemical processes are still not fully understood. This study uses the 13-year Drake Passage Time-series, the longest year-round biogeochemical time series in the Southern Ocean, to quantify nutrient availability and variability on seasonal time scales. Across Drake Passage, temperatures decrease and nutrients increase toward Antarctica, exhibiting sharp gradients at currents and creating conditions favoring distinct phytoplankton groups. Nutrients are used by phytoplankton in summer and regenerated and resupplied by mixing in winter; these processes draw surface ocean carbon down in summer and increase carbon in winter. While nitrate is a necessary nutrient for all phytoplankton, silicate is only required by a single major phytoplankton group. Simultaneous observations of both nutrients allows us to better understand group-specific productivity and, ultimately, its impact on climate.
BibTeX:
@article{freeman19a,
  author = {Freeman, Natalie M. and Munro, David R. and Sprintall, Janet and Mazloff, Matthew R. and Purkey, Sarah and Rosso, Isabella and DeRanek, Carissa A. and Sweeney, Colm},
  title = {The Observed Seasonal Cycle of Macronutrients in Drake Passage: Relationship to Fronts and Utility as a Model Metric},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2019},
  volume = {124},
  number = {7},
  pages = {4763--4783},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JC015052},
  doi = {https://doi.org/10.1029/2019JC015052}
}
Fu, D., Chen, B., Zhang, H., Wang, J., Black, T.A., Amiro, B.D., Bohrer, G., Bolstad, P., Coulter, R., Rahman, A.F., Dunn, A., McCaughey, J.H., Meyers, T. and Verma, S. Estimating landscape net ecosystem exchange at high spatial-temporal resolution based on Landsat data, an improved upscaling model framework, and eddy covariance flux measurements {2014} REMOTE SENSING OF ENVIRONMENT
Vol. {141}, pp. 90-104 
article DOI  
Abstract: More accurate estimation of the carbon dioxide flux depends on the
improved scientific understanding of the terrestrial carbon cycle.
Remote-sensing-based approaches to continental-scale estimation of net
ecosystem exchange (NEE) have been developed but coarse spatial
resolution is a source of errors. Here we demonstrate a satellite-based
method of estimating NEE using Landsat TM/ETM + data and an upscaling
framework. The upscaling framework contains flux-footprint climatology
modeling, modified regression tree (MRT) analysis and image fusion. By
scaling NEE measured at flux towers to landscape and regional scales,
this satellite-based method can improve NEE estimation at high
spatial-temporal resolution at the landscape scale relative to methods
based on MODIS data with coarser spatial-temporal resolution. This
method was applied to sixteen flux sites from the Canadian Carbon
Program and AmeriFlux networks located in North America, covering
forest, grass, and cropland biomes. Compared to a similar method using
MODIS data, our estimation is more effective for diagnosing landscape
NEE with the same temporal resolution and higher spatial resolution (30
m versus 1 km) (r(2) = 0.7548 vs. 0.5868, RMSE = 1.3979 vs. 1.7497 g C
m-(2) day(-1), average error = 0.8950 vs. 1.0178 g C m(-2) day(-1),
relative error = 0.47 vs. 0.54 for fused Landsat and MODIS imagery,
respectively). We also compared the regional NEE estimations using
Carbon Tracker, our method and eddy-covariance observations. This study
demonstrates that the data-driven satellite-based NEE diagnosed model
can be used to upscale eddy-flux observations to landscape scales with
high spatial-temporal resolutions. (C) 2013 Elsevier Inc. All rights
reserved.
BibTeX:
@article{fu14a,
  author = {Fu, Dongjie and Chen, Baozhang and Zhang, Huifang and Wang, Juan and Black, T. Andy and Amiro, Brian D. and Bohrer, Gil and Bolstad, Paul and Coulter, Richard and Rahman, Abdullah F. and Dunn, Allison and McCaughey, J. Harry and Meyers, Tilden and Verma, Shashi},
  title = {Estimating landscape net ecosystem exchange at high spatial-temporal resolution based on Landsat data, an improved upscaling model framework, and eddy covariance flux measurements},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2014},
  volume = {141},
  pages = {90--104},
  doi = {https://doi.org/10.1016/j.rse.2013.10.029}
}
Fu, C., Ma, Z., Ai, L., Guo, W., Wang, S. and Zhang, R. LAND-ATMOSPHERE INTERACTION IN SEMI-ARID REGIONS: ASIA PERSPECTIVE BASED ON OBSERVATION AND MODELING 2017   book URL 
Abstract: Atmospheric chemistry in background areas is strongly influenced by natural vegetation. Boreal coniferous forests are known to produce large quantities of volatile vapours, especially terpenes to the surrounding air 1. These compounds react with OH and O3, and …
BibTeX:
@book{fu17a,
  author = {Congbin Fu and Zhuguo Ma and Likun Ai and Weidong Guo and Shuyu Wang and Renjian Zhang},
  title = {LAND-ATMOSPHERE INTERACTION IN SEMI-ARID REGIONS: ASIA PERSPECTIVE BASED ON OBSERVATION AND MODELING},
  publisher = {World Scientific Series on Asia-Pacific Weather and Climate},
  year = {2017},
  url = {https://ileaps.org/sites/default/files/Oral_presentations.pdf}
}
Fu, Y., Liao, H., Tian, X., Gao, H., Jia, B. and Han, R. Impact of Prior Terrestrial Carbon Fluxes on Simulations of Atmospheric CO2 Concentrations 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(18) 
article DOI  
Abstract: Terrestrial ecosystems have a significant role in shaping the
distribution of atmospheric CO2, but it is uncertain how much they
affect CO2 concentrations. We assessed the impact of terrestrial fluxes
derived from different biosphere models in the Multi-scale Synthesis and
Terrestrial Model Intercomparison Project (MsTMIP) on atmospheric CO2
estimations based on a global chemical transport model (GEOS-Chem) when
these fluxes were applied as prior information. We examined the
spatiotemporal uncertainty in terrestrial flux estimations from 15
MsTMIP terrestrial fluxes. We found high uncertainties in the
terrestrial fluxes for temperate North America, tropical and temperate
South America, southern Africa, Europe and tropical Asia. Sensitivity
simulations showed that the annual mean CO2 concentration changed by
6.0-8.0 ppmv with the spread of the terrestrial fluxes. The interannual
trend in the terrestrial fluxes could significantly affect the simulated
trend of atmospheric CO2 concentrations. As a result of the spread in
the prior terrestrial fluxes, large differences in the daily mean CO2
anomalies changed with an interquartile range of -1.0 to +1.0 ppmv and
the magnitude of change in the sub-daily CO2 concentrations was in the
range 4.0-6.0 ppmv for China, the USA and Europe. Our results suggest an
urgent need to increase the reliability of terrestrial flux estimates in
CO2 simulations. Surface seasonal CO2 concentrations were simulated to
change by +/- 2.0 ppmv in most regions of the world due to the
differences in the ensemble mean fluxes, reflecting the impact of the
uncertainties in the existing optimized terrestrial fluxes on CO2
simulations.
BibTeX:
@article{fu21a,
  author = {Fu, Yu and Liao, Hong and Tian, Xiangjun and Gao, Hao and Jia, Binghao and Han, Rui},
  title = {Impact of Prior Terrestrial Carbon Fluxes on Simulations of Atmospheric CO2 Concentrations},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {18},
  doi = {https://doi.org/10.1029/2021JD034794}
}
Gabrys, J. Sink: the dirt of systems 2009 Environment and Planning D: Society and Space
Vol. 27(4), pp. 666-681 
article DOI  
BibTeX:
@article{gabrys09a,
  author = {Gabrys, Jennifer},
  title = {Sink: the dirt of systems},
  journal = {Environment and Planning D: Society and Space},
  year = {2009},
  volume = {27},
  number = {4},
  pages = {666--681},
  doi = {https://doi.org/10.1068/d5708}
}
Gahlot, S., Shu, S., Jain, A. and Roy, S.B. Estimating Trends and Variation of Net Biome Productivity in India for 1980--2012 Using a Land Surface Model 2017 Geophysical Research Letters  article  
BibTeX:
@article{gahlot17a,
  author = {S Gahlot and S Shu and AK Jain and S Baidya Roy},
  title = {Estimating Trends and Variation of Net Biome Productivity in India for 1980--2012 Using a Land Surface Model},
  journal = {Geophysical Research Letters},
  year = {2017}
}
Gately, C.K., Hutyra, L.R., Wing, I.S. and Brondfield, M.N. A Bottom up Approach to on-Road CO2 Emissions Estimates: Improved Spatial Accuracy and Applications for Regional Planning {2013} ENVIRONMENTAL SCIENCE & TECHNOLOGY
Vol. {47}({5}), pp. 2423-2430 
article DOI  
Abstract: On-road transportation is responsible for 28% of all U.S. fossil-fuel
CO2 emissions. Mapping vehicle emissions at regional scales is
challenging due to data limitations. Existing emission inventories use
spatial proxies such as population and road density to downscale
national or state-level data. Such procedures introduce errors where the
proxy variables and actual emissions are weakly correlated, and limit
analysis of the relationship between emissions and demographic trends at
local scales. We develop an onroad emission inventory product for
Massachusetts-based on roadway-level traffic data obtained from the
Highway Performance Monitoring System (HPMS). We provide annual
estimates of on-road CO2 emissions at a 1 x 1 km grid scale for the
years 1980 through 2008. We compared our results with on-road emissions
estimates from the Emissions Database for Global Atmospheric Research
(EDGAR), with the Vulcan Product, and with estimates derived from state
fuel consumption statistics reported by the Federal Highway
Administration (FHWA). Our model differs from FHWA estimates by less
than 8.5% on average, and is within 596 of Vulcan estimates. We found
that EDGAR estimates systematically exceed FHWA by an average of 22.8%.
Panel regression analysis of per-mile CO2 emissions on population
density at the town scale shows a statistically significant correlation
that varies systematically in sign and magnitude as population density
increases. Population density has a positive correlation with per-mile
CO2 emissions for densities below 2000 persons km(-2), above which
increasing density correlates negatively with per-mile emissions.
BibTeX:
@article{gately13a,
  author = {Gately, Conor K. and Hutyra, Lucy R. and Wing, Ian Sue and Brondfield, Max N.},
  title = {A Bottom up Approach to on-Road CO2 Emissions Estimates: Improved Spatial Accuracy and Applications for Regional Planning},
  journal = {ENVIRONMENTAL SCIENCE & TECHNOLOGY},
  year = {2013},
  volume = {47},
  number = {5},
  pages = {2423--2430},
  doi = {https://doi.org/10.1021/es304238v}
}
Gately, C.K. Emissions from mobile sources: Improved understanding of the drivers of emissions and their spatial patterns 2016 School: Boston University  phdthesis URL 
BibTeX:
@phdthesis{gately16a,
  author = {Gately, Conor Kennedy},
  title = {Emissions from mobile sources: Improved understanding of the drivers of emissions and their spatial patterns},
  school = {Boston University},
  year = {2016},
  url = {http://search.proquest.com/openview/660fb3eced8341af00fe6f17a1aee2f4/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Gately, C.K. and Hutyra, L.R. Large Uncertainties in Urban-Scale Carbon Emissions {2017} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {122}({20}), pp. 11242-11260 
article DOI  
Abstract: Accurate estimates of fossil fuel carbon dioxide (FFCO2) emissions are a
critical component of local, regional, and global climate agreements.
Current global inventories of FFCO2 emissions do not directly quantify
emissions at local scales; instead, spatial proxies like population
density, nighttime lights, and power plant databases are used to
downscale emissions from national totals. We have developed a
high-resolution (hourly, 1 km(2)) bottom-up Anthropogenic Carbon
Emissions System (ACES) for FFCO2, based on local activity data for the
year 2011 across the northeastern U.S. We compare ACES with three widely
used global inventories, finding significant differences at regional
(20%) and city scales (50-250%). At a spatial resolution of 0.1
degrees, inventories differ by over 100% for half of the grid cells in
the domain, with the largest differences in urban areas and oil and gas
production regions. Given recent U.S. federal policy pull backs
regarding greenhouse gas emissions reductions, inventories like ACES are
crucial for U.S. actions, as the impetus for climate leadership has
shifted to city and state governments. The development of a robust
carbon monitoring system to track carbon fluxes is critical for
emissions benchmarking and verification. We show that existing
downscaled inventories are not suitable for urban emissions monitoring,
as they do not consider important local activity patterns. The ACES
methodology is designed for easy updating, making it suitable for
emissions monitoring under most city, regional, and state greenhouse gas
mitigation initiatives, in particular, for the small-and medium-sized
cities that lack the resources to regularly perform their own bottom-up
emissions inventories.
BibTeX:
@article{gately17a,
  author = {Gately, C. K. and Hutyra, L. R.},
  title = {Large Uncertainties in Urban-Scale Carbon Emissions},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2017},
  volume = {122},
  number = {20},
  pages = {11242--11260},
  doi = {https://doi.org/10.1002/2017JD027359}
}
Gaubert, B., Stephens, B.B., Basu, S., Chevallier, F., Deng, F., Kort, E.A., Patra, P.K., Peters, W., Roedenbeck, C., Saeki, T., Schimel, D., Van der Laan-Luijkx, I., Wofsy, S. and Yin, Y. Global atmospheric CO2 inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate {2019} BIOGEOSCIENCES
Vol. {16}({1}), pp. {117-134} 
article DOI URL 
Abstract: We have compared a suite of recent global CO2 atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical (NET) vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO2 concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft campaigns over the mid-Pacific in 2009-2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their broad latitudinal separation of land fluxes has converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom 3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80% since TransCom 3 and 70% since RECCAP. Most modeled CO2 fields agree reasonably well with the HIPPO observations, specifically for the annual mean vertical gradients in the Northern Hemisphere. Northern Hemisphere vertical mixing no longer appears to be a dominant driver of northern versus tropical (T) annual flux differences. Our newer suite of models still gives northern extratropical land uptake that is modest relative to previous estimates (Gurney et al., 2002; Peylin et al., 2013) and near-neutral tropical land uptake for 2009-2011. Given estimates of emissions from deforestation, this implies a continued uptake in intact tropical forests that is strong relative to historical estimates (Gurney et al., 2002; Peylin et al., 2013). The results from these models for other time periods (2004-2014, 2001-2004, 1992-1996) and re-evaluation of the TransCom 3 Level 2 and RECCAP results confirm that tropical land carbon fluxes including deforestation have been near neutral for several decades. However, models still have large disagreements on ocean-land partitioning. The fossil fuel (FF) and the atmospheric growth rate terms have been thought to be the best-known terms in the global carbon budget, but we show that they currently limit our ability to assess regional-scale terrestrial fluxes and ocean-land partitioning from the model ensemble.
BibTeX:
@article{gaubert19a,
  author = {Gaubert, Benjamin and Stephens, Britton B. and Basu, Sourish and Chevallier, Frederic and Deng, Feng and Kort, Eric A. and Patra, Prabir K. and Peters, Wouter and Roedenbeck, Christian and Saeki, Tazu and Schimel, David and Van der Laan-Luijkx, Ingrid and Wofsy, Steven and Yin, Yi},
  title = {Global atmospheric CO2 inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate},
  journal = {BIOGEOSCIENCES},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {16},
  number = {1},
  pages = {117--134},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://bg.copernicus.org/articles/16/117/2019/},
  doi = {https://doi.org/10.5194/bg-16-117-2019}
}
Gaudet, B.J., Davis, K.J., Pal, S., Jacobson, A., Schuh, A., Lauvaux, T., Feng, S. and Browell, E. Regional-scale, sector-specific evaluation of global CO2 inversion models using aircraft data from the ACT-America project 2021 Journal of Geophysical Research -- Atmospheres  article URL 
Abstract: We use 148 airborne vertical profiles of CO2 for frontal cases from the summer 2016 Atmospheric Carbon and Transport---America (ACT‐America) campaign to evaluate the skill of 10 global CO2 in situ inversion models from the version 7 Orbiting Carbon Observatory--2 …
BibTeX:
@article{gaudet21a,
  author = {B. J. Gaudet and K. J. Davis and S. Pal and A.R. Jacobson and A. Schuh and T. Lauvaux and S. Feng and E.V. Browell},
  title = {Regional-scale, sector-specific evaluation of global CO2 inversion models using aircraft data from the ACT-America project},
  journal = {Journal of Geophysical Research -- Atmospheres},
  year = {2021},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JD033623}
}
Geibel, M.C. Measurement of climate-relevant trace gases via infrared spectroscopy 2011 School: Friedrich-Schiller-Universitat Jena  phdthesis URL 
BibTeX:
@phdthesis{geibel11a,
  author = {Geibel, Marc Christoph},
  title = {Measurement of climate-relevant trace gases via infrared spectroscopy},
  school = {Friedrich-Schiller-Universitat Jena},
  year = {2011},
  url = {https://d-nb.info/1016620160/34}
}
Gennaretti, F., Gea-Izquierdo, G., Boucher, E., Berninger, F., Arseneault, D. and Guiot, J. Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest {2017} BIOGEOSCIENCES
Vol. {14}({21}), pp. 4851-4866 
article DOI  
Abstract: A better understanding of the coupling between photosynthesis and carbon
allocation in the boreal forest, together with its associated
environmental factors and mechanistic rules, is crucial to accurately
predict boreal forest carbon stocks and fluxes, which are significant
components of the global carbon budget. Here, we adapted the MAIDEN
ecophysiological forest model to consider important processes for boreal
tree species, such as nonlinear acclimation of photosynthesis to
temperature changes, canopy development as a function of previous-year
climate variables influencing bud formation and the temperature
dependence of carbon partition in summer. We tested these modifications
in the eastern Canadian taiga using black spruce (Picea mariana (Mill.)
B.S.P.) gross primary production and ring width data. MAIDEN explains
90% of the observed daily gross primary production variability, 73% of
the annual ring width variability and 20-30% of its high-frequency
component (i.e., when decadal trends are removed). The positive effect
on stem growth due to climate warming over the last several decades is
well captured by the model. In addition, we illustrate how we improve
the model with each introduced model adaptation and compare the model
results with those of linear response functions. Our results demonstrate
that MAIDEN simulates robust relationships with the most important
climate variables (those detected by classical response-function
analysis) and is a powerful tool for understanding how environmental
factors interact with black spruce ecophysiol-ogy to influence
present-day and future boreal forest carbon fluxes.
BibTeX:
@article{gennaretti17a,
  author = {Gennaretti, Fabio and Gea-Izquierdo, Guillermo and Boucher, Etienne and Berninger, Frank and Arseneault, Dominique and Guiot, Joel},
  title = {Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest},
  journal = {BIOGEOSCIENCES},
  year = {2017},
  volume = {14},
  number = {21},
  pages = {4851--4866},
  doi = {https://doi.org/10.5194/bg-14-4851-2017}
}
Georgoulias, A.K., Kourtidis, K.A., Buchwitz, M., Schneising, O. and Burrows, J.P. A case study on the application of SCIAMACHY satellite methane measurements for regional studies: the Greater Area of the Eastern Mediterranean {2011} INTERNATIONAL JOURNAL OF REMOTE SENSING
Vol. {32}({3}), pp. 787-813 
article DOI  
Abstract: Many studies have focused on geological formations, such as mud
volcanoes, which abound in the Greater Area of the Eastern Mediterranean
(GAEM; 25 degrees N-50 degrees N, 5 degrees E-55 degrees E). This
geological source is thought to provide a significant portion of the
global methane (CH4) emissions. However, studies in the GAEM have
focused on specific locations rather than extensive areas, which has led
to a gap in our understanding of the spatial and temporal variability of
CH4 atmospheric mixing ratios. Here, we present characteristics of
methane loading over land in the GAEM using dry air columnar data (XCH4)
retrieved from SCIAMACHY (Scanning Imaging Absorption Spectrometer for
Atmospheric Cartography) satellite measurements with the Weighting
Function Modified Differential Optical Absorption Spectroscopy
(WFM-DOAS) version 1.0 algorithm. We defined methane annual, seasonal
and monthly spatial patterns over the area using 2003 and 2004
measurements. The annual mean XCH4 levels over the study area were
estimated to be 1761 +/- 27 ppb for 2003 and 1758 +/- 26 ppb for 2004. A
seasonal variability with a summer-autumn peak was observed for both
2003 and 2004, August being the month with the highest methane
concentrations. The northeastern part of the area exhibits the highest
XCH4 values while the high elevation regions defined by the triangle of
eastern Turkey, the Persian Gulf and the Caspian Sea and the region of
the eastern coast of the Red Sea exhibit the lowest levels. A
latitudinal gradient was observed for the area during 2003 and 2004. A
comparison of measured XCH4 levels above two of the world's most
renowned mud volcano regions situated in the GAEM with anticipated
methane columnar concentrations as modelled for eruption cases shows
that no mud volcano eruptions were observed from SCIAMACHY during 2003
or 2004.
BibTeX:
@article{georgoulias11a,
  author = {Georgoulias, A. K. and Kourtidis, K. A. and Buchwitz, M. and Schneising, O. and Burrows, J. P.},
  title = {A case study on the application of SCIAMACHY satellite methane measurements for regional studies: the Greater Area of the Eastern Mediterranean},
  journal = {INTERNATIONAL JOURNAL OF REMOTE SENSING},
  year = {2011},
  volume = {32},
  number = {3},
  pages = {787--813},
  doi = {https://doi.org/10.1080/01431161.2010.517791}
}
Gerbig, C., Dolman, A.J. and Heimann, M. On observational and modelling strategies targeted at regional carbon exchange over continents {2009} BIOGEOSCIENCES
Vol. {6}({10}), pp. 1949-1959 
article DOI  
Abstract: Estimating carbon exchange at regional scales is paramount to
understanding feedbacks between climate and the carbon cycle, but also
to verifying climate change mitigation such as emission reductions and
strategies compensating for emissions such as carbon sequestration. This
paper discusses evidence for a number of important shortcomings of
current generation modelling frameworks designed to provide regional
scale budgets from atmospheric observations. Current top-down and
bottom-up approaches targeted at deriving consistent regional scale
carbon exchange estimates for biospheric and anthropogenic sources and
sinks are hampered by a number of issues: we show that top-down
constraints using point measurements made from tall towers, although
sensitive to larger spatial scales, are however influenced by local
areas much more strongly than previously thought. On the other hand,
classical bottom-up approaches using process information collected at
the local scale, such as from eddy covariance data, need up-scaling and
validation on larger scales. We therefore argue for a combination of
both approaches, implicitly providing the important local scale
information for the top-down constraint, and providing the atmospheric
constraint for up-scaling of flux measurements. Combining these data
streams necessitates quantifying their respective representation errors,
which are discussed. The impact of these findings on future network
design is highlighted, and some recommendations are given.
BibTeX:
@article{gerbig09a,
  author = {Gerbig, C. and Dolman, A. J. and Heimann, M.},
  title = {On observational and modelling strategies targeted at regional carbon exchange over continents},
  journal = {BIOGEOSCIENCES},
  year = {2009},
  volume = {6},
  number = {10},
  pages = {1949--1959},
  doi = {https://doi.org/10.5194/bg-6-1949-2009}
}
Gerken, T., Feng, S., Keller, K., Lauvaux, T., DiGangi, J.P., Choi, Y., Baier, B. and Davis, K.J. Examining CO2 Model Observation Residuals Using ACT-America Data 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(18) 
article DOI  
Abstract: Atmospheric CO2 inversion typically relies on the specification of prior
flux and atmospheric model transport errors, which have large
uncertainties. Here, we used ACT-America airborne observations to
compare CO2 model observation mismatch in the eastern U.S. and during
four climatological seasons for the mesoscale WRF(-Chem) and global
scale CarbonTracker/TM5 (CT) models. Models used identical surface
carbon fluxes, and CT was used as CO2 boundary condition for WRF. Both
models showed reasonable agreement with observations, and CO2 residuals
follow near symmetric peaked (i.e., non-Gaussian) distribution with
near-zero bias of both models (CT: -0.34 +/- 3.12 ppm; WRF: 0.82 +/-
4.37 ppm). We also found large magnitude residuals at the tails of the
distribution that contribute considerably to overall bias. Atmospheric
boundary-layer biases (1-10 ppm) were much larger than free tropospheric
biases (0.5-1 ppm) and were of same magnitude as model-model
differences, whereas free tropospheric biases were mostly governed by
CO2 background conditions. Results revealed systematic differences in
atmospheric transport, most pronounced in the warm and cold sectors of
synoptic systems, highlighting the importance of transport for CO2
residuals. While CT could reproduce the principal CO2 dynamics
associated with synoptic systems, WRF showed a clearer distinction for
CO2 differences across fronts. Variograms were used to quantify spatial
correlation of residuals and showed characteristic residual length
scales of approximately 100-300 km. Our findings suggest that inclusion
of synoptic weather-dependent and non-Gaussian error structure may
benefit inversion systems.
BibTeX:
@article{gerken21a,
  author = {Gerken, Tobias and Feng, Sha and Keller, Klaus and Lauvaux, Thomas and DiGangi, Joshua P. and Choi, Yonghoon and Baier, Bianca and Davis, Kenneth J.},
  title = {Examining CO2 Model Observation Residuals Using ACT-America Data},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {18},
  doi = {https://doi.org/10.1029/2020JD034481}
}
Geyer, N.M. Time-filtered inverse modeling of land-atmosphere carbon exchange 2015 School: Colorado State University  phdthesis URL 
BibTeX:
@phdthesis{geyer15a,
  author = {Geyer, Nicholas M},
  title = {Time-filtered inverse modeling of land-atmosphere carbon exchange},
  school = {Colorado State University},
  year = {2015},
  url = {http://search.proquest.com/openview/e038a9c458ca8f6d6358546eff579bf6/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Gilmanov, T.G., Aires, L., Barcza, Z., Baron, V.S., Belelli, L., Beringer, J., Billesbach, D., Bonal, D., Bradford, J., Ceschia, E., Cook, D., Corradi, C., Frank, A., Gianelle, D., Gimeno, C., Gruenwald, T., Guo, H., Hanan, N., Haszpra, L., Heilman, J., Jacobs, A., Jones, M.B., Johnson, D.A., Kiely, G., Li, S., Magliulo, V., Moors, E., Nagy, Z., Nasyrov, M., Owensby, C., Pinter, K., Pio, C., Reichstein, M., Sanz, M.J., Scott, R., Soussana, J.F., Stoy, P.C., Svejcar, T., Tuba, Z. and Zhou, G. Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements {2010} RANGELAND ECOLOGY & MANAGEMENT
Vol. {63}({1}), pp. 16-39 
article DOI  
Abstract: Grasslands and agroecosystems occupy one-third of the terrestrial area,
but their contribution to the global carbon cycle remains uncertain. We
used a set of 316 site-years of CO(2) exchange measurements to quantify
gross primary productivity, respiration, and light-response parameters
of grasslands, shrublands/savanna, wetlands, and cropland ecosystems
worldwide. We analyzed data from 72 global flux-tower sites partitioned
into gross photosynthesis and ecosystem respiration with the use of the
light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z.
Saliendra. 2003. Growing season CO(2) fluxes in a sagebrushsteppe
ecosystem in Idaho: Bowen ratio/energy balance measurements and
modeling. Basic and Applied Ecology 4:167-183) from the RANGEFLUX and
WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET
La Thuile data set partitioned with the use of the temperature-response
method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini,
M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T.
Gilmanov, A. Granier, T. Grunwald, K. Havrankova, D. Janous, A. Knohl,
T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F.
Miglietta, J.M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E.
Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and
D. Yakir. 2005. On the separation of net ecosystem exchange into
assimilation and ecosystem respiration: review and improved algorithm.
Global Change Biology 11: 1.424-1439). Maximum values of the quantum
yield (alpha = 75 mmol.mol(-1)), photosynthetic capacity (A(max) = 3.4
mg CO(2) . m(-2).s-1), gross photosynthesis (P(g,max) = 1.16 g CO(2) .
m(-2).d(-1)), and ecological light-use efficiency (epsilon(ecol) = 59
mmol . mol(-1)) of managed grasslands and high-production croplands
exceeded those of most forest ecosystems, indicating the potential of
nonforest ecosystems for uptake of atmospheric CO(2). Maximum values of
gross primary production (8 600 g CO(2) . m(-2).yr(-1)), total ecosystem
respiration (7 900 g CO(2) . m(-2).yr(-1)), and net CO(2) exchange (2
400 g CO(2) . m(-2).yr(-1)) were observed for intensively managed
grasslands and high-yield crops, and are comparable to or higher than
those for forest ecosystems, excluding some tropical forests. On
average, 80% of the nonforest sites were apparent sinks for atmospheric
CO(2), with mean net uptake of 700 g CO(2) . m(-2).yr(-1) for intensive
grasslands and 933 g CO(2) . m(-2).d(-1) for croplands. However, part of
these apparent sinks is accumulated in crops and forage, which are
carbon pools that are harvested, transported, and decomposed off site.
Therefore, although agricultural fields may be predominantly sinks for
atmospheric CO(2), this does not imply that they are necessarily
increasing their carbon stock.
BibTeX:
@article{gilmanov10a,
  author = {Gilmanov, Tagir G. and Aires, L. and Barcza, Z. and Baron, V. S. and Belelli, L. and Beringer, J. and Billesbach, D. and Bonal, D. and Bradford, J. and Ceschia, E. and Cook, D. and Corradi, C. and Frank, A. and Gianelle, D. and Gimeno, C. and Gruenwald, T. and Guo, Haiqiang and Hanan, N. and Haszpra, L. and Heilman, J. and Jacobs, A. and Jones, M. B. and Johnson, D. A. and Kiely, G. and Li, Shenggong and Magliulo, V. and Moors, E. and Nagy, Z. and Nasyrov, M. and Owensby, C. and Pinter, K. and Pio, C. and Reichstein, M. and Sanz, M. J. and Scott, R. and Soussana, J. F. and Stoy, P. C. and Svejcar, T. and Tuba, Z. and Zhou, Guangsheng},
  title = {Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements},
  journal = {RANGELAND ECOLOGY & MANAGEMENT},
  year = {2010},
  volume = {63},
  number = {1},
  pages = {16--39},
  doi = {https://doi.org/10.2111/REM-D-09-00072.1}
}
Glaser, R., Castello-Blindt, P.O. and Yin, J. Biomimetic Approaches to Reversible CO2 Capture from Air. N-Methylcarbaminic Acid Formation in Rubsico-Inspired Models 2013 New and Future Developments in Catalysis: Activation of Carbon Dioxide, pp. 501-534  article URL 
BibTeX:
@article{glaser13a,
  author = {Glaser, Rainer and Castello-Blindt, Paula O and Yin, Jian},
  title = {Biomimetic Approaches to Reversible CO2 Capture from Air. N-Methylcarbaminic Acid Formation in Rubsico-Inspired Models},
  journal = {New and Future Developments in Catalysis: Activation of Carbon Dioxide},
  year = {2013},
  pages = {501--534},
  url = {https://faculty.missouri.edu/ glaserr/vitpub/NMCA_Chapter.pdf}
}
Gockede, M., Michalak, A.M., Vickers, D., Turner, D.P. and Law, B.E. Atmospheric inverse modeling to constrain regional-scale CO2 budgets at high spatial and temporal resolution {2010} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {115} 
article DOI  
Abstract: We present an inverse modeling framework designed to constrain CO2
budgets at regional scales. The approach captures atmospheric transport
processes in high spatiotemporal resolution by coupling a mesoscale
model with Lagrangian Stochastic backward trajectories. Terrestrial
biosphere CO2 emissions are generated through a simple diagnostic flux
model that splits the net ecosystem exchange into its major components
of gross primary productivity and autotrophic and heterotrophic
respirations. The modeling framework assimilates state-of-the-art data
sets for advected background CO2 and anthropogenic fossil fuel emissions
as well as highly resolved remote sensing products. We introduce a
Bayesian inversion setup, optimizing a posteriori flux base rates for
surface types that are defined through remote sensing information. This
strategy significantly reduces the number of parameters to be optimized
compared with solving fluxes for each individual grid cell, thus
permitting description of the surface in a very high resolution. The
model is tested using CO2 concentrations measured in the fall and winter
of 2006 at two AmeriFlux sites in Oregon. Because this database does not
cover a full seasonal cycle, we focus on conducting model sensitivity
tests rather than producing quantitative CO2 flux estimates. Sensitivity
tests on the influence of spatial and temporal resolution indicate that
optimum results can be obtained using 4 h time steps and grid sizes of 6
km or less. Further tests demonstrate the importance of dividing biome
types by ecoregions to capture their different biogeochemical responses
to external forcings across climatic gradients. Detailed stand age
information was shown to have a positive effect on model performance.
BibTeX:
@article{gockede10a,
  author = {Gockede, Mathias and Michalak, Anna M. and Vickers, Dean and Turner, David P. and Law, Beverly E.},
  title = {Atmospheric inverse modeling to constrain regional-scale CO2 budgets at high spatial and temporal resolution},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2010},
  volume = {115},
  doi = {https://doi.org/10.1029/2009JD012257}
}
Gockede, M., Turner, D.P., Michalak, A.M., Vickers, D. and Law, B.E. Sensitivity of a subregional scale atmospheric inverse CO2 modeling framework to boundary conditions {2010} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {115} 
article DOI  
Abstract: We present an atmospheric inverse modeling framework to constrain
terrestrial biosphere CO2 exchange processes at subregional scales. The
model is operated at very high spatial and temporal resolution, using
the state of Oregon in the northwestern United States as the model
domain. The modeling framework includes mesoscale atmospheric
simulations coupled to Lagrangian transport, a biosphere flux model that
considers, e.g., the effects of drought stress and disturbance on
photosynthesis and respiration CO2 fluxes, and a Bayesian optimization
approach. This study focuses on the impact of uncertainties in advected
background mixing ratios and fossil fuel emissions on simulated flux
fields, both taken from external data sets. We found the simulations to
be highly sensitive to systematic changes in advected background CO2,
while shifts in fossil fuel emissions played a minor role. Correcting
for offsets in the background mixing ratios shifted annual CO2 budgets
by about 47% and improved the correspondence with the output produced
by bottom-up modeling frameworks. Inversion results were robust against
shifts in fossil fuel emissions, which is likely a consequence of
relatively low emission rates in Oregon.
BibTeX:
@article{gockede10b,
  author = {Gockede, Mathias and Turner, David P. and Michalak, Anna M. and Vickers, Dean and Law, Beverly E.},
  title = {Sensitivity of a subregional scale atmospheric inverse CO2 modeling framework to boundary conditions},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2010},
  volume = {115},
  doi = {https://doi.org/10.1029/2010JD014443}
}
Gomes, D., Vicente, L.E., Silva, R., Paula, S., Maçorano, R.P., Victoria, D. and Batistella, M. Uso de dados MODIS e AIRS para obten¸ cão de parâmetros de corre¸ cão atmosférica 2013 Simpósio Brasileiro de Sensoriamento Remoto
Vol. 16, pp. 8019-8026 
article URL 
BibTeX:
@article{gomes13a,
  author = {Gomes, Daniel and Vicente, Luiz Eduardo and Silva, RFB and Paula, SC and Maçorano, Renan Pfister and Victoria, DC and Batistella, Mateus},
  title = {Uso de dados MODIS e AIRS para obten¸ cão de parâmetros de corre¸ cão atmosférica},
  journal = {Simpósio Brasileiro de Sensoriamento Remoto},
  year = {2013},
  volume = {16},
  pages = {8019--8026},
  url = {https://ainfo.cnptia.embrapa.br/digital/bitstream/item/82762/1/DanielSBSR.pdf}
}
Gourdji, S.M., Hirsch, A.I., Mueller, K.L., Yadav, V., Andrews, A.E. and Michalak, A.M. Regional-scale geostatistical inverse modeling of North American CO2 fluxes: a synthetic data study {2010} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {10}({13}), pp. 6151-6167 
article DOI  
Abstract: A series of synthetic data experiments is performed to investigate the
ability of a regional atmospheric inversion to estimate grid-scale CO2
fluxes during the growing season over North America. The inversions are
performed within a geostatistical framework without the use of any prior
flux estimates or auxiliary variables, in order to focus on the
atmospheric constraint provided by the nine towers collecting
continuous, calibrated CO2 measurements in 2004. Using synthetic
measurements and their associated concentration footprints, flux and
model-data mismatch covariance parameters are first optimized, and then
fluxes and their uncertainties are estimated at three different temporal
resolutions. These temporal resolutions, which include a four-day
average, a four-day-average diurnal cycle with 3-hourly increments, and
3-hourly fluxes, are chosen to help assess the impact of temporal
aggregation errors on the estimated fluxes and covariance parameters.
Estimating fluxes at a temporal resolution that can adjust the diurnal
variability is found to be critical both for recovering covariance
parameters directly from the atmospheric data, and for inferring
accurate ecoregion-scale fluxes. Accounting for both spatial and
temporal a priori covariance in the flux distribution is also found to
be necessary for recovering accurate a posteriori uncertainty bounds on
the estimated fluxes. Overall, the results suggest that even a fairly
sparse network of 9 towers collecting continuous CO2 measurements across
the continent, used with no auxiliary information or prior estimates of
the flux distribution in time or space, can be used to infer relatively
accurate monthly ecoregion scale CO2 surface fluxes over North America
within estimated uncertainty bounds. Simulated random transport error is
shown to decrease the quality of flux estimates in under-constrained
areas at the ecoregion scale, although the uncertainty bounds remain
realistic. While these synthetic data inversions do not consider all
potential issues associated with using actual measurement data, e.g.
systematic transport errors or problems with the boundary conditions,
they help to highlight the impact of inversion setup choices, and help
to provide a baseline set of CO2 fluxes for comparison with estimates
from future real-data inversions.
BibTeX:
@article{gourdji10a,
  author = {Gourdji, S. M. and Hirsch, A. I. and Mueller, K. L. and Yadav, V. and Andrews, A. E. and Michalak, A. M.},
  title = {Regional-scale geostatistical inverse modeling of North American CO2 fluxes: a synthetic data study},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2010},
  volume = {10},
  number = {13},
  pages = {6151--6167},
  doi = {https://doi.org/10.5194/acp-10-6151-2010}
}
Gourdji, S.M. Improved estimates of regional-scale land-atmosphere Carbon dioxide exchange using geostatistical atmospheric inverse models 2011 School: University of Michigan  phdthesis URL 
BibTeX:
@phdthesis{gourdji11a,
  author = {Gourdji, Sharon Muzli},
  title = {Improved estimates of regional-scale land-atmosphere Carbon dioxide exchange using geostatistical atmospheric inverse models},
  school = {University of Michigan},
  year = {2011},
  url = {http://search.proquest.com/openview/331603ec402236ba8e528454f7373a97/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Gourdji, S.M., Mueller, K.L., Yadav, V., Huntzinger, D.N., Andrews, A.E., Trudeau, M., Petron, G., Nehrkorn, T., Eluszkiewicz, J., Henderson, J., Wen, D., Lin, J., Fischer, M., Sweeney, C. and Michalak, A.M. North American CO2 exchange: inter-comparison of modeled estimates with results from a fine-scale atmospheric inversion {2012} BIOGEOSCIENCES
Vol. {9}({1}), pp. 457-475 
article DOI  
Abstract: Atmospheric inversion models have the potential to quantify CO2 fluxes
at regional, sub-continental scales by taking advantage of near-surface
CO2 mixing ratio observations collected in areas with high flux
variability. This study presents results from a series of regional
geostatistical inverse models (GIM) over North America for 2004, and
uses them as the basis for an inter-comparison to other inversion
studies and estimates from biospheric models collected through the North
American Carbon Program Regional and Continental Interim Synthesis.
Because the GIM approach does not require explicit prior flux estimates
and resolves fluxes at fine spatiotemporal scales (i.e. 1 degrees x 1
degrees, 3-hourly in this study), it avoids temporal and spatial
aggregation errors and allows for the recovery of realistic spatial
patterns from the atmospheric data relative to previous inversion
studies. Results from a GIM inversion using only available atmospheric
observations and a fine-scale fossil fuel inventory were used to confirm
the quality of the inventory and inversion setup. An inversion
additionally including auxiliary variables from the North American
Regional Reanalysis found inferred relationships with flux consistent
with physiological understanding of the biospheric carbon cycle.
Comparison of GIM results with bottom-up biospheric models showed
stronger agreement during the growing relative to the dormant season, in
part because most of the biospheric models do not fully represent
agricultural land-management practices and the fate of both residual
biomass and harvested products. Comparison to earlier inversion studies
pointed to aggregation errors as a likely source of bias in previous
subcontinental scale flux estimates, particularly for inversions that
adjust fluxes at the coarsest scales and use atmospheric observations
averaged over long periods. Finally, whereas the continental CO2
boundary conditions used in the GIM inversions have a minor impact on
spatial patterns, they have a substantial impact on the continental
carbon budget, with a difference of 0.8 PgC yr(-1) in the total
continental flux resulting from the use of two plausible sets of
boundary CO2 mixing ratios. Overall, this inter-comparison study helps
to assess the state of the science in estimating regional-scale CO2
fluxes, while pointing towards the path forward for improvements in
future top-down and bottom-up modeling efforts.
BibTeX:
@article{gourdji12a,
  author = {Gourdji, S. M. and Mueller, K. L. and Yadav, V. and Huntzinger, D. N. and Andrews, A. E. and Trudeau, M. and Petron, G. and Nehrkorn, T. and Eluszkiewicz, J. and Henderson, J. and Wen, D. and Lin, J. and Fischer, M. and Sweeney, C. and Michalak, A. M.},
  title = {North American CO2 exchange: inter-comparison of modeled estimates with results from a fine-scale atmospheric inversion},
  journal = {BIOGEOSCIENCES},
  year = {2012},
  volume = {9},
  number = {1},
  pages = {457--475},
  doi = {https://doi.org/10.5194/bg-9-457-2012}
}
Graven, H.D. and Gruber, N. Continental-scale enrichment of atmospheric (CO2)-C-14 from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO2 {2011} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {11}({23}), pp. 12339-12349 
article DOI  
Abstract: The C-14-free fossil carbon added to atmospheric CO2 by combustion
dilutes the atmospheric C-14/C ratio (Delta C-14), potentially providing
a means to verify fossil CO2 emissions calculated using economic
inventories. However, sources of C-14 from nuclear power generation and
spent fuel reprocessing can counteract this dilution and may bias
C-14/C-based estimates of fossil fuel-derived CO2 if these nuclear
influences are not correctly accounted for. Previous studies have
examined nuclear influences on local scales, but the potential for
continental-scale influences on Delta C-14 has not yet been explored. We
estimate annual C-14 emissions from each nuclear site in the world and
conduct an Eulerian transport modeling study to investigate the
continental-scale, steady-state gradients of Delta C-14 caused by
nuclear activities and fossil fuel combustion. Over large regions of
Europe, North America and East Asia, nuclear enrichment may offset at
least 20% of the fossil fuel dilution in Delta C-14, corresponding to
potential biases of more than -0.25 ppm in the CO2 attributed to fossil
fuel emissions, larger than the bias from plant and soil respiration in
some areas. Model grid cells including high C-14-release reactors or
fuel reprocessing sites showed much larger nuclear enrichment, despite
the coarse model resolution of 1.8 degrees x 1.8 degrees. The recent
growth of nuclear C-14 emissions increased the potential nuclear bias
over 1985-2005, suggesting that changing nuclear activities may
complicate the use of Delta C-14 observations to identify trends in
fossil fuel emissions. The magnitude of the potential nu-clear bias is
largely independent of the choice of reference station in the context of
continental-scale Eulerian transport and inversion studies, but could
potentially be reduced by an appropriate choice of reference station in
the context of local-scale assessments.
BibTeX:
@article{graven11a,
  author = {Graven, H. D. and Gruber, N.},
  title = {Continental-scale enrichment of atmospheric (CO2)-C-14 from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO2},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2011},
  volume = {11},
  number = {23},
  pages = {12339--12349},
  doi = {https://doi.org/10.5194/acp-11-12339-2011}
}
Guan, K. Hydrological variability on vegetation seasonality, productivity and composition in tropical ecosystems of Africa 2013 School: Princeton University  phdthesis URL 
BibTeX:
@phdthesis{guan13a,
  author = {Guan, Kaiyu},
  title = {Hydrological variability on vegetation seasonality, productivity and composition in tropical ecosystems of Africa},
  school = {Princeton University},
  year = {2013},
  url = {http://search.proquest.com/openview/bdb3c89d79b0a9555cf6e3419d6a81d0/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Guan, K., Medvigy, D., Wood, E.F., Caylor, K.K., Li, S. and Jeong, S.-J. Deriving Vegetation Phenological Time and Trajectory Information Over Africa Using SEVIRI Daily LAI {2014} IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
Vol. {52}({2}), pp. 1113-1130 
article DOI  
Abstract: Vegetation phenology is closely connected to the terrestrial carbon
budget, and interacts with the atmosphere through surface water and
energy exchange. A comprehensive and detailed characterization of the
spatio-temporal pattern of vegetation phenology can be used to improve
the understanding of interactions between vegetation and climate in
Africa. This research provides an approach to derive phenology time and
trajectory parameters by optimally fitting a double-logistic curve to
daily remotely sensed leaf area index (LAI) from the spinning enhanced
visible and infrared imager. The proposed algorithm can reconstruct the
temporal LAI trajectory based on the optimized parameters with a high
accuracy, and provides user-defined phenological timing information
(e.g., start/end of the growing season) and trajectory information
(e.g., leaf emergence/senescence rate and length) using these fitted
parameters. Both single and double growing-season cases have been
considered with a spatial classification scheme implemented over Africa.
The newly derived vegetation phenology of Africa exhibits emerging
spatial patterns in growing season length, asymmetric green-up and
green-off length/rate, and distinctive phenological features of cropland
and natural vegetation. This approach has the potential to be applied
globally, and the derived vegetation phenological information will
improve dynamic vegetation modeling and climate prediction.
BibTeX:
@article{guan14a,
  author = {Guan, Kaiyu and Medvigy, David and Wood, Eric F. and Caylor, Kelly K. and Li, Shi and Jeong, Su-Jong},
  title = {Deriving Vegetation Phenological Time and Trajectory Information Over Africa Using SEVIRI Daily LAI},
  journal = {IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING},
  year = {2014},
  volume = {52},
  number = {2},
  pages = {1113--1130},
  doi = {https://doi.org/10.1109/TGRS.2013.2247611}
}
Guerlet, S., Butz, A., Schepers, D., Basu, S., Hasekamp, O.P., Kuze, A., Yokota, T., Blavier, J.F., Deutscher, N.M., Griffith, D.W.T., Hase, F., Kyro, E., Morino, I., Sherlock, V., Sussmann, R., Galli, A. and Aben, I. Impact of aerosol and thin cirrus on retrieving and validating XCO2 from GOSAT shortwave infrared measurements {2013} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {118}({10}), pp. 4887-4905 
article DOI  
Abstract: Inadequate treatment of aerosol scattering can be a significant source
of error when retrieving column-averaged dry-air mole fractions of CO2
(XCO2) from space-based measurements of backscattered solar shortwave
radiation. We have developed a retrieval algorithm, RemoTeC, that
retrieves three aerosol parameters (amount, size, and height)
simultaneously with XCO2. Here we evaluate the ability of RemoTeC to
account for light path modifications by clouds, subvisual cirrus, and
aerosols when retrieving XCO2 from Greenhouse Gases Observing Satellite
(GOSAT) Thermal and Near-infrared Sensor for carbon Observation
(TANSO)-Fourier Transform Spectrometer (FTS) measurements. We first
evaluate a cloud filter based on measurements from the Cloud and Aerosol
Imager and a cirrus filter that uses radiances measured by TANSO-FTS in
the 2micron spectral region, with strong water absorption. For the
cloud-screened scenes, we then evaluate errors due to aerosols. We find
that RemoTeC is well capable of accounting for scattering by aerosols
for values of aerosol optical thickness at 750nm up to 0.25. While no
significant correlation of errors is found with albedo, correlations are
found with retrieved aerosol parameters. To further improve the XCO2
accuracy, we propose and evaluate a bias correction scheme. Measurements
from 12 ground-based stations of the Total Carbon Column Observing
Network (TCCON) are used as a reference in this study. We show that
spatial colocation criteria may be relaxed using additional constraints
based on modeled XCO2 gradients, to increase the size and diversity of
validation data and provide a more robust evaluation of GOSAT
retrievals. Global-scale validation of satellite data remains
challenging and would be improved by increasing TCCON coverage.
BibTeX:
@article{guerlet13a,
  author = {Guerlet, S. and Butz, A. and Schepers, D. and Basu, S. and Hasekamp, O. P. and Kuze, A. and Yokota, T. and Blavier, J. -F. and Deutscher, N. M. and Griffith, D. W. T. and Hase, F. and Kyro, E. and Morino, I. and Sherlock, V. and Sussmann, R. and Galli, A. and Aben, I.},
  title = {Impact of aerosol and thin cirrus on retrieving and validating XCO2 from GOSAT shortwave infrared measurements},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2013},
  volume = {118},
  number = {10},
  pages = {4887--4905},
  doi = {https://doi.org/10.1002/jgrd.50332}
}
Gunn, K.M., Buda, A.R., Preisendanz, H.E., Cibin, R., Kennedy, C.D. and Veith, T.L. INTEGRATING DAILY CO2 CONCENTRATIONS IN SWAT-VSA TO EXAMINE CLIMATE CHANGE IMPACTS ON HYDROLOGY IN A KARST WATERSHED 2021 TRANSACTIONS OF THE ASABE
Vol. 64(4), pp. 1303-1318 
article DOI  
Abstract: Characterizing the effects of climate change on hydrology is important
to watershed management. In this study, we used SWAT-VSA to examine the
effects of climate change and increasing atmospheric CO2 (CO2) on the
water balance of Spring Creek watershed, a mixed land-use karst basin in
the Upper Chesapeake Bay watershed. First, we modified the stomatal
conductance and leaf area index (LAI) routines of SWAT-VSA's
Penman-Monteith evapotranspiration (ET) procedure and enabled the model
to accept daily CO2 data. Using downscaled climate projections from nine
global climate models (GCMs), we then compared water balance estimations
from baseline SWAT-VSA against two modified versions of SWAT-VSA. One
SWAT-VSA version integrated daily CO2 levels (SWAT-VSA_CO2), while
another version added flexible stomatal conductance and LAI routines
(SWAT-VSA_CO2+Plant) to the dynamic CO2 capacity. Under current climate
(1985-2015), the three SWAT-VSA models produced generally similar water
balance estimations, with 51% of precipitation lost to ET and the
remainder converted to runoff (10%), lateral flow (9%), and percolate
(30%). For future climate (2020-2065), water balance simulations
diverged between baseline SWAT-VSA and the two modified SWAT-VSA models
with CO2. Notably, variable stomatal conductance and LAI routines
produced no detectable effects beyond that of CO2. For the 2020-2065
period, baseline SWAT-VSA projected ET increases of 0.7 mm year(-1),
while SWAT-VSA models with CO2 suggested that annual ET could decline by
approximately -0.4 mm year(-1) over the same period. As a result, the
two CO2-based SWATVSA models predicted streamflow increases of almost
1.6 mm year(-1) over the 2020-2065 period, which were roughly double the
streamflow increases projected by baseline SWAT-VSA. In general,
SWAT-VSA models with CO2 effects produced 22.4% more streamflow in
2045-2065 than the SWAT-VSA model without CO2. Results also showed that
adding daily CO2 to SWAT-VSA reduced ET in wetter parts of Spring Creek
watershed, leading to greater runoff losses from variable source areas
compared to baseline SWAT-VSA. Findings from the study highlight the
importance of considering increasing atmospheric CO2 concentrations in
water balance simulations with SWAT-VSA in order to gain a fuller
appreciation of the hydrologic uncertainties with climate change.
BibTeX:
@article{gunn21a,
  author = {Gunn, Kpoti M. and Buda, Anthony R. and Preisendanz, Heather E. and Cibin, Raj and Kennedy, Casey D. and Veith, Tamie L.},
  title = {INTEGRATING DAILY CO2 CONCENTRATIONS IN SWAT-VSA TO EXAMINE CLIMATE CHANGE IMPACTS ON HYDROLOGY IN A KARST WATERSHED},
  journal = {TRANSACTIONS OF THE ASABE},
  year = {2021},
  volume = {64},
  number = {4},
  pages = {1303-1318},
  doi = {https://doi.org/10.13031/trans.13711}
}
Hakkarainen, J., Ialongo, I., Maksyutov, S. and Crisp, D. Analysis of Four Years of Global XCO2 Anomalies as Seen by Orbiting Carbon Observatory-2 {2019} REMOTE SENSING
Vol. {11}({7}) 
article DOI  
Abstract: NASA's carbon dioxide mission, Orbiting Carbon Observatory-2, began operating in September 2014. In this paper, we analyze four years (2015-2018) of global (60 degrees S-60 degrees N) XCO2 anomalies and their annual variations and seasonal patterns. We show that the anomaly patterns in the column-averaged CO2 dry air mole fraction, XCO2, are robust and consistent from year-to-year. We evaluate the method by comparing the anomalies to fluxes from anthropogenic, biospheric, and biomass burning and to model-simulated local concentration enhancements. We find that, despite the simplicity of the method, the anomalies describe the spatio-temporal variability of XCO2 (including anthropogenic emissions and seasonal variability related to vegetation and biomass burning) consistently with more complex model-based approaches. We see, for example, that positive anomalies correspond to fossil fuel combustion over the major industrial areas (e.g., China, eastern USA, central Europe, India, and the Highveld region in South Africa), shown as large positive XCO2 enhancements in the model simulations. We also find corresponding positive anomalies and fluxes over biomass burning areas during different fire seasons. On the other hand, the largest negative anomalies correspond to the growing season in the northern middle latitudes, characterized by negative XCO2 enhancements from simulations and high solar-induced chlorophyll fluorescence (SIF) values (indicating the occurrence of photosynthesis). The largest discrepancies between the anomaly patterns and the model-based results are observed in the tropical regions, where OCO-2 shows persistent positive anomalies over every season of every year included in this study. Finally, we demonstrate how XCO2 anomalies enable the detection of anthropogenic signatures for several local scale case studies, both in the Northern and Southern Hemisphere. In particular, we analyze the XCO2 anomalies collocated with the recent TROPOspheric Monitoring Instrument NO2 observations (used as indicator of anthropogenic fossil fuel combustion) over the Highveld region in South Africa. The results highlight the capability of satellite-based observations to monitor natural and man-made CO2 signatures on global scale.
BibTeX:
@article{hakkarainen19a,
  author = {Hakkarainen, Janne and Ialongo, Iolanda and Maksyutov, Shamil and Crisp, David},
  title = {Analysis of Four Years of Global XCO2 Anomalies as Seen by Orbiting Carbon Observatory-2},
  journal = {REMOTE SENSING},
  publisher = {MDPI},
  year = {2019},
  volume = {11},
  number = {7},
  doi = {https://doi.org/10.3390/rs11070850}
}
Halder, S., Tiwari, Y.K., Valsala, V., Sreeush, M.G., Sijikumar, S., Janardanan, R. and Maksyutov, S. Quantification of Enhancement in Atmospheric CO2 Background Due to Indian Biospheric Fluxes and Fossil Fuel Emissions 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(13) 
article DOI  
Abstract: Regional carbon emissions impact global atmospheric carbon dioxide (CO2)
background concentrations. This study quantified the enhancement in the
atmospheric CO2 mole fractions due to biospheric and fossil fuel fluxes
from India. Sensitivity experiments using model simulations were
conducted, allowing CO2 enhancement due to biospheric and fossil fuel
fluxes from India to diffuse into the global atmospheric background. The
areal extent of column-averaged enhancement of 0.2 ppm and above due to
Indian fluxes are spread over a larger area covering the Indian
subcontinent, neighboring Asian regions, and the north Indian Ocean in
all four seasons. The boundary layer CO2 enhancement due to biospheric
fluxes (fossil fuel fluxes) have a maximum range of -2.6 to +1.4 ppm
(1.8-2.0 ppm) most time of the year. At higher altitude, the amplitudes
of enhancement are reduced from 1.8 to 0.6 ppm as we go up from 850 to
500 hPa due to diffusion by prevailing atmospheric dynamics and
convection. With the information of the areal extent of >0.2 ppm CO2
enhancement due to Indian fluxes, we have evaluated the
representativeness of satellite observations (GOSAT and OCO-2) in
capturing those enhancements. Both the satellite coverage show a similar
number of observations (0.1 per day) during all seasons except for June
to August, wherein the cloud screening eliminates almost all the
satellite data over the region. Within this areal extent, the satellite
XCO2 shows average anomalies of nearly 2.0 ppm; it is a valuable piece
of information because it is well above the retrieval uncertainty, yet
capturing the potential enhancement due to fluxes from India. The study
implies that the regions of enhancement greater than 0.2 ppm can be
considered locations for surface observations representing Indian
fluxes. Similarly, the region with enhancement greater than one ppm
could be covered by satellites/airborne observations to discern
enhancement in the atmospheric CO2 mole fractions due to Indian fluxes.
Plain Language Summary This study calculates the seasonal enhancement of
the atmospheric CO2 concentration (in ppm) due to biospheric fluxes and
fossil fuel emissions from India. The regional fluxes of fossil fuel and
biospheric activities contribute to the global atmospheric CO2 within a
few ppm. Using a global atmospheric tracer transport model and regional
fluxes, we show that the enhancement of the atmospheric CO2 due to
India's biospheric fluxes and fossil fuel emission spread over a large
extent over India and surrounding regions. A tangible value of 1.8 ppm
and above can be found in most parts of India and its surrounding
regions during significant seasons. The areal extent grows from the
boundary layer to the upper atmosphere due to corresponding atmospheric
mixing and dynamics. On the surface, the enhancement due to biospheric
fluxes is about -2.6 to +1.4 ppm in all four seasons, whereas the
enhancement due to fossil fuel shows about 1.8-2 ppm. The extent of
discernible enhancement in the global atmospheric background due to
Indian fluxes helps us understand the optimum location where all
observational efforts should be made to sample Indian emission scenarios
from global backgrounds. This study also points out the capability in
observing the enhancement of XCO2 by the satellite over India and its
surroundings. Satellite observations are crucial where the observations
of atmospheric CO2 are limited to constrain the surface fluxes in the
inverse modeling study. Satellite measurements can capture the
enhancement except June to August when the observations are screened out
for cloud contamination. Therefore, surface observations are necessary
to capture the enhancement of Indian emissions in the global atmospheric
CO2 background in all seasons.
Key Points
Indian carbon fluxes significantly contribute to the CO2 concentrations
as large as +/- 2.0 ppm over India and neighboring regions throughout
the year at surface level (i.e., 975 hPa)
Satellites are capable of representing the XCO2 anomalies up to +/- 2.0
ppm over corresponding regions; however, they have no data coverage
during rainy seasons
The study recommends both ground-based and satellite/aircraft
measurements of CO2 be employed to observe the larger area of Indian CO2
enhancements
BibTeX:
@article{halder21a,
  author = {Halder, Santanu and Tiwari, Yogesh K. and Valsala, Vinu and Sreeush, M. G. and Sijikumar, S. and Janardanan, Rajesh and Maksyutov, Shamil},
  title = {Quantification of Enhancement in Atmospheric CO2 Background Due to Indian Biospheric Fluxes and Fossil Fuel Emissions},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {13},
  doi = {https://doi.org/10.1029/2021JD034545}
}
Halloran, P.R. Does atmospheric CO2 seasonality play an important role in governing the air-sea flux of CO2? {2012} BIOGEOSCIENCES
Vol. {9}({6}), pp. 2311-2323 
article DOI  
Abstract: The amplitude, phase, and form of the seasonal cycle of atmospheric CO2
concentrations varies on many time and space scales (Peters et al.,
2007). Intra-annual CO2 variation is primarily driven by seasonal uptake
and release of CO2 by the terrestrial biosphere (Machta et al., 1977;
Buchwitz et al., 2007), with a small (Cadule et al., 2010; Heimann et
al., 1998), but potentially changing (Gorgues et al., 2010) contribution
from the ocean. Variability in the magnitude, spatial distribution, and
seasonal drivers of terrestrial net primary productivity (NPP) will be
induced by, amongst other factors, anthropogenic CO2 release (Keeling et
al., 1996), land-use change (Zimov et al., 1999) and planetary orbital
variability, and will lead to changes in CO2atm seasonality. Despite
CO2atm seasonality being a dynamic and prominent feature of the Earth
System, its potential to drive changes in the air-sea flux of CO2 has
not previously (to the best of my knowledge) been explored. It is
important that we investigate the impact of CO2atm seasonality change,
and the potential for carbon-cycle feedbacks to operate through the
modification of the CO2atm seasonal cycle, because the decision had been
made to prescribe CO2atm concentrations (rather than emissions) within
model simulations for the fifth IPCC climate assessment (Taylor et al.,
2009). In this study I undertake ocean-model simulations within which
different magnitude CO2atm seasonal cycles are prescribed. These
simulations allow me to examine the effect of a change in CO2atm
seasonal cycle magnitude on the air-sea CO2 flux. I then use an offline
model to isolate the drivers of the identified air-sea CO2 flux change,
and propose mechanisms by which this change may come about. Three
mechanisms are identified by which co-variability of the seasonal cycles
in atmospheric CO2 concentration, and seasonality in sea-ice extent,
wind-speed and ocean temperature, could potentially lead to changes in
the air-sea flux of CO2 at mid-to-high latitudes. The sea-ice driven
mechanism responds to an increase in CO2atm seasonality by pumping CO2
into the ocean, the wind-speed and solubility-driven mechanisms, by
releasing CO2 from the ocean (in a relative sense). The relative
importance of the mechanisms will be determined by, amongst other
variables, the seasonal extent of sea-ice. To capture the described
feedbacks within earth system models, CO2atm concentrations must be
allowed to evolve freely, forced only by anthropogenic emissions rather
than prescribed CO2atm concentrations; however, time-integrated ocean
simulations imply that the cumulative net air-sea flux could be at most
equivalent to a few ppm CO2atm. The findings presented here suggest
that, at least under pre-industrial conditions, the prescription of
CO2atm concentrations rather than emissions within simulations will have
little impact on the marine anthropogenic CO2 sink.
BibTeX:
@article{halloran12a,
  author = {Halloran, P. R.},
  title = {Does atmospheric CO2 seasonality play an important role in governing the air-sea flux of CO2?},
  journal = {BIOGEOSCIENCES},
  year = {2012},
  volume = {9},
  number = {6},
  pages = {2311--2323},
  doi = {https://doi.org/10.5194/bg-9-2311-2012}
}
Hari, M. and Tyagi, B. Terrestrial carbon cycle: tipping edge of climate change between the atmosphere and biosphere ecosystems 2022 ENVIRONMENTAL SCIENCE-ATMOSPHERES
Vol. 2(5), pp. 867-890 
article DOI  
Abstract: Owing to its tendency to couple with multiple elements, carbon forms
complex molecules, which is the basic chemistry of life. Given that the
climate system is inextricably coupled with the biosphere, understanding
the terrestrial mechanistic pathway of carbon is critical in the
transformation of the augmenting atmospheric carbon dioxide (CO2) in
future. Although the global terrestrial carbon sink reduces the
accumulation of atmospheric CO2, which is contingent on the climate and
ecosystem, the underlying key biophysical function that controls the
ecosystem-carbon-climate responses and their feedback is uncertain.
Accordingly, numerous unprecedented multi-scale studies have highlighted
the dynamics of terrestrial carbon by strategically employing in situ,
earth observation and process-based models; however, to date, the
driving force for its dynamics remains unclassified. Besides, the
significant variability in carbon is related to the large uncertainties
from changes in land use, unambiguously increasing the regional carbon
source from the seasonal to interannual scale but without long-term
positive or negative feedback. Accordingly, in this review, we attempt
to present a holistic understanding of the terrestrial carbon cycle by
addressing its nature and different key drivers. The heterogenetic data
platforms that reliably address the terrestrial carbon sink and its
source dynamics are discussed in detail to demonstrate the potential of
systematic quantification. Moreover, we summarize the complexity of
carbon-climate feedbacks and their associates, extending the pathway for
understanding the recent terrestrial carbon allocation, where India's
environment is highlighted. This comprehensive review can be valuable to
the research community in understanding the importance of the present
and future carbon-climate feedback.
BibTeX:
@article{hari22a,
  author = {Hari, Manoj and Tyagi, Bhishma},
  title = {Terrestrial carbon cycle: tipping edge of climate change between the atmosphere and biosphere ecosystems},
  journal = {ENVIRONMENTAL SCIENCE-ATMOSPHERES},
  year = {2022},
  volume = {2},
  number = {5},
  pages = {867-890},
  doi = {https://doi.org/10.1039/d1ea00102g}
}
Haszpra, L., Ramonet, M., Schmidt, M., Barcza, Z., Patkai, Z., Tarczay, K., Yver, C., Tarniewicz, J. and Ciais, P. Variation of CO2 mole fraction in the lower free troposphere, in the boundary layer and at the surface {2012} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {12}({18}), pp. 8865-8875 
article DOI  
Abstract: Eight years of occasional flask air sampling and 3 years of frequent in
situ measurements of carbon dioxide (CO2) vertical profiles on board of
a small aircraft, over a tall tower greenhouse gases monitoring site in
Hungary are used for the analysis of the variations of vertical profile
of CO2 mole fraction. Using the airborne vertical profiles and the
measurements along the 115 m tall tower it is shown that the
measurements at the top of the tower estimate the mean boundary layer
CO2 mole fraction during the mid-afternoon fairly well, with an
underestimation of 0.27-0.85 mu mol mol(-1) in summer, and an
overestimation of 0.66-1.83 mu mol mol(-1) in winter. The seasonal cycle
of CO2 mole fraction is damped with elevation. While the amplitude of
the seasonal cycle is 28.5 mu mol mol(-1) at 10 m above the ground, it
is only 10.7 mu mol mol(-1) in the layer of 2500-3000 m corresponding to
the lower free atmosphere above the well-mixed boundary layer. The
maximum mole fraction in the layer of 2500-3000 m can be observed around
25 March on average, two weeks ahead of that of the marine boundary
layer reference (GLOBALVIEW). By contrast, close to the ground, the
maximum CO2 mole fraction is observed late December, early January. The
specific seasonal behavior is attributed to the climatology of vertical
mixing of the atmosphere in the Carpathian Basin.
BibTeX:
@article{haszpra12a,
  author = {Haszpra, L. and Ramonet, M. and Schmidt, M. and Barcza, Z. and Patkai, Zs and Tarczay, K. and Yver, C. and Tarniewicz, J. and Ciais, P.},
  title = {Variation of CO2 mole fraction in the lower free troposphere, in the boundary layer and at the surface},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2012},
  volume = {12},
  number = {18},
  pages = {8865--8875},
  doi = {https://doi.org/10.5194/acp-12-8865-2012}
}
Hayashida, S., Ono, A., Yoshizaki, S., Frankenberg, C., Takeuchi, W. and Yan, X. Methane concentrations over Monsoon Asia as observed by SCIAMACHY: Signals of methane emission from rice cultivation {2013} REMOTE SENSING OF ENVIRONMENT
Vol. {139}, pp. 246-256 
article DOI  
Abstract: We have analyzed the column-averaged CH4 concentration (xCH(4)) using
scanning imaging absorption spectrometer for atmospheric chartography
(SCIAMACHY) and compared the data with the bottom-up emission inventory
data sets and other satellite-derived indices such as the land-surface
water coverge (LSWC) and the normalized difference vegetation index
(NDVI). The geographical distribution of high CH4 values corresponds to
strong emissions from regions where rice is cultivated, as indicated in
the inventory maps. The Pearson's correlation coefficients (r) between
xCH(4) and the rice emission inventory data are observed to be greater
than similar to 0.6 over typical rice fields, with outstanding r-values
of similar to 0.8 in the Ganges Basin, Myanmar, and Thailand. This
suggests that the emission of CH4 from rice cultivation mainly controls
the seasonality of the CH4 concentration over such regions. The
correlation between xCH(4) and LSWC and NDVI is also as large as 0.6. In
Southeast Asia, the r-values of xCH4 with bottom-up inventory data that
includes all categories are not as high as those with the emission, as
estimated from the rice category only. This is indicative of the
relative importance of rice emissions among all other emission
categories in Southeast Asia. (C) 2013 Elsevier Inc. All rights
reserved.
BibTeX:
@article{hayashida13a,
  author = {Hayashida, S. and Ono, A. and Yoshizaki, S. and Frankenberg, C. and Takeuchi, W. and Yan, X.},
  title = {Methane concentrations over Monsoon Asia as observed by SCIAMACHY: Signals of methane emission from rice cultivation},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2013},
  volume = {139},
  pages = {246--256},
  doi = {https://doi.org/10.1016/j.rse.2013.08.008}
}
Hayes, D.J., Turner, D.P., Stinson, G., McGuire, A.D., Wei, Y., West, T.O., Heath, L.S., Dejong, B., McConkey, B.G., Birdsey, R.A., Kurz, W.A., Jacobson, A.R., Huntzinger, D.N., Pan, Y., Mac Post, W. and Cook, R.B. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data {2012} GLOBAL CHANGE BIOLOGY
Vol. {18}({4}), pp. 1282-1299 
article DOI  
Abstract: We develop an approach for estimating net ecosystem exchange (NEE) using
inventory-based information over North America (NA) for a recent 7-year
period (ca. 2000-2006). The approach notably retains information on the
spatial distribution of NEE, or the vertical exchange between land and
atmosphere of all non-fossil fuel sources and sinks of CO2, while
accounting for lateral transfers of forest and crop products as well as
their eventual emissions. The total NEE estimate of a -327 similar to
+/-similar to 252 similar to TgC similar to yr-1 sink for NA was driven
primarily by CO2 uptake in the Forest Lands sector (-248 similar to TgC
similar to yr-1), largely in the Northwest and Southeast regions of the
US, and in the Crop Lands sector (-297 similar to TgC similar to yr-1),
predominantly in the Midwest US states. These sinks are counteracted by
the carbon source estimated for the Other Lands sector (+218 similar to
TgC similar to yr-1), where much of the forest and crop products are
assumed to be returned to the atmosphere (through livestock and human
consumption). The ecosystems of Mexico are estimated to be a small net
source (+18 similar to TgC similar to yr-1) due to land use change
between 1993 and 2002. We compare these inventory-based estimates with
results from a suite of terrestrial biosphere and atmospheric inversion
models, where the mean continental-scale NEE estimate for each ensemble
is -511 similar to TgC similar to yr-1 and -931 similar to TgC similar
to yr-1, respectively. In the modeling approaches, all sectors,
including Other Lands, were generally estimated to be a carbon sink,
driven in part by assumed CO2 fertilization and/or lack of consideration
of carbon sources from disturbances and product emissions. Additional
fluxes not measured by the inventories, although highly uncertain, could
add an additional -239 similar to TgC similar to yr-1 to the
inventory-based NA sink estimate, thus suggesting some convergence with
the modeling approaches.
BibTeX:
@article{hayes12a,
  author = {Hayes, Daniel J. and Turner, David P. and Stinson, Graham and McGuire, A. David and Wei, Yaxing and West, Tristram O. and Heath, Linda S. and Dejong, Bernardus and McConkey, Brian G. and Birdsey, Richard A. and Kurz, Werner A. and Jacobson, Andrew R. and Huntzinger, Deborah N. and Pan, Yude and Mac Post, W. and Cook, Robert B.},
  title = {Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data},
  journal = {GLOBAL CHANGE BIOLOGY},
  year = {2012},
  volume = {18},
  number = {4},
  pages = {1282--1299},
  doi = {https://doi.org/10.1111/j.1365-2486.2011.02627.x}
}
Hayes, D. and Turner, D. The need for ``apples‐to‐apples'' comparisons of carbon dioxide source and sink estimates 2012 Eos, Transactions American Geophysical Union
Vol. 93(41), pp. 404-405 
article DOI  
BibTeX:
@article{hayes12b,
  author = {Hayes, Daniel and Turner, David},
  title = {The need for ``apples‐to‐apples'' comparisons of carbon dioxide source and sink estimates},
  journal = {Eos, Transactions American Geophysical Union},
  year = {2012},
  volume = {93},
  number = {41},
  pages = {404--405},
  doi = {https://doi.org/10.1029/2012EO410007/full}
}
Hazan, L., Tarniewicz, J., Ramonet, M., Laurent, O. and Abbaris, A. Automatic processing of atmospheric CO2 and CH4 mole fractions at the ICOS Atmosphere Thematic Centre {2016} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {9}({9}), pp. 4719-4736 
article DOI  
Abstract: The Integrated Carbon Observation System Atmosphere Thematic Centre
(ICOS ATC) automatically processes atmospheric greenhouse gases mole
fractions of data coming from sites of the ICOS network. Daily
transferred raw data files are automatically processed and archived.
Data are stored in the ICOS atmospheric database, the backbone of the
system, which has been developed with an emphasis on the traceability of
the data processing. Many data products, updated daily, explore the data
through different angles to support the quality control of the dataset
performed by the principal operators in charge of the instruments. The
automatic processing includes calibration and water vapor corrections as
described in the paper. The mole fractions calculated in near-real time
(NRT) are automatically revaluated as soon as a new instrument
calibration is processed or when the station supervisors perform quality
control. By analyzing data from 11 sites, we determined that the average
calibration corrections are equal to 1.7 +/- 0.3 mu mol mol(-1) for CO2
and 2.8 +/- 3 nmol mol(-1) for CH4. These biases are important to
correct to avoid artificial gradients between stations that could lead
to error in flux estimates when using atmospheric inversion techniques.
We also calculated that the average drift between two successive
calibrations separated by 15 days amounts to +/- 0.05 mu mol mol(-1) and
+/- 0.7 nmol mol(-1) for CO2 and CH4, respectively. Outliers are
generally due to errors in the instrument configuration and can be
readily detected thanks to the data products provided by the ATC.
Several developments are still ongoing to improve the processing,
including automated spike detection and calculation of time-varying
uncertainties.
BibTeX:
@article{hazan16a,
  author = {Hazan, Lynn and Tarniewicz, Jerome and Ramonet, Michel and Laurent, Olivier and Abbaris, Amara},
  title = {Automatic processing of atmospheric CO2 and CH4 mole fractions at the ICOS Atmosphere Thematic Centre},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2016},
  volume = {9},
  number = {9},
  pages = {4719--4736},
  doi = {https://doi.org/10.5194/amt-9-4719-2016}
}
He, Z., Zeng, Z.-C., Lei, L., Bie, N. and Yang, S. A Data-Driven Assessment of Biosphere-Atmosphere Interaction Impact on Seasonal Cycle Patterns of XCO2 Using GOSAT and MODIS Observations {2017} REMOTE SENSING
Vol. {9}({3}) 
article DOI  
Abstract: Using measurements of the column-averaged CO2 dry air mole fraction
(XCO2) from GOSAT and biosphere parameters, including normalized
difference vegetation index (NDVI), enhanced vegetation index (EVI),
leaf area index (LAI), gross primary production (GPP), and land surface
temperature (LST) from MODIS, this study proposes a data-driven approach
to assess the impacts of terrestrial biosphere activities on the
seasonal cycle pattern of XCO2. A unique global land mapping dataset of
XCO2 with a resolution of 1 degrees by 1 degrees in space, and three
days in time, from June 2009 to May 2014, which facilitates the
assessment at a fine scale, is first produced from GOSAT XCO2
retrievals. We then conduct a statistical fitting method to obtain the
global map of seasonal cycle amplitudes (SCA) of XCO2 and NDVI, and
implement correlation analyses of seasonal variation between XCO2 and
the vegetation parameters. As a result, the spatial distribution of XCO2
SCA decreases globally with latitude from north to south, which is in
good agreement with that of simulated XCO2 from CarbonTracker. The
spatial pattern of XCO2 SCA corresponds well to the vegetation seasonal
activity revealed by NDVI, with a strong correlation coefficient of 0.74
in the northern hemisphere (NH). Some hotspots in the subtropical areas,
including Northern India (with SCA of 8.68 +/- 0.49 ppm on average) and
Central Africa (with SCA of 8.33 +/- 0.25 ppm on average), shown by
satellite measurements, but missed by model simulations, demonstrate the
advantage of satellites in observing the biosphere-atmosphere
interactions at local scales. Results from correlation analyses between
XCO2 and NDVI, EVI, LAI, or GPP show a consistent spatial distribution,
and NDVI and EVI have stronger negative correlations over all latitudes.
This may suggest that NDVI and EVI can be better vegetation parameters
in characterizing the seasonal variations of XCO2 and its driving
terrestrial biosphere activities. We, furthermore, present the global
distribution of phase lags of XCO2 compared to NDVI in seasonal
variation, which, to our knowledge, is the first such map derived from a
completely data-driven approach using satellite observations. The impact
of retrieval error of GOSAT data on the mapping data, especially over
high-latitude areas, is further discussed. Results from this study
provide reference for better understanding the distribution of the
strength of carbon sink by terrestrial ecosystems and utilizing remote
sensing data in assessing the impact of biosphere-atmosphere
interactions on the seasonal cycle pattern of atmospheric CO2 columns.
BibTeX:
@article{he17a,
  author = {He, Zhonghua and Zeng, Zhao-Cheng and Lei, Liping and Bie, Nian and Yang, Shaoyuan},
  title = {A Data-Driven Assessment of Biosphere-Atmosphere Interaction Impact on Seasonal Cycle Patterns of XCO2 Using GOSAT and MODIS Observations},
  journal = {REMOTE SENSING},
  year = {2017},
  volume = {9},
  number = {3},
  doi = {https://doi.org/10.3390/rs9030251}
}
He, Z., Lei, L., Welp, L.R., Zeng, Z.-C., Bie, N., Yang, S. and Liu, L. Detection of Spatiotemporal Extreme Changes in Atmospheric CO2 Concentration Based on Satellite Observations 2018 Remote Sensing
Vol. 10 
article URL 
BibTeX:
@article{he18a,
  author = {Zhonghua He and Liping Lei and Lisa R. Welp and Zhao-Cheng Zeng and Nian Bie and Shaoyuan Yang and Liangyun Liu},
  title = {Detection of Spatiotemporal Extreme Changes in Atmospheric CO2 Concentration Based on Satellite Observations},
  journal = {Remote Sensing},
  year = {2018},
  volume = {10},
  url = {https://www.mdpi.com/2072-4292/10/6/839}
}
He, W., Ju, W., Schwaim, C.R., Sippel, S., Wu, X., He, Q., Song, L., Zhang, C., Li, J., Sitch, S., Viovy, N., Friedlingstein, P. and Jain, A.K. Large-Scale Droughts Responsible for Dramatic Reductions of Terrestrial Net Carbon uptake Over North America in 2011 and 2012 {2018} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {123}({7}), pp. {2053-2071} 
article DOI  
Abstract: Recently, severe droughts that occurred in North America are likely to
have impacted its terrestrial carbon sink. However, process-based
understanding of how meteorological conditions prior to the onset of
drought, for instance warm or cold springs, affect drought-induced
carbon cycle effects remains scarce. Here we assess and compare the
response of terrestrial carbon fluxes to summer droughts in 2011 and
2012 characterized by contrasting spring conditions. The analysis is
based on a comprehensive ensemble of carbon cycle models, including
FLUXCOM, TRENDY v5, SiBCASA, CarbonTracker Europe, and CarbonTracker,
and emerging Earth observations. In 2011, large reductions of net
ecosystem production (NEP; -0.24 +/- 0.17 Pg C/year) are due to
decreased gross primary production (-0.17 +/- 0.18 Pg C/year) and
slightly increased ecosystem respiration (+0.07 +/- 0.17 Pg C/year).
Conversely, in 2012, NEP reductions (-0.17 +/- 0.25 Pg C/year) are
attributed to a larger increase of ecosystem respiration (+0.48 +/- 0.27
Pg C/year) than gross primary production (+0.31 +/- 0.29 Pg C/year),
induced predominantly by an extra warmer spring prior to summer drought.
Two temperate ecoregions crops/agriculture and the grass/shrubs
contribute largest to these reductions and also dominate the interannual
variations of NEP during 2007-2014. Moreover, the warming spring
compensated largely the negative carbon anomaly due to summer drought,
consistent with earlier studies; however, the compensation occurred only
in some specific ecoregions. Overall, our analysis offers a refined view
on recent carbon cycle variability and extremes in North America. It
corroborates earlier results but also highlights differences with
respect to ecoregion-specific carbon cycle responses to drought and
heat.
BibTeX:
@article{he18b,
  author = {He, Wei and Ju, Weimin and Schwaim, Christopher R. and Sippel, Sebastian and Wu, Xiaocui and He, Qiaoning and Song, Lian and Zhang, Chunhua and Li, Jing and Sitch, Stephen and Viovy, Nicolas and Friedlingstein, Pierre and Jain, Atul K.},
  title = {Large-Scale Droughts Responsible for Dramatic Reductions of Terrestrial Net Carbon uptake Over North America in 2011 and 2012},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2018},
  volume = {123},
  number = {7},
  pages = {2053-2071},
  doi = {https://doi.org/10.1029/2018JG004520}
}
He, W., van der Velde, I.R., Andrews, A.E., Sweeney, C., Miller, J., Tans, P., van der Laan-Luijkx, I.T., Nehrkorn, T., Mountain, M., Ju, W., Peters, W. and Chen, H. CTDAS-Lagrange v1. 0: A high-resolution data assimilation system for regional carbon dioxide observations 2018 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 11, pp. 3515-3536 
article URL 
BibTeX:
@article{he18c,
  author = {Wei He and Ivar R. van der Velde and Arlyn E. Andrews and Colm Sweeney and John Miller and Pieter Tans and Ingrid T. van der Laan-Luijkx and Thomas Nehrkorn and Marikate Mountain and Weimin Ju and Wouter Peters and Huilin Chen},
  title = {CTDAS-Lagrange v1. 0: A high-resolution data assimilation system for regional carbon dioxide observations},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  year = {2018},
  volume = {11},
  pages = {3515-3536},
  url = {https://www.geosci-model-dev.net/11/3515/2018/gmd-11-3515-2018.pdf}
}
He, L., Magney, T., Dutta, D., Yin, Y., Kohler, P., Grossmann, K., Stutz, J., Dold, C., Hatfield, J., Guan, K., Peng, B. and Frankenberg, C. From the Ground to Space: Using Solar-Induced Chlorophyll Fluorescence to Estimate Crop Productivity {2020} GEOPHYSICAL RESEARCH LETTERS
Vol. {47}({7}) 
article DOI URL 
Abstract: Timely and accurate monitoring of crops is essential for food security. Here, we examine how well solar-induced chlorophyll fluorescence (SIF) can inform crop productivity across the United States. Based on tower-level observations and process-based modeling, we find highly linear gross primary production (GPP):SIF relationships for C4 crops, while C3 crops show some saturation of GPP at high light when SIF continues to increase. C4 crops yield higher GPP:SIF ratios (30-50%) primarily because SIF is most sensitive to the light reactions (does not account for photorespiration). Scaling to the satellite, we compare SIF from the TROPOspheric Monitoring Instrument (TROPOMI) against tower-derived GPP and county-level crop statistics. Temporally, TROPOMI SIF strongly agrees with GPP observations upscaled across a corn and soybean dominated cropland (R-2 = 0.89). Spatially, county-level TROPOMI SIF correlates with crop productivity (R-2 = 0.72; 0.86 when accounting for planted area and C3/C4 contributions), highlighting the potential of SIF for reliable crop monitoring. Plain Language Summary Crop monitoring is essential for ensuring food security, but reliable, instantaneous production estimates at the global scale are lacking. The monitoring of crop production in a changing climate is of paramount importance to sustainable food security. Accurate estimates of crop production are dependent on adequately quantifying crop photosynthesis. Our paper demonstrates that solar-induced chlorophyll fluorescence (SIF), an emission of red to far-red light from chlorophyll is highly correlated with crop photosynthesis. We show that a new high spatial resolution satellite SIF data set is highly correlated with crop productivity in the United States, which is benchmarked by the United States Department of Agriculture county-level crop statistics. These results will improve the understanding of crop production and carbon flux over agricultural lands, as well as provide an accurate, large-scale, and timely monitoring method for global crop production estimates.
BibTeX:
@article{he20a,
  author = {He, Liyin and Magney, Troy and Dutta, Debsunder and Yin, Yi and Kohler, Philipp and Grossmann, Katja and Stutz, Jochen and Dold, Christian and Hatfield, Jerry and Guan, Kaiyu and Peng, Bin and Frankenberg, Christian},
  title = {From the Ground to Space: Using Solar-Induced Chlorophyll Fluorescence to Estimate Crop Productivity},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {47},
  number = {7},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087474},
  doi = {https://doi.org/10.1029/2020GL087474}
}
He, Z., Lei, L., Zeng, Z.-C., Sheng, M. and Welp, L.R. Evidence of Carbon Uptake Associated with Vegetation Greening Trends in Eastern China {2020} REMOTE SENSING
Vol. {12}({4}) 
article DOI  
Abstract: Persistent and widespread increase of vegetation cover, identified as greening, has been observed in areas of the planet over late 20th century and early 21st century by satellite-derived vegetation indices. It is difficult to verify whether these regions are net carbon sinks or sources by studying vegetation indices alone. In this study, we investigate greening trends in Eastern China (EC) and corresponding trends in atmospheric CO2 concentrations. We used multiple vegetation indices including NDVI and EVI to characterize changes in vegetation activity over EC from 2003 to 2016. Gap-filled time series of column-averaged CO2 dry air mole fraction (XCO2) from January 2003 to May 2016, based on observations from SCIAMACHY, GOSAT, and OCO-2 satellites, were used to calculate XCO2 changes during growing season for 13 years. We derived a relationship between XCO2 and surface net CO2 fluxes from two inversion model simulations, CarbonTracker and Monitoring Atmospheric Composition and Climate (MACC), and used those relationships to estimate the biospheric CO2 flux enhancement based on satellite observed XCO2 changes. We observed significant growing period (GP) greening trends in NDVI and EVI related to cropland intensification and forest growth in the region. After removing the influence of large urban center CO2 emissions, we estimated an enhanced XCO2 drawdown during the GP of -0.070 to -0.084 ppm yr(-1). Increased carbon uptake during the GP was estimated to be 28.41 to 46.04 Tg C, mainly from land management, which could offset about 2-3% of EC's annual fossil fuel emissions. These results show the potential of using multi-satellite observed XCO2 to estimate carbon fluxes from the regional biosphere, which could be used to verify natural sinks included as national contributions of greenhouse gas emissions reduction in international climate change agreements like the UNFCC Paris Accord.
BibTeX:
@article{he20b,
  author = {He, Zhonghua and Lei, Liping and Zeng, Zhao-Cheng and Sheng, Mengya and Welp, Lisa R.},
  title = {Evidence of Carbon Uptake Associated with Vegetation Greening Trends in Eastern China},
  journal = {REMOTE SENSING},
  publisher = {MDPI},
  year = {2020},
  volume = {12},
  number = {4},
  doi = {https://doi.org/10.3390/rs12040718}
}
He, Z., Lei, L., Zhang, Y., Sheng, M., Wu, C., Li, L., Zeng, Z.-C. and We, L.R. Spatio-Temporal Mapping of Multi-Satellite Observed Column Atmospheric CO2 Using Precision-Weighted Kriging Method {2020} REMOTE SENSING
Vol. {12}({3}) 
article DOI  
Abstract: Column-averaged dry air mole fraction of atmospheric CO2 (XCO2), obtained by multiple satellite observations since 2003 such as ENVISAT/SCIAMACHY, GOSAT, and OCO-2 satellite, is valuable for understanding the spatio-temporal variations of atmospheric CO2 concentrations which are related to carbon uptake and emissions. In order to construct long-term spatio-temporal continuous XCO2 from multiple satellites with different temporal and spatial periods of observations, we developed a precision-weighted spatio-temporal kriging method for integrating and mapping multi-satellite observed XCO2. The approach integrated XCO2 from different sensors considering differences in vertical sensitivity, overpass time, the field of view, repeat cycle and measurement precision. We produced globally mapped XCO2 (GM-XCO2) with spatial/temporal resolution of 1 x 1 degree every eight days from 2003 to 2016 with corresponding data precision and interpolation uncertainty in each grid. The predicted GM-XCO2 precision improved in most grids compared with conventional spatio-temporal kriging results, especially during the satellites overlapping period (0.3-0.5 ppm). The method showed good reliability with R-2 of 0.97 from cross-validation. GM-XCO2 showed good accuracy with a standard deviation of bias from total carbon column observing network (TCCON) measurements of 1.05 ppm. This method has potential applications for integrating and mapping XCO2 or other similar datasets observed from multiple satellite sensors. The resulting GM-XCO2 product may be also used in different carbon cycle research applications with different precision requirements.
BibTeX:
@article{he20c,
  author = {He, Zhonghua and Lei, Liping and Zhang, Yuhui and Sheng, Mengya and Wu, Changjiang and Li, Liang and Zeng, Zhao-Cheng and We, Lisa R.},
  title = {Spatio-Temporal Mapping of Multi-Satellite Observed Column Atmospheric CO2 Using Precision-Weighted Kriging Method},
  journal = {REMOTE SENSING},
  publisher = {MDPI},
  year = {2020},
  volume = {12},
  number = {3},
  doi = {https://doi.org/10.3390/rs12030576}
}
He, W., Jiang, F., Wu, M., Ju, W., Scholze, M., Chen, J.M., Byrne, B., Liu, J., Wang, H., Wang, J., Wang, S., Zhou, Y., Zhang, C., Nguyen, N.T., Shen, Y. and Chen, Z. China's Terrestrial Carbon Sink Over 2010-2015 Constrained by Satellite Observations of Atmospheric CO2 and Land Surface Variables 2022 JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. 127(2) 
article DOI  
Abstract: The magnitude and distribution of China's terrestrial carbon sink remain
uncertain due to insufficient constraints at large scales, whereby
satellite data offer great potential for reducing the uncertainty. Here,
we present two carbon sink estimates for China constrained either by
satellite CO2 column concentrations (XCO2) within the Global Carbon
Assimilation System or by remotely sensed soil moisture and Fraction of
Absorbed Photosynthetically Active Radiation (FAPAR) in addition to in
situ CO2 observations within the Carbon Cycle Data Assimilation System.
They point to a moderate size of carbon sinks of 0.34 +/- 0.14 (mean +/-
unc.) and 0.43 +/- 0.09 PgC/yr during 2010-2015, which are supported by
an inventory-based estimate for forest and soil carbon sink (0.26
PgC/yr) and fall in the range of contemporary ensemble atmospheric
inversions (0.25-0.48 PgC/yr). They also agree reasonably well on
interannual variations, which reflect the carbon sink anomalies induced
by regional droughts in southwest China. Furthermore, their spatial
distributions are broadly consistent that of the forest inventory-based
estimate, indicating that the largest carbon sinks locate in central and
eastern China. Their estimates for forest carbon sink coincide fairly
well with the inventory-based estimate across different regions,
especially when aggregated to the north and south of China. Although
enhanced recently by afforestation, China's carbon sink was also
significantly weakened by regional droughts, which were often not fully
represented in previous in situ CO2-based inversions due to insufficient
observations. Our results suggest that satellite-based atmospheric CO2
and land surface observations are vital in characterizing terrestrial
net carbon fluxes at regional scales.
BibTeX:
@article{he22a,
  author = {He, Wei and Jiang, Fei and Wu, Mousong and Ju, Weimin and Scholze, Marko and Chen, Jing M. and Byrne, Brendan and Liu, Junjie and Wang, Hengmao and Wang, Jun and Wang, Songhan and Zhou, Yanlian and Zhang, Chunhua and Ngoc Tu Nguyen and Shen, Yang and Chen, Zhi},
  title = {China's Terrestrial Carbon Sink Over 2010-2015 Constrained by Satellite Observations of Atmospheric CO2 and Land Surface Variables},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2022},
  volume = {127},
  number = {2},
  doi = {https://doi.org/10.1029/2021JG006644}
}
Helbig, M., Chasmer, L.E., Desai, A.R., Kljun, N., Quinton, W.L. and Sonnentag, O. Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest-wetland landscape {2017} GLOBAL CHANGE BIOLOGY
Vol. {23}({8}), pp. 3231-3248 
article DOI  
Abstract: In the sporadic permafrost zone of northwestern Canada, boreal forest
carbon dioxide (CO2) fluxes will be altered directly by climate change
through changing meteorological forcing and indirectly through changes
in landscape functioning associated with thaw-induced collapse-scar bog
(` wetland') expansion. However, their combined effect on
landscape-scale net ecosystem CO2 exchange (NEELAND), resulting from
changing gross primary productivity (GPP) and ecosystem respiration
(ER), remains unknown. Here, we quantify indirect land cover change
impacts on NEELAND and direct climate change impacts on modeled
temperature-and light-limited NEELAND of a boreal forestwetland
landscape. Using nested eddy covariance flux towers, we find both GPP
and ER to be larger at the landscape compared to the wetland level.
However, annual NEELAND (-20 g C m(-2)) and wetland NEE (-24 g C m(-2))
were similar, suggesting negligible wetland expansion effects on
NEELAND. In contrast, we find non-negligible direct climate change
impacts when modeling NEELAND using projected air temperature and
incoming shortwave radiation. At the end of the 21st century, modeled
GPP mainly increases in spring and fall due to reduced temperature
limitation, but becomes more frequently light-limited in fall. In a
warmer climate, ER increases year-round in the absence of moisture
stress resulting in net CO2 uptake increases in the shoulder seasons and
decreases during the summer. Annually, landscape net CO2 uptake is
projected to decline by 25 +/- 14 g C m(-2) for a moderate and 103 +/-
38 g C m(-2) for a high warming scenario, potentially reversing recently
observed positive net CO2 uptake trends across the boreal biome. Thus,
even without moisture stress, net CO2 uptake of boreal forest-wetland
landscapes may decline, and ultimately, these landscapes may turn into
net CO2 sources under continued anthropogenic CO2 emissions. We conclude
that NEELAND changes are more likely to be driven by direct climate
change rather than by indirect land cover change impacts.
BibTeX:
@article{helbig17a,
  author = {Helbig, Manuel and Chasmer, Laura E. and Desai, Ankur R. and Kljun, Natascha and Quinton, William L. and Sonnentag, Oliver},
  title = {Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest-wetland landscape},
  journal = {GLOBAL CHANGE BIOLOGY},
  year = {2017},
  volume = {23},
  number = {8},
  pages = {3231--3248},
  doi = {https://doi.org/10.1111/gcb.13638}
}
Hernandez-Carrasco, I., Sudre, J., Garcon, V., Yahia, H., Garbe, C., Paulmier, A., Dewitte, B., Illig, S., Dadou, I., Gonzalez-Davila, M. and Santana-Casiano, J.M. Reconstruction of super-resolution ocean pCO(2) and air-sea fluxes of CO2 from satellite imagery in the southeastern Atlantic {2015} BIOGEOSCIENCES
Vol. {12}({17}), pp. 5229-5245 
article DOI  
Abstract: An accurate quantification of the role of the ocean as source/sink of
greenhouse gases (GHGs) requires to access the high-resolution of the
GHG air-sea flux at the interface. In this paper we present a novel
method to reconstruct maps of surface ocean partial pressure of CO2
(pCO(2)) and air-sea CO2 fluxes at super resolution (4 km, i.e., 1/32
degrees at these latitudes) using sea surface temperature (SST) and
ocean color (OC) data at this resolution, and CarbonTracker CO2 fluxes
data at low resolution (110 km). Inference of super-resolution pCO(2)
and air-sea CO2 fluxes is performed using novel nonlinear signal
processing methodologies that prove efficient in the context of
oceanography. The theoretical background comes from the microcanonical
multi-fractal formalism which unlocks the geometrical determination of
cascading properties of physical intensive variables. As a consequence,
a multi-resolution analysis performed on the signal of the so-called
singularity exponents allows for the correct and near optimal
cross-scale inference of GHG fluxes, as the inference suits the
geometric realization of the cascade. We apply such a methodology to the
study offshore of the Benguela area. The inferred representation of
oceanic partial pressure of CO2 improves and enhances the description
provided by CarbonTracker, capturing the small-scale variability. We
examine different combinations of ocean color and sea surface
temperature products in order to increase the number of valid points and
the quality of the inferred pCO(2) field. The methodology is validated
using in situ measurements by means of statistical errors. We find that
mean absolute and relative errors in the inferred values of pCO(2) with
respect to in situ measurements are smaller than for CarbonTracker.
BibTeX:
@article{hernandez-carrasco15a,
  author = {Hernandez-Carrasco, I. and Sudre, J. and Garcon, V. and Yahia, H. and Garbe, C. and Paulmier, A. and Dewitte, B. and Illig, S. and Dadou, I. and Gonzalez-Davila, M. and Santana-Casiano, J. M.},
  title = {Reconstruction of super-resolution ocean pCO(2) and air-sea fluxes of CO2 from satellite imagery in the southeastern Atlantic},
  journal = {BIOGEOSCIENCES},
  year = {2015},
  volume = {12},
  number = {17},
  pages = {5229--5245},
  doi = {https://doi.org/10.5194/bg-12-5229-2015}
}
Hernandez-Carrasco, I., Garcon, V., Sudre, J., Garbe, C. and Yahia, H. Increasing the Resolution of Ocean pCO(2) Maps in the South Eastern Atlantic Ocean Merging Multifractal Satellite-Derived Ocean Variables {2018} IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
Vol. {56}({11}), pp. {6596-6610} 
article DOI  
Abstract: A new methodology has been developed in order to improve the description
of the spatial and temporal variability of not well-resolved oceanic
variables from other well-observed high-resolution oceanic variables.
The method is based on the cross-scale inference of information,
incorporating the common features of different multifractal
high-resolution variables into a coarser one. An exercise of validation
of the methodology has been performed based on the outputs of coupled
physical-biogeochemical Regional Ocean Modeling System adapted to the
eastern boundary upwelling systems at two spatial resolutions. Once the
algorithm has been proved to he effective in increasing the spatial
resolution of modeled partial pressure of CO2 at the surface ocean
(pCO(2)), we have investigated the capability of our methodology when it
is applied to remote sensing data, focusing on the improvement of the
temporal description. In this regard, we have inferred daily pCO(2) maps
at high resolution (4 km, i.e., 1/24 degrees) fusing monthly pCO(2) data
at low resolution (100 kin, i.e., 1 degrees) with the small-scale
features contained in daily high-resolution maps of satellite sea
surface temperature and Chlorophyll-a. The algorithm has been applied to
the South Eastern Atlantic Ocean opening the possibility to obtain an
accurate quantification of the CO2 fluxes in relevant coastal regions,
such as the eastern boundary upwelling systems. Outputs of our algorithm
have been compared with in situ measurements, showing that daily maps
inferred from monthly products are in average 6 mu atm closer to the in
situ values than the original coarser monthly maps. Furthermore, values
of pCO(2) have been improved in points close to the coast with respect
to the original input data.
BibTeX:
@article{hernandez-carrasco18a,
  author = {Hernandez-Carrasco, Ismael and Garcon, Veronique and Sudre, Joel and Garbe, Christoph and Yahia, Hussein},
  title = {Increasing the Resolution of Ocean pCO(2) Maps in the South Eastern Atlantic Ocean Merging Multifractal Satellite-Derived Ocean Variables},
  journal = {IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING},
  year = {2018},
  volume = {56},
  number = {11},
  pages = {6596-6610},
  doi = {https://doi.org/10.1109/TGRS.2018.2840526}
}
Hewitt, A.J. Investigating land-air carbon fluxes using a Lagrangian model and satellite retrieved carbon dioxide 2010 School: University of Leicester  phdthesis URL 
Abstract: The existing generation of satellite instruments (such as SCIAMACHY and AIRS) has allowed the retrieval of atmospheric mixing ratios of carbon dioxide. The feasibility of using these and later satellites (OCO-like or GOSAT) to investigate carbon fluxes between the …
BibTeX:
@phdthesis{hewitt10a,
  author = {Alan James Hewitt},
  title = {Investigating land-air carbon fluxes using a Lagrangian model and satellite retrieved carbon dioxide},
  school = {University of Leicester},
  year = {2010},
  url = {https://leicester.figshare.com/articles/thesis/Investigating_land-air_carbon_fluxes_using_a_Lagrangian_model_and_satellite_retrieved_carbon_dioxide/10098698/1}
}
Heymann, J., Schneising, O., Reuter, M., Buchwitz, M., Rozanov, V.V., Velazco, V.A., Bovensmann, H. and Burrows, J.P. SCIAMACHY WFM-DOAS XCO2: comparison with CarbonTracker XCO2 focusing on aerosols and thin clouds {2012} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {5}({8}), pp. 1935-1952 
article DOI  
Abstract: Carbon dioxide (CO2) is the most important greenhouse gas whose
atmospheric loading has been significantly increased by anthropogenic
activity leading to global warming. Accurate measurements and models are
needed in order to reliably predict our future climate. This, however,
has challenging requirements. Errors in measurements and models need to
be identified and minimised.
In this context, we present a comparison between satellite-derived
column-averaged dry air mole fractions of CO2, denoted XCO2, retrieved
from SCIAMACHY/ENVISAT using the WFM-DOAS (weighting function modified
differential optical absorption spectroscopy) algorithm, and output from
NOAA's global CO2 modelling and assimilation system CarbonTracker. We
investigate to what extent differences between these two data sets are
influenced by systematic retrieval errors due to aerosols and
unaccounted clouds. We analyse seven years of SCIAMACHY WFM-DOAS version
2.1 retrievals (WFMDv2.1) using CarbonTracker version 2010.
We investigate to what extent the difference between SCIAMACHY and
CarbonTracker XCO2 are temporally and spatially correlated with global
aerosol and cloud data sets. For this purpose, we use a global aerosol
data set generated within the European GEMS project, which is based on
assimilated MODIS satellite data. For clouds, we use a data set derived
from CALIOP/CALIPSO.
We find significant correlations of the SCIAMACHY minus CarbonTracker
XCO2 difference with thin clouds over the Southern Hemisphere. The
maximum temporal correlation we find for Darwin, Australia (r(2) =
54%). Large temporal correlations with thin clouds are also observed
over other regions of the Southern Hemisphere (e. g. 43% for South
America and 31% for South Africa). Over the Northern Hemisphere the
temporal correlations are typically much lower. An exception is India,
where large temporal correlations with clouds and aerosols have also
been found. For all other regions the temporal correlations with aerosol
are typically low. For the spatial correlations the picture is less
clear. They are typically low for both aerosols and clouds, but
depending on region and season, they may exceed 30% (the maximum value
of 46% has been found for Darwin during September to November).
Overall we find that the presence of thin clouds can potentially explain
a significant fraction of the difference between SCIAMACHY WFMDv2.1 XCO2
and CarbonTracker over the Southern Hemisphere. Aerosols appear to be
less of a problem. Our study indicates that the quality of the satellite
derived XCO2 will significantly benefit from a reduction of scattering
related retrieval errors at least for the Southern Hemisphere.
BibTeX:
@article{heymann12a,
  author = {Heymann, J. and Schneising, O. and Reuter, M. and Buchwitz, M. and Rozanov, V. V. and Velazco, V. A. and Bovensmann, H. and Burrows, J. P.},
  title = {SCIAMACHY WFM-DOAS XCO2: comparison with CarbonTracker XCO2 focusing on aerosols and thin clouds},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2012},
  volume = {5},
  number = {8},
  pages = {1935--1952},
  doi = {https://doi.org/10.5194/amt-5-1935-2012}
}
Heymann, J., Bovensmann, H., Buchwitz, M., Burrows, J.P., Deutscher, N.M., Notholt, J., Rettinger, M., Reuter, M., Schneising, O., Sussmann, R. and Warneke, T. SCIAMACHY WFM-DOAS XCO2: reduction of scattering related errors {2012} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {5}({10}), pp. 2375-2390 
article DOI  
Abstract: Global observations of column-averaged dry air mole fractions of carbon
dioxide (CO2), denoted by XCO2, retrieved from SCIAMACHY on-board
ENVISAT can provide important and missing global information on the
distribution and magnitude of regional CO2 surface fluxes. This
application has challenging precision and accuracy requirements.
In a previous publication (Heymann et al., 2012), it has been shown by
analysing seven years of SCIAMACHY WFM-DOAS XCO2 (WFMDv2.1) that
unaccounted thin cirrus clouds can result in significant errors.
In order to enhance the quality of the SCIAMACHY XCO2 data product, we
have developed a new version of the retrieval algorithm (WFMDv2.2),
which is described in this manuscript. It is based on an improved cloud
filtering and correction method using the 1.4 mu m strong water vapour
absorption and 0.76 mu m O-2-A bands. The new algorithm has been used to
generate a SCIAMACHY XCO2 data set covering the years 2003-2009.
The new XCO2 data set has been validated using ground-based observations
from the Total Carbon Column Observing Network (TCCON). The validation
shows a significant improvement of the new product (v2.2) in comparison
to the previous product (v2.1). For example, the standard deviation of
the difference to TCCON at Darwin, Australia, has been reduced from 4
ppm to 2 ppm. The monthly regional-scale scatter of the data (defined as
the mean intra-monthly standard deviation of all quality filtered XCO2
retrievals within a radius of 350 km around various locations) has also
been reduced, typically by a factor of about 1.5. Overall, the
validation of the new WFMDv2.2 XCO2 data product can be summarised by a
single measurement precision of 3.8 ppm, an estimated regional-scale
(radius of 500 km) precision of monthly averages of 1.6 ppm and an
estimated regional-scale relative accuracy of 0.8 ppm.
In addition to the comparison with the limited number of TCCON sites, we
also present a comparison with NOAA's global CO2 modelling and
assimilation system Carbon-Tracker. This comparison also shows
significant improvements especially over the Southern Hemisphere.
BibTeX:
@article{heymann12b,
  author = {Heymann, J. and Bovensmann, H. and Buchwitz, M. and Burrows, J. P. and Deutscher, N. M. and Notholt, J. and Rettinger, M. and Reuter, M. and Schneising, O. and Sussmann, R. and Warneke, T.},
  title = {SCIAMACHY WFM-DOAS XCO2: reduction of scattering related errors},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2012},
  volume = {5},
  number = {10},
  pages = {2375--2390},
  doi = {https://doi.org/10.5194/amt-5-2375-2012}
}
Heymann, J. Satellite measurements of carbon dioxide: impact and consideration of atmospheric scattering on the data retrieval and interpretation 2013 School: Universität Bremen  phdthesis URL 
BibTeX:
@phdthesis{heymann13a,
  author = {Heymann, Jens},
  title = {Satellite measurements of carbon dioxide: impact and consideration of atmospheric scattering on the data retrieval and interpretation},
  school = {Universität Bremen},
  year = {2013},
  url = {https://d-nb.info/1072047985/34}
}
Heymann, J., Reuter, M., Hilker, M., Buchwitz, M., Schneising, O., Bovensmann, H., Burrows, J.P., Kuze, A., Suto, H., Deutscher, N.M., Dubey, M.K., Griffith, D.W.T., Hase, F., Kawakami, S., Kivi, R., Morino, I., Petri, C., Roehl, C., Schneider, M., Sherlock, V., Sussmann, R., Velazco, V.A., Warneke, T. and Wunch, D. Consistent satellite XCO2 retrievals from SCIAMACHY and GOSAT using the BESD algorithm {2015} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {8}({7}), pp. 2961-2980 
article DOI  
Abstract: Consistent and accurate long-term data sets of global atmospheric
concentrations of carbon dioxide (CO2) are required for carbon cycle and
climate-related research. However, global data sets based on satellite
observations may suffer from inconsistencies originating from the use of
products derived from different satellites as needed to cover a long
enough time period. One reason for inconsistencies can be the use of
different retrieval algorithms. We address this potential issue by
applying the same algorithm, the Bremen Optimal Estimation DOAS (BESD)
algorithm, to different satellite instruments, SCIAMACHY on-board
ENVISAT (March 2002-April 2012) and TANSO-FTS onboard GOSAT (launched in
January 2009), to retrieve XCO2, the column-averaged dry-air mole
fraction of CO2. BESD has been initially developed for SCIAMACHY XCO2
retrievals. Here, we present the first detailed assessment of the new
GOSAT BESD XCO2 product. GOSAT BESD XCO2 is a product generated and
delivered to the MACC project for assimilation into ECMWF's Integrated
Forecasting System. We describe the modifications of the BESD algorithm
needed in order to retrieve XCO2 from GOSAT and present de-tailed
comparisons with ground-based observations of XCO2 from the Total Carbon
Column Observing Network (TCCON). We discuss detailed comparison results
between all three XCO2 data sets (SCIAMACHY, GOSAT and TCCON). The
comparison results demonstrate the good consistency between SCIAMACHY
and GOSAT XCO2. For example, we found a mean difference for daily
averages of -0.60 +/- 1.56 ppm (mean difference +/- standard deviation)
for GOSAT-SCIAMACHY (linear correlation coefficient r = 0.82), -0.34 +/-
1.37 ppm (r = 0.86) for GOSAT-TCCON and 0.10 +/- 1.79 ppm (r = 0.75) for
SCIAMACHY-TCCON. The remaining differences between GOSAT and SCIAMACHY
are likely due to non-perfect collocation (+/- 2 h, 10 degrees x 10
degrees around TCCON sites), i.e. the observed air masses are not
exactly identical but likely also due to a still non-perfect BESD
retrieval algorithm, which will be continuously improved in the future.
Our overarching goal is to generate a satellite-derived XCO2 data set
appropriate for climate and carbon cycle research covering the longest
possible time period. We therefore also plan to extend the existing
SCIAMACHY and GOSAT data set discussed here by also using data from
other missions (e.g. OCO-2, GOSAT-2, CarbonSat) in the future.
BibTeX:
@article{heymann15a,
  author = {Heymann, J. and Reuter, M. and Hilker, M. and Buchwitz, M. and Schneising, O. and Bovensmann, H. and Burrows, J. P. and Kuze, A. and Suto, H. and Deutscher, N. M. and Dubey, M. K. and Griffith, D. W. T. and Hase, F. and Kawakami, S. and Kivi, R. and Morino, I. and Petri, C. and Roehl, C. and Schneider, M. and Sherlock, V. and Sussmann, R. and Velazco, V. A. and Warneke, T. and Wunch, D.},
  title = {Consistent satellite XCO2 retrievals from SCIAMACHY and GOSAT using the BESD algorithm},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2015},
  volume = {8},
  number = {7},
  pages = {2961--2980},
  doi = {https://doi.org/10.5194/amt-8-2961-2015}
}
Heymann, J., Reuter, M., Buchwitz, M., Schneising, O., Bovensmann, H., Burrows, J.P., Massart, S., Kaiser, J.W. and Crisp, D. CO2 emission of Indonesian fires in 2015 estimated from satellite-derived atmospheric CO2 concentrations {2017} GEOPHYSICAL RESEARCH LETTERS
Vol. {44}({3}), pp. 1537-1544 
article DOI  
Abstract: Indonesia experienced an exceptional number of fires in 2015 as a result
of droughts related to the recent El Nio event and human activities.
These fires released large amounts of carbon dioxide (CO2) into the
atmosphere. Emission databases such as the Global Fire Assimilation
System version 1.2 and the Global Fire Emission Database version 4s
estimated the CO2 emission to be approximately 1100 MtCO(2) in the time
period from July to November 2015. This emission was indirectly
estimated by using parameters like burned area, fire radiative power,
and emission factors. In the study presented in this paper, we estimate
the Indonesian fire CO2 emission by using the column-averaged dry air
mole fraction of CO2, XCO2, derived from measurements of the Orbiting
Carbon Observatory-2 satellite mission. The estimated CO2 emission is
748 +/- 209 MtCO(2), which is about 30% lower than provided by the
emission databases.
BibTeX:
@article{heymann17a,
  author = {Heymann, J. and Reuter, M. and Buchwitz, M. and Schneising, O. and Bovensmann, H. and Burrows, J. P. and Massart, S. and Kaiser, J. W. and Crisp, D.},
  title = {CO2 emission of Indonesian fires in 2015 estimated from satellite-derived atmospheric CO2 concentrations},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2017},
  volume = {44},
  number = {3},
  pages = {1537--1544},
  doi = {https://doi.org/10.1002/2016GL072042}
}
Hilton, T.W. Spatial structure in North American terrestrial biological carbon fluxes and flux model errors evaluated with a simple land surface model 2011 School: The Pennsylvania State University  phdthesis URL 
BibTeX:
@phdthesis{hilton11a,
  author = {Hilton, Timothy William},
  title = {Spatial structure in North American terrestrial biological carbon fluxes and flux model errors evaluated with a simple land surface model},
  school = {The Pennsylvania State University},
  year = {2011},
  url = {http://search.proquest.com/openview/ad1f013a7f8d52fe468d7ba861602aa1/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Hilton, T.W., Davis, K.J., Keller, K. and Urban, N.M. Improving North American terrestrial CO2 flux diagnosis using spatial structure in land surface model residuals {2013} BIOGEOSCIENCES
Vol. {10}({7}), pp. 4607-4625 
article DOI  
Abstract: We evaluate spatial structure in North American CO2 flux observations
using a simple diagnostic land surface model. The vegetation
photosynthesis respiration model (VPRM) calculates net ecosystem
exchange (NEE) using locally observed temperature and photosynthetically
active radiation (PAR) along with satellite-derived phenology and
moisture. We use observed NEE from a group of 65 North American eddy
covariance tower sites spanning North America to estimate VPRM
parameters for these sites. We investigate spatial coherence in regional
CO2 fluxes at several different time scales by using geostatistical
methods to examine the spatial structure of model-data residuals. We
find that persistent spatial structure does exist in the model-data
residuals at a length scale of approximately 400 km (median 402 km, mean
712 km, standard deviation 931 km). This spatial structure defines a
flux-tower-based VPRM residual covariance matrix. The residual
covariance matrix is useful in constructing prior fluxes for atmospheric
CO2 concentration inversion calculations, as well as for constructing a
VPRM North American CO2 flux map optimized to eddy covariance
observations. Finally (and secondarily), the estimated VPRM parameter
values do not separate clearly by plant functional type (PFT). This
calls into question whether PFTs can successfully partition ecosystems'
fundamental ecological drivers when the viewing lens is a simple model.
BibTeX:
@article{hilton13a,
  author = {Hilton, T. W. and Davis, K. J. and Keller, K. and Urban, N. M.},
  title = {Improving North American terrestrial CO2 flux diagnosis using spatial structure in land surface model residuals},
  journal = {BIOGEOSCIENCES},
  year = {2013},
  volume = {10},
  number = {7},
  pages = {4607--4625},
  doi = {https://doi.org/10.5194/bg-10-4607-2013}
}
Hilton, T.W., Davis, K.J. and Keller, K. Evaluating terrestrial CO2 flux diagnoses and uncertainties from a simple land surface model and its residuals {2014} BIOGEOSCIENCES
Vol. {11}({2}), pp. 217-235 
article DOI  
Abstract: Global terrestrial atmosphere-ecosystem carbon dioxide fluxes are well
constrained by the concentration and isotopic composition of atmospheric
carbon dioxide. In contrast, considerable uncertainty persists
surrounding regional contributions to the net global flux as well as the
impacts of atmospheric and biological processes that drive the net flux.
These uncertainties severely limit our ability to make confident
predictions of future terrestrial biological carbon fluxes. Here we use
a simple light-use efficiency land surface model (the Vegetation
Photosynthesis Respiration Model, VPRM) driven by remotely sensed
temperature, moisture, and phenology to diagnose North American gross
ecosystem exchange (GEE), ecosystem respiration, and net ecosystem
exchange (NEE) for the period 2001 to 2006. We optimize VPRM parameters
to eddy covariance (EC) NEE observations from 65 North American FluxNet
sites. We use a separate set of 27 cross-validation FluxNet sites to
evaluate a range of spatial and temporal resolutions for parameter
estimation. With these results we demonstrate that different spatial and
temporal groupings of EC sites for parameter estimation achieve similar
sum of squared residuals values through radically different spatial
patterns of NEE. We also derive a regression model to estimate observed
VPRM errors as a function of VPRM NEE, temperature, and precipitation.
Because this estimate is based on model-observation residuals it is
comprehensive of all the error sources present in modeled fluxes. We
find that 1 km interannual variability in VPRM NEE is of similar
magnitude to estimated 1 km VPRM NEE errors.
BibTeX:
@article{hilton14a,
  author = {Hilton, T. W. and Davis, K. J. and Keller, K.},
  title = {Evaluating terrestrial CO2 flux diagnoses and uncertainties from a simple land surface model and its residuals},
  journal = {BIOGEOSCIENCES},
  year = {2014},
  volume = {11},
  number = {2},
  pages = {217--235},
  doi = {https://doi.org/10.5194/bg-11-217-2014}
}
Hiyama, T., Ueyama, M., Kotani, A., Iwata, H., Nakai, T., Okamura, M., Ohta, T., Harazono, Y., Petrov, R.E. and Maximov, T.C. Lessons learned from more than a decade of greenhouse gas flux measurements at boreal forests in eastern Siberia and interior Alaska 2020 Polar Science  article URL 
Abstract: We summarized our recently-published papers on greenhouse gas exchanges at two important boreal regions underlain by permafrost: eastern Siberia and interior Alaska. Relevant literatures were also referred to, and future research directions on the high-latitude …
BibTeX:
@article{hiyama20a,
  author = {Tetsuya Hiyama and Masahito Ueyama and Ayumi Kotani and Hiroki Iwata and Taro Nakai and Mikita Okamura and Takeshi Ohta and Yoshinobu Harazono and Roman E. Petrov and Trofim C. Maximov},
  title = {Lessons learned from more than a decade of greenhouse gas flux measurements at boreal forests in eastern Siberia and interior Alaska},
  journal = {Polar Science},
  year = {2020},
  url = {https://www.sciencedirect.com/science/article/pii/S1873965220301250}
}
Hiyama, T., Ueyama, M., Kotani, A., Iwata, H., Nakai, T., Okamura, M., Ohta, T., Harazono, Y., Petrov, R.E. and Maximov, T.C. Lessons learned from more than a decade of greenhouse gas flux measurements at boreal forests in eastern Siberia and interior Alaska 2021 POLAR SCIENCE
Vol. 27 
article DOI  
Abstract: We summarized our recently-published papers on greenhouse gas exchanges
at two important boreal regions underlain by permafrost: eastern Siberia
and interior Alaska. Relevant literatures were also referred to, and
future research directions on the high-latitude terrestrial processes
were suggested. Long-term monitoring of CO2 fluxes at the boreal forests
revealed that anomalous weather and disturbances changed the CO2
balance. More than a decade is required to return to a CO2 sink at
burned forests in interior Alaska. Anomalous high precipitation altered
the forest structure in eastern Siberia, shifting the
overstory/understory contributions to the CO2 balance. The CH4 emissions
were higher in the two boreal forests than in the other boreal forests.
Upscaling the in-situ observations and comparisons with top-down
approaches revealed considerable inconsistencies exist among the
approaches. We recommend the following directions in future research.
First, long-term monitoring is indispensable to detect the effect of
climate change on ecosystems. Second, disturbance impacts, including
fire, thermokarst, and wet spells, need to be quantified. Third, further
observations are necessary for constraining CH4 exchange models.
Finally, reconciling top-down and bottom-up approaches is required to
reduce uncertainty. Prompt sharing of observed data and model products
is crucial to improve our understanding of high-latitude processes.
BibTeX:
@article{hiyama21a,
  author = {Hiyama, Tetsuya and Ueyama, Masahito and Kotani, Ayumi and Iwata, Hiroki and Nakai, Taro and Okamura, Mikita and Ohta, Takeshi and Harazono, Yoshinobu and Petrov, Roman E. and Maximov, Trofim C.},
  title = {Lessons learned from more than a decade of greenhouse gas flux measurements at boreal forests in eastern Siberia and interior Alaska},
  journal = {POLAR SCIENCE},
  year = {2021},
  volume = {27},
  doi = {https://doi.org/10.1016/j.polar.2020.100607}
}
Ho, D.T. and Schanze, J.J. Precipitation-Induced Reduction in Surface Ocean pCO(2): Observations From the Eastern Tropical Pacific Ocean {2020} GEOPHYSICAL RESEARCH LETTERS
Vol. {47}({15}) 
article DOI  
Abstract: Determining air-sea CO2 fluxes using pCO(2) disequilibrium requires knowing the gas transfer velocity and air-sea pCO(2) difference. Most pCO(2) measurements are made from ships, whose uncontaminated seawater intakes are located at >5-m depth to prevent ingestion of air. However, there could be bias in determinations of CO2 fluxes if there is disagreement between pCO(2) measurements at the surface and 5 m. Seawater measurements made at the near surface and 5 m in the eastern Equatorial Pacific Ocean show that precipitation can dilute surface seawater salinity and lower the pCO(2) and dissolved inorganic carbon and raise pH of the same water, and that these changes in ocean chemistry are largely missed by measurements at 5 m. This finding implies that estimates of ocean CO2 uptake might be underestimated, since rain will lower surface ocean pCO(2) in both source and sink regions and, hence, increase uptake in sink regions and decrease outgassing in source regions.
BibTeX:
@article{ho20a,
  author = {Ho, David T. and Schanze, Julian J.},
  title = {Precipitation-Induced Reduction in Surface Ocean pCO(2): Observations From the Eastern Tropical Pacific Ocean},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {47},
  number = {15},
  doi = {https://doi.org/10.1029/2020GL088252}
}
Honeycutt, W.T., Kim, T., Ley, M.T. and Materer, N.F. Sensor array for wireless remote monitoring of carbon dioxide and methane near carbon sequestration and oil recovery sites {2021} RSC ADVANCES
Vol. {11}({12}), pp. {6972-6984} 
article DOI  
Abstract: Carbon sequestration and enhanced oil recovery are two important geochemical applications currently deployed using carbon dioxide (CO2), a prevalent greenhouse gas. Despite the push to find ways to use and store excess CO2, the development of a large-area monitoring system is lacking. For these applications, there is little literature reporting the development and testing of sensor systems capable of operating in remote areas without maintenance and having significantly low cost to allow their deployment across a large land area. This paper presents the design and validation of a low-cost solar-power distributed sensing architecture using a wireless mesh network integrated, at selective nodes, into a cellular network. This combination allows an ``internet of things'' approach in remote locations and the integration of a large number of sensor units to monitor CO2 and methane (CH4). This system will allow efficient large area monitoring of both rare catastrophic leaks along with the common micro-seepage of greenhouse gas near carbon sequestration and oil recovery sites. The deployment and testing of the sensor system was performed in an open field at Oklahoma State University. The two-tear network functionality and robustness were determined from a multi-year field study. The reliability of the system was benchmarked by correlating the measured temperature, pressure, and humidity measurement by the network of devices to existing weather data. The CO2 and CH4 gas concentration tracked their expected daily and seasonal cycles. This multi-year field study established that this system can operate in remote areas with minimal human interactions.
BibTeX:
@article{honeycutt21a,
  author = {Honeycutt, Wesley T. and Kim, Taehwan and Ley, M. Tyler and Materer, Nicholas F.},
  title = {Sensor array for wireless remote monitoring of carbon dioxide and methane near carbon sequestration and oil recovery sites},
  journal = {RSC ADVANCES},
  publisher = {ROYAL SOC CHEMISTRY},
  year = {2021},
  volume = {11},
  number = {12},
  pages = {6972--6984},
  doi = {https://doi.org/10.1039/d0ra08593f}
}
Houweling, S., Aben, I., Breon, F.-M., Chevallier, F., Deutscher, N., Engelen, R., Gerbig, C., Griffith, D., Hungershoefer, K., Macatangay, R., Marshall, J., Notholt, J., Peters, W. and Serrar, S. The importance of transport model uncertainties for the estimation of CO2 sources and sinks using satellite measurements {2010} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {10}({20}), pp. 9981-9992 
article DOI  
Abstract: This study presents a synthetic model intercomparison to investigate the
importance of transport model errors for estimating the sources and
sinks of CO2 using satellite measurements. The experiments were designed
for testing the potential performance of the proposed CO2 lidar A-SCOPE,
but also apply to other space borne missions that monitor total column
CO2. The participating transport models IFS, LMDZ, TM3, and TM5 were run
in forward and inverse mode using common a priori CO2 fluxes and initial
concentrations. Forward simulations of column averaged CO2 (xCO(2))
mixing ratios vary between the models by sigma = 0.5 ppm over the
continents and sigma = 0.27 ppm over the oceans. Despite the fact that
the models agree on average on the sub-ppm level, these modest
differences nevertheless lead to significant discrepancies in the
inverted fluxes of 0.1 PgC/yr per 10(6) km(2) over land and 0.03 PgC/yr
per 10(6) km(2) over the ocean. These transport model induced flux
uncertainties exceed the target requirement that was formulated for the
A-SCOPE mission of 0.02 PgC/yr per 10(6) km(2), and could also limit the
overall performance of other CO2 missions such as GOSAT. A variable, but
overall encouraging agreement is found in comparison with FTS
measurements at Park Falls, Darwin, Spitsbergen, and Bremen, although
systematic differences are found exceeding the 0.5 ppm level. Because of
this, our estimate of the impact of transport model uncerainty is likely
to be conservative. It is concluded that to make use of the remote
sensing technique for quantifying the sources and sinks of CO2 not only
requires highly accurate satellite instruments, but also puts stringent
requirements on the performance of atmospheric transport models.
Improving the accuracy of these models should receive high priority,
which calls for a closer collaboration between experts in atmospheric
dynamics and tracer transport.
BibTeX:
@article{houweling10a,
  author = {Houweling, S. and Aben, I. and Breon, F-M and Chevallier, F. and Deutscher, N. and Engelen, R. and Gerbig, C. and Griffith, D. and Hungershoefer, K. and Macatangay, R. and Marshall, J. and Notholt, J. and Peters, W. and Serrar, S.},
  title = {The importance of transport model uncertainties for the estimation of CO2 sources and sinks using satellite measurements},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2010},
  volume = {10},
  number = {20},
  pages = {9981--9992},
  doi = {https://doi.org/10.5194/acp-10-9981-2010}
}
Houweling, S., Krol, M., Bergamaschi, P., Frankenberg, C., Dlugokencky, E.J., Morino, I., Notholt, J., Sherlock, V., Wunch, D., Beck, V., Gerbig, C., Chen, H., Kort, E.A., Rockmann, T. and Aben, I. A multi-year methane inversion using SCIAMACHY, accounting for systematic errors using TCCON measurements {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({8}), pp. 3991-4012 
article DOI  
Abstract: This study investigates the use of total column CH4 (XCH4) retrievals
from the SCIAMACHY satellite instrument for quantifying large-scale
emissions of methane. A unique data set from SCIAMACHY is available
spanning almost a decade of measurements, covering a period when the
global CH4 growth rate showed a marked transition from stable to
increasing mixing ratios. The TM5 4DVAR inverse modelling system has
been used to infer CH4 emissions from a combination of satellite and
surface measurements for the period 2003-2010. In contrast to earlier
inverse modelling studies, the SCIAMACHY retrievals have been corrected
for systematic errors using the TCCON network of ground-based Fourier
transform spectrometers. The aim is to further investigate the role of
bias correction of satellite data in inversions. Methods for bias
correction are discussed, and the sensitivity of the optimized emissions
to alternative bias correction functions is quantified. It is found that
the use of SCIAMACHY retrievals in TM5 4DVAR increases the estimated
inter-annual variability of large-scale fluxes by 22% compared with the
use of only surface observations. The difference in global methane
emissions between 2-year periods before and after July 2006 is estimated
at 27-35 Tg yr(-1). The use of SCIAMACHY retrievals causes a shift in
the emissions from the extra-tropics to the tropics of 50 +/- 25 Tg
yr(-1). The large uncertainty in this value arises from the uncertainty
in the bias correction functions. Using measurements from the HIPPO and
BARCA aircraft campaigns, we show that systematic errors in the
SCIAMACHY measurements are a main factor limiting the performance of the
inversions. To further constrain tropical emissions of methane using
current and future satellite missions, extended validation capabilities
in the tropics are of critical importance.
BibTeX:
@article{houweling14a,
  author = {Houweling, S. and Krol, M. and Bergamaschi, P. and Frankenberg, C. and Dlugokencky, E. J. and Morino, I. and Notholt, J. and Sherlock, V. and Wunch, D. and Beck, V. and Gerbig, C. and Chen, H. and Kort, E. A. and Rockmann, T. and Aben, I.},
  title = {A multi-year methane inversion using SCIAMACHY, accounting for systematic errors using TCCON measurements},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {8},
  pages = {3991--4012},
  doi = {https://doi.org/10.5194/acp-14-3991-2014}
}
Houweling, S., Bergamaschi, P., Chevallier, F., Heimann, M., Kaminski, T., Krol, M., Michalak, A.M. and Patra, P. Global inverse modeling of CH4 sources and sinks: an overview of methods {2017} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {17}({1}), pp. 235-256 
article DOI  
Abstract: The aim of this paper is to present an overview of inverse modeling
methods that have been developed over the years for estimating the
global sources and sinks of CH4. It provides insight into how techniques
and estimates have evolved over time and what the remaining shortcomings
are. As such, it serves a didactical purpose of introducing apprentices
to the field, but it also takes stock of developments so far and
reflects on promising new directions. The main focus is on
methodological aspects that are particularly relevant for CH4, such as
its atmospheric oxidation, the use of methane isotopologues, and
specific challenges in atmospheric transport modeling of CH4. The use of
satellite retrievals receives special attention as it is an active field
of methodological development, with special requirements on the sampling
of the model and the treatment of data uncertainty. Regional scale flux
estimation and attribution is still a grand challenge, which calls for
new methods capable of combining information from multiple data streams
of different measured parameters. A process model representation of
sources and sinks in atmospheric transport inversion schemes allows the
integrated use of such data. These new developments are needed not only
to improve our understanding of the main processes driving the observed
global trend but also to support international efforts to reduce
greenhouse gas emissions.
BibTeX:
@article{houweling17a,
  author = {Houweling, Sander and Bergamaschi, Peter and Chevallier, Frederic and Heimann, Martin and Kaminski, Thomas and Krol, Maarten and Michalak, Anna M. and Patra, Prabir},
  title = {Global inverse modeling of CH4 sources and sinks: an overview of methods},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2017},
  volume = {17},
  number = {1},
  pages = {235--256},
  doi = {https://doi.org/10.5194/acp-17-235-2017}
}
Howe, S. Model Validation and Estimation of the Complete Carbon Cycle in the Northeastern United States 2019 School: University of Maryland  phdthesis URL 
Abstract: To obtain accurate greenhouse gas emissions estimates, it is important to understand the influence of the biosphere on atmospheric carbon dioxide (CO2). This is difficult as observations are sparse over large spatial domains. The Northeastern United States is an …
BibTeX:
@phdthesis{howe19a,
  author = {Shaun Howe},
  title = {Model Validation and Estimation of the Complete Carbon Cycle in the Northeastern United States},
  school = {University of Maryland},
  year = {2019},
  url = {https://aosc.umd.edu/sites/default/files/dissertations-theses/Shaun%20Howe-Thesis-2019.pdf}
}
Hsueh, D. New York City's Metropolitan Dome: past and present CO2 concentration patterns from an urban to rural gradient 2009 School: Columbia University, New York  mastersthesis  
BibTeX:
@mastersthesis{hsueh09a,
  author = {Hsueh, Diana},
  title = {New York City's Metropolitan Dome: past and present CO2 concentration patterns from an urban to rural gradient},
  school = {Columbia University, New York},
  year = {2009}
}
Hsueh, Y.-H., Li, K.-F., Lin, L.-C., Bhattacharya, S.K., Laskar, A.H. and Liang, M.-C. East Asian CO2 level change caused by Pacific Decadal Oscillation 2021 REMOTE SENSING OF ENVIRONMENT
Vol. 264 
article DOI  
Abstract: Accurate projection of CO2 concentration in time and space remains
challenging because of complex interplay between anthropogenic
emissions, biospheric responses, and climatic variabilities. While the
increase of atmospheric CO2 concentration is due primarily to fossil
fuel burning, natural climate variabilities are known to introduce
intermittent changes in the global CO2 growth rates. Thus, understanding
the correlation of climate and carbon cycling systems is important in
assessing the anthropogenic and natural impacts. Here, we report decadal
CO2 variabilities in western Pacific based on data from several
ground-based stations in the region and Atmospheric Infrared Sounder
(AIRS). In addition to the well-established El Nino-Southern Oscillation
(ENSO), there exists a decadal changing CO2 trend in the datasets
mentioned above. Analysis of ground-based CO2 measurements in northern
Taiwan shows a decadal signal at amplitudes of -5 ppm. In contrast, AIRS
shows a similar trend but at a reduced amplitude of -1 ppm. We attribute
the decadal signal to dynamical factors related to the Pacific Decadal
Oscillation (PDO). This decadal signal, however, is not reproduced by
the state-of-the-art data assimilation system, CarbonTacker, suggesting
a gap in our knowledge of the modulation of carbon cycling systems and
climate.
BibTeX:
@article{hsueh21a,
  author = {Hsueh, Yu-Hsin and Li, King-Fai and Lin, Li-Ching and Bhattacharya, Sourendra Kumar and Laskar, Amzad H. and Liang, Mao-Chang},
  title = {East Asian CO2 level change caused by Pacific Decadal Oscillation},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2021},
  volume = {264},
  doi = {https://doi.org/10.1016/j.rse.2021.112624}
}
Hu, L., Montzka, S.A., Miller, J.B., Andrews, A.E., Lehman, S.J., Miller, B.R., Thoning, K., Sweeney, C., Chen, H., Godwin, D.S., Masarie, K., Bruhwiler, L., Fischer, M.L., Biraud, S.C., Torn, M.S., Mountain, M., Nehrkorn, T., Eluszkiewicz, J., Miller, S., Draxler, R.R., Stein, A.F., Hall, B.D., Elkins, J.W. and Tans, P.P. US emissions of HFC-134a derived for 2008-2012 from an extensive flask-air sampling network {2015} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {120}({2}), pp. 801-825 
article DOI  
Abstract: U.S. national and regional emissions of HFC-134a are derived for
2008-2012 based on atmospheric observations from ground and aircraft
sites across the U.S. and a newly developed regional inverse model.
Synthetic data experiments were first conducted to optimize the model
assimilation design and to assess model-data mismatch errors and prior
flux error covariances computed using a maximum likelihood estimation
technique. The synthetic data experiments also tested the sensitivity of
derived national and regional emissions to a range of assumed prior
emissions, with the goal of designing a system that was minimally
reliant on the prior. We then explored the influence of additional
sources of error in inversions with actual observations, such as those
associated with background mole fractions and transport uncertainties.
Estimated emissions of HFC-134a range from 52 to 61 Gg yr(-1) for the
contiguous U.S. during 2008-2012 for inversions using air transport from
Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model
driven by the 12km resolution meteorogical data from North American
Mesoscale Forecast System (NAM12) and all tested combinations of prior
emissions and background mole fractions. Estimated emissions for
2008-2010 were 20% lower when specifying alternative transport from
Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by
the Weather Research and Forecasting (WRF) meteorology. Our estimates
(for HYSPLIT-NAM12) are consistent with annual emissions reported by
U.S. Environmental Protection Agency for the full study interval. The
results suggest a 10-20% drop in U.S. national HFC-134a emission in
2009 coincident with a reduction in transportation-related fossil fuel
CO2 emissions, perhaps related to the economic recession. All inversions
show seasonal variation in national HFC-134a emissions in all years,
with summer emissions greater than winter emissions by 20-50%.
BibTeX:
@article{hu15a,
  author = {Hu, Lei and Montzka, Stephen A. and Miller, John B. and Andrews, Aryln E. and Lehman, Scott J. and Miller, Benjamin R. and Thoning, Kirk and Sweeney, Colm and Chen, Huilin and Godwin, David S. and Masarie, Kenneth and Bruhwiler, Lori and Fischer, Marc L. and Biraud, Sebastien C. and Torn, Margaret S. and Mountain, Marikate and Nehrkorn, Thomas and Eluszkiewicz, Janusz and Miller, Scot and Draxler, Roland R. and Stein, Ariel F. and Hall, Bradley D. and Elkins, James W. and Tans, Pieter P.},
  title = {US emissions of HFC-134a derived for 2008-2012 from an extensive flask-air sampling network},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2015},
  volume = {120},
  number = {2},
  pages = {801--825},
  doi = {https://doi.org/10.1002/2014JD022617}
}
Hu, C., Griffis, T.J., Lee, X., Millet, D.B., Chen, Z., Baker, J.M. and Xiao, K. Top-Down Constraints on Anthropogenic CO2 Emissions Within an Agricultural-Urban Landscape {2018} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {123}({9}), pp. {4674-4694} 
article DOI  
Abstract: Anthropogenic carbon dioxide (CO2) emissions dominate the atmospheric
greenhouse gas radiative forcing budget. However, these emissions are
poorly constrained at the regional (10(2)-10(6)km(2)) and seasonal
scales. Here we use a combination of tall tower CO2 mixing ratio and
carbon isotope ratio observations and inverse modeling techniques to
constrain anthropogenic CO2 emissions within a highly heterogeneous
agricultural landscape near Saint Paul, Minnesota, in the Upper
Midwestern United States. The analyses indicate that anthropogenic
emissions contributed 6.6, 6.8, and 7.4mol/mol annual CO2 enhancements
(i.e., departures from the background values) in 2008, 2009, and 2010,
respectively. Oil refinery, the energy industry (power and heat
generation), and residential emissions (home heating and cooking)
contributed 2.9 (42.5%), 1.4 (19.8%), and 1.1mol/mol (15.8%) of the
total anthropogenic enhancement over the 3-year period according to a
priori inventories. The total anthropogenic signal was further
partitioned into CO2 emissions derived from fuel oil, natural gas, coal,
gasoline, and diesel consumption using inverse modeling and carbon
isotope ratio analyses. The results indicate that fuel oil and natural
gas consumption accounted for 52.5% of the anthropogenic CO2 sources in
winter. Here the a posteriori CO2 emission from natural gas was
79.04.1% (a priori 20.0%) and accounted for 63% of the total CO2
enhancement including both biological and anthropogenic sources. The a
posteriori CO2 emission from fuel oil was 8.43.8% (a priori
32.5%)suggesting a more important role of residential heating in
winter. The modeled carbon isotope ratio of the CO2 source (delta
C-13(s), -29.3 +/- 0.4%) was relatively more enriched in C-13-CO2
compared to that derived from Miller-Tans plot analyses (-35.5 parts per
thousand to -34.8 parts per thousand), supporting that natural gas
consumption was underestimated for this region.
BibTeX:
@article{hu18a,
  author = {Hu, Cheng and Griffis, Timothy J. and Lee, Xuhui and Millet, Dylan B. and Chen, Zichong and Baker, John M. and Xiao, Ke},
  title = {Top-Down Constraints on Anthropogenic CO2 Emissions Within an Agricultural-Urban Landscape},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2018},
  volume = {123},
  number = {9},
  pages = {4674-4694},
  doi = {https://doi.org/10.1029/2017JD027881}
}
Hu, H., Landgraf, J., Detmers, R., Borsdorff, T., de Brugh, J.A., Aben, I., Butz, A. and Hasekamp, O. Toward Global Mapping of Methane With TROPOMI: First Results and Intersatellite Comparison to GOSAT {2018} GEOPHYSICAL RESEARCH LETTERS
Vol. {45}({8}), pp. {3682-3689} 
article DOI  
Abstract: The TROPOspheric Monitoring Instrument (TROPOMI), launched on 13 October
2017, aboard the Sentinel-5 Precursor satellite, measures reflected
sunlight in the ultraviolet, visible, near-infrared, and shortwave
infrared spectral range. It enables daily global mapping of key
atmospheric species for monitoring air quality and climate. We present
the first methane observations from November and December 2017, using
TROPOMI radiance measurements in the shortwave infrared band around 2.3
mu m. We compare our results with the methane product obtained from the
Greenhouse gases Observing SAT-ellite (GOSAT). Although different
spectral ranges and retrieval methods are used, we find excellent
agreement between the methane products acquired from the two satellites
with a mean difference of 13.6 ppb, standard deviation of 19.6 ppb, and
Pearson's correlation coefficient of 0.95. Our preliminary results
capture the latitudinal gradient and show expected regional
enhancements, for example, in the African Sudd wetlands, with much more
detail than has been observed before.
Plain Language Summary Methane is the second most important
anthropogenic greenhouse gas. Improved knowledge about methane
variations and detection of localized sources is of great importance for
scientists, policy makers, and private companies. One of the goals of
the recently launched European Space Agency Sentinel-5 Precursor
satellite, with on board the cutting-edge TROPOspheric Monitoring
Instrument (TROPOMI), is to measure methane with an unprecedented
combination of accuracy, spatial coverage, and resolution. This work
presents the first TROPOMI methane measurements and shows that these are
in excellent agreement with methane measurements from the validated
Japanese Greenhouse gases Observing SATellite satellite.
BibTeX:
@article{hu18b,
  author = {Hu, Haili and Landgraf, Jochen and Detmers, Rob and Borsdorff, Tobias and de Brugh, Joost Aan and Aben, Ilse and Butz, Andre and Hasekamp, Otto},
  title = {Toward Global Mapping of Methane With TROPOMI: First Results and Intersatellite Comparison to GOSAT},
  journal = {GEOPHYSICAL RESEARCH LETTERS},
  year = {2018},
  volume = {45},
  number = {8},
  pages = {3682-3689},
  doi = {https://doi.org/10.1002/2018GL077259}
}
Hu, C., Liu, S., Wang, Y., Zhang, M., Xiao, W., Wang, W. and Xu, J. Anthropogenic CO2 emissions from a megacity in the Yangtze River Delta of China {2018} ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Vol. {25}({23, SI}), pp. {23157-23169} 
article DOI  
Abstract: Anthropogenic CO2 emissions from cities represent a major source
contributing to the global atmospheric CO2 burden. Here, we examined the
enhancement of atmospheric CO2 mixing ratios by anthropogenic emissions
within the Yangtze River Delta (YRD), China, one of the world's most
densely populated regions (population greater than 150 million). Tower
measurements of CO2 mixing ratios were conducted from March 2013 to
August 2015 and were combined with numerical source footprint modeling
to help constrain the anthropogenic CO2 emissions. We simulated the CO2
enhancements (i.e., fluctuations superimposed on background values) for
winter season (December, January, and February). Overall, we observed
mean diurnal variation of CO2 enhancement of 23.5 similar to 49.7 mu mol
mol(-1), 21.4 similar to 52.4 mu mol mol(-1), 28.1 similar to 55.4 mu
mol mol(-1), and 29.5 similar to 42.4 mu mol mol(-1) in spring, summer,
autumn, and winter, respectively. These enhancements were much larger
than previously reported values for other countries. The diurnal CO2
enhancements reported here showed strong similarity for all 3 years of
the study. Results from source footprint modeling indicated that our
tower observations adequately represent emissions from the broader YRD
area. Here, the east of Anhui and the west of Jiangsu province
contributed significantly more to the anthropogenic CO2 enhancement
compared to the other sectors of YRD. The average anthropogenic CO2
emission in 2014 was 0.162 (+/- 0.005) mg m(-2) s(-1) and was 7 +/- 3%
higher than 2010 for the YRD. Overall, our emission estimates were
significantly smaller (9.5%) than those estimated (0.179 mg m(-2)
s(-1)) from the EDGAR emission database.
BibTeX:
@article{hu18c,
  author = {Hu, Cheng and Liu, Shoudong and Wang, Yongwei and Zhang, Mi and Xiao, Wei and Wang, Wei and Xu, Jiaping},
  title = {Anthropogenic CO2 emissions from a megacity in the Yangtze River Delta of China},
  journal = {ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH},
  year = {2018},
  volume = {25},
  number = {23, SI},
  pages = {23157-23169},
  doi = {https://doi.org/10.1007/s11356-018-2325-3}
}
Hu, C., Griffis, T.J., Liu, S., Xiao, W., Hu, N., Huang, W., Yang, D. and Lee, X. Anthropogenic Methane Emission and Its Partitioning for the Yangtze River Delta Region of China {2019} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {124}({5}), pp. {1148-1170} 
article DOI URL 
Abstract: Urban areas are global methane (CH4) hotspots. Yet large uncertainties still remain for the CH4 budget of these domains. The Yangtze River Delta (YRD), China, is one of the world's most densely populated regions where a large number of cities are located. To estimate anthropogenic CH4 emissions in YRD, we conducted simultaneous atmospheric CH4 and CO2 mixing ratio measurements from June 2010 to April 2011. By combining these measurements with the Weather Research and Forecasting and Stochastic Time-Inverted Lagrangian Transport models and a priori Emission Database for Global Atmospheric Research emission inventories, we applied three top-down approaches to constrain anthropogenic CH4 emissions. These three approaches included multiplicative scaling factors, flux ratio, and scale factor Bayesian inversion. The posteriori CH4 flux density estimated from the three approaches showed high consistency and were 36.32 (9.17), 35.66 (2.92), and 36.03(14.25) nmolm(-2)s(-1), respectively, for the duration of the study period (November 2010 to April 2011). The total annual anthropogenic CH4 emission was 6.52(1.59) Tg for the YRD region based on the average of these three approaches. Our emission estimates were 30.2(+/- 17.6)%, 31.5 (+/- 5.6)%, and 30.8 (+/- 27.4)% lower than the a priori Emission Database for Global Atmospheric Research v432 emission inventory estimate. The scale factor Bayesian inversion results indicate that the overestimate was mainly caused by two source categories including fuel exploitation and agricultural soil emissions (rice cultivation). The posteriori flux densities for agricultural soil and fuel exploitation were 10.68 and 6.34nmolm(-2)s(-1), respectively, and were 47.8% and 29.2% lower than the a priori inventory. Agricultural soil was the largest source contribution and accounted for 29.6% of the YRD CH4 budget during the study period.
BibTeX:
@article{hu19a,
  author = {Hu, Cheng and Griffis, Timothy J. and Liu, Shoudong and Xiao, Wei and Hu, Ning and Huang, Wenjing and Yang, Dong and Lee, Xuhui},
  title = {Anthropogenic Methane Emission and Its Partitioning for the Yangtze River Delta Region of China},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2019},
  volume = {124},
  number = {5},
  pages = {1148--1170},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JG004850},
  doi = {https://doi.org/10.1029/2018JG004850}
}
Hu, L., Andrews, A.E., Thoning, K.W., Sweeney, C., Miller, J.B., Michalak, A.M., Dlugokencky, E., Tans, P.P., Shiga, Y.P., Mountain, M., Nehrkorn, T., Montzka, S.A., McKain, K., Kofler, J., Trudeau, M., Michel, S.E., Biraud, S.C., Fischer, M.L., Worthy, D.E.J., Vaughn, B.H., White, J.W.C., Yadav, V., Basu, S. and van der Velde, I.R. Enhanced North American carbon uptake associated with El Nino {2019} SCIENCE ADVANCES
Vol. {5}({6}) 
article DOI URL 
Abstract: Long-term atmospheric CO2 mole fraction and delta(CO2)-C-13 observations over North America document persistent responses to the El Nino-Southern Oscillation. We estimate these responses corresponded to 0.61 (0.45 to 0.79) PgC year(-1) more North American carbon uptake during El Nino than during La Nina between 2007 and 2015, partially offsetting increases of net tropical biosphere-to-atmosphere carbon flux around El Nino. Anomalies in derived North American net ecosystem exchange (NEE) display strong but opposite correlations with surface air temperature between seasons, while their correlation with water availability was more constant throughout the year, such that water availability is the dominant control on annual NEE variability over North America. These results suggest that increased water availability and favorable temperature conditions (warmer spring and cooler summer) caused enhanced carbon uptake over North America near and during El Nino.
BibTeX:
@article{hu19b,
  author = {Hu, Lei and Andrews, Arlyn E. and Thoning, Kirk W. and Sweeney, Colm and Miller, John B. and Michalak, Anna M. and Dlugokencky, Ed and Tans, Pieter P. and Shiga, Yoichi P. and Mountain, Marikate and Nehrkorn, Thomas and Montzka, Stephen A. and McKain, Kathryn and Kofler, Jonathan and Trudeau, Michael and Michel, Sylvia E. and Biraud, Sebastien C. and Fischer, Marc L. and Worthy, Doug E. J. and Vaughn, Bruce H. and White, James W. C. and Yadav, Vineet and Basu, Sourish and van der Velde, Ivar R.},
  title = {Enhanced North American carbon uptake associated with El Nino},
  journal = {SCIENCE ADVANCES},
  publisher = {AMER ASSOC ADVANCEMENT SCIENCE},
  year = {2019},
  volume = {5},
  number = {6},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://advances.sciencemag.org/content/5/6/eaaw0076?intcmp=trendmd-adv},
  doi = {https://doi.org/10.1126/sciadv.aaw0076}
}
Hu, X.-M., Crowell, S., Wang, Q., Zhang, Y., Davis, K.J., Xue, M., Xiao, X., Moore, B., Wu, X., Choi, Y. and DiGangi, J.P. Dynamical Downscaling of CO2 in 2016 Over the Contiguous United States Using WRF-VPRM, a Weather-Biosphere-Online-Coupled Model {2020} JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
Vol. {12}({4}) 
article DOI URL 
Abstract: Ecosystem function (particularly CO2 fluxes and the subsequent atmospheric transport), synoptic-scale weather (e.g., midlatitude cyclones), and interactions between ecosystems and the atmosphere can be investigated using a weather-biosphere-online-coupled model. The Vegetation Photosynthesis and Respiration Model (VPRM) was coupled with the Weather Research and Forecasting (WRF) model in 2008 to simulate ``weather-aware'' biospheric CO2 fluxes and subsequent transport and dispersion. The ability of the coupled WRF-VPRM modeling system to simulate the CO2 structures within midlatitude cyclones, however, has not been evaluated due to the lack of data within these weather systems. In this study, VPRM parameters previously calibrated off-line using eddy covariance tower data over North America are implemented into WRF-VPRM. The updated WRF-VPRM is then used to simulate spatiotemporal variations of CO2 over the contiguous United States at a horizontal grid spacing of 12 km for 2016 using an optimized downscaling configuration. The downscaled fields are evaluated using remotely sensed data from the Orbiting Carbon Observatory-2, Total Carbon Column Observing Network, and in situ aircraft measurements from Atmospheric Carbon and Transport-America missions. Evaluations show that WRF-VPRM captures the monthly variation of column-averaged CO2 concentrations (XCO2) and episodic variations associated with frontal passages. The downscaling also successfully captures the horizontal CO2 gradients across fronts and vertical CO2 contrast between the boundary layer and the free troposphere. WRF-VPRM modeling results indicate that from May to September, biogenic fluxes dominate variability in XCO2 over most of the contiguous United States, except over a few metropolitan areas such as Los Angeles.
BibTeX:
@article{hu20a,
  author = {Hu, Xiao-Ming and Crowell, Sean and Wang, Qingyu and Zhang, Yao and Davis, Kenneth J. and Xue, Ming and Xiao, Xiangming and Moore, Berrien and Wu, Xiaocui and Choi, Yonghoon and DiGangi, Joshua P.},
  title = {Dynamical Downscaling of CO2 in 2016 Over the Contiguous United States Using WRF-VPRM, a Weather-Biosphere-Online-Coupled Model},
  journal = {JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {12},
  number = {4},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019MS001875},
  doi = {https://doi.org/10.1029/2019MS001875}
}
Hu, X.-M., Hu, J., Gao, L., Cai, C., Jiang, Y., Xue, M., Zhao, T. and Crowell, S.M.R. Multisensor and Multimodel Monitoring and Investigation of a Wintertime Air Pollution Event Ahead of a Cold Front Over Eastern China 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(10) 
article DOI  
Abstract: Given the limitations in pollutant measurements (e.g., coverage,
observation errors) and air quality model uncertainties (e.g., with
parameterizations and emissions), a multisensor and multimodel approach
offers additional benefits compared to a single-instrument and
deterministic approach for monitoring, investigating, and predicting air
pollution events. In this study, we use multisensors (including the
spaceborne MODIS, OCO-2, AIRS, and OMPS instruments as well as surface
instruments) and multimodels (including WRF-Chem and WRF-CO2) to
investigate a severe air pollution event on December 9, 2016 over
eastern China. During this episode, a strong cold front moved southward.
At the leading edge of the front, WRF-CO2 simulates an enhanced XCO2
belt while WRF-Chem simulates a belt of high PM2.5 concentration. The
XCO2 and PM2.5 belts are generally colocated, due to coemission of CO2
and pollutants (or their precursors). Satellite observations including
MODIS AOD, OCO-2 XCO2, OMPS NO2, AIRS CO, and surface data confirm the
simulated pollution and XCO2 belts. Later on, the front became distorted
due to terrain blocking and mountain channel flows. Both observations
and simulations show that the channel winds between Mountains Dabie and
Huang transport the haze plume into Jiangxi province, enhancing
pollution in the region. It is concluded that the multisensor (including
space-based and ground-based instruments) and multimodel (e.g., WRF-CO2,
WRF-Chem) approach can be used to collectively monitor and investigate
air pollution events, given that emissions of the involved species have
generally similar spatial distributions.
BibTeX:
@article{hu21a,
  author = {Hu, Xiao-Ming and Hu, Jun and Gao, Lan and Cai, Changjie and Jiang, Yujun and Xue, Ming and Zhao, Tianliang and Crowell, Sean M. R.},
  title = {Multisensor and Multimodel Monitoring and Investigation of a Wintertime Air Pollution Event Ahead of a Cold Front Over Eastern China},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {10},
  doi = {https://doi.org/10.1029/2020JD033538}
}
Hu, X.-M., Gourdji, S.M., Davis, K.J., Wang, Q., Zhang, Y., Xue, M., Feng, S., Moore, B. and Crowell, S.M.R. Implementation of Improved Parameterization of Terrestrial Flux in WRF-VPRM Improves the Simulation of Nighttime CO2 Peaks and a Daytime CO2 Band Ahead of a Cold Front 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(10) 
article DOI  
Abstract: Enhanced CO2 mole fraction bands were often observed immediately ahead
of cold front during the Atmospheric Carbon and Transport (ACT)-America
mission and their formation mechanism is undetermined. Improved
understanding and correct simulation of these CO2 bands are needed for
unbiased inverse CO2 flux estimation. Such CO2 bands are hypothesized to
be related to nighttime CO2 respiration and investigated in this study
using WRF-VPRM, a weather-biosphere-online-coupled model, in which the
biogenic fluxes are handled by the Vegetation Photosynthesis and
Respiration Model (VPRM). While the default VPRM satisfactorily
parameterizes gross ecosystem exchange, its treatment of terrestrial
respiration as a linear function of temperature was inadequate as
respiration is a nonlinear function of temperature and also depends on
the amount of biomass and soil wetness. An improved ecosystem
respiration parameterization including enhanced vegetation index, a
water stress factor, and a quadratic temperature dependence is
incorporated into WRF-VPRM and evaluated in a year-long simulation
before applied to the investigation of the frontal CO2 band on August 4,
2016. The evaluation shows that the modified WRF-VPRM increases
ecosystem respiration during the growing season, and improves model
skill in reproducing nighttime near-surface CO2 peaks. A nested-domain
WRF-VPRM simulation is able to capture the main characteristics of the
August 4 CO2 band and informs its formation mechanism. Nighttime
terrestrial respiration leads to accumulation of near-surface CO2 in the
region. As the cold front carrying low-CO2 air moves southeastward, and
strong photosynthesis depletes CO2 further southeast of the front, a CO2
band develops immediately ahead of the front.
BibTeX:
@article{hu21b,
  author = {Hu, Xiao-Ming and Gourdji, Sharon M. and Davis, Kenneth J. and Wang, Qingyu and Zhang, Yao and Xue, Ming and Feng, Sha and Moore, Berrien and Crowell, Sean M. R.},
  title = {Implementation of Improved Parameterization of Terrestrial Flux in WRF-VPRM Improves the Simulation of Nighttime CO2 Peaks and a Daytime CO2 Band Ahead of a Cold Front},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {10},
  doi = {https://doi.org/10.1029/2020JD034362}
}
Hu, C., Xu, J., Liu, C., Chen, Y., Yang, D., Huang, W., Deng, L., Liu, S., Griffis, T.J. and Lee, X. Anthropogenic and natural controls on atmospheric delta C-13-CO2 variations in the Yangtze River delta: insights from a carbon isotope modeling framework 2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(13), pp. 10015-10037 
article DOI  
Abstract: The atmospheric carbon dioxide (CO2) mixing ratio and its carbon isotope
(delta C-13-CO2) composition contain important CO2 sink and source
information spanning from ecosystem to global scales. The observation
and simulation for both CO2 and delta C-13-CO2 can be used to constrain
regional emissions and better understand the anthropogenic and natural
mechanisms that control delta C-13-CO2 variations. Such work remains
rare for urban environments, especially megacities. Here, we used
near-continuous CO2 and delta C-13-CO2 measurements, from September 2013
to August 2015, and inverse modeling to constrain the CO2 budget and
investigate the main factors that dominated delta C-13-CO2 variations
for the Yangtze River delta (YRD) region, one of the largest
anthropogenic CO2 hotspots and densely populated regions in China. We
used the WRF-STILT model framework with category-specified EDGAR v4.3.2
CO2 inventories to simulate hourly CO2 mixing ratios and delta C-13-CO2,
evaluated these simulations with observations, and constrained the total
anthropogenic CO2 emission. We show that (1) top-down and bottom-up
estimates of anthropogenic CO2 emissions agreed well (bias < 6 %) on an
annual basis, (2) the WRF-STILT model can generally reproduce the
observed diel and seasonal atmospheric delta C-13-CO2 variations, and
(3) anthropogenic CO2 emissions played a much larger role than
ecosystems in controlling the delta C-13-CO2 seasonality. When excluding
ecosystem respiration and photosynthetic discrimination in the YRD area,
delta C-13-CO2 seasonality increased from 1.53% to 1.66 %. (4)
Atmospheric transport processes in summer amplified the cement CO2
enhancement proportions in the YRD area, which dominated monthly
delta(s) (the mixture of delta C-13-CO2 from all regional end-members)
variations. These findings show that the combination of long-term
atmospheric carbon isotope observations and inverse modeling can provide
a powerful constraint on the carbon cycle of these complex megacities.
BibTeX:
@article{hu21c,
  author = {Hu, Cheng and Xu, Jiaping and Liu, Cheng and Chen, Yan and Yang, Dong and Huang, Wenjing and Deng, Lichen and Liu, Shoudong and Griffis, Timothy J. and Lee, Xuhui},
  title = {Anthropogenic and natural controls on atmospheric delta C-13-CO2 variations in the Yangtze River delta: insights from a carbon isotope modeling framework},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2021},
  volume = {21},
  number = {13},
  pages = {10015-10037},
  doi = {https://doi.org/10.5194/acp-21-10015-2021}
}
Hu, C., Liu, C., Hu, N., Hong, J. and Ai, X. Government environmental control measures on CO2 emission during the 2014 Youth Olympic Games in Nanjing: Perspectives from a top-down approach 2022 JOURNAL OF ENVIRONMENTAL SCIENCES
Vol. 113, pp. 165-178 
article DOI  
Abstract: Strict air pollution control measures were conducted during the Youth
Olympic Games (YOG) period at Nanjing city and surrounding areas in
August 2014. This event provides a unique chance to evaluate the effect
of government control measures on regional atmospheric pollution and
greenhouse gas emissions. Many previous studies have observed
significant reductions of atmospheric pollution species and improvement
in air quality, while no study has quantified its synergism on
anthropogenic CO2 emissions, which can be co-reduced with air
pollutants. To better understand to what extent these pollution control
measures have reduced anthropogenic CO2 emissions, we conducted
atmospheric CO2 measurements at the suburban site in Nanjing city from
1st July to 30th September 2014 and 1st August to 31st August 2015,
obvious decrease in atmospheric CO2 was observed between YOG and the
rest period. By coupling the a priori emission inventory with
atmospheric transport model, we applied the scale factor Bayesian
inversion approach to derive the posteriori CO2 emissions in YOG period
and regular period. Results indicate CO2 emissions from power industry
decreased by 45%, and other categories also decreased by 16% for
manufacturing combusting, and 37% for non-metallic mineral production.
Monthly total anthropogenic CO2 emissions were 9.8 (+/- 3.6) x 10(9)
kg/month CO2 for regular period and decreased to 6.2 (+/- 1.9) x 10(9)
kg/month during the YOG period in Nanjing city, with a 36.7% reduction.
When scaling up to whole Jiangsu Province, anthropogenic CO2 emissions
were 7.1 (+/- 2.4) x 10(10) kg/month CO2 for regular period and
decreased to 4.4 (+/- 1.2) x 10(10) kg/month CO2 during the YOG period,
yielding a 38.0% reduction. (C) 2021 The Research Center for
Eco-Environmental Sciences, Chinese Academy of Sciences. Published by
Elsevier B.V.
BibTeX:
@article{hu22a,
  author = {Hu, Cheng and Liu, Cheng and Hu, Ning and Hong, Jun and Ai, Xinyue},
  title = {Government environmental control measures on CO2 emission during the 2014 Youth Olympic Games in Nanjing: Perspectives from a top-down approach},
  journal = {JOURNAL OF ENVIRONMENTAL SCIENCES},
  year = {2022},
  volume = {113},
  pages = {165-178},
  doi = {https://doi.org/10.1016/j.jes.2021.04.016}
}
Huang, W.-J., Kao, K.-J., Lin, Y.-S., Chen, C.-T.A. and Liu, J.T. Daily to weekly impacts of mixing and biological activity on carbonate dynamics in a large river-dominated shelf {2020} ESTUARINE COASTAL AND SHELF SCIENCE
Vol. {245} 
article DOI URL 
Abstract: Large eutrophic river plumes can lead to hypoxic near-bottom water during summer. However, how the carbonate system in this stratified water column varies at a daily-to-weekly scale is still unclear. At the end of the first severe El Nino Southern Oscillation event in the 21st century during 2015/2016, high temperature, high salinity water was observed in the middle of the Pearl River plume on the northern South China Sea shelf over 6 d (July 24-29, 2016). We deployed a sensor pack (conductivity, temperature, pressure, and dissolved oxygen [DO]) along the water column each hour and took discrete samples, including total alkalinity and dissolved inorganic carbon every 3 h, to calculate pH. We observe a pH reduction rate of 0.011 pH unit. d(-1) and an oxygen consumption rate of 4.4 mu mol kg(-1).d(-1) in the near-bottom water. The temporal variations in calculated net community production rate and excess DO (measured DO - saturated DO) implies the switch in the dominance of net respiration to net photosynthesis in the near-surface water during this mixing event. We suggest that both net photosynthesis and net respiration were in the water with oversaturated DO on a short-term scale. The pH reduction and oxygen consumption rates in this study could help to estimate the level of coastal acidification and hypoxia better.
BibTeX:
@article{huang20a,
  author = {Huang, Wei-Jen and Kao, Kai-Jung and Lin, Yu-Shih and Chen, Chen-Tung Arthur and Liu, James T.},
  title = {Daily to weekly impacts of mixing and biological activity on carbonate dynamics in a large river-dominated shelf},
  journal = {ESTUARINE COASTAL AND SHELF SCIENCE},
  publisher = {ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD},
  year = {2020},
  volume = {245},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://www.sciencedirect.com/science/article/pii/S0272771419309084},
  doi = {https://doi.org/10.1016/j.ecss.2020.106914}
}
Humpage, N., Boesch, H., Palmer, P.I., Vick, A., Parr-Burman, P., Wells, M., Pearson, D., Strachan, J. and Bezawada, N. GreenHouse gas Observations of the Stratosphere and Troposphere (GHOST): an airborne shortwave-infrared spectrometer for remote sensing of greenhouse gases {2018} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {11}({9}), pp. {5199-5222} 
article DOI  
Abstract: GHOST is a novel, compact shortwave-infrared grating spectrometer,
designed for remote sensing of tropospheric columns of greenhouse gases
(GHGs) from an airborne platform. It observes solar radiation at medium
to high spectral resolution (better than 0.3 nm), which has been
reflected by the Earth's surface using similar methods to those used by
polar-orbiting satellites such as the JAXA GOSAT mission, NASA's OCO-2,
and the Copernicus Sentinel-5 Precursor. By using an original design
comprising optical fibre inputs along with a single diffraction grating
and detector array, GHOST is able to observe CO2 absorption bands
centred around 1.61 and 2.06 mu m (the same wavelength regions used by
OCO-2 and GOSAT) whilst simultaneously measuring CH4 absorption at 1.65
mu m (also observed by GOSAT) and CH4 and CO at 2.30 mu m (observed by
Sentinel-5P). With emissions expected to become more concentrated
towards city sources as the global population residing in urban areas
increases, there emerges a clear requirement to bridge the spatial scale
gap between small-scale urban emission sources and global-scale GHG
variations. In addition to the benefits achieved in spatial coverage
through being able to remotely sense GHG tropospheric columns from an
aircraft, the overlapping spectral ranges and comparable spectral
resolutions mean that GHOST has unique potential for providing
validation opportunities for these platforms, particularly over the
ocean, where ground-based validation measurements are not available. In
this paper we provide an overview of the GHOST instrument, calibration,
and data processing, demonstrating the instrument's performance and
suitability for GHG remote sensing. We also report on the first GHG
observations made by GHOST during its maiden science flights on board
the NASA Global Hawk unmanned aerial vehicle, which took place over the
eastern Pacific Ocean in March 2015 as part of the CAST/ATTREX joint
Global Hawk flight campaign.
BibTeX:
@article{humpage18a,
  author = {Humpage, Neil and Boesch, Hartmut and Palmer, Paul I. and Vick, Andy and Parr-Burman, Phil and Wells, Martyn and Pearson, David and Strachan, Jonathan and Bezawada, Naidu},
  title = {GreenHouse gas Observations of the Stratosphere and Troposphere (GHOST): an airborne shortwave-infrared spectrometer for remote sensing of greenhouse gases},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2018},
  volume = {11},
  number = {9},
  pages = {5199-5222},
  doi = {https://doi.org/10.5194/amt-11-5199-2018}
}
Hungershoefer, K., Breon, F.M., Peylin, P., Chevallier, F., Rayner, P., Klonecki, A., Houweling, S. and Marshall, J. Evaluation of various observing systems for the global monitoring of CO2 surface fluxes {2010} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {10}({21}), pp. 10503-10520 
article DOI  
Abstract: In the context of rising greenhouse gas concentrations, and the
potential feedbacks between climate and the carbon cycle, there is an
urgent need to monitor the exchanges of carbon between the atmosphere
and both the ocean and the land surfaces. In the so-called top-down
approach, the surface fluxes of CO2 are inverted from the observed
spatial and temporal concentration gradients. The concentrations of CO2
are measured in-situ at a number of surface stations unevenly
distributed over the Earth while several satellite missions may be used
to provide a dense and better-distributed set of observations to
complement this network. In this paper, we compare the ability of
different CO2 concentration observing systems to constrain surface
fluxes. The various systems are based on realistic scenarios of sampling
and precision for satellite and in-situ measurements.
It is shown that satellite measurements based on the differential
absorption technique (such as those of SCIAMACHY, GOSAT or OCO) provide
more information than the thermal infrared observations (such as those
of AIRS or IASI). The OCO observations will provide significantly better
information than those of GOSAT. A CO2 monitoring mission based on an
active (lidar) technique could potentially provide an even better
constraint. This constraint can also be realized with the very dense
surface network that could be built with the same funding as that of the
active satellite mission. Despite the large uncertainty reductions on
the surface fluxes that may be expected from these various observing
systems, these reductions are still insufficient to reach the highly
demanding requirements for the monitoring of anthropogenic emissions of
CO2 or the oceanic fluxes at a spatial scale smaller than that of
oceanic basins. The scientific objective of these observing system
should therefore focus on the fluxes linked to vegetation and land
ecosystem dynamics.
BibTeX:
@article{hungershoefer10a,
  author = {Hungershoefer, K. and Breon, F. -M. and Peylin, P. and Chevallier, F. and Rayner, P. and Klonecki, A. and Houweling, S. and Marshall, J.},
  title = {Evaluation of various observing systems for the global monitoring of CO2 surface fluxes},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2010},
  volume = {10},
  number = {21},
  pages = {10503--10520},
  doi = {https://doi.org/10.5194/acp-10-10503-2010}
}
Huntzinger, D.N., Gourdji, S.M., Mueller, K.L. and Michalak, A.M. The utility of continuous atmospheric measurements for identifying biospheric CO2 flux variability {2011} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {116} 
article DOI  
Abstract: Motivated by the need to improve the modeling of land-atmosphere carbon
exchange, this study examines the extent to which continuous atmospheric
carbon dioxide (CO2) observations can be used to evaluate flux
variability at regional scales. The net ecosystem exchange estimates of
four terrestrial biospheric models (TBMs) are used to represent
plausible scenarios of surface flux distributions, which are compared in
terms of their resulting atmospheric signals. The analysis focuses on
North America using the nine towers of the continuous observation
network that were operational in 2004. Four test cases are designed to
isolate the influence on the atmospheric observations of (1) overall
flux differences, (2) magnitude differences in flux across large
regions, (3) differences in the flux patterns within ecoregions, and (4)
flux variability in the near and far field of observation locations. The
CO2 signals generated from the different representations of surface flux
distribution are compared using a Chi-square test of variance.
Differences found to be significant are driven primarily by differences
in flux magnitude over large scales, and the fine-scale (primarily
temporal) variability of fluxes within the near field of observation
locations. Differences in the spatial distribution of fluxes within
individual ecoregions, on the other hand, do not translate into
significant differences in the observed signals at the towers. Thus,
given the types of variation in flux represented by the four TBMs, the
atmospheric data may be most informative in the evaluation of aggregated
fluxes over large spatial scales (e. g., ecoregions), as well as in the
improvement of how the diurnal cycle of fluxes is represented in TBMs,
particularly in areas close to tower locations.
BibTeX:
@article{huntzinger11a,
  author = {Huntzinger, Deborah N. and Gourdji, Sharon M. and Mueller, Kimberly L. and Michalak, Anna M.},
  title = {The utility of continuous atmospheric measurements for identifying biospheric CO2 flux variability},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2010JD015048}
}
Huntzinger, D.N., Gourdji, S.M., Mueller, K.L. and Michalak, A.M. A systematic approach for comparing modeled biospheric carbon fluxes across regional scales {2011} BIOGEOSCIENCES
Vol. {8}({6}), pp. 1579-1593 
article DOI  
Abstract: Given the large differences between biospheric model estimates of
regional carbon exchange, there is a need to understand and reconcile
the predicted spatial variability of fluxes across models. This paper
presents a set of quantitative tools that can be applied to
systematically compare flux estimates despite the inherent differences
in model formulation. The presented methods include variogram analysis,
variable selection, and geostatistical regression. These methods are
evaluated in terms of their ability to assess and identify differences
in spatial variability in flux estimates across North America among a
small subset of models, as well as differences in the environmental
drivers that best explain the spatial variability of predicted fluxes.
The examined models are the Simple Biosphere (SiB 3.0), Carnegie Ames
Stanford Approach (CASA), and CASA coupled with the Global Fire
Emissions Database (CASA GFEDv2), and the analyses are performed on
model-predicted net ecosystem exchange, gross primary production, and
ecosystem respiration. Variogram analysis reveals consistent seasonal
differences in spatial variability among modeled fluxes at a 1 degrees x
1 degrees spatial resolution. However, significant differences are
observed in the overall magnitude of the carbon flux spatial variability
across models, in both net ecosystem exchange and component fluxes.
Results of the variable selection and geostatistical regression analyses
suggest fundamental differences between the models in terms of the
factors that explain the spatial variability of predicted flux. For
example, carbon flux is more strongly correlated with percent land cover
in CASA GFEDv2 than in SiB or CASA. Some of the differences in spatial
patterns of estimated flux can be linked back to differences in model
formulation, and would have been difficult to identify simply by
comparing net fluxes between models. Overall, the systematic approach
presented here provides a set of tools for comparing predicted
grid-scale fluxes across models, a task that has historically been
difficult unless standardized forcing data were prescribed, or a
detailed sensitivity analysis performed.
BibTeX:
@article{huntzinger11b,
  author = {Huntzinger, D. N. and Gourdji, S. M. and Mueller, K. L. and Michalak, A. M.},
  title = {A systematic approach for comparing modeled biospheric carbon fluxes across regional scales},
  journal = {BIOGEOSCIENCES},
  year = {2011},
  volume = {8},
  number = {6},
  pages = {1579--1593},
  doi = {https://doi.org/10.5194/bg-8-1579-2011}
}
Hutjes, R.W.A., Vellinga, U.S., Gioli, B. and Miglietta, F. Dis-aggregation of airborne flux measurements using footprint analysis {2010} AGRICULTURAL AND FOREST METEOROLOGY
Vol. {150}({7-8}), pp. 966-983 
article DOI  
Abstract: Aircraft measurements of turbulent fluxes are generally being made with
the objective to obtain an estimate of regional exchanges between land
surface and atmosphere, to investigate the spatial variability of these
fluxes, but also to learn something about the fluxes from some or all of
the land cover types that make up the landscape. In this study we
develop a method addressing this last objective, an approach to
disentangle blended fluxes from a landscape into the component fluxes
emanating from the various land cover classes making up that landscape.
The method relies on using a footprint model to determine which part of
the landscape the airborne flux observation refers to, using a high
resolution land cover map to determine the fractional covers of the
various land cover classes within that footprint, and finally using
multiple linear regression on many such flux/fractional cover data
records to estimate the component fluxes. The method is developed in the
context of three case studies of increasing complexity and the analysis
covers three scalar fluxes: sensible and latent heat fluxes and carbon
dioxide flux, as well as the momentum flux.
A basic assumption under the dis-aggregation method is that the
composite flux, i.e. the landscape flux, is a linear average of the
component fluxes, i.e. the fluxes from the various land elements. We
test and justify this assumption by comparing linear averages of
component fluxes in simple `binary landscapes', weighted by their
relative area, with directly aircraft observed fluxes.
In all case studies dis-aggregation of mixed values for fluxes from
heterogeneous areas into component land cover class specific fluxes is
feasible using robust least squares regression, both in simple binary
`landscapes' and in more complex cases. Both the differences between
land cover classes and the differences between synoptic conditions can
be resolved, for those land cover classes that make up sufficiently
large fractions of the landscape. The regression F-statistic and the
closely associated p-values are good indicators for this latter
prerequisite and for other sources of uncertainty in the dis-aggregated
flux estimates that render it meaningful or not. An analysis of the
effect of various sources of errors in input data, footprint estimates
and of skewed land cover class distributions is presented. A validation
of flux estimates obtained through the dis-aggregation method against
independent ground data proved satisfactorily. Recommendations for the
use of the method are given as are suggestions for further development.
(C) 2010 Elsevier B.V. All rights reserved.
BibTeX:
@article{hutjes10a,
  author = {Hutjes, R. W. A. and Vellinga, U. S. and Gioli, B. and Miglietta, F.},
  title = {Dis-aggregation of airborne flux measurements using footprint analysis},
  journal = {AGRICULTURAL AND FOREST METEOROLOGY},
  year = {2010},
  volume = {150},
  number = {7-8},
  pages = {966--983},
  doi = {https://doi.org/10.1016/j.agrformet.2010.03.004}
}
Hutjes, R., Bosveld, F., Dolman, A., Houweling, S., Peters, W., Meesters, A., Moene, A., Neubert, R., KleinBaltink, H., Unal, C. and others Titel rapport AN ASSESSMENT OF THE POTENTIAL FOR ATMOSPHERIC EMISSION VERIFICATION IN THE NETHERLANDS 2012 School: Wageningen University and Research Centre  techreport URL 
BibTeX:
@techreport{hutjes12a,
  author = {Hutjes, RWA and Bosveld, FC and Dolman, AJ and Houweling, S and Peters, W and Meesters, AGCA and Moene, A and Neubert, REM and KleinBaltink, H and Unal, CMH and others},
  title = {Titel rapport AN ASSESSMENT OF THE POTENTIAL FOR ATMOSPHERIC EMISSION VERIFICATION IN THE NETHERLANDS},
  school = {Wageningen University and Research Centre},
  year = {2012},
  url = {https://www.researchgate.net/profile/Ronald_Hutjes/publication/283419017_An_assessment_of_the_potential_for_atmospheric_emission_verification_in_The_Netherlands/links/5640741a08ae34e98c4e8221/An-assessment-of-the-potential-for-atmospheric-emission-verification-in-The-Netherlands.pdf}
}
Isaac, L.I.D., Lauvaux, T., Davis, K.J., Miles, N.L., Richardson, S.J., Jacobson, A.R. and Andrews, A.E. Model-data comparison of MCI field campaign atmospheric CO2 mole fractions {2014} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {119}({17}) 
article DOI  
Abstract: Atmospheric transport model errors are a major contributor to
uncertainty in CO2 inverse flux estimates. Our study compares CO2 mole
fraction observations from the North American Carbon Program
Mid-Continental Intensive (MCI) field campaign and modeled mole
fractions from two atmospheric transport models: the global Transport
Model 5 from NOAA's CarbonTracker system and the mesoscale Weather
Research and Forecasting model. Both models are coupled to identical CO2
fluxes and lateral boundary conditions from CarbonTracker (CT2009
release). Statistical analyses were performed for two periods of 2007
using observed daily daytime average mole fractions of CO2 to test the
ability of these models to reproduce the observations and to infer
possible causes of the discrepancies. TM5-CT2009 overestimates midsummer
planetary boundary layer CO2 for sites in the U. S. corn belt by 10 ppm.
Weather Research and Forecasting (WRF)-CT2009 estimates diverge from the
observations with similar magnitudes, but the signs of the differences
vary from site to site. The modeled mole fractions are highly correlated
with the observed seasonal cycle (r >= 0.7) but less correlated in the
growing season, where weather-related changes in CO2 dominate the
observed variability. Spatial correlations in residuals from TM5-CT2009
are higher than WRF-CT2009 perhaps due to TM5's coarse horizontal
resolution and shallow vertical mixing. Vertical mixing appears to have
influenced CO2 residuals from both models. TM5-CT2009 has relatively
weak vertical mixing near the surface limiting the connection between
local CO2 surface fluxes and boundary layer. WRF-CT2009 has stronger
vertical mixing that may increase the connections between local surface
fluxes and the boundary layer.
BibTeX:
@article{isaac14a,
  author = {Isaac, Liza I. Diaz and Lauvaux, Thomas and Davis, Kenneth J. and Miles, Natasha L. and Richardson, Scott J. and Jacobson, Andrew R. and Andrews, Arlyn E.},
  title = {Model-data comparison of MCI field campaign atmospheric CO2 mole fractions},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2014},
  volume = {119},
  number = {17},
  doi = {https://doi.org/10.1002/2014JD021593}
}
Ishidoya, S., Aoki, S., Goto, D., Nakazawa, T., Taguchi, S. and Patra, P.K. Time and space variations of the O-2/N-2 ratio in the troposphere over Japan and estimation of the global CO2 budget for the period 2000-2010 {2012} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {64} 
article DOI  
Abstract: Systematic measurements of the atmospheric O-2/N-2 ratio have been made
using aircraft and ground-based stations in Japan since 1999. The
observed seasonal cycles of the O-2/N-2 ratio and atmospheric potential
oxygen (APO) vary almost in opposite phase to that of the CO2
concentration at all altitudes, and their amplitudes and phases are
generally reduced and delayed, respectively, with increasing altitude.
Simulations of APO using two atmospheric transport models reproduce
general features of the observed seasonal cycle, but both models fail to
reproduce the phase at an altitude ranging from 8 km to the tropopause.
By analysing the observed secular trends of APO and CO2 concentration,
and assuming a global net oceanic O-2 outgassing of 0.2 +/- 0.5 GtC
yr(-1), we estimate global average terrestrial biospheric and oceanic
CO2 uptake for the period 2000-2010 to be 1.0 +/- 0.8 and 2.5 +/- 0.7
GtC yr(-1), respectively.
BibTeX:
@article{ishidoya12a,
  author = {Ishidoya, Shigeyuki and Aoki, Shuji and Goto, Daisuke and Nakazawa, Takakiyo and Taguchi, Shoichi and Patra, Prabir K.},
  title = {Time and space variations of the O-2/N-2 ratio in the troposphere over Japan and estimation of the global CO2 budget for the period 2000-2010},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2012},
  volume = {64},
  doi = {https://doi.org/10.3402/tellusb.v64i0.18964}
}
Ishii, M., Feely, R.A., Rodgers, K.B., Park, G.H., Wanninkhof, R., Sasano, D., Sugimoto, H., Cosca, C.E., Nakaoka, S., Telszewski, M., Nojiri, Y., Fletcher, S.E.M., Niwa, Y., Patra, P.K., Valsala, V., Nakano, H., Lima, I., Doney, S.C., Buitenhuis, E.T., Aumont, O., Dunne, J.P., Lenton, A. and Takahashi, T. Air-sea CO2 flux in the Pacific Ocean for the period 1990-2009 {2014} BIOGEOSCIENCES
Vol. {11}({3}), pp. 709-734 
article DOI  
Abstract: Air-sea CO2 fluxes over the Pacific Ocean are known to be characterized
by coherent large-scale structures that reflect not only ocean
subduction and upwelling patterns, but also the combined effects of
wind-driven gas exchange and biology. On the largest scales, a large net
CO2 influx into the extratropics is associated with a robust seasonal
cycle, and a large net CO2 efflux from the tropics is associated with
substantial interannual variability. In this work, we have synthesized
estimates of the net air-sea CO2 flux from a variety of products,
drawing upon a variety of approaches in three sub-basins of the Pacific
Ocean, i. e., the North Pacific extratropics (18-66 degrees N), the
tropical Pacific (18 degrees S-18 degrees N), and the South Pacific
extratropics (44.5-18 degrees S). These approaches include those based
on the measurements of CO2 partial pressure in surface seawater
(pCO(2)sw), inversions of ocean-interior CO2 data, forward ocean
biogeochemistry models embedded in the ocean general circulation models
(OBGCMs), a model with assimilation of pCO(2)sw data, and inversions of
atmospheric CO2 measurements. Long-term means, interannual variations
and mean seasonal variations of the regionally integrated fluxes were
compared in each of the sub-basins over the last two decades, spanning
the period from 1990 through 2009. A simple average of the long-term
mean fluxes obtained with surface water pCO(2) diagnostics and those
obtained with ocean-interior CO2 inversions are -0.47 +/- 0.13 Pg
Cyr(-1) in the North Pacific extratropics, +/- 0.44 +/- 0.14 Pg Cyr(-1)
in the tropical Pacific, and -0.37 +/- 0.08 Pg C yr(-1) in the South
Pacific extratropics, where positive fluxes are into the atmosphere.
This suggests that approximately half of the CO2 taken up over the North
and South Pacific extratropics is released back to the atmosphere from
the tropical Pacific. These estimates of the regional fluxes are also
supported by the estimates from OBGCMs after adding the riverine CO2
flux, i.e., -0.49 +/- 0.02 Pg Cyr(-1) in the North Pacific extratropics,
+0.41 +/- 0.05 Pg Cyr(-1) in the tropical Pacific, and -0.39 +/- 0.11 Pg
Cyr(-1) in the South Pacific extratropics. The estimates from the
atmospheric CO2 inversions show large variations amongst different
inversion systems, but their median fluxes are consistent with the
estimates from climatological pCO(2)sw data and pCO(2)sw diagnostics. In
the South Pacific extratropics, where CO2 variations in the surface and
ocean interior are severely undersampled, the difference in the air-sea
CO2 flux estimates between the diagnostic models and ocean-interior CO2
inversions is larger (0.18 Pg Cyr(-1)). The range of estimates from
forward OBGCMs is also large (-0.19 to -0.72 Pg Cyr(-1)). Regarding
interannual variability of air-sea CO2 fluxes, positive and negative
anomalies are evident in the tropical Pacific during the cold and warm
events of the El Nino-Southern Oscillation in the estimates from
pCO(2)sw diagnostic models and from OBGCMs. They are consistent in phase
with the Southern Oscillation Index, but the peak-to-peak amplitudes
tend to be higher in OBGCMs (0.40 +/- 0.09 Pg Cyr(-1)) than in the
diagnostic models (0.27 +/- 0.07 Pg Cyr(-1)).
BibTeX:
@article{ishii14a,
  author = {Ishii, M. and Feely, R. A. and Rodgers, K. B. and Park, G. -H. and Wanninkhof, R. and Sasano, D. and Sugimoto, H. and Cosca, C. E. and Nakaoka, S. and Telszewski, M. and Nojiri, Y. and Fletcher, S. E. Mikaloff and Niwa, Y. and Patra, P. K. and Valsala, V. and Nakano, H. and Lima, I. and Doney, S. C. and Buitenhuis, E. T. and Aumont, O. and Dunne, J. P. and Lenton, A. and Takahashi, T.},
  title = {Air-sea CO2 flux in the Pacific Ocean for the period 1990-2009},
  journal = {BIOGEOSCIENCES},
  year = {2014},
  volume = {11},
  number = {3},
  pages = {709--734},
  doi = {https://doi.org/10.5194/bg-11-709-2014}
}
Ito, A. Decadal Variability in the Terrestrial Carbon Budget Caused by the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation {2011} JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
Vol. {89}({5}), pp. 441-454 
article DOI  
Abstract: The terrestrial carbon dioxide (CO2) budget interacts with the Earth's
climate system on diurnal to centennial and longer time scales, making
it critical for climatic prediction and stabilization. Atmospheric
observations and global syntheses of CO2 data indicate that the
terrestrial biosphere is one the major sources of interannual
variability, but the underlying mechanisms operating on different
time-scales and the potential impacts of this on future projections
remain unclear. Here it is shown that the El Nino and Southern
Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic
Multidecadal Oscillation (AMO) regime affect temporal variability in the
terrestrial carbon budget with different time scales. The terrestrial
carbon budget, estimated using a process-based model (VISIT) for the
period 1910-2005, was correlated with the indices of PDO, AMO, and ENSO
with various smoothing periods and lag lengths. ENSO showed the highest
short-term correlation, corresponding to interannual terrestrial
variability, whereas PDO and AMO had higher correlations at the decadal
time scale. Such correlations with the meteorological regimes occurred
heterogeneously over the land surface. Tin; study suggests that
long-term monitoring is needed to elucidate the temporal variability,
and that decadal predictability of climate and terrestrial models should
be improved further.
BibTeX:
@article{ito11a,
  author = {Ito, Akihiko},
  title = {Decadal Variability in the Terrestrial Carbon Budget Caused by the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation},
  journal = {JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN},
  year = {2011},
  volume = {89},
  number = {5},
  pages = {441--454},
  doi = {https://doi.org/10.2151/jmsj.2011-503}
}
Ito, A. Disequilibrium of terrestrial ecosystem CO2 budget caused by disturbance-induced emissions and non-CO2 carbon export flows: a global model assessment {2019} EARTH SYSTEM DYNAMICS
Vol. {10}({4}), pp. {685-709} 
article DOI  
Abstract: The global carbon budget of terrestrial ecosystems is chiefly determined by major flows of carbon dioxide (CO2) such as photosynthesis and respiration, but various minor flows exert considerable influence in determining carbon stocks and their turnover. This study assessed the effects of eight minor carbon flows on the terrestrial carbon budget using a process-based model, the Vegetation Integrative SImulator for Trace gases (VISIT), which included non-CO2 carbon flows, such as methane and biogenic volatile organic compound (BVOC) emissions and subsurface carbon exports and disturbances such as biomass burning, land-use changes, and harvest activities. The range of model-associated uncertainty was evaluated through parameter-ensemble simulations and the results were compared with corresponding observational and modeling studies. In the historical period of 1901-2016, the VISIT simulation indicated that the minor flows substantially influenced terrestrial carbon stocks, flows, and budgets. The simulations estimated mean net ecosystem production in 2000-2009 as 3.21 +/- 1.1 Pg C yr(-1) without minor flows and 6.85 +/- 0.9 Pg C yr(-1) with minor flows. Including minor carbon flows yielded an estimated net biome production of 1.62 +/- 1.0 Pg C yr(-1) in the same period. Biomass burning, wood harvest, export of organic carbon by water erosion, and BVOC emissions had impacts on the global terrestrial carbon budget amounting to around 1 Pg C yr(-1) with specific interannual variabilities. After including the minor flows, ecosystem carbon storage was suppressed by about 440 Pg C, and its mean residence time was shortened by about 2.4 years. The minor flows occur heterogeneously over the land, such that BVOC emission, subsurface export, and wood harvest occur mainly in the tropics, and biomass burning occurs extensively in boreal forests. They also differ in their decadal trends, due to differences in their driving factors. Aggregating the simulation results by land-cover type, cropland fraction, and annual precipitation yielded more insight into the contributions of these minor flows to the terrestrial carbon budget. Considering their substantial and unique roles, these minor flows should be taken into account in the global carbon budget in an integrated manner.
BibTeX:
@article{ito19a,
  author = {Ito, Akihiko},
  title = {Disequilibrium of terrestrial ecosystem CO2 budget caused by disturbance-induced emissions and non-CO2 carbon export flows: a global model assessment},
  journal = {EARTH SYSTEM DYNAMICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {10},
  number = {4},
  pages = {685--709},
  doi = {https://doi.org/10.5194/esd-10-685-2019}
}
Ito, G., Romanou, A., Kiang, N.Y., Faluvegi, G., Aleinov, I., Ruedy, R., Russell, G., Lerner, P., Kelley, M. and Lo, K. Global Carbon Cycle and Climate Feedbacks in the NASA GISS ModelE2.1 {2020} JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
Vol. {12}({10}) 
article DOI URL 
Abstract: We present results from the NASA GISS ModelE2.1-G-CC Earth System Model with coupled climate-carbon cycle simulations that were submitted to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) Coupled Climate-Carbon Cycle MIP (C4MIP). Atmospheric CO2 concentration and carbon budgets for the land and ocean in the historical simulations were generally consistent with observations. Low simulated atmospheric CO2 concentrations during 1850-1950 were due to excess uptake from prescribed land cover change, which erroneously replaced arid shrublands with higher biomass crops, and assumed high 2004 LAI values in vegetated lands throughout the historical simulation. At the end of the historical period, slightly higher simulated CO2 than observed resulted from the land being an insufficient net carbon sink, despite the net effect of CO2 fertilization and warming-induced increases to leaf photosynthetic capacity. The global ocean carbon uptake agreed well with the observations with the largest discrepancies in the low latitudes. Future climate projection at 2091-2100 agreed with CMIP5 models in the northward shift, of temperate deciduous forest climate and expansion across Eurasia along 60 degrees N latitude, and dramatic regional biome shifts from drying and warming in continental Europe. Carbon feedback parameters were largely similar to the CMIP5 model ensemble. For our model, the variation of land feedback parameters within the uncertainty arises from the fertilization feedback being less sensitive due to lack of increased vegetation growth, and the comparably more negative ocean carbon-climate feedback is due to the large slowdown of the Atlantic overturning circulation.
BibTeX:
@article{ito20a,
  author = {Ito, Gen and Romanou, Anastasia and Kiang, Nancy Y. and Faluvegi, Gregory and Aleinov, Igor and Ruedy, Reto and Russell, Gary and Lerner, Paul and Kelley, Maxwell and Lo, Ken},
  title = {Global Carbon Cycle and Climate Feedbacks in the NASA GISS ModelE2.1},
  journal = {JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {12},
  number = {10},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019MS002030},
  doi = {https://doi.org/10.1029/2019MS002030}
}
Jacob, D.J., Turner, A.J., Maasakkers, J.D., Sheng, J., Sun, K., Liu, X., Chance, K., Aben, I., McKeever, J. and Frankenberg, C. Satellite observations of atmospheric methane and their value for quantifying methane emissions {2016} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {16}({22}), pp. 14371-14396 
article DOI  
Abstract: Methane is a greenhouse gas emitted by a range of natural and
anthropogenic sources. Atmospheric methane has been measured
continuously from space since 2003, and new instruments are planned for
launch in the near future that will greatly expand the capabilities of
space-based observations. We review the value of current, future, and
proposed satellite observations to better quantify and understand
methane emissions through inverse analyses, from the global scale down
to the scale of point sources and in combination with suborbital
(surface and aircraft) data. Current global observations from Greenhouse
Gases Observing Satellite (GOSAT) are of high quality but have sparse
spatial coverage. They can quantify methane emissions on a regional
scale (100-1000 km) through multiyear averaging. The Tropospheric
Monitoring Instrument (TROPOMI), to be launched in 2017, is expected to
quantify daily emissions on the regional scale and will also effectively
detect large point sources. A different observing strategy by GHGSat
(launched in June 2016) is to target limited viewing domains with very
fine pixel resolution in order to detect a wide range of methane point
sources. Geostationary observation of methane, still in the proposal
stage, will have the unique capability of mapping source regions with
high resolution, detecting transient ``super-emitter'' point sources
and resolving diurnal variation of emissions from sources such as
wetlands and manure. Exploiting these rapidly expanding satellite
measurement capabilities to quantify methane emissions requires a
parallel effort to construct high-quality spatially and sectorally
resolved emission inventories. Partnership between top-down inverse
analyses of atmospheric data and bottom-up construction of emission
inventories is crucial to better understanding methane emission
processes and subsequently informing climate policy.
BibTeX:
@article{jacob16a,
  author = {Jacob, Daniel J. and Turner, Alexander J. and Maasakkers, Joannes D. and Sheng, Jianxiong and Sun, Kang and Liu, Xiong and Chance, Kelly and Aben, Ilse and McKeever, Jason and Frankenberg, Christian},
  title = {Satellite observations of atmospheric methane and their value for quantifying methane emissions},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2016},
  volume = {16},
  number = {22},
  pages = {14371--14396},
  doi = {https://doi.org/10.5194/acp-16-14371-2016}
}
Jamroensan, A. Improving bottom-up and top-down estimates of carbon fluxes in the Midwestern USA 2013 School: The University of Iowa  phdthesis URL 
BibTeX:
@phdthesis{jamroensan13a,
  author = {Jamroensan, Aditsuda},
  title = {Improving bottom-up and top-down estimates of carbon fluxes in the Midwestern USA},
  school = {The University of Iowa},
  year = {2013},
  url = {http://search.proquest.com/openview/0101c608a315817af6e44eee3c2c3053/1?pq-origsite=gscholar&cbl=18750&diss=y}
}
Jiang, F., Wang, H.W., Chen, J.M., Zhou, L.X., Ju, W.M., Ding, A.J., Liu, L.X. and Peters, W. Nested atmospheric inversion for the terrestrial carbon sources and sinks in China {2013} BIOGEOSCIENCES
Vol. {10}({8}), pp. 5311-5324 
article DOI  
Abstract: In this study, we establish a nested atmospheric inversion system with a
focus on China using the Bayesian method. The global surface is
separated into 43 regions based on the 22 TransCom large regions, with
13 small regions in China. Monthly CO2 concentrations from 130
GlobalView sites and 3 additional China sites are used in this system.
The core component of this system is an atmospheric transport matrix,
which is created using the TM5 model with a horizontal resolution of 3
degrees x 2 degrees. The net carbon fluxes over the 43 global land and
ocean regions are inverted for the period from 2002 to 2008. The
inverted global terrestrial carbon sinks mainly occur in boreal Asia,
South and Southeast Asia, eastern America and southern South America.
Most China areas appear to be carbon sinks, with strongest carbon sinks
located in Northeast China. From 2002 to 2008, the global terrestrial
carbon sink has an increasing trend, with the lowest carbon sink in
2002. The inter-annual variation (IAV) of the land sinks shows
remarkable correlation with the El Nino Southern Oscillation (ENSO). The
terrestrial carbon sinks in China also show an increasing trend.
However, the IAV in China is not the same as that of the globe. There is
relatively stronger land sink in 2002, lowest sink in 2006, and
strongest sink in 2007 in China. This IAV could be reasonably explained
with the IAVs of temperature and precipitation in China. The mean global
and China terrestrial carbon sinks over the period 2002-2008 are -3.20
+/- 0.63 and -0.28 +/- 0.18 PgC yr(-1), respectively. Considering the
carbon emissions in the form of reactive biogenic volatile organic
compounds (BVOCs) and from the import of wood and food, we further
estimate that China's land sink is about -0.31 PgC yr(-1).
BibTeX:
@article{jiang13a,
  author = {Jiang, F. and Wang, H. W. and Chen, J. M. and Zhou, L. X. and Ju, W. M. and Ding, A. J. and Liu, L. X. and Peters, W.},
  title = {Nested atmospheric inversion for the terrestrial carbon sources and sinks in China},
  journal = {BIOGEOSCIENCES},
  year = {2013},
  volume = {10},
  number = {8},
  pages = {5311--5324},
  doi = {https://doi.org/10.5194/bg-10-5311-2013}
}
Jiang, F., Chen, J.M., Zhou, L., Ju, W., Zhang, H., Machida, T., Ciais, P., Peters, W., Wang, H., Chen, B., Liu, L., Zhang, C., Matsueda, H. and Sawa, Y. A comprehensive estimate of recent carbon sinks in China using both top-down and bottom-up approaches {2016} SCIENTIFIC REPORTS
Vol. {6} 
article DOI  
Abstract: Atmospheric inversions use measurements of atmospheric CO2 gradients to
constrain regional surface fluxes. Current inversions indicate a net
terrestrial CO2 sink in China between 0.16 and 0.35 PgC/yr. The
uncertainty of these estimates is as large as the mean because the
atmospheric network historically contained only one high altitude
station in China. Here, we revisit the calculation of the terrestrial
CO2 flux in China, excluding emissions from fossil fuel burning and
cement production, by using two inversions with three new CO2 monitoring
stations in China as well as aircraft observations over Asia. We
estimate a net terrestrial CO2 uptake of 0.39-0.51 PgC/yr with a mean of
0.45 PgC/yr in 2006-2009. After considering the lateral transport of
carbon in air and water and international trade, the annual mean carbon
sink is adjusted to 0.35 PgC/yr. To evaluate this top-down estimate, we
constructed an independent bottom-up estimate based on ecosystem data,
and giving a net land sink of 0.33 PgC/yr. This demonstrates closure
between the top-down and bottom-up estimates. Both top-down and
bottom-up estimates give a higher carbon sink than previous estimates
made for the 1980s and 1990s, suggesting a trend towards increased
uptake by land ecosystems in China.
BibTeX:
@article{jiang16a,
  author = {Jiang, Fei and Chen, Jing M. and Zhou, Lingxi and Ju, Weimin and Zhang, Huifang and Machida, Toshinobu and Ciais, Philippe and Peters, Wouter and Wang, Hengmao and Chen, Baozhang and Liu, Lixin and Zhang, Chunhua and Matsueda, Hidekazu and Sawa, Yousuke},
  title = {A comprehensive estimate of recent carbon sinks in China using both top-down and bottom-up approaches},
  journal = {SCIENTIFIC REPORTS},
  year = {2016},
  volume = {6},
  doi = {https://doi.org/10.1038/srep22130}
}
Jiang, X., Crisp, D., Olsen, E.T., Kulawik, S.S., Miller, C.E., Pagano, T.S., Liang, M. and Yung, Y.L. CO2 annual and semiannual cycles from multiple satellite retrievals and models 2016 Earth and Space Science
Vol. 3(2), pp. 78-87 
article DOI  
BibTeX:
@article{jiang16b,
  author = {Jiang, Xun and Crisp, David and Olsen, Edward T and Kulawik, Susan S and Miller, Charles E and Pagano, Thomas S and Liang, Maochang and Yung, Yuk L},
  title = {CO2 annual and semiannual cycles from multiple satellite retrievals and models},
  journal = {Earth and Space Science},
  year = {2016},
  volume = {3},
  number = {2},
  pages = {78--87},
  doi = {https://doi.org/10.1002/2014EA000045/full}
}
Jiang, F., Wang, H., Chen, J.M., Ju, W., Tian, X., Feng, S., Li, G., Chen, Z., Zhang, S., Lu, X., Liu, J., Wang, H., Wang, J., He, W. and Wu, M. Regional CO2 fluxes from 2010 to 2015 inferred from GOSAT XCO2 retrievals using a new version of the Global Carbon Assimilation System {2021} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {21}({3}), pp. {1963-1985} 
article DOI URL 
Abstract: Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) could help to improve carbon flux estimation due to their good spatial coverage. In this study, in order to assimilate the GOSAT (Greenhouse Gases Observing Satellite) XCO2 retrievals, the Global Carbon Assimilation System (GCAS) is upgraded with new assimilation algorithms, procedures, a localization scheme, and a higher assimilation parameter resolution. This upgraded system is referred to as GCASv2. Based on this new system, the global terrestrial ecosystem (BIO) and ocean (OCN) carbon fluxes from 1 May 2009 to 31 December 2015 are constrained using the GOSAT ACOS (Atmospheric CO2 Observations from Space) XCO2 retrievals (Version 7.3). The posterior carbon fluxes from 2010 to 2015 are independently evaluated using CO2 observations from 52 surface flask sites. The results show that the posterior carbon fluxes could significantly improve the modeling of atmospheric CO2 concentrations, with global mean bias decreases from a prior value of 1.6 +/- 1.8 ppm to -0.5 +/- 1.8 ppm. The uncertainty reduction (UR) of the global BIO flux is 17 %, and the highest monthly regional UR could reach 51 %. Globally, the mean annual BIO and OCN carbon sinks and their interannual variations inferred in this study are very close to the estimates of CarbonTracker 2017 (CT2017) during the study period, and the inferred mean atmospheric CO2 growth rate and its interannual changes are also very close to the observations. Regionally, over the northern lands, the strongest carbon sinks are seen in temperate North America, followed by Europe, boreal Asia, and temperate Asia; in the tropics, there are strong sinks in tropical South America and tropical Asia, but a very weak sink in Africa. This pattern is significantly different from the estimates of CT2017, but the estimated carbon sinks for each continent and some key regions like boreal Asia and the Amazon are comparable or within the range of previous bottom-up estimates. The inversion also changes the interannual variations in carbon fluxes in most TransCom land regions, which have a better relationship with the changes in severe drought area (SDA) or leaf area index (LAI), or are more consistent with previous estimates for the impact of drought. These results suggest that the GCASv2 system works well with the GOSAT XCO2 retrievals and shows good performance with respect to estimating the sur- face carbon fluxes; meanwhile, our results also indicate that the GOSAT XCO2 retrievals could help to better understand the interannual variations in regional carbon fluxes.
BibTeX:
@article{jiang21a,
  author = {Jiang, Fei and Wang, Hengmao and Chen, Jing M. and Ju, Weimin and Tian, Xiangjun and Feng, Shuzhuang and Li, Guicai and Chen, Zhuoqi and Zhang, Shupeng and Lu, Xuehe and Liu, Jane and Wang, Haikun and Wang, Jun and He, Wei and Wu, Mousong},
  title = {Regional CO2 fluxes from 2010 to 2015 inferred from GOSAT XCO2 retrievals using a new version of the Global Carbon Assimilation System},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2021},
  volume = {21},
  number = {3},
  pages = {1963--1985},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://acp.copernicus.org/articles/21/1963/2021/acp-21-1963-2021.html},
  doi = {https://doi.org/10.5194/acp-21-1963-2021}
}
Jiang, F., He, W., Ju, W., Wang, H., Wu, M., Wang, J., Feng, S., Zhang, L. and Chen, J.M. The status of carbon neutrality of the world's top 5 CO2 emitters as seen by carbon satellites 2022 FUNDAMENTAL RESEARCH
Vol. 2(3), pp. 357-366 
article DOI  
Abstract: China, the Unite States (US), the European Union (EU), India, and Russia
are the world's top 5 fossil fuel and cement CO2 (FFC) emitting
countries or regions (CRs). It is very important to understand their
status of carbon neutrality, and to monitor their future changes of net
carbon fluxes (NCFs). In this study, we implemented a well-established
global carbon assimilation system (GCAS, Version 2) to infer global
surface carbon fluxes from May 2009 to December 2019 using both GOSAT
and OCO-2 XCO2 retrievals. The reductions of flux uncertainty and XCO2
bias, and the evaluation of posterior flux show that GCAS has comparable
and good performance in the 5 CRs. The results suggest that Russia has
achieved carbon neutrality, but the other 4 are still far from being
carbon neutral, especially China. The mean annual NCFs in China, the US,
the EU, India, and Russia are 2.33 +/- 0.29, 0.82 +/- 0.20, 0.42 +/-
0.16, 0.50 +/- 0.12, and -0.33 +/- 0.23 PgC yr(-1), respectively. From
2010 to 2019, the NCFs showed an increasing trend in the US and India, a
slight downward trend after 2013 in China, and were stable in the EU.
The changes of land sinks in China and the US might be the main reason
for their trends. India's trend was mainly due to the increase of FFC
emission. The relative contributions of NCFs to the global land net
carbon emission of China and the EU have decreased, while those of the
US and India have increased, implying the US and India must take more
active measures to control carbon emissions or increase their sinks.
This study indicates that satellite XCO2 could be successfully used to
monitor the changes of regional NCFs, which is of great significance for
major countries to achieve greenhouse gas control goals.
BibTeX:
@article{jiang22a,
  author = {Jiang, Fei and He, Wei and Ju, Weimin and Wang, Hengmao and Wu, Mousong and Wang, Jun and Feng, Shuzhuang and Zhang, Lingyu and Chen, Jing M.},
  title = {The status of carbon neutrality of the world's top 5 CO2 emitters as seen by carbon satellites},
  journal = {FUNDAMENTAL RESEARCH},
  year = {2022},
  volume = {2},
  number = {3},
  pages = {357-366},
  doi = {https://doi.org/10.1016/j.fmre.2022.02.001}
}
Jin, C., Xue, Y., Jiang, X., Zhao, L., Yuan, T., Sun, Y., Wu, S. and Wang, X. A long-term global XCO2 dataset: Ensemble of satellite products 2022 ATMOSPHERIC RESEARCH
Vol. 279 
article DOI  
Abstract: Many satellites such as SCIAMACHY (scanning imaging absorption
spectrometer for atmospheric cartography), GOSAT-1/2 (greenhouse gases
observing satellite), OCO-2/3 (orbiting carbon observatory) and TanSat
(Car-bonSat, Tan means ``carbon'' in Chinese) provide key observations
of atmospheric CO2 concentration and different XCO2 retrieval algorithms
have been developed for these satellite measurements. However, limited
by the revisit period and scanning swath of the satellites, the
effective daily observation coverage of satellites mentioned above is
very small (<1%), which is a great challenge for high-resolution
mapping of global XCO2. In this paper, we re-evaluated the uncertainty
of each XCO2 pixel with 0.5 x 0.5 degrees spatial resolution in
the global based on season, AOD (aerosol optical depth), surface albedo,
uncertainty parameters of SCIAMACHY, GOSAT-1/ 2, OCO-2/3 and TanSat XCO2
products by TCCON (Total Carbon Column Observing Network) data. Then, a
30-day time window was used to smooth XCO2 datasets from satellite
observations and filled in the missing values according to
CarbonTracker. Finally, we ensembled global XCO2 datasets using maximum
likelihood estimation (MLE) method and optimal interpolation (OI) based
on the re-evaluated uncertainty. The ensemble XCO2 dataset at 0.5
degrees x 0.5 degrees spatial resolution for every three hours from
January 2003 to August 2020 was generated. Compared to TCCON and WDCGG
(World Data Centre for Greenhouse Gases) measurements separately on the
global scale, we obtained the correlation coefficient R = 0.96, the Root
Mean Square Error (RMSE) of 2.62 ppm for TCCON and R = 0.82, the RMSE of
6.75 ppm for WDCGG, respectively. The RMSE of the ensemble dataset was 6
ppm lower than that of the satellites' XCO2 used for fusion compared
with WDCGG and the coverage is greatly improved at a higher spatial and
temporal resolution, proving the feasibility and high precision of the
method.
BibTeX:
@article{jin22a,
  author = {Jin, Chunlin and Xue, Yong and Jiang, Xingxing and Zhao, Liang and Yuan, Tao and Sun, Yuxin and Wu, Shuhui and Wang, Xiangkai},
  title = {A long-term global XCO2 dataset: Ensemble of satellite products},
  journal = {ATMOSPHERIC RESEARCH},
  year = {2022},
  volume = {279},
  doi = {https://doi.org/10.1016/j.atmosres.2022.106385}
}
Jing, Y., Shi, J., Wang, T. and Sussmann, R. Mapping Global Atmospheric CO2 Concentration at High Spatiotemporal Resolution {2014} ATMOSPHERE
Vol. {5}({4}), pp. 870-888 
article DOI  
Abstract: Satellite measurements of the spatiotemporal distributions of
atmospheric CO2 concentrations are a key component for better
understanding global carbon cycle characteristics. Currently, several
satellite instruments such as the Greenhouse gases Observing SATellite
(GOSAT), SCanning Imaging Absorption Spectrometer for Atmospheric
CHartographY (SCIAMACHY), and Orbiting Carbon Observatory-2 can be used
to measure CO2 column-averaged dry air mole fractions. However, because
of cloud effects, a single satellite can only provide limited CO2 data,
resulting in significant uncertainty in the characterization of the
spatiotemporal distribution of atmospheric CO2 concentrations. In this
study, a new physical data fusion technique is proposed to combine the
GOSAT and SCIAMACHY measurements. On the basis of the fused dataset, a
gap-filling method developed by modeling the spatial correlation
structures of CO2 concentrations is presented with the goal of
generating global land CO2 distribution maps with high spatiotemporal
resolution. The results show that, compared with the single satellite
dataset (i.e., GOSAT or SCIAMACHY), the global spatial coverage of the
fused dataset is significantly increased (reaching up to approximately
20%), and the temporal resolution is improved by two or three times.
The spatial coverage and monthly variations of the generated global CO2
distributions are also investigated. Comparisons with ground-based Total
Carbon Column Observing Network (TCCON) measurements reveal that CO2
distributions based on the gap-filling method show good agreement with
TCCON records despite some biases. These results demonstrate that the
fused dataset as well as the gap-filling method are rather effective to
generate global CO2 distribution with high accuracies and high
spatiotemporal resolution.
BibTeX:
@article{jing14a,
  author = {Jing, Yingying and Shi, Jiancheng and Wang, Tianxing and Sussmann, Ralf},
  title = {Mapping Global Atmospheric CO2 Concentration at High Spatiotemporal Resolution},
  journal = {ATMOSPHERE},
  year = {2014},
  volume = {5},
  number = {4},
  pages = {870--888},
  doi = {https://doi.org/10.3390/atmos5040870}
}
Jing, Y., Shi, J. and Wang, T. FUSION OF SPACE-BASED CO2 PRODUCTS AND ITS COMPARISON WITH OTHER AVAILABLE CO2 ESTIMATES {2014} 2014 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS), pp. 2363-2366  inproceedings DOI  
Abstract: Currently, ascertaining and quantifying the global distribution of
carbon dioxide from space-based measurements are greatly valuable for
understanding the causes of global warming and predicting the tendency
of climate change. Nevertheless, the number of valid XCO2 data points
from a single space-based sensor is generally limited on the earth.
Based on this problem, a fused XCO2 dataset is used to generate a
continuous spatio-temporal distribution of global CO2 concentration by
combining GOSAT with SCIAMACHY in this study. And this dataset is also
compared with a data assimilation system Carbon Tracker as well as
ground-based TCCON sites. The results reveal that the spatial coverage
of the fused data is wider than individual space-based XCO2 measurements
(GOSAT or SCIAMCHY) on the global scale. Meanwhile, compared to that of
GOSAT or SCIAMACHY, the correlation between the fused data and Carbon
Tracker is relatively better. In addition, the fused data show a good
agreement with CO2 retrieval of ACOS and BESD as well as that of TCCON
sites although a little biases exist.
BibTeX:
@inproceedings{jing14b,
  author = {Jing, Yingying and Shi, Jiancheng and Wang, Tianxing},
  title = {FUSION OF SPACE-BASED CO2 PRODUCTS AND ITS COMPARISON WITH OTHER AVAILABLE CO2 ESTIMATES},
  booktitle = {2014 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS)},
  year = {2014},
  pages = {2363--2366},
  note = {IEEE Joint International Geoscience and Remote Sensing Symposium (IGARSS) / 35th Canadian Symposium on Remote Sensing, Quebec City, CANADA, JUL 13-18, 2014},
  doi = {https://doi.org/10.1109/IGARSS.2014.6946946}
}
Jing, Y., Wang, T. and Shi, J. TOWARD ACCURATE XCO2 LEVEL 2 MEASUREMENTS BY COMBINING DIFFERENT CO2 RETRIEVALS FROM GOSAT AND SCIAMACHY {2014} 2014 THIRD INTERNATIONAL WORKSHOP ON EARTH OBSERVATION AND REMOTE SENSING APPLICATIONS (EORSA 2014)  inproceedings  
Abstract: Carbon dioxide (CO2) is one of the most important anthropogenic
greenhouse gases causing global warming. Although various space-based
observations have been used to derive and identify regional and global
distribution of CO2 source and sink, uncertainties and biases are still
subsistent. A high spatial and temporal resolution is important to
remove the CO2 uncertainties and biases. In this study, an improved
ensemble median algorithm is developed by fully accounting for the
variation of XCO2 on synoptic timescales. Based on this, XCO2 data sets
from the improved method and EMMA are compared in terms of their
spatiotemporal distributions and correlations. Meanwhile, XCO2
measurements from three TCCON sites are used to compare with these two
datasets. The results reveal that although there is a good correlation
between the XCO2 from improved method and that of EMMA at annual scale,
large discrepancies can be still detected at most places over the world.
It seems that a higher time resolution is necessary to remove the
outliers. In addition, the season cycle of the two methods is generally
in agreement with ground measurements. However, our improved method
shows less divergence compared to that of EMMA at three ground sites. To
some extent, these results proved the effectiveness of our new method
and thus demonstrated the necessity for refining the Level 2 XCO2
measurements at a shorter time averaging period.
BibTeX:
@inproceedings{jing14c,
  author = {Jing, Yingying and Wang, Tianxing and Shi, Jiancheng},
  title = {TOWARD ACCURATE XCO2 LEVEL 2 MEASUREMENTS BY COMBINING DIFFERENT CO2 RETRIEVALS FROM GOSAT AND SCIAMACHY},
  booktitle = {2014 THIRD INTERNATIONAL WORKSHOP ON EARTH OBSERVATION AND REMOTE SENSING APPLICATIONS (EORSA 2014)},
  year = {2014},
  note = {3rd International Workshop on Earth Observation and Remote Sensing Applications (EORSA), Changsha, PEOPLES R CHINA, JUN 11-14, 2014}
}
Jing, Y., Shi, J. and Wang, T. EVALUATION AND COMPARISON OF ATMOSPHERIC CO2 CONCENTRATIONS FROM MODELS AND SATELLITE RETRIEVALS {2015} 2015 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS), pp. 2202-2205  inproceedings  
Abstract: In recent years, global warming caused by increased atmospheric CO2 has
greatly drawn widespread attention from the public. Although satellite
observations and model-simulation offer us two effective approaches to
monitor and assess the global atmospheric CO2, quantification of the
differences between these two different CO2 data is not fully
investigated yet. In this paper, these CO2 products including satellite
observations and model-simulation are inter-compared in terms of
magnitude and their spatiotemporal distributions. The results reveal
that these CO2 data from different data source show a good agreement all
over the world, whereas many discrepancies still exist between satellite
observations and model-simulation, especially in the Northern Sphere.
BibTeX:
@inproceedings{jing15a,
  author = {Jing, Yingying and Shi, Jiancheng and Wang, Tianxing},
  title = {EVALUATION AND COMPARISON OF ATMOSPHERIC CO2 CONCENTRATIONS FROM MODELS AND SATELLITE RETRIEVALS},
  booktitle = {2015 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS)},
  year = {2015},
  pages = {2202--2205},
  note = {IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Milan, ITALY, JUL 26-31, 2015}
}
Jing, Y., Wang, T., Zhang, P., Chen, L., Xu, N. and Ma, Y. Global Atmospheric CO2 Concentrations Simulated by GEOS-Chem: Comparison with GOSAT, Carbon Tracker and Ground-Based Measurements 2018 Atmosphere
Vol. 9(5), pp. 175 
article URL 
BibTeX:
@article{jing18a,
  author = {Jing, Yingying and Wang, Tianxing and Zhang, Peng and Chen, Lin and Xu, Na and Ma, Ya},
  title = {Global Atmospheric CO2 Concentrations Simulated by GEOS-Chem: Comparison with GOSAT, Carbon Tracker and Ground-Based Measurements},
  journal = {Atmosphere},
  year = {2018},
  volume = {9},
  number = {5},
  pages = {175},
  url = {https://www.mdpi.com/2073-4433/9/5/175/htm}
}
Jones, L.A., Kimball, J.S., Reichle, R.H., Madani, N., Glassy, J., Ardizzone, J.V., Colliander, A., Cleverly, J., Desai, A.R., Eamus, D., Euskirchen, E.S., Hutley, L., Macfarlane, C. and Scott, R.L. The SMAP Level 4 Carbon Product for Monitoring Ecosystem Land-Atmosphere CO2 Exchange {2017} IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
Vol. {55}({11}), pp. 6517-6532 
article DOI  
Abstract: The National Aeronautics and Space Administration's Soil Moisture Active
Passive (SMAP) mission Level 4 Carbon (L4C) product provides model
estimates of the Net Ecosystem CO2 exchange (NEE) incorporating SMAP
soil moisture information. The L4C product includes NEE, computed as
total ecosystem respiration less gross photosynthesis, at a daily time
step posted to a 9-km global grid by plant functional type. Component
carbon fluxes, surface soil organic carbon stocks, underlying
environmental constraints, and detailed uncertainty metrics are also
included. The L4C model is driven by the SMAP Level 4 Soil Moisture data
assimilation product, with additional inputs from the Goddard Earth
Observing System, Version 5 weather analysis, and Moderate Resolution
Imaging Spectroradiometer satellite vegetation data. The L4C data record
extends from March 31, 2015 to present with ongoing production and 8-12
day latency. Comparisons against concurrent global CO2 eddy flux tower
measurements, satellite solar-induced canopy florescence, and other
independent observation benchmarks show favorable L4C performance and
accuracy, capturing the dynamic biosphere response to recent weather
anomalies. Model experiments and L4C spatiotemporal variability were
analyzed to understand the independent value of soil moisture and SMAP
observations relative to other sources of input information. This
analysis highlights the potential for microwave observations to inform
models where soil moisture strongly controls land CO2 flux variability;
however, skill improvement relative to flux towers is not yet
discernable within the relatively short validation period. These results
indicate that SMAP provides a unique and promising capability for
monitoring the linked global terrestrial water and carbon cycles.
BibTeX:
@article{jones17a,
  author = {Jones, Lucas A. and Kimball, John S. and Reichle, Rolf H. and Madani, Nima and Glassy, Joe and Ardizzone, Joe V. and Colliander, Andreas and Cleverly, James and Desai, Ankur R. and Eamus, Derek and Euskirchen, Eugenie S. and Hutley, Lindsay and Macfarlane, Craig and Scott, Russell L.},
  title = {The SMAP Level 4 Carbon Product for Monitoring Ecosystem Land-Atmosphere CO2 Exchange},
  journal = {IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING},
  year = {2017},
  volume = {55},
  number = {11},
  pages = {6517--6532},
  doi = {https://doi.org/10.1109/TGRS.2017.2729343}
}
Kanakidou, M., Dameris, M., Elbern, H., Beekmann, M., Konovalov, I.B., Nieradzik, L., Strunk, A. and Krol, M.C. Synergistic Use of Retrieved Trace Constituent Distributions and Numerical Modelling {2011} REMOTE SENSING OF TROPOSPHERIC COMPOSITION FROM SPACE, pp. 451-492  incollection DOI  
BibTeX:
@incollection{kanakidou11a,
  author = {Kanakidou, Maria and Dameris, Martin and Elbern, Hendrik and Beekmann, Matthias and Konovalov, Igor B. and Nieradzik, Lars and Strunk, Achim and Krol, Maarten C.},
  title = {Synergistic Use of Retrieved Trace Constituent Distributions and Numerical Modelling},
  booktitle = {REMOTE SENSING OF TROPOSPHERIC COMPOSITION FROM SPACE},
  publisher = {Springer},
  year = {2011},
  pages = {451--492},
  doi = {https://doi.org/10.1007/978-3-642-14791-3%5C_9}
}
Kang, J.-S., Kalnay, E., Liu, J., Fung, I., Miyoshi, T. and Ide, K. ``Variable localization'' in an ensemble Kalman filter: Application to the carbon cycle data assimilation {2011} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {116} 
article DOI  
Abstract: In ensemble Kalman filter, space localization is used to reduce the
impact of long-distance sampling errors in the ensemble estimation of
the forecast error covariance. When two variables are not physically
correlated, their error covariance is still estimated by the ensemble
and, therefore, it is dominated by sampling errors. We introduce a
``variable localization'' method, zeroing out such covariances between
unrelated variables to the problem of assimilating carbon dioxide
concentrations into a dynamical model using the local ensemble transform
Kalman filter (LETKF) in an observing system simulation experiments
(OSSE) framework. A system where meteorological and carbon variables are
simultaneously assimilated is used to estimate surface carbon fluxes
that are not directly observed. A range of covariance structures are
explored for the LETKF, with emphasis on configurations allowing nonzero
error covariance between carbon variables and the wind field, which
affects transport of atmospheric CO2, but not between CO2 and the other
meteorological variables. Such variable localization scheme zeroes out
the background error covariance among prognostic variables that are not
physically related, thus reducing sampling errors. Results from the
identical twin experiments show that the performance in the estimation
of surface carbon fluxes obtained using variable localization is much
better than that using a standard full covariance approach. The relative
improvement increases when the surface fluxes change with time and model
error becomes significant.
BibTeX:
@article{kang11a,
  author = {Kang, Ji-Sun and Kalnay, Eugenia and Liu, Junjie and Fung, Inez and Miyoshi, Takemasa and Ide, Kayo},
  title = {``Variable localization'' in an ensemble Kalman filter: Application to the carbon cycle data assimilation},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2011},
  volume = {116},
  doi = {https://doi.org/10.1029/2010JD014673}
}
Kang, J.-S., Kalnay, E., Miyoshi, T., Liu, J. and Fung, I. Estimation of surface carbon fluxes with an advanced data assimilation methodology {2012} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {117} 
article DOI  
Abstract: We perform every 6 h a simultaneous data assimilation of surface CO2
fluxes and atmospheric CO2 concentrations along with meteorological
variables using the Local Ensemble Transform Kalman Filter (LETKF)
within an Observing System Simulation Experiments framework. In this
paper, we focus on the impact of advanced variance inflation methods and
vertical localization of column CO2 data on the analysis of CO2. With
both additive inflation and adaptive multiplicative inflation, we are
able to obtain encouraging multiseasonal analyses of surface CO2 fluxes
in addition to atmospheric CO2 and meteorological analyses. Furthermore,
we examine strategies for vertical localization in the assimilation of
simulated CO2 from GOSAT that has nearly uniform sensitivity from the
surface to the upper troposphere. Since atmospheric CO2 is forced by
surface fluxes, its short-term variability should be largest near the
surface. We take advantage of this by updating observed changes only
into the lower tropospheric CO2 rather than into the full column. This
results in a more accurate analysis of CO2 in terms of both RMS error
and spatial patterns. Assimilating synthetic CO2 ground-based
observations and CO2 retrievals from GOSAT and AIRS with the enhanced
LETKF, we obtain an accurate estimation of the evolving surface fluxes
even in the absence of any a priori information. We also test the system
with a longer assimilation window and find that a short window with an
efficient treatment for wind uncertainty is beneficial to flux
inversion. Since this study assumes a perfect forecast model, future
research will explore the impact of model errors. Citation: Kang, J.-S.,
E. Kalnay, T. Miyoshi, J. Liu, and I. Fung (2012), Estimation of surface
carbon fluxes with an advanced data assimilation methodology, J.
Geophys. Res., 117, D24101, doi: 10.1029/2012JD018259.
BibTeX:
@article{kang12a,
  author = {Kang, Ji-Sun and Kalnay, Eugenia and Miyoshi, Takemasa and Liu, Junjie and Fung, Inez},
  title = {Estimation of surface carbon fluxes with an advanced data assimilation methodology},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2012},
  volume = {117},
  doi = {https://doi.org/10.1029/2012JD018259}
}
Karion, A., Sweeney, C., Tans, P. and Newberger, T. AirCore: An Innovative Atmospheric Sampling System {2010} JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY
Vol. {27}({11}), pp. 1839-1853 
article DOI  
Abstract: This work describes the Air Core, a simple and innovative atmospheric
sampling system. The AirCore used in this study is a 150-m-long
stainless steel tube, open at one end and closed at the other, that
relies on positive changes in ambient pressure for passive sampling of
the atmosphere. The Air Core evacuates while ascending to a high
altitude and collects a sample of the ambient air as it descends. It is
sealed upon recovery and measured with a continuous analyzer for trace
gas mole fraction. The Air Core tubing can be shaped into a variety of
configurations to accommodate any sampling platform; for the testing
done in this work it was shaped into a 0,75-m-diameter coil.
Measurements of CO(2) and CH(4) mole fractions in laboratory tests
indicate a repeatability and lack of bias to better than 0.07 ppm (one
sigma) for CO, and 0.4 ppb for CH(4) under various conditions.
Comparisons of AirCore data with flask data from aircraft flights
indicate a standard deviation of differences of 0.3 ppm and 5 ppb for
CO(2) and CH(4), respectively, with no apparent bias. Accounting for
longitudinal mixing, the expected measurement resolution for CO2 is 110
m at sea level, 260 m at 8000 m. and 1500 m at 20 000 m ASL after 3 h of
storage, decreasing to 170, 390, and 2300 m, after 12 h. Validation
tests confirm that the AirCore is a robust sampling device for many
species on a variety of platforms, including balloons, unmanned aerial
vehicles (UAVs), and aircraft.
BibTeX:
@article{karion10a,
  author = {Karion, Anna and Sweeney, Colm and Tans, Pieter and Newberger, Timothy},
  title = {AirCore: An Innovative Atmospheric Sampling System},
  journal = {JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY},
  year = {2010},
  volume = {27},
  number = {11},
  pages = {1839--1853},
  doi = {https://doi.org/10.1175/2010JTECHA1448.1}
}
Karion, A., Callahan, W., Stock, M., Prinzivalli, S., Verhulst, K.R., Kim, J., Salameh, P.K., Lopez-Coto, I. and Whetstone, J. Greenhouse gas observations from the Northeast Corridor tower network {2020} EARTH SYSTEM SCIENCE DATA
Vol. {12}({1}), pp. {699-717} 
article DOI URL 
Abstract: We present the organization, structure, instrumentation, and measurements of the Northeast Corridor greenhouse gas observation network. This network of tower-based in situ carbon dioxide and methane observation stations was established in 2015 with the goal of quantifying emissions of these gases in urban areas in the northeastern United States. A specific focus of the network is the cities of Baltimore, MD, and Washington, DC, USA, with a high density of observation stations in these two urban areas. Additional observation stations are scattered throughout the northeastern US, established to complement other existing urban and regional networks and to investigate emissions throughout this complex region with a high population density and multiple metropolitan areas. Data described in this paper are archived at the National Institute of Standards and Technology and can be found at https://doi.org/10.18434/M32126 (Karion et al., 2019).
BibTeX:
@article{karion20a,
  author = {Karion, Anna and Callahan, William and Stock, Michael and Prinzivalli, Steve and Verhulst, Kristal R. and Kim, Jooil and Salameh, Peter K. and Lopez-Coto, Israel and Whetstone, James},
  title = {Greenhouse gas observations from the Northeast Corridor tower network},
  journal = {EARTH SYSTEM SCIENCE DATA},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2020},
  volume = {12},
  number = {1},
  pages = {699--717},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://essd.copernicus.org/articles/12/699/2020/},
  doi = {https://doi.org/10.5194/essd-12-699-2020}
}
Karion, A., Lopez-Coto, I., Gourdji, S.M., Mueller, K., Ghosh, S., Callahan, W., Stock, M., DiGangi, E., Prinzivalli, S. and Whetstone, J. Background conditions for an urban greenhouse gas network in the Washington, DC, and Baltimore metropolitan region 2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(8), pp. 6257-6273 
article DOI  
Abstract: As city governments take steps towards establishing emissions reduction
targets, the atmospheric research community is increasingly able to
assist in tracking emissions reductions. Researchers have established
systems for observing atmospheric greenhouse gases in urban areas with
the aim of attributing greenhouse gas concentration enhancements (and
thus emissions) to the region in question. However, to attribute
enhancements to a particular region, one must isolate the component of
the observed concentration attributable to fluxes inside the region by
removing the background, which is the component due to fluxes outside.
In this study, we demonstrate methods to construct several versions of a
background for our carbon dioxide and methane observing network in the
Washington, DC, and Baltimore, MD, metropolitan region. Some of these
versions rely on transport and flux models, while others are based on
observations upwind of the domain. First, we evaluate the backgrounds in
a synthetic data framework, and then we evaluate against real
observations from our urban network. We find that backgrounds based on
upwind observations capture the variability better than model-based
backgrounds, although care must be taken to avoid bias from biospheric
carbon dioxide fluxes near background stations in summer. Model-based
backgrounds also perform well when upwind fluxes can be modeled
accurately. Our study evaluates different background methods and
provides guidance in determining background methodology that can impact
the design of urban monitoring networks.
BibTeX:
@article{karion21a,
  author = {Karion, Anna and Lopez-Coto, Israel and Gourdji, Sharon M. and Mueller, Kimberly and Ghosh, Subhomoy and Callahan, William and Stock, Michael and DiGangi, Elizabeth and Prinzivalli, Steve and Whetstone, James},
  title = {Background conditions for an urban greenhouse gas network in the Washington, DC, and Baltimore metropolitan region},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2021},
  volume = {21},
  number = {8},
  pages = {6257-6273},
  doi = {https://doi.org/10.5194/acp-21-6257-2021}
}
Kassem, I.I., Joshi, P., Sigler, V., Heckathorn, S. and Wang, Q. Effect of Elevated CO2 and Drought on Soil Microbial Communities Associated with Andropogon gerardii {2008} JOURNAL OF INTEGRATIVE PLANT BIOLOGY
Vol. {50}({11}), pp. 1406-1415 
article DOI  
Abstract: Our understanding of the effects of elevated atmospheric CO2, singly and
in combination with other environmental changes, on plant-soil
interactions is incomplete. Elevated CO2 effects on C-4 plants, though
smaller than on C-3 species, are mediated mostly via decreased stomatal
conductance and thus water loss. Therefore, we characterized the
interactive effect of elevated CO2 and drought on soil microbial
communities associated with a dominant C-4 prairie grass, Andropogon
gerardii Vitman. Elevated CO2 and drought both affected resources
available to the soil microbial community. For example, elevated CO2
increased the soil C:N ratio and water content during drought, whereas
drought alone decreased both. Drought significantly decreased soil
microbial biomass. In contrast, elevated CO2 increased biomass while
ameliorating biomass decreases that were induced under drought. Total
and active direct bacterial counts and carbon substrate use (overall use
and number of used sources) increased significantly under elevated CO2.
Denaturing gradient gel electrophoresis analysis revealed that drought
and elevated CO2, singly and combined, did not affect the soil bacteria
community structure. We conclude that elevated CO2 alone increased
bacterial abundance and microbial activity and carbon use, probably in
response to increased root exudation. Elevated CO2 also limited
drought-related impacts on microbial activity and biomass, which likely
resulted from decreased plant water use under elevated CO2. These are
among the first results showing that elevated CO2 and drought work in
opposition to modulate plant-associated soil-bacteria responses, which
should then influence soil resources and plant and ecosystem function.
BibTeX:
@article{kassem08a,
  author = {Kassem, Issmat I. and Joshi, Puneet and Sigler, Von and Heckathorn, Scott and Wang, Qi},
  title = {Effect of Elevated CO2 and Drought on Soil Microbial Communities Associated with Andropogon gerardii},
  journal = {JOURNAL OF INTEGRATIVE PLANT BIOLOGY},
  year = {2008},
  volume = {50},
  number = {11},
  pages = {1406--1415},
  doi = {https://doi.org/10.1111/j.1744-7909.2008.00752.x}
}
Kavitha, M. and Nair, P.R. Region-dependent seasonal pattern of methane over Indian region as observed by SCIAMACHY {2016} ATMOSPHERIC ENVIRONMENT
Vol. {131}, pp. 316-325 
article DOI  
Abstract: The column averaged mixing ratio of methane (XCH4) from SCanning Imaging
Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY)
on-board satellite ENVISAT has been used to study its regional pattern
and seasonal cycle over Indian region for the period 2003-2009. XCH4
varies from 1740 to 1890 ppbv over Indian region with distinct spatial
and temporal features. The peak values are observed in monsoon and post
monsoon and minimum in winter months, except over southern Peninsular
India which shows the distinctly different seasonal behavior with peak
in October/November. The mean background level of XCH4 over Indian
region is estimated as similar to 1795 ppbv. While regional patterns are
strongly associated with livestock distribution, wetland emissions,
including rice fields, the seasonal variations in XCH4 are predominantly
associated with the rice cultivation as revealed by analysis of NDVI.
(C) 2016 Elsevier Ltd. All rights reserved.
BibTeX:
@article{kavitha16a,
  author = {Kavitha, M. and Nair, Prabha R.},
  title = {Region-dependent seasonal pattern of methane over Indian region as observed by SCIAMACHY},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2016},
  volume = {131},
  pages = {316--325},
  doi = {https://doi.org/10.1016/j.atmosenv.2016.02.008}
}
Kavitha, M. and Nair, P.R. SCIAMACHY observed changes in the column mixing ratio of methane over the Indian region and a comparison with global scenario {2017} ATMOSPHERIC ENVIRONMENT
Vol. {166}, pp. 454-466 
article DOI  
Abstract: The trends in the column averaged mixing ratio of methane (XCH4) over
the Indian region during 2003 2009 periods were studied using the
SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY
(SCIAMACHY) observations. Considering the sensor degradation, the trends
were analyzed for 2003 to 2005 and 2006 to 2009 separately. Over India,
the trend in XCH4 varied from 5.2 to 7.6 ppb per year after 2005,
exhibiting a 2-4 fold increase compared to 2003-2005. While the increase
over Northern parts of India is attributed to increasing CH4 emissions
from rice cultivation and livestock population, those over Southern
regions are due to increased oil and gas mining activities. A comparison
of these trends with those over most of the hotspot regions over the
globe revealed that those regions exhibited higher growth rates of XCH4
compared to Indian regions during 2006-2009. The seasonal patterns of
XCH4 and near-surface CH4 at selected global network stations were also
examined in detail. This analysis revealed hemispheric difference and
varying seasonal patterns suggesting the inhomogeneous vertical
distribution of CH4. The observed differences in the seasonal patterns
of near-surface CH4 and XCH4 suggest that the surface emissions need not
replicate at higher altitudes due to long-range transport, the boundary
layer meteorology and lifetime of CH4 in the atmosphere. (C) 2017
Elsevier Ltd. All rights reserved.
BibTeX:
@article{kavitha17a,
  author = {Kavitha, M. and Nair, Prabha R.},
  title = {SCIAMACHY observed changes in the column mixing ratio of methane over the Indian region and a comparison with global scenario},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2017},
  volume = {166},
  pages = {454--466},
  doi = {https://doi.org/10.1016/j.atmosenv.2017.07.044}
}
Keeling, R. and Manning, A. 5.15 - Studies of Recent Changes in Atmospheric O2\ Content 2014 Treatise on Geochemistry (Second Edition), pp. 385-404  incollection DOI URL 
Abstract: Abstract A very close coupling exists between changes in atmospheric O2\ and CO2\ concentrations, owing to the chemistry of photosynthesis, respiration, and combustion. The coupling is not perfect, however, because CO2\ variations are partially buffered by reactions involving the inorganic carbon system in seawater, which has no effect on O2. Measurements over the past two decades document variations in O2\ on a range of space and time scales, including a long-term decrease driven mostly by fossil fuel burning and seasonal cycles driven by exchanges with the land biosphere and the oceans. In this chapter, these and other features seen in the measurements are described, also discussing variations in the tracer `atmospheric potential oxygen,' which is a linear combination of O2\ and CO2\ designed to be insensitive to exchanges from the land biosphere and thereby sensitive mostly to oceanic processes. Challenges associated with measuring variations in O2\ are addressed, and various applications of the observations are discussed, including quantifying the magnitude of the global land and ocean carbon sinks and testing ocean biogeochemical models. An updated budget for global carbon sinks based on O2\ measurements from the Scripps O2\ program is presented for the decades of the 1990s and 2000s.
BibTeX:
@incollection{keeling14a,
  author = {R.F. Keeling and A.C. Manning},
  title = {5.15 - Studies of Recent Changes in Atmospheric O2\ Content},
  booktitle = {Treatise on Geochemistry (Second Edition)},
  publisher = {Elsevier},
  year = {2014},
  pages = {385--404},
  url = {https://www.sciencedirect.com/science/article/pii/B9780080959757004204},
  doi = {https://doi.org/10.1016/B978-0-08-095975-7.00420-4}
}
Kenea, S.T., Oh, Y.-S., Rhee, J.-S., Goo, T.-Y., Byun, Y.-H., Li, S., Labzovskii, L.D., Lee, H. and Banks, R.F. Evaluation of Simulated CO2 Concentrations from the CarbonTracker-Asia Model Using In-situ Observations over East Asia for 2009-2013 {2019} ADVANCES IN ATMOSPHERIC SCIENCES
Vol. {36}({6}), pp. {603-613} 
article DOI URL 
Abstract: The CarbonTracker (CT) model has been used in previous studies for understanding and predicting the sources, sinks, and dynamics that govern the distribution of atmospheric CO2 at varying ranges of spatial and temporal scales. However, there are still challenges for reproducing accurate model-simulated CO2 concentrations close to the surface, typically associated with high spatial heterogeneity and land cover. In the present study, we evaluated the performance of nested-grid CT model simulations of CO2 based on the CT2016 version through comparison with in-situ observations over East Asia covering the period 2009-13. We selected sites located in coastal, remote, inland, and mountain areas. The results are presented at diurnal and seasonal time periods. At target stations, model agreement with in-situ observations was varied in capturing the diurnal cycle. Overall, biases were less than 6.3 ppm on an all-hourly mean basis, and this was further reduced to a maximum of 4.6 ppm when considering only the daytime. For instance, at Anmyeondo, a small bias was obtained in winter, on the order of 0.2 ppm. The model revealed a diurnal amplitude of CO2 that was nearly flat in winter at Gosan and Anmyeondo stations, while slightly overestimated in the summertime. The model's performance in reproducing the diurnal cycle remains a challenge and requires improvement. The model showed better agreement with the observations in capturing the seasonal variations of CO2 during daytime at most sites, with a correlation coefficient ranging from 0.70 to 0.99. Also, model biases were within -0.3 and 1.3 ppm, except for inland stations (7.7 ppm).
BibTeX:
@article{kenea19a,
  author = {Kenea, Samuel Takele and Oh, Young-Suk and Rhee, Jae-Sang and Goo, Tae-Young and Byun, Young-Hwa and Li, Shanlan and Labzovskii, Lev D. and Lee, Haeyoung and Banks, Robert F.},
  title = {Evaluation of Simulated CO2 Concentrations from the CarbonTracker-Asia Model Using In-situ Observations over East Asia for 2009-2013},
  journal = {ADVANCES IN ATMOSPHERIC SCIENCES},
  publisher = {SCIENCE PRESS},
  year = {2019},
  volume = {36},
  number = {6},
  pages = {603--613},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://link.springer.com/article/10.1007/s00376-019-8150-x},
  doi = {https://doi.org/10.1007/s00376-019-8150-x}
}
Kenea, S.T., Labzovskii, L.D., Goo, T.-Y., Li, S., Oh, Y.-S. and Byun, Y.-H. Comparison of Regional Simulation of Biospheric CO2 Flux from the Updated Version of CarbonTracker Asia with FLUXCOM and Other Inversions over Asia {2020} REMOTE SENSING
Vol. {12}({1}) 
article DOI  
Abstract: There are still large uncertainties in the estimates of net ecosystem exchange of CO2 (NEE) with atmosphere in Asia, particularly in the boreal and eastern part of temperate Asia. To understand these uncertainties, we assessed the CarbonTracker Asia (CTA2017) estimates of the spatial and temporal distributions of NEE through a comparison with FLUXCOM and the global inversion models from the Copernicus Atmospheric Monitoring Service (CAMS), Monitoring Atmospheric Composition and Climate (MACC), and Jena CarboScope in Asia, as well as examining the impact of the nesting approach on the optimized NEE flux during the 2001-2013 period. The long-term mean carbon uptake is reduced in Asia, which is -0.32 +/- 0.22 PgC yr(-1), whereas -0.58 +/- 0.26 PgC yr(-1) is shown from CT2017 (CarbonTracker global). The domain aggregated mean carbon uptake from CTA2017 is found to be lower by 23.8%, 44.8%, and 60.5% than CAMS, MACC, and Jena CarboScope, respectively. For example, both CTA2017 and CT2017 models captured the interannual variability (IAV) of the NEE flux with a different magnitude and this leads to divergent annual aggregated results. Differences in the estimated interannual variability of NEE in response to El Nino-Southern Oscillation (ENSO) may result from differences in the transport model resolutions. These inverse models' results have a substantial difference compared to FLUXCOM, which was found to be -5.54 PgC yr(-1). On the one hand, we showed that the large NEE discrepancies between both inversion models and FLUXCOM stem mostly from the tropical forests. On the other hand, CTA2017 exhibits a slightly better correlation with FLUXCOM over grass/shrub, fields/woods/savanna, and mixed forest than CT2017. The land cover inconsistency between CTA2017 and FLUXCOM is therefore one driver of the discrepancy in the NEE estimates. The diurnal averaged NEE flux between CTA2017 and FLUXCOM exhibits better agreement during the carbon uptake period than the carbon release period. Both CTA2017 and CT2017 revealed that the overall spatial patterns of the carbon sink and source are similar, but the magnitude varied with seasons and ecosystem types, which is mainly attributed to differences in the transport model resolutions. Our findings indicate that substantial inconsistencies in the inversions and FLUXCOM mainly emerge during the carbon uptake period and over tropical forests. The main problems are underrepresentation of FLUXCOM NEE estimates by limited eddy covariance flux measurements, the role of CO2 emissions from land use change not accounted for by FLUXCOM, sparseness of surface observations of CO2 concentrations used by the assimilation systems, and land cover inconsistency. This suggested that further scrutiny on the FLUXCOM and inverse estimates is most likely required. Such efforts will reduce inconsistencies across various NEE estimates over Asia, thus mitigating ecosystem-driven errors that propagate the global carbon budget. Moreover, this work also recommends further investigation on how the changes/updates made in CarbonTracker affect the interannual variability of the aggregate and spatial pattern of NEE flux in response to the ENSO effect over the region of interest.
BibTeX:
@article{kenea20a,
  author = {Kenea, Samuel Takele and Labzovskii, Lev D. and Goo, Tae-Young and Li, Shanlan and Oh, Young-Suk and Byun, Young-Hwa},
  title = {Comparison of Regional Simulation of Biospheric CO2 Flux from the Updated Version of CarbonTracker Asia with FLUXCOM and Other Inversions over Asia},
  journal = {REMOTE SENSING},
  publisher = {MDPI},
  year = {2020},
  volume = {12},
  number = {1},
  doi = {https://doi.org/10.3390/rs12010145}
}
Kenea, S.T., Lee, H., Patra, P.K., Li, S., Labzovskii, L.D. and Joo, S. Long-term changes in CH4 emissions: Comparing Delta CH4/Delta CO2 ratios between observation and proved model in East Asia (2010-2020) 2023 ATMOSPHERIC ENVIRONMENT
Vol. 293 
article DOI  
Abstract: To understand the changes in CH4 emissions in East Asia, mainly in
China, we analyzed the synoptic scale variability (SSV) of CO2 and CH4
mole fractions at Anmyeondo (AMY; 36.53 degrees N, 126.32 degrees E, 46
m above sea level) in South Korea using near-surface in-situ
observations and an atmospheric chemical transport model (ACTM) to
investigate the role of prescribed surface fluxes on SSV. The SSV of the
tracers at AMY was mainly caused by emission variations from eastern and
northeastern China during the winters in 2010-2020, as indicated by the
simulated concentration footprints at AMY observed using the WRF-STILT
model. The estimated SSV of Delta CH4/Delta CO2 mole fraction ratios
from the observations was 4.2-6.2 ppb ppm(-1), with a mean of 5.7 +/-
0.93 ppb ppm(-1) during the winters in 2010-2020. We also calculated the
CH4/CO2 emission ratio from China's total annual fossil-fuel emissions,
excluding seasonal sources estimated from the Emission Database for
Global Atmospheric Research. We found that the ratio was overestimated
by similar to 98.1% compared to observations, which was likely driven
either due to the overestimation of CH4 or underestimation of CO2. We
discerned that the model-simulated SSV of the Delta CH4/Delta CO2 ratios
generally reproduced the observations when the CH4 FixCoal simulation
case was used. This implies that CH4 from coal was a major contributor
to the observed variations in the winter period Delta CH4/Delta CO2
ratios. However, the model did not reproduce the observed ratio in
2012-this discrepancy requires further study. The trend of Delta
CH4/Delta CO2 was a slight decrease over time, which was attributed to
the earlier onset of CH4 emissions relative to fossil-fuel CO2,
predominantly due to the reduction of CH4 emissions from coal. In 2013,
a relatively low tracer ratio was noted, which was caused by the large
contribution of CO2 from biomass burning. Overall, the observed AMY
Delta CH4/Delta CO2 ratios provide an efficient approach for validating
the existing estimates of East Asian sectoral emissions of CH4.
BibTeX:
@article{kenea23a,
  author = {Kenea, Samuel Takele and Lee, Haeyoung and Patra, Prabir K. and Li, Shanlan and Labzovskii, Lev D. and Joo, Sangwon},
  title = {Long-term changes in CH4 emissions: Comparing Delta CH4/Delta CO2 ratios between observation and proved model in East Asia (2010-2020)},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2023},
  volume = {293},
  doi = {https://doi.org/10.1016/j.atmosenv.2022.119437}
}
Keppel-Aleks, G., Wennberg, P.O. and Schneider, T. Sources of variations in total column carbon dioxide {2011} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {11}({8}), pp. 3581-3593 
article DOI  
Abstract: Observations of gradients in the total CO(2) column, < CO(2)>, are
expected to provide improved constraints on surface fluxes of CO(2).
Here we use a general circulation model with a variety of prescribed
carbon fluxes to investigate how variations in < CO(2)> arise. On
diurnal scales, variations are small and are forced by both local fluxes
and advection. On seasonal scales, gradients are set by the north-south
flux distribution. On synoptic scales, variations arise due to
large-scale eddy-driven disturbances of the meridional gradient. In this
case, because variations in < CO(2)> are tied to synoptic activity,
significant correlations exist between < CO(2)> and dynamical tracers.
We illustrate how such correlations can be used to describe the
north-south gradients of < CO(2)> and the underlying fluxes on
continental scales. These simulations suggest a novel analysis framework
for using column observations in carbon cycle science.
BibTeX:
@article{keppel-aleks11a,
  author = {Keppel-Aleks, G. and Wennberg, P. O. and Schneider, T.},
  title = {Sources of variations in total column carbon dioxide},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2011},
  volume = {11},
  number = {8},
  pages = {3581--3593},
  doi = {https://doi.org/10.5194/acp-11-3581-2011}
}
Keppel-Aleks, G., Wennberg, P.O., Washenfelder, R.A., Wunch, D., Schneider, T., Toon, G.C., Andres, R.J., Blavier, J.F., Connor, B., Davis, K.J., Desai, A.R., Messerschmidt, J., Notholt, J., Roehl, C.M., Sherlock, V., Stephens, B.B., Vay, S.A. and Wofsy, S.C. The imprint of surface fluxes and transport on variations in total column carbon dioxide {2012} BIOGEOSCIENCES
Vol. {9}({3}), pp. 875-891 
article DOI  
Abstract: New observations of the vertically integrated CO2 mixing ratio,
aYCO(2)aY (c), from ground-based remote sensing show that variations in
CO(2)aY (c) are primarily determined by large-scale flux patterns. They
therefore provide fundamentally different information than observations
made within the boundary layer, which reflect the combined influence of
large-scale and local fluxes. Observations of both aYCO(2)aY (c) and CO2
concentrations in the free troposphere show that large-scale spatial
gradients induce synoptic-scale temporal variations in aYCO(2)aY (c) in
the Northern Hemisphere midlatitudes through horizontal advection.
Rather than obscure the signature of surface fluxes on atmospheric CO2,
these synoptic-scale variations provide useful information that can be
used to reveal the meridional flux distribution. We estimate the
meridional gradient in aYCO(2)aY (c) from covariations in aYCO(2)aY (c)
and potential temperature, theta, a dynamical tracer, on synoptic
timescales to evaluate surface flux estimates commonly used in carbon
cycle models. We find that simulations using Carnegie Ames Stanford
Approach (CASA) biospheric fluxes underestimate both the aYCO(2)aY (c)
seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes
and the meridional gradient during the growing season. Simulations using
CASA net ecosystem exchange (NEE) with increased and phase-shifted
boreal fluxes better fit the observations. Our simulations suggest that
climatological mean CASA fluxes underestimate boreal growing season NEE
(between 45-65A degrees N) by ˜40%. We describe the implications for
this large seasonal exchange on inference of the net Northern Hemisphere
terrestrial carbon sink.
BibTeX:
@article{keppel-aleks12a,
  author = {Keppel-Aleks, G. and Wennberg, P. O. and Washenfelder, R. A. and Wunch, D. and Schneider, T. and Toon, G. C. and Andres, R. J. and Blavier, J. -F. and Connor, B. and Davis, K. J. and Desai, A. R. and Messerschmidt, J. and Notholt, J. and Roehl, C. M. and Sherlock, V. and Stephens, B. B. and Vay, S. A. and Wofsy, S. C.},
  title = {The imprint of surface fluxes and transport on variations in total column carbon dioxide},
  journal = {BIOGEOSCIENCES},
  year = {2012},
  volume = {9},
  number = {3},
  pages = {875--891},
  doi = {https://doi.org/10.5194/bg-9-875-2012}
}
Keppel-Aleks, G., Wennberg, P.O., O'Dell, C.W. and Wunch, D. Towards constraints on fossil fuel emissions from total column carbon dioxide {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({8}), pp. 4349-4357 
article DOI  
Abstract: We assess the large-scale, top-down constraints on regional fossil fuel
emissions provided by observations of atmospheric total column CO2,
X-CO2. Using an atmospheric general circulation model (GCM) with
underlying fossil emissions, we determine the influence of regional
fossil fuel emissions on global X-CO2 fields. We quantify the regional
contrasts between source and upwind regions and probe the sensitivity of
atmospheric X-CO2 to changes in fossil fuel emissions. Regional fossil
fuel X-CO2 contrasts can exceed 0.7 ppm based on 2007 emission
estimates, but have large seasonal variations due to biospheric fluxes.
Contamination by clouds reduces the discernible fossil signatures.
Nevertheless, our simulations show that atmospheric fossil X-CO2 can be
tied to its source region and that changes in the regional XCO2
contrasts scale linearly with emissions. We test the GCM results against
X-CO2 data from the GOSAT satellite. Regional X-CO2 contrasts in GOSAT
data generally scale with the predictions from the GCM, but the
comparison is limited by the moderate precision of and relatively few
observations from the satellite. We discuss how this approach may be
useful as a policy tool to verify national fossil emissions, as it
provides an independent, observational constraint.
BibTeX:
@article{keppel-aleks13a,
  author = {Keppel-Aleks, G. and Wennberg, P. O. and O'Dell, C. W. and Wunch, D.},
  title = {Towards constraints on fossil fuel emissions from total column carbon dioxide},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {8},
  pages = {4349--4357},
  doi = {https://doi.org/10.5194/acp-13-4349-2013}
}
Kiel, M., O'Dell, C.W., Fisher, B., Eldering, A., Nassar, R., MacDonald, C.G. and Wennberg, P.O. How bias correction goes wrong: measurement of X-CO2 affected by erroneous surface pressure estimates {2019} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {12}({4}), pp. {2241-2259} 
article DOI URL 
Abstract: All measurements of X-CO2 from space have systematic errors. To reduce a large fraction of these errors, a bias correction is applied to X-CO2 retrieved from GOSAT and OCO-2 spectra using the ACOS retrieval algorithm. The bias correction uses, among other parameters, the surface pressure difference between the retrieval and the meteorological reanalysis. Relative errors in the surface pressure estimates, however, propagate nearly 1 V 1 into relative errors in biascorrected X-CO2. For OCO-2, small errors in the knowledge of the pointing of the observatory (up to similar to 130 arcsec) introduce a bias in X-CO2 in regions with rough topography. Erroneous surface pressure estimates are also caused by a coding error in ACOS version 8, sampling meteorological analyses at wrong times ( up to 3 h after the overpass time). Here, we derive new geolocations for OCO-2' s eight footprints and show how using improved knowledge of surface pressure estimates in the bias correction reduces errors in OCO-2' s v9 X-CO2 data.
BibTeX:
@article{kiel19a,
  author = {Kiel, Matthaus and O'Dell, Christopher W. and Fisher, Brendan and Eldering, Annmarie and Nassar, Ray and MacDonald, Cameron G. and Wennberg, Paul O.},
  title = {How bias correction goes wrong: measurement of X-CO2 affected by erroneous surface pressure estimates},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {12},
  number = {4},
  pages = {2241--2259},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://amt.copernicus.org/articles/12/2241/2019/},
  doi = {https://doi.org/10.5194/amt-12-2241-2019}
}
Kim, M.G. Errors in mixed layer heights over North America: a multi-model comparison 2011 School: University of Waterloo  mastersthesis URL 
BibTeX:
@mastersthesis{kim11a,
  author = {Kim, Myung Gwang},
  title = {Errors in mixed layer heights over North America: a multi-model comparison},
  school = {University of Waterloo},
  year = {2011},
  url = {https://uwspace.uwaterloo.ca/handle/10012/5968}
}
Kim, J., Kim, H.M. and Cho, C.-H. Application of Carbon Tracking System based on ensemble Kalman Filter on the diagnosis of Carbon Cycle in Asia 2012 Atmosphere
Vol. 22(4), pp. 415-427 
article URL 
BibTeX:
@article{kim12a,
  author = {Kim, JinWoong and Kim, Hyun Mee and Cho, Chun-Ho},
  title = {Application of Carbon Tracking System based on ensemble Kalman Filter on the diagnosis of Carbon Cycle in Asia},
  journal = {Atmosphere},
  year = {2012},
  volume = {22},
  number = {4},
  pages = {415--427},
  url = {http://www.koreascience.or.kr/article/ArticleFullRecord.jsp?cn=KSHHDL_2012_v22n4_415}
}
Kim, J., Kim, H.M. and Cho, C.-H. The effect of optimization and the nesting domain on carbon flux analyses in Asia using a carbon tracking system based on the ensemble Kalman filter {2014} ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
Vol. {50}({3}), pp. 327-344 
article DOI  
Abstract: To estimate the surface carbon flux in Asia and investigate the effect
of the nesting domain on carbon flux analyses in Asia, two experiments
with different nesting domains were conducted using the CarbonTracker
developed by the National Oceanic and Atmospheric Administration.
CarbonTracker is an inverse modeling system that uses an ensemble Kalman
filter (EnKF) to estimate surface carbon fluxes from surface CO2
observations. One experiment was conducted with a nesting domain
centered in Asia and the other with a nesting domain centered in North
America. Both experiments analyzed the surface carbon fluxes in Asia
from 2001 to 2006. The results showed that prior surface carbon fluxes
were underestimated in Asia compared with the optimized fluxes. The
optimized biosphere fluxes of the two experiments exhibited roughly
similar spatial patterns but different magnitudes. Weekly cumulative
optimized fluxes showed more diverse patterns than the prior fluxes,
indicating that more detailed flux analyses were conducted during the
optimization. The nesting domain in Asia produced a detailed estimate of
the surface carbon fluxes in Asia and exhibited better agreement with
the CO2 observations. Finally, the simulated background atmospheric CO2
concentrations in the experiment with the nesting domain in Asia were
more consistent with the observed CO2 concentrations than those in the
experiment with the nesting domain in North America. The results of this
study suggest that surface carbon fluxes in Asia can be estimated more
accurately using an EnKF when the nesting domain is centered in Asian
regions.
BibTeX:
@article{kim14a,
  author = {Kim, Jinwoong and Kim, Hyun Mee and Cho, Chun-Ho},
  title = {The effect of optimization and the nesting domain on carbon flux analyses in Asia using a carbon tracking system based on the ensemble Kalman filter},
  journal = {ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES},
  year = {2014},
  volume = {50},
  number = {3},
  pages = {327--344},
  doi = {https://doi.org/10.1007/s13143-014-0020-y}
}
Kim, J., Kim, H.M. and Cho, C.H. Influence of CO2 observations on the optimized CO2 flux in an ensemble Kalman filter {2014} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {14}({24}), pp. 13515-13530 
article DOI  
Abstract: In this study, the effect of CO2 observations on an analysis of surface
CO2 flux was calculated using an influence matrix in the CarbonTracker,
which is an inverse modeling system for estimating surface CO2 flux
based on an ensemble Kalman filter. The influence matrix represents a
sensitivity of the analysis to observations. The experimental period was
from January 2000 to December 2009. The diagonal element of the
influence matrix (i.e., analysis sensitivity) is globally 4.8% on
average, which implies that the analysis extracts 4.8% of the
information from the observations and 95.2% from the background each
assimilation cycle. Because the surface CO2 flux in each week is
optimized by 5 weeks of observations, the cumulative impact over 5 weeks
is 19.1 %, much greater than 4.8 %. The analysis sensitivity is
inversely proportional to the number of observations used in the
assimilation, which is distinctly apparent in continuous observation
categories with a sufficient number of observations. The time series of
the globally averaged analysis sensitivities shows seasonal variations,
with greater sensitivities in summer and lower sensitivities in winter,
which is attributed to the surface CO2 flux uncertainty. The
time-averaged analysis sensitivities in the Northern Hemisphere are
greater than those in the tropics and the Southern Hemisphere. The trace
of the influence matrix (i.e., information content) is a measure of the
total information extracted from the observations. The information
content indicates an imbalance between the observation coverage in North
America and that in other regions. Approximately half of the total
observational information is provided by continuous observations, mainly
from North America, which indicates that continuous observations are the
most informative and that comprehensive coverage of additional
observations in other regions is necessary to estimate the surface CO2
flux in these areas as accurately as in North America.
BibTeX:
@article{kim14b,
  author = {Kim, J. and Kim, H. M. and Cho, C. -H.},
  title = {Influence of CO2 observations on the optimized CO2 flux in an ensemble Kalman filter},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2014},
  volume = {14},
  number = {24},
  pages = {13515--13530},
  doi = {https://doi.org/10.5194/acp-14-13515-2014}
}
Kim, H., Kim, H.M., Kim, J. and Cho, C.-H. A Comparison of the Atmospheric CO2 Concentrations Obtained by an Inverse Modeling System and Passenger Aircraft Based Measurement 2016 Atmosphere
Vol. 26(3), pp. 387-400 
article URL 
BibTeX:
@article{kim16a,
  author = {Hyunjung Kim and Hyun Mee Kim and Jinwoong Kim and Chun-Ho Cho},
  title = {A Comparison of the Atmospheric CO2 Concentrations Obtained by an Inverse Modeling System and Passenger Aircraft Based Measurement},
  journal = {Atmosphere},
  year = {2016},
  volume = {26},
  number = {3},
  pages = {387--400},
  url = {http://www.j-komes.or.kr/xml/07935/07935.pdf}
}
Kim, J., Kim, H.M., Cho, C.-H., Boo, K.-O., Jacobson, A.R., Sasakawa, M., Machida, T., Arshinov, M. and Fedoseev, N. Impact of Siberian observations on the optimization of surface CO2 flux {2017} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {17}({4}), pp. 2881-2899 
article DOI  
Abstract: To investigate the effect of additional CO2 observations in the Siberia
region on the Asian and global surface CO2 flux analyses, two
experiments using different observation data sets were performed for
2000-2009. One experiment was conducted using a data set that includes
additional observations of Siberian tower measurements (Japan-Russia
Siberian Tall Tower Inland Observation Network: JR-STATION), and the
other experiment was conducted using a data set without the above
additional observations. The results show that the global balance of the
sources and sinks of surface CO2 fluxes was maintained for both
experiments with and without the additional observations. While the
magnitude of the optimized surface CO2 flux uptake and flux uncertainty
in Siberia decreased from 1.17 +/- 0.93 to 0.77 +/- 0.70 PgC yr(-1), the
magnitude of the optimized surface CO2 flux uptake in the other regions
(e.g., Europe) of the Northern Hemisphere (NH) land increased for the
experiment with the additional observations, which affect the
longitudinal distribution of the total NH sinks. This change was mostly
caused by changes in the magnitudes of surface CO2 flux in June and
July. The observation impact measured by uncertainty reduction and
self-sensitivity tests shows that additional observations provide useful
information on the estimated surface CO2 flux. The average uncertainty
reduction of the conifer forest of Eurasian boreal (EB) is 29.1% and
the average self-sensitivities at the JR-STATION sites are approximately
60% larger than those at the towers in North America. It is expected
that the Siberian observations play an important role in estimating
surface CO2 flux in the NH land (e.g., Siberia and Europe) in the
future.
BibTeX:
@article{kim17a,
  author = {Kim, Jinwoong and Kim, Hyun Mee and Cho, Chun-Ho and Boo, Kyung-On and Jacobson, Andrew R. and Sasakawa, Motoki and Machida, Toshinobu and Arshinov, Mikhail and Fedoseev, Nikolay},
  title = {Impact of Siberian observations on the optimization of surface CO2 flux},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2017},
  volume = {17},
  number = {4},
  pages = {2881--2899},
  doi = {https://doi.org/10.5194/acp-17-2881-2017}
}
Kim, H., Kim, H.M., Kim, J. and Cho, C.-H. Effect of data assimilation parameters on the optimized surface CO2 flux in Asia 2017 Asia-Pacific Journal of Atmospheric Sciences, pp. 1-17  article DOI  
Abstract: In this study, CarbonTracker, an inverse modeling system based on the ensemble Kalman filter, was used to evaluate the effects of data assimilation parameters (assimilation window length and ensemble size) on the estimation of surface CO2 fluxes in Asia. Several experiments with different parameters were conducted, and the results were verified using CO2 concentration observations. The assimilation window lengths tested were 3, 5, 7, and 10 weeks, and the ensemble sizes were 100, 150, and 300. Therefore, a total of 12 experiments using combinations of these parameters were conducted. The experimental period was from January 2006 to December 2009. Differences between the optimized surface CO2 fluxes of the experiments were largest in the Eurasian Boreal (EB) area, followed by Eurasian Temperate (ET) and Tropical Asia (TA), and were larger in boreal summer than in boreal winter. The effect of ensemble size on the optimized biosphere flux is larger than the effect of the assimilation window length in Asia, but the importance of them varies in specific regions in Asia. The optimized biosphere flux was more sensitive to the assimilation window length in EB, whereas it was sensitive to the ensemble size as well as the assimilation window length in ET. The larger the ensemble size and the shorter the assimilation window length, the larger the uncertainty (i.e., spread of ensemble) of optimized surface CO2 fluxes. The 10-week assimilation window and 300 ensemble size were the optimal configuration for CarbonTracker in the Asian region based on several verifications using CO2 concentration measurements.
BibTeX:
@article{kim17b,
  author = {Kim, Hyunjung and Kim, Hyun Mee and Kim, Jinwoong and Cho, Chun-Ho},
  title = {Effect of data assimilation parameters on the optimized surface CO2 flux in Asia},
  journal = {Asia-Pacific Journal of Atmospheric Sciences},
  year = {2017},
  pages = {1--17},
  doi = {https://doi.org/10.1007/s13143-017-0049-9}
}
Kim, H., Kim, H.M., Cho, M., Park, J. and Kim, D.-H. Development of the Aircraft CO2 Measurement Data Assimilation System to Improve the Estimation of Surface CO2 Fluxes Using an Inverse Modeling System {2018} ATMOSPHERE-KOREA
Vol. {28}({2}), pp. {113-121} 
article DOI  
Abstract: In order to monitor greenhouse gases including CO2, various types of
surface-, aircraft-, and satellite-based measurement projects have been
conducted. These data help understand the variations of greenhouse gases
and are used in atmospheric inverse modeling systems to simulate surface
fluxes for greenhouse gases. CarbonTracker is a system for estimating
surface CO2 flux, using an atmospheric inverse modeling method, based on
only surface observation data. Because of the insufficient surface
observation data available for accurate estimation of the surface CO2
flux, additional observations would be required. In this study, a system
that assimilates aircraft CO2 measurement data in CarbonTracker
(CT2013B) is developed, and the estimated results from this data
assimilation system are evaluated. The aircraft CO2 measurement data
used are obtained from the Comprehensive Observation Network for Trace
gases by the Airliner (CONTRAIL) project. The developed system includes
the preprocessor of the raw observation data, the observation operator,
and the ensemble Kalman filter (EnKF) data assimilation process. After
preprocessing the raw data, the modeled value corresponding spatially
and temporally to each observation is calculated using the observation
operator. These modeled values and observations are then averaged in
space and time, and used in the EnKF data assimilation process. The
modeled values are much closer to the observations and show smaller
biases and root-mean-square errors, after the assimilation of the
aircraft CO2 measurement data. This system could also be used to
assimilate other aircraft CO2 measurement data in CarbonTracker.
BibTeX:
@article{kim18a,
  author = {Kim, Hyunjung and Kim, Hyun Mee and Cho, Minkwang and Park, Jun and Kim, Dae-Hui},
  title = {Development of the Aircraft CO2 Measurement Data Assimilation System to Improve the Estimation of Surface CO2 Fluxes Using an Inverse Modeling System},
  journal = {ATMOSPHERE-KOREA},
  year = {2018},
  volume = {28},
  number = {2},
  pages = {113-121},
  doi = {https://doi.org/10.14191/Atmos.2018.28.2.113}
}
Kim, J., Polavarapu, S.M., Chan, D. and Neish, M. The Canadian atmospheric transport model for simulating greenhouse gas evolution on regional scales: GEM-MACH-GHG v.137-reg {2020} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {13}({1}), pp. {269-295} 
article DOI URL 
Abstract: In this study, we present the development of a regional atmospheric transport model for greenhouse gas (GHG) simulation based on an operational weather forecast model and a chemical transport model at Environment and Climate Change Canada (ECCC), with the goal of improving our understanding of the high-spatiotemporal-resolution interaction between the atmosphere and surface GHG fluxes over Canada and the United States. The regional model uses 10 kmx10 km horizontal grid spacing and 80 vertical levels spanning the ground to 0.1 hPa. The lateral boundary conditions of meteorology and tracers are provided by the global transport model used for GHG simulation at ECCC. The performance of the regional model and added benefit of the regional model over our lower-resolution global models is investigated in terms of modelled CO2 concentration and meteorological forecast quality for multiple seasons in 2015. We find that our regional model has the capability to simulate the high spatial (horizontal and vertical) and temporal scales of atmospheric CO2 concentrations based on comparisons to surface and aircraft observations. In addition, the bias and standard deviation of forecast error in boreal summer are reduced by the regional model. Better representation of model topography in the regional model results in improved simulation of the CO2 diurnal cycle compared to the global model at Walnut Grove, California. The new regional model will form the basis of a flux inversion system that estimates regional-scale fluxes of GHGs over Canada.
BibTeX:
@article{kim20a,
  author = {Kim, Jinwoong and Polavarapu, Saroja M. and Chan, Douglas and Neish, Michael},
  title = {The Canadian atmospheric transport model for simulating greenhouse gas evolution on regional scales: GEM-MACH-GHG v.137-reg},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2020},
  volume = {13},
  number = {1},
  pages = {269--295},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://gmd.copernicus.org/articles/13/269/2020/},
  doi = {https://doi.org/10.5194/gmd-13-269-2020}
}
Kim, J., Polavarapu, S.M., Jones, D.B.A., Chan, D. and Neish, M. The Resolvable Scales of Regional-Scale CO2 Transport in the Context of Imperfect Meteorology: The Predictability of CO2 in a Limited-Area Model 2021 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 126(20) 
article DOI  
Abstract: Transport model error is an important source of uncertainty when
estimating surface CO2 fluxes via an atmospheric model inversion. In
this study, the transport error due to uncertainty of meteorological
fields is investigated with a high resolution, limited-area model. We
characterize the extent to which errors in meteorological initial
conditions (ICs) and lateral boundary conditions (LBCs) impact the
quality of atmospheric CO2 transport across spatial scales. A series of
experiments is conducted using different meteorological ICs and LBCs
that possess varying levels of accuracy. We find that the transport
error of CO2 is more sensitive to errors in meteorology at smaller
scales O(10 km) than at larger scales O(1,000 km), and that surface CO2
fluxes can explain the predictability of CO2 at the largest scales. We
also determine the spatial scales resolvable in the context of uncertain
meteorology. These findings have implications for the development of
regional-scale inverse modeling systems. When assimilating CO2
observations near the surface, using accurate meteorological ICs is
important for resolving fine-scale spatial variability of CO2 because
CO2 transport at lower levels is more sensitive to meteorological ICs
and surface CO2 fluxes than to meteorological LBCs. However, when
assimilating aircraft CO2 measurements or XCO2 satellite retrievals
which contain information at higher altitudes, using accurate
meteorological LBCs is also important. Improvement in meteorological
inputs through a data assimilation system could be helpful in further
resolving finer spatial scales of CO2 at regional scales.
BibTeX:
@article{kim21a,
  author = {Kim, Jinwoong and Polavarapu, Saroja M. and Jones, Dylan B. A. and Chan, Douglas and Neish, Michael},
  title = {The Resolvable Scales of Regional-Scale CO2 Transport in the Context of Imperfect Meteorology: The Predictability of CO2 in a Limited-Area Model},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2021},
  volume = {126},
  number = {20},
  doi = {https://doi.org/10.1029/2021JD034896}
}
Kimball, J.S., Jones, L.A., Glassy, J., Stavros, E.N., Madani, N., Reichle, R.H., Jackson, T. and Colliander, A. Soil Moisture Active Passive Mission L4_C Data Product Assessment (Version 2 Validated Release) 2016   misc URL 
Abstract: The SMAP satellite was successfully launched January 31st 2015, and began acquiring Earth observation data following in-orbit sensor calibration. Global data products derived from the SMAP L-band microwave measurements include Level 1 calibrated and geolocated …
BibTeX:
@misc{kimball16a,
  author = {John S. Kimball and Lucas A. Jones and Joseph Glassy and E. Natasha Stavros and Nima Madani and Rolf H. Reichle and Thomas Jackson and Andreas Colliander},
  title = {Soil Moisture Active Passive Mission L4_C Data Product Assessment (Version 2 Validated Release)},
  year = {2016},
  url = {https://gmao.gsfc.nasa.gov/GMAO_personnel/Reichle_Rolf/other_docs/Kimball852.pdf}
}
King, A.W., Andres, R.J., Davis, K.J., Hafer, M., Hayes, D.J., Huntzinger, D.N., de Jong, B., Kurz, W.A., McGuire, A.D., Vargas, R., Wei, Y., West, T.O. and Woodall, C.W. North America's net terrestrial CO2 exchange with the atmosphere 1990-2009 {2015} BIOGEOSCIENCES
Vol. {12}({2}), pp. 399-414 
article DOI  
Abstract: Scientific understanding of the global carbon cycle is required for
developing national and international policy to mitigate fossil fuel CO2
emissions by managing terrestrial carbon uptake. Toward that
understanding and as a contribution to the REgional Carbon Cycle
Assessment and Processes (RECCAP) project, this paper provides a
synthesis of net land-atmosphere CO2 exchange for North America (Canada,
United States, and Mexico) over the period 1990-2009. Only CO2 is
considered, not methane or other greenhouse gases. This synthesis is
based on results from three different methods: atmospheric inversion,
inventory-based methods and terrestrial biosphere modeling. All methods
indicate that the North American land surface was a sink for atmospheric
CO2, with a net transfer from atmosphere to land. Estimates ranged from
-890 to -280 TgC yr(-1), where the mean of atmospheric inversion
estimates forms the lower bound of that range (a larger land sink) and
the inventory-based estimate using the production approach the upper (a
smaller land sink). This relatively large range is due in part to
differences in how the approaches represent trade, fire and other
disturbances and which ecosystems they include. Integrating across
estimates, ``best'' estimates (i.e., measures of central tendency) are
-472 +/- 281 TgC yr(-1) based on the mean and standard deviation of the
distribution and -360 TgC yr(-1) (with an interquartile range of -496 to
-337) based on the median. Considering both the fossil fuel emissions
source and the land sink, our analysis shows that North America was,
however, a net contributor to the growth of CO2 in the atmosphere in the
late 20th and early 21st century. With North America's mean annual
fossil fuel CO2 emissions for the period 1990-2009 equal to 1720 Tg C
yr(-1) and assuming the estimate of -472 TgC yr(-1) as an approximation
of the true terrestrial CO2 sink, the continent's source : sink ratio
for this time period was 1720 : 472, or nearly 4 : 1.
BibTeX:
@article{king15a,
  author = {King, A. W. and Andres, R. J. and Davis, K. J. and Hafer, M. and Hayes, D. J. and Huntzinger, D. N. and de Jong, B. and Kurz, W. A. and McGuire, A. D. and Vargas, R. and Wei, Y. and West, T. O. and Woodall, C. W.},
  title = {North America's net terrestrial CO2 exchange with the atmosphere 1990-2009},
  journal = {BIOGEOSCIENCES},
  year = {2015},
  volume = {12},
  number = {2},
  pages = {399--414},
  doi = {https://doi.org/10.5194/bg-12-399-2015}
}
Kivi, R. and Heikkinen, P. Fourier transform spectrometer measurements of column CO2 at Sodankyla, Finland {2016} GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS
Vol. {5}({2}), pp. 271-279 
article DOI  
Abstract: Fourier transform spectrometer (FTS) observations at Sodankyla, Finland
(67.4 degrees N, 26.6 degrees E) have been performed since early 2009.
The FTS instrument is participating in the Total Carbon Column Observing
Network (TCCON) and has been optimized to measure abundances of the key
greenhouse gases in the atmosphere. Sodankyla is the only TCCON station
in the Fennoscandia region. Here we report the measured CO2 time series
over a 7-year period (2009-2015) and provide a description of the FTS
system and data processing at Sodankyla. We find the lowest monthly
column CO2 values in August and the highest monthly values during the
February-May season. Inter-annual variability is the highest in the
June-September period, which correlates with the growing season. During
the time period of FTS measurements from 2009 to 2015, we have observed
a 2.2 +/- 0.2 ppm increase per year in column CO2. The monthly mean
column CO2 values have exceeded 400 ppm level for the first time in
February 2014.
BibTeX:
@article{kivi16a,
  author = {Kivi, Rigel and Heikkinen, Pauli},
  title = {Fourier transform spectrometer measurements of column CO2 at Sodankyla, Finland},
  journal = {GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS},
  year = {2016},
  volume = {5},
  number = {2},
  pages = {271--279},
  doi = {https://doi.org/10.5194/gi-5-271-2016}
}
Klappenbach, F., Bertleff, M., Kostinek, J., Hase, F., Blumenstock, T., Agusti-Panareda, A., Razinger, M. and Butz, A. Accurate mobile remote sensing of XCO2 and XCH4 latitudinal transects from aboard a research vessel {2015} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {8}({12}), pp. 5023-5038 
article DOI  
Abstract: A portable Fourier transform spectrometer (FTS), model EM27/SUN, was
deployed onboard the research vessel Polarstern to measure the
column-average dry air mole fractions of carbon dioxide (XCO2) and
methane (XCH4) by means of direct sunlight absorption spectrometry. We
report on technical developments as well as data calibration and
reduction measures required to achieve the targeted accuracy of
fractions of a percent in retrieved XCO2 and XCH4 while operating the
instrument under field conditions onboard the moving platform during a
6-week cruise on the Atlantic from Cape Town (South Africa, 34 degrees
S, 18 degrees E; 5 March 2014) to Bremerhaven (Germany, 54 degrees N, 19
degrees E; 14 April 2014). We demonstrate that our solar tracker
typically achieved a tracking precision of better than 0.05 degrees
toward the center of the sun throughout the ship cruise which
facilitates accurate XCO2 and XCH4 retrievals even under harsh ambient
wind conditions. We define several quality filters that screen spectra,
e.g., when the field of view was partially obstructed by ship structures
or when the lines-of-sight crossed the ship exhaust plume. The
measurements in clean oceanic air, can be used to characterize a
spurious air-mass dependency. After the campaign, deployment of the
spectrometer alongside the TCCON (Total Carbon Column Observing Network)
instrument at Karlsruhe, Germany, allowed for determining a calibration
factor that makes the entire campaign record traceable to World
Meteorological Organization (WMO) standards. Comparisons to observations
of the GOSAT satellite and concentration fields modeled by the European
Centre for Medium-Range Weather Forecasts (ECMWF) Copernicus Atmosphere
Monitoring Service (CAMS) demonstrate that the observational setup is
well suited to provide validation opportunities above the ocean and
along interhemispheric transects.
BibTeX:
@article{klappenbach15a,
  author = {Klappenbach, F. and Bertleff, M. and Kostinek, J. and Hase, F. and Blumenstock, T. and Agusti-Panareda, A. and Razinger, M. and Butz, A.},
  title = {Accurate mobile remote sensing of XCO2 and XCH4 latitudinal transects from aboard a research vessel},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2015},
  volume = {8},
  number = {12},
  pages = {5023--5038},
  doi = {https://doi.org/10.5194/amt-8-5023-2015}
}
Klappenbach, F.W. Mobile spectroscopic measurements of atmospheric carbon dioxide and methane 2016 School: Karlsruher Instituts für Technologie  phdthesis URL 
BibTeX:
@phdthesis{klappenbach16a,
  author = {Klappenbach, Friedrich Wilhelm},
  title = {Mobile spectroscopic measurements of atmospheric carbon dioxide and methane},
  school = {Karlsruher Instituts für Technologie},
  year = {2016},
  url = {https://d-nb.info/1114312576/34}
}
Koffi, E.N., Rayner, P.J., Scholze, M., Chevallier, F. and Kaminski, T. Quantifying the constraint of biospheric process parameters by CO2 concentration and flux measurement networks through a carbon cycle data assimilation system {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({21}), pp. 10555-10572 
article DOI  
Abstract: The sensitivity of the process parameters of the Biosphere Energy
Transfer HYdrology (BETHY) model to choices of atmospheric concentration
network, high frequency terrestrial fluxes, and the choice of flux
measurement network is investigated by using a carbon cycle data
assimilation system. We use BETHY-generated fluxes as a proxy of flux
measurements. Results show that monthly mean or low-frequency
observations of CO2 concentration provide strong constraints on
parameters relevant for net flux (NEP) but only weak constraints for
parameters controlling gross fluxes. The use of high-frequency CO2
concentration observations, which has led to great refinement of spatial
scales in inversions of net flux, adds little to the observing system in
the Carbon Cycle Data Assimilation System (CCDAS) case. This unexpected
result is explained by the fact that the stations of the CO2
concentration network we use are not well placed to measure such high
frequency signals. Indeed, CO2 concentration sensitivities relevant for
such high frequency fluxes are found to be largely confined in the
vicinity of the corresponding fluxes, and are therefore not well
observed by background monitoring stations. In contrast, our results
clearly show the potential of flux measurements to better constrain the
model parameters relevant for gross primary productivity (GPP) and net
primary productivity (NPP). Given uncertainties in the spatial
description of ecosystem functions, we recommend a combined observing
strategy.
BibTeX:
@article{koffi13a,
  author = {Koffi, E. N. and Rayner, P. J. and Scholze, M. and Chevallier, F. and Kaminski, T.},
  title = {Quantifying the constraint of biospheric process parameters by CO2 concentration and flux measurement networks through a carbon cycle data assimilation system},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {21},
  pages = {10555--10572},
  doi = {https://doi.org/10.5194/acp-13-10555-2013}
}
Kondo, M., Ichii, K., Takagi, H. and Sasakawa, M. Comparison of the data-driven top-down and bottom-up global terrestrial CO2 exchanges: GOSAT CO2 inversion and empirical eddy flux upscaling {2015} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {120}({7}), pp. 1226-1245 
article DOI  
Abstract: We examined the consistency between terrestrial biosphere fluxes
(terrestrial CO2 exchanges) from data-driven top-down (GOSAT CO2
inversion) and bottom-up (empirical eddy flux upscaling based on a
support vector regression (SVR) model) approaches over 42 global
terrestrial regions from June 2009 to October 2011. Seasonal variations
of the biosphere fluxes by the two approaches agreed well in boreal and
temperate regions across the Northern Hemisphere. Both fluxes also
exhibited strong anomalous signals in response to contrasting anomalous
spring temperatures observed in North America and boreal Eurasia. This
indicates that the CO2 concentration data integrated in the GOSAT
inversion and the meteorological and vegetation data in the SVR models
are equally effective in producing spatiotemporal variations of
biosphere flux. Meanwhile, large differences in seasonality were found
in subtropical and tropical South America, South Asia, and Africa. The
GOSAT inversion showed seasonal variations that pivoted around CO2
neutral, while the SVR model showed seasonal variations that tended
toward CO2 sink. Thus, a large difference in CO2 budget was identified
between the two approaches in subtropical and tropical regions across
the Southern Hemisphere. Examination of the integrated data revealed
that the large tropical sink of CO2 by the SVR model was an artifact due
to the underrepresented biosphere fluxes predicted by limited eddy flux
data for tropical biomes. Because of the global coverage of CO2
concentration data, the GOSAT inversion provides better estimates of
continental CO2 flux than the SVR model in the Southern Hemisphere.
BibTeX:
@article{kondo15a,
  author = {Kondo, Masayuki and Ichii, Kazuhito and Takagi, Hiroshi and Sasakawa, Motoki},
  title = {Comparison of the data-driven top-down and bottom-up global terrestrial CO2 exchanges: GOSAT CO2 inversion and empirical eddy flux upscaling},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2015},
  volume = {120},
  number = {7},
  pages = {1226--1245},
  doi = {https://doi.org/10.1002/2014JG002866}
}
Kondo, M., Patra, P.K., Sitch, S., Friedlingstein, P., Poulter, B., Chevallier, F., Ciais, P., Canadell, J.G., Bastos, A., Lauerwald, R., Calle, L., Ichii, K., Anthoni, P., Arneth, A., Haverd, V., Jain, A.K., Kato, E., Kautz, M., Law, R.M., Lienert, S., Lombardozzi, D., Maki, T., Nakamura, T., Peylin, P., Rödenbeck, C., Zhuravlev, R., Saeki, T., Tian, H., Zhu, D. and Ziehn, T. State of the science in reconciling top‐down and bottom‐up approaches for terrestrial CO2 budget 2020 GLOBAL CHANGE BIOLOGY
Vol. 26(3), pp. 1068-1084 
article  
Abstract: Robust estimates of CO2 budget, CO2 exchanged between the atmosphere and terrestrial biosphere, are necessary to better understand the role of the terrestrial biosphere in mitigating anthropogenic CO2 emissions. Over the past decade, this field of research has …
BibTeX:
@article{kondo20a,
  author = {Masayuki Kondo and Prabir K. Patra and Stephen Sitch and Pierre Friedlingstein and Benjamin Poulter and Frederic Chevallier and Philippe Ciais and Josep G. Canadell and Ana Bastos and Ronny Lauerwald and Leonardo Calle and Kazuhito Ichii and Peter Anthoni and Almut Arneth and Vanessa Haverd and Atul K. Jain and Etsushi Kato and Markus Kautz and Rachel M. Law and Sebastian Lienert and Danica Lombardozzi and Takashi Maki and Takashi Nakamura and Philippe Peylin and Christian Rödenbeck and Ruslan Zhuravlev and Tazu Saeki and Hanqin Tian and Dan Zhu and Tilo Ziehn},
  title = {State of the science in reconciling top‐down and bottom‐up approaches for terrestrial CO2 budget},
  journal = {GLOBAL CHANGE BIOLOGY},
  year = {2020},
  volume = {26},
  number = {3},
  pages = {1068-1084}
}
Kong, Y., Chen, B. and Measho, S. Spatio-Temporal Consistency Evaluation of XCO2 Retrievals from GOSAT and OCO-2 Based on TCCON and Model Data for Joint Utilization in Carbon Cycle Research {2019} ATMOSPHERE
Vol. {10}({7}) 
article DOI  
Abstract: The global carbon cycle research requires precise and sufficient observations of the column-averaged dry-air mole fraction of CO2 (XCO2) in addition to conventional surface mole fraction observations. In addition, assessing the consistency of multi-satellite data are crucial for joint utilization to better infer information about CO2 sources and sinks. In this work, we evaluate the consistency of long-term XCO2 retrievals from the Greenhouse Gases Observing Satellite (GOSAT), Orbiting Carbon Observatory 2 (OCO-2) in comparison with Total Carbon Column Observing Network (TCCON) and the 3D model of CO2 mole fractions data from CarbonTracker 2017 (CT2017). We create a consistent joint dataset and compare it with the long-term model data to assess their abilities to characterize the carbon cycle climate. The results show that, although slight increasing differences are found between the GOSAT and TCCON XCO2 in the northern temperate latitudes, the GOSAT and OCO-2 XCO2 retrievals agree well in general, with a mean bias +/- standard deviation of differences of 0.21 +/- 1.3 ppm. The differences are almost within +/- 2 ppm and are independent of time, indicating that they are well calibrated. The differences between OCO-2 and CT2017 XCO2 are much larger than those between GOSAT and CT XCO2, which can be attributed to the significantly different spatial representatives of OCO-2 and the CT-transport model 5 (TM5). The time series of the combined OCO-2/GOSAT dataset and the modeled XCO2 agree well, and both can characterize significantly increasing atmospheric CO2 under the impact of a large El Nino during 2015 and 2016. The trend calculated from the dataset using the seasonal Kendall (S-K) method indicates that atmospheric CO2 is increasing by 2-2.6 ppm per year.
BibTeX:
@article{kong19a,
  author = {Kong, Yawen and Chen, Baozhang and Measho, Simon},
  title = {Spatio-Temporal Consistency Evaluation of XCO2 Retrievals from GOSAT and OCO-2 Based on TCCON and Model Data for Joint Utilization in Carbon Cycle Research},
  journal = {ATMOSPHERE},
  publisher = {MDPI},
  year = {2019},
  volume = {10},
  number = {7},
  doi = {https://doi.org/10.3390/atmos10070354}
}
Kong, Y., Zheng, B., Zhang, Q. and He, K. Global and regional carbon budget for 2015-2020 inferred from OCO-2 based on an ensemble Kalman filter coupled with GEOS-Chem 2022 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 22(16), pp. 10769-10788 
article DOI  
Abstract: Understanding carbon sources and sinks across the Earth's surface is
fundamental in climate science and policy; thus, these topics have been
extensively studied but have yet to be fully resolved and are associated
with massive debate regarding the sign and magnitude of the carbon
budget from global to regional scales. Developing new models and
estimates based on state-of-the-art algorithms and data constraints can
provide valuable knowledge and contribute to a final ensemble model in
which various optimal carbon budget estimates are integrated, such as
the annual global carbon budget paper. Here, we develop a new
atmospheric inversion system based on the 4D local ensemble transform
Kalman filter (4D-LETKF) coupled with the GEOS-Chem global transport
model to infer surface-to-atmosphere net carbon fluxes from Orbiting
Carbon Observatory-2 (000-2) Vl0r XCO2 retrievals. The 4D-LETKF
algorithm is adapted to an OCO-2-based global carbon inversion system
for the first time in this work. On average, the mean annual terrestrial
and oceanic fluxes between 2015 and 2020 are estimated as - 2.02 and -
2.34 GtC yr(-1), respectively, compensating for 21 % and 24 %,
respectively, of global fossil carbon dioxide (CO2) emissions (9.80 GtC
yr(-1)). Our inversion results agree with the CO2 atmospheric growth
rates reported by the National Oceanic and Atmospheric Administration
(NOAA) and reduce the modeled CO2 concentration biases relative to the
prior fluxes against surface and aircraft measurements. Our
inversion-based carbon fluxes are broadly consistent with those provided
by other global atmospheric inversion models, although discrepancies
still occur in the land-ocean flux partitioning schemes and seasonal
flux amplitudes over boreal and tropical regions, possibly due to the
sparse observational constraints of the OCO-2 satellite and the
divergent prior fluxes used in different inversion models. Four
sensitivity experiments are performed herein to vary the prior fluxes
and uncertainties in our inversion system, suggesting that regions that
lack OCO-2 coverage are sensitive to the priors, especially over the
tropics and high latitudes. In the further development of our inversion
system, we will optimize the data-assimilation configuration to fully
utilize current observations and increase the spatial and seasonal
representativeness of the prior fluxes over regions that lack
observations.
BibTeX:
@article{kong22a,
  author = {Kong, Yawen and Zheng, Bo and Zhang, Qiang and He, Kebin},
  title = {Global and regional carbon budget for 2015-2020 inferred from OCO-2 based on an ensemble Kalman filter coupled with GEOS-Chem},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2022},
  volume = {22},
  number = {16},
  pages = {10769-10788},
  doi = {https://doi.org/10.5194/acp-22-10769-2022}
}
Konopka, P., Ploeger, F., Tao, M. and Riese, M. Regionally Resolved Diagnostic of Transport: A Simplified Forward Model for CO2 {2017} JOURNAL OF THE ATMOSPHERIC SCIENCES
Vol. {74}({8}), pp. 2689-2700 
article DOI  
Abstract: Simply diagnostic tools are useful for understanding transport processes
in complex chemistry transport models (CTMs). For this purpose, a
combined use of the airmass origin fractions (AOFs) and regionally
resolved mean ages (RMAs) is presented. This approach merges the concept
of the origin of air with the well-known theory of the mean age of air
(AoA) for different regions covering the whole Earth. The authors show
how the AoA calculated relative to Earth's surface can be decomposed
into regionally resolved components (i.e., into RMAs). Using both AOFs
and RMAs, the authors discuss differences in the seasonality of
transport from the Northern and Southern Hemispheres into the tropical
tropopause layer (TTL), the asymmetries of the interhemispheric
exchange, and differences in relation to the continental or oceanic
origin of air. Furthermore, a simplified transport model for a
chemically passive species (tracer) is formulated that has some
potential to approximate the full transport within a CTM. This analytic
approach uses the AOFs as well as the RMAs as parameters to propagate a
tracer prescribed on Earth's surface (lower boundary condition). This
method is exactly valid for sources that change linearly with time in
each of the considered regions. The authors analyze how well this
approach approximates the propagation of CO2 from the planetary boundary
layer (PBL) into the whole atmosphere. The CO2 values in the PBL are
specified by the CarbonTracker dataset. The authors discuss how this
approach can be used for inverse modeling of CO2.
BibTeX:
@article{konopka17a,
  author = {Konopka, Paul and Ploeger, Felix and Tao, Mengchu and Riese, Martin},
  title = {Regionally Resolved Diagnostic of Transport: A Simplified Forward Model for CO2},
  journal = {JOURNAL OF THE ATMOSPHERIC SCIENCES},
  year = {2017},
  volume = {74},
  number = {8},
  pages = {2689--2700},
  doi = {https://doi.org/10.1175/JAS-D-16-0367.1}
}
Konopka, P., Tao, M., Ploeger, F., Diallo, M. and Riese, M. Tropospheric mixing and parametrization of unresolved convective updrafts as implemented in the Chemical Lagrangian Model of the Stratosphere (CLaMS v2.0) {2019} GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. {12}({6}), pp. {2441-2462} 
article DOI URL 
Abstract: Inaccurate representation of mixing in chemistry transport models, mainly suffering from an excessive numerical diffusion, strongly influences the quantitative estimates of the stratosphere-troposphere exchange (STE). The Lagrangian view of transport offers an alternative to exploit the numerical diffusion for parametrization of the physical mixing. Here, we follow this concept and discuss how to extend the representation of tropospheric transport in the Chemical Lagrangian Model of the Stratosphere (CLaMS). Although the current transport scheme in CLaMS (v1.0) shows a good ability to represent transport of tracers in the stably stratified stratosphere (Pommrich et al., 2014, and the references therein), there are deficiencies in the representation of the effects of convective uplift and mixing due to weak vertical stability in the troposphere. We show how the CLaMS transport scheme was modified by including additional tropospheric mixing and vertical transport due to unresolved convective updrafts by parametrizing these processes in terms of the dry and moist Brunt-Vaisala frequencies. The regions with enhanced convective updrafts in the novel CLaMS simulation covering the 2005-2008 period coincide with regions of enhanced convection as diagnosed from the satellite observations of the outgoing longwave radiation (OLR). We analyze how well this approach improves the CLaMS representation of CO2 in the upper troposphere and lower stratosphere, in particular the propagation of the CO2 seasonal cycle from the planetary boundary layer (PBL) into the lower stratosphere. The CO2 values in the PBL are specified by the CarbonTracker data set (version CT2013B), and the Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) observations are used to validate themodel. The proposed extension of tropospheric transport increases the influence of the PBL in the middle and upper troposphere and at the same time impacts the STE. The effect on mean age away from the troposphere in the deep stratosphere is weak.
BibTeX:
@article{konopka19a,
  author = {Konopka, Paul and Tao, Mengchu and Ploeger, Felix and Diallo, Mohamadou and Riese, Martin},
  title = {Tropospheric mixing and parametrization of unresolved convective updrafts as implemented in the Chemical Lagrangian Model of the Stratosphere (CLaMS v2.0)},
  journal = {GEOSCIENTIFIC MODEL DEVELOPMENT},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {12},
  number = {6},
  pages = {2441--2462},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://gmd.copernicus.org/articles/12/2441/2019/},
  doi = {https://doi.org/10.5194/gmd-12-2441-2019}
}
Koren, G., Schneider, L., van der Velde, I.R., van Schaik, E., Gromov, S.S., Adnew, G.A., Martino, D.J.M., Hofmann, M.E.G., Liang, M.-C., Mahata, S., Bergamaschi, P., van der Laan-Luijkx, I.T., Krol, M.C., Rockmann, T. and Peters, W. Global 3-D Simulations of the Triple Oxygen Isotope Signature Delta O-17 in Atmospheric CO2 {2019} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {124}({15}), pp. {8808-8836} 
article DOI  
Abstract: The triple oxygen isotope signature Delta O-17 in atmospheric CO2, also known as its ``O-17 excess,'' has been proposed as a tracer for gross primary production (the gross uptake of CO2 by vegetation through photosynthesis). We present the first global 3-D model simulations for Delta O-17 in atmospheric CO2 together with a detailed model description and sensitivity analyses. In our 3-D model framework we include the stratospheric source of Delta O-17 in CO2 and the surface sinks from vegetation, soils, ocean, biomass burning, and fossil fuel combustion. The effect of oxidation of atmospheric CO on Delta O-17 in CO2 is also included in our model. We estimate that the global mean Delta O-17 (defined as Delta O-17=ln(delta O-17+1)-lambda RL center dot ln(delta O-18+1) with lambda(RL) = 0.5229) of CO2 in the lowest 500m of the atmosphere is 39.6per meg, which is similar to 20per meg lower than estimates from existing box models. We compare our model results with a measured stratospheric Delta O-17 in CO2 profile from Sodankyla (Finland), which shows good agreement. In addition, we compare our model results with tropospheric measurements of Delta O-17 in CO2 from Gottingen (Germany) and Taipei (Taiwan), which shows some agreement but we also find substantial discrepancies that are subsequently discussed. Finally, we show model results for Zotino (Russia), Mauna Loa (United States), Manaus (Brazil), and South Pole, which we propose as possible locations for future measurements of Delta O-17 in tropospheric CO2 that can help to further increase our understanding of the global budget of Delta O-17 in atmospheric CO2.
BibTeX:
@article{koren19a,
  author = {Koren, Gerbrand and Schneider, Linda and van der Velde, Ivar R. and van Schaik, Erik and Gromov, Sergey S. and Adnew, Getachew A. and Martino, Dorota J. Mrozek and Hofmann, Magdalena E. G. and Liang, Mao-Chang and Mahata, Sasadhar and Bergamaschi, Peter and van der Laan-Luijkx, Ingrid T. and Krol, Maarten C. and Rockmann, Thomas and Peters, Wouter},
  title = {Global 3-D Simulations of the Triple Oxygen Isotope Signature Delta O-17 in Atmospheric CO2},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2019},
  volume = {124},
  number = {15},
  pages = {8808--8836},
  doi = {https://doi.org/10.1029/2019JD030387}
}
Kostinek, J., Roiger, A., Eckl, M., Fiehn, A., Luther, A., Wildmann, N., Klausner, T., Fix, A., Knote, C., Stohl, A. and Butz, A. Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling 2020 ATMOSPHERIC CHEMISTRY AND PHYSICS  article URL 
Abstract: Abundant mining and industrial activities located in the Upper Silesian Coal Basin (USCB) lead to large emissions of the potent greenhouse gas (GHG) methane (CH 4). The strong localization of CH 4 emitters (mostly confined to known coal mine ventilation shafts) and the …
BibTeX:
@article{kostinek20a,
  author = {Julian Kostinek and Anke Roiger and Maximilian Eckl and Alina Fiehn and Andreas Luther and Norman Wildmann and Theresa Klausner and Andreas Fix and Christoph Knote and Andreas Stohl and André́ Butz},
  title = {Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2020},
  url = {https://acp.copernicus.org/preprints/acp-2020-962/}
}
Kostinek, J., Roiger, A., Eckl, M., Fiehn, A., Luther, A., Wildmann, N., Klausner, T., Fix, A., Knote, C., Stohl, A. and Butz, A. Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling 2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(11), pp. 8791-8807 
article DOI  
Abstract: Abundant mining and industrial activities located in the Upper Silesian
Coal Basin (USCB) lead to large emissions of the potent greenhouse gas
(GHG) methane (CH4). The strong localization of CH4 emitters (mostly
confined to known coal mine ventilation shafts) and the large emissions
of 448 and 720 kt CH4 yr(-1) reported in the European Pollutant Release
and Transfer Register (E-PRTR 2017) and the Emissions Database for
Global Atmospheric Research (EDGAR v4.3.2), respectively, make the USCB
a prime research target for validating and improving CH4 flux estimation
techniques. High-precision observations of this GHG were made downwind
of local (e.g., single facilities) to regional-scale (e.g.,
agglomerations) sources in the context of the CoMet 1.0 campaign in
early summer 2018. A quantum cascade-interband cascade laser
(QCL-ICL)-based spectrometer adapted for airborne research was deployed
aboard the German Aerospace Center (DLR) Cessna 208B to sample the
planetary boundary layer (PBL) in situ. Regional CH4 emission estimates
for the USCB are derived using a model approach including assimilated
wind soundings from three ground-based Doppler lidars. Although
retrieving estimates for individual emitters is difficult using only
single flights due to sparse data availability, the combination of two
flights allows for exploiting different meteorological conditions
(analogous to a sparse tomography algorithm) to establish confidence on
facility-level estimates. Emission rates from individual sources not
only are needed for unambiguous comparisons between bottom-up and
top-down inventories but also become indispensable if (independently
verifiable) sanctions are to be imposed on individual companies emitting
GHGs. An uncertainty analysis is presented for both the regional-scale
and facility-level emission estimates. We find instantaneous coal mine
emission estimates of 451/423 +/- 77/79 kt CH4 yr(-1) for the
morning/afternoon flight of 6 June 2018. The derived fuel-exploitation
emission rates coincide (+/- 6 %) with annual-average inventorial data
from E-PRTR 2017 although they are distinctly lower (-28 %/-32 %) than
values reported in EDGAR v4.3.2. Discrepancies in available emission
inventories could potentially be narrowed down with sufficient
observations using the method described herein to bridge the gap between
instantaneous emission estimates and yearly averaged inventories.
BibTeX:
@article{kostinek21a,
  author = {Kostinek, Julian and Roiger, Anke and Eckl, Maximilian and Fiehn, Alina and Luther, Andreas and Wildmann, Norman and Klausner, Theresa and Fix, Andreas and Knote, Christoph and Stohl, Andreas and Butz, Andre},
  title = {Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2021},
  volume = {21},
  number = {11},
  pages = {8791-8807},
  doi = {https://doi.org/10.5194/acp-21-8791-2021}
}
Xing-Xia, K., Zhang, M.-G. and Peng, Z. Numerical Simulation of CO2 Concentrations in East Asia with RAMS-CMAQ 2013 Atmospheric and Oceanic Science Letters
Vol. 6(4), pp. 179-184 
article  
BibTeX:
@article{kou13a,
  author = {Kou Xing-Xia and Zhang, Mei-Gen and Peng, Zhen},
  title = {Numerical Simulation of CO2 Concentrations in East Asia with RAMS-CMAQ},
  journal = {Atmospheric and Oceanic Science Letters},
  year = {2013},
  volume = {6},
  number = {4},
  pages = {179--184}
}
Kou, X., Zhang, M., Peng, Z. and Wang, Y. Assessment of the biospheric contribution to surface atmospheric CO2 concentrations over East Asia with a regional chemical transport model {2015} ADVANCES IN ATMOSPHERIC SCIENCES
Vol. {32}({3}), pp. 287-300 
article DOI  
Abstract: A regional chemical transport model, RAMS-CMAQ, was employed to assess
the impacts of biosphere-atmosphere C-2 exchange on seasonal variations
in atmospheric C-2 concentrations over East Asia. Simulated C-2
concentrations were compared with observations at 12 surface stations
and the comparison showed they were generally in good agreement. Both
observations and simulations suggested that surface C-2 over East Asia
features a summertime trough due to biospheric absorption, while in some
urban areas surface C-2 has a distinct summer peak, which could be
attributed to the strong impact from anthropogenic emissions. Analysis
of the model results indicated that biospheric fluxes and fossil-fuel
emissions are comparably important in shaping spatial distributions of
C-2 near the surface over East Asia. Biospheric flux plays an important
role in the prevailing spatial pattern of C-2 enhancement and reduction
on the synoptic scale due to the strong seasonality of biospheric C-2
flux. The elevation of C-2 levels by the biosphere during winter was
found to be larger than 5 ppm in North China and Southeast China, and
during summertime a significant depletion (a (c) 3/4 7 ppm) occurred in
most areas, except for the Indo-China Peninsula where positive bioflux
values were found.
BibTeX:
@article{kou15a,
  author = {Kou, Xingxia and Zhang, Meigen and Peng, Zhen and Wang, Yinghong},
  title = {Assessment of the biospheric contribution to surface atmospheric CO2 concentrations over East Asia with a regional chemical transport model},
  journal = {ADVANCES IN ATMOSPHERIC SCIENCES},
  year = {2015},
  volume = {32},
  number = {3},
  pages = {287--300},
  doi = {https://doi.org/10.1007/s00376-014-4059-6}
}
Kou, X., Tian, X., Zhang, M., Peng, Z. and Zhang, X. Accounting for CO2 Variability over East Asia with a Regional Joint Inversion System and Its Preliminary Evaluation {2017} JOURNAL OF METEOROLOGICAL RESEARCH
Vol. {31}({5}), pp. 834-851 
article DOI  
Abstract: A regional surface carbon dioxide (CO2) flux inversion system, the
Tan-Tracker-Region, was developed by incorporating an assimilation
scheme into the Community Multiscale Air Quality (CMAQ) regional
chemical transport model to resolve fine-scale CO2 variability over East
Asia. The proper orthogonal decomposition-based ensemble
four-dimensional variational data assimilation approach (POD-4DVar) is
the core algorithm for the joint assimilation framework, and
simultaneous assimilations of CO2 concentrations and surface CO2 fluxes
are applied to help reduce the uncertainty in initial CO2
concentrations. A persistence dynamical model was developed to describe
the evolution of the surface CO2 fluxes and help avoid the
``signal-to-noise'' problem; thus, CO2 fluxes could be estimated as a
whole at the model grid scale, with better use of observation
information. The performance of the regional inversion system was
evaluated through a group of single-observation-based observing system
simulation experiments (OSSEs). The results of the experiments suggest
that a reliable performance of Tan-Tracker-Region is dependent on
certain assimilation parameter choices, for example, an optimized window
length of approximately 3 h, an ensemble size of approximately 100, and
a covariance localization radius of approximately 320 km. This is
probably due to the strong diurnal variation and spatial heterogeneity
in the fine-scale CMAQ simulation, which could affect the performance of
the regional inversion system. In addition, because all observations can
be artificially obtained in OSSEs, the performance of Tan-Tracker-Region
was further evaluated through different densities of the artificial
observation network in different CO2 flux situations. The results
indicate that more observation sites would be useful to systematically
improve the estimation of CO2 concentration and flux in large areas over
the model domain. The work presented here forms a foundation for future
research in which a thorough estimation of CO2 flux variability over
East Asia could be performed with the regional inversion system.
BibTeX:
@article{kou17a,
  author = {Kou, Xingxia and Tian, Xiangjun and Zhang, Meigen and Peng, Zhen and Zhang, Xiaoling},
  title = {Accounting for CO2 Variability over East Asia with a Regional Joint Inversion System and Its Preliminary Evaluation},
  journal = {JOURNAL OF METEOROLOGICAL RESEARCH},
  year = {2017},
  volume = {31},
  number = {5},
  pages = {834--851},
  doi = {https://doi.org/10.1007/s13351-017-6149-8}
}
Kountouris, P., Gerbig, C., Totsche, K.U., Dolman, A.J., Meesters, A.G.C.A., Broquet, G., Maignan, F., Gioli, B., Montagnani, L. and Helfter, C. An objective prior error quantification for regional atmospheric inverse applications {2015} BIOGEOSCIENCES
Vol. {12}({24}), pp. 7403-7421 
article  
Abstract: Assigning proper prior uncertainties for inverse modelling of CO2 is of
high importance, both to regularise the otherwise ill-constrained
inverse problem and to quantitatively characterise the magnitude and
structure of the error between prior and `true' flux. We use surface
fluxes derived from three biosphere models - VPRM, ORCHIDEE, and 5PM -
and compare them against daily averaged fluxes from 53 eddy covariance
sites across Europe for the year 2007 and against repeated aircraft flux
measurements encompassing spatial transects. In addition we create
synthetic observations using modelled fluxes instead of the observed
ones to explore the potential to infer prior uncertainties from
model-model residuals. To ensure the realism of the synthetic data
analysis, a random measurement noise was added to the modelled tower
fluxes which were used as reference. The temporal autocorrelation time
for tower model-data residuals was found to be around 30 days for both
VPRM and ORCHIDEE but significantly different for the 5PM model with 70
days. This difference is caused by a few sites with large biases between
the data and the 5PM model. The spatial correlation of the model-data
residuals for all models was found to be very short, up to few tens of
kilometres but with uncertainties up to 100 % of this estimation.
Propagating this error structure to annual continental scale yields an
uncertainty of 0.06 Gt C and strongly underestimates uncertainties
typically used from atmospheric inversion systems, revealing another
potential source of errors. Long spatial e-folding correlation lengths
up to several hundreds of kilometres were determined when synthetic data
were used. Results from repeated aircraft transects in south-western
France are consistent with those obtained from the tower sites in terms
of spatial autocorrelation (35 km on average) while temporal
autocorrelation is markedly lower (13 days). Our findings suggest that
the different prior models have a common temporal error structure.
Separating the analysis of the statistics for the model data residuals
by seasons did not result in any significant differences of the spatial
e-folding correlation lengths.
BibTeX:
@article{kountouris15a,
  author = {Kountouris, P. and Gerbig, C. and Totsche, K. -U. and Dolman, A. J. and Meesters, A. G. C. A. and Broquet, G. and Maignan, F. and Gioli, B. and Montagnani, L. and Helfter, C.},
  title = {An objective prior error quantification for regional atmospheric inverse applications},
  journal = {BIOGEOSCIENCES},
  year = {2015},
  volume = {12},
  number = {24},
  pages = {7403--7421}
}
Kountouris, P., Gerbig, C., Rodenbeck, C., Karstens, U., Koch, T.F. and Heimann, M. Technical Note: Atmospheric CO2 inversions on the mesoscale using data-driven prior uncertainties: methodology and system evaluation {2018} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {18}({4}), pp. {3027-3045} 
article DOI  
Abstract: Atmospheric inversions are widely used in the optimization of surface
carbon fluxes on a regional scale using information from atmospheric CO2
dry mole fractions. In many studies the prior flux uncertainty applied
to the inversion schemes does not directly reflect the true flux
uncertainties but is used to regularize the inverse problem. Here, we
aim to implement an inversion scheme using the Jena inversion system and
applying a prior flux error structure derived from a model-data residual
analysis using high spatial and temporal resolution over a full year
period in the European domain. We analyzed the performance of the
inversion system with a synthetic experiment, in which the flux
constraint is derived following the same residual analysis but applied
to the model-model mismatch. The synthetic study showed a quite good
agreement between posterior and ``true'' fluxes on European, country,
annual and monthly scales. Posterior monthly and country-aggregated
fluxes improved their correlation coefficient with the ``known truth''
by 7% compared to the prior estimates when compared to the reference,
with a mean correlation of 0.92. The ratio of the SD between the
posterior and reference and between the prior and reference was also
reduced by 33% with a mean value of 1.15. We identified temporal and
spatial scales on which the inversion system maximizes the derived
information; monthly temporal scales at around 200 km spatial resolution
seem to maximize the information gain.
BibTeX:
@article{kountouris18a,
  author = {Kountouris, Panagiotis and Gerbig, Christoph and Rodenbeck, Christian and Karstens, Ute and Koch, Thomas Frank and Heimann, Martin},
  title = {Technical Note: Atmospheric CO2 inversions on the mesoscale using data-driven prior uncertainties: methodology and system evaluation},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2018},
  volume = {18},
  number = {4},
  pages = {3027-3045},
  doi = {https://doi.org/10.5194/acp-18-3027-2018}
}
Koven, C.D. Role of CO2, climate and land use in regulating the seasonal amplitude increase of carbon fluxes in terrestrial ecosystems: a multimodel analysis 2016 Biogeosciences
Vol. 13(17), pp. 5121 
article URL 
BibTeX:
@article{koven16a,
  author = {Koven, Charles D},
  title = {Role of CO2, climate and land use in regulating the seasonal amplitude increase of carbon fluxes in terrestrial ecosystems: a multimodel analysis},
  journal = {Biogeosciences},
  year = {2016},
  volume = {13},
  number = {17},
  pages = {5121},
  url = {http://search.proquest.com/openview/6b2e171c3b3e9903f77f7fd2002927a3/1?pq-origsite=gscholar&cbl=105740}
}
Kretschmer, R., Gerbig, C., Karstens, U. and Koch, F.T. Error characterization of CO2 vertical mixing in the atmospheric transport model WRF-VPRM {2012} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {12}({5}), pp. 2441-2458 
article DOI  
Abstract: One of the dominant uncertainties in inverse estimates of regional CO2
surface-atmosphere fluxes is related to model errors in vertical
transport within the planetary boundary layer (PBL). In this study we
present the results from a synthetic experiment using the atmospheric
model WRF-VPRM to realistically simulate transport of CO2 for large
parts of the European continent at 10 km spatial resolution. To
elucidate the impact of vertical mixing error on modeled CO2 mixing
ratios we simulated a month during the growing season (August 2006) with
different commonly used parameterizations of the PBL
(Mellor-Yamada-JanjiA double dagger (MYJ) and Yonsei-University (YSU)
scheme). To isolate the effect of transport errors we prescribed the
same CO2 surface fluxes for both simulations. Differences in simulated
CO2 mixing ratios (model bias) were on the order of 3 ppm during daytime
with larger values at night. We present a simple method to reduce this
bias by 70-80% when the true height of the mixed layer is known.
BibTeX:
@article{kretschmer12a,
  author = {Kretschmer, R. and Gerbig, C. and Karstens, U. and Koch, F. -T.},
  title = {Error characterization of CO2 vertical mixing in the atmospheric transport model WRF-VPRM},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2012},
  volume = {12},
  number = {5},
  pages = {2441--2458},
  doi = {https://doi.org/10.5194/acp-12-2441-2012}
}
Kubicki, J.D. and Watts, H.D. Quantum Mechanical Modeling of the Vibrational Spectra of Minerals with a Focus on Clays {2019} MINERALS
Vol. {9}({3}) 
article DOI  
Abstract: We present an overview of how to use quantum mechanical calculations to predict vibrational frequencies of molecules and materials such as clays and silicates. Other methods of estimating vibrational frequencies are mentioned, such as classical molecular dynamics simulations; references are given for additional information on these approaches. Herein, we discuss basic vibrational theory, calculating Raman and infrared intensities, steps for creating realistic models, and applications to spectroscopy, thermodynamics, and isotopic fractionation. There are a wide variety of programs and methods that can be employed to model vibrational spectra, but this work focuses on hybrid density functional theory (DFT) approaches. Many of the principles are the same when used in other programs and DFT methods, so a novice can benefit from simple examples that illustrate key points to consider when modeling vibrational spectra. Other methods and programs are listed to give the beginner a starting point for exploring and choosing which approach will be best for a given problem. The modeler should also be aware of the numerous analytical methods available for obtaining information on vibrations of atoms in molecules and materials. In addition to traditional infrared and Raman spectroscopy, sum-frequency generation (SFG) and inelastic neutron scattering (INS) are also excellent techniques for obtaining vibrational frequency information in certain circumstances.
BibTeX:
@article{kubicki19a,
  author = {Kubicki, James D. and Watts, Heath D.},
  title = {Quantum Mechanical Modeling of the Vibrational Spectra of Minerals with a Focus on Clays},
  journal = {MINERALS},
  publisher = {MDPI},
  year = {2019},
  volume = {9},
  number = {3},
  doi = {https://doi.org/10.3390/min9030141}
}
Kulawik, S.S., Jones, D.B.A., Nassar, R., Irion, F.W., Worden, J.R., Bowman, K.W., Machida, T., Matsueda, H., Sawa, Y., Biraud, S.C., Fischer, M.L. and Jacobson, A.R. Characterization of Tropospheric Emission Spectrometer (TES) CO2 for carbon cycle science {2010} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {10}({12}), pp. 5601-5623 
article DOI  
BibTeX:
@article{kulawik10a,
  author = {Kulawik, S. S. and Jones, D. B. A. and Nassar, R. and Irion, F. W. and Worden, J. R. and Bowman, K. W. and Machida, T. and Matsueda, H. and Sawa, Y. and Biraud, S. C. and Fischer, M. L. and Jacobson, A. R.},
  title = {Characterization of Tropospheric Emission Spectrometer (TES) CO2 for carbon cycle science},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2010},
  volume = {10},
  number = {12},
  pages = {5601--5623},
  doi = {https://doi.org/10.5194/acp-10-5601-2010}
}
Kulawik, S.S., Worden, J.R., Wofsy, S.C., Biraud, S.C., Nassar, R., Jones, D.B.A., Olsen, E.T., Jimenez, R., Park, S., Santoni, G.W., Daube, B.C., Pittman, J.V., Stephens, B.B., Kort, E.A., Osterman, G.B. and Team, T. Comparison of improved Aura Tropospheric Emission Spectrometer CO2 with HIPPO and SGP aircraft profile measurements {2013} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {13}({6}), pp. 3205-3225 
article DOI  
BibTeX:
@article{kulawik13a,
  author = {Kulawik, S. S. and Worden, J. R. and Wofsy, S. C. and Biraud, S. C. and Nassar, R. and Jones, D. B. A. and Olsen, E. T. and Jimenez, R. and Park, S. and Santoni, G. W. and Daube, B. C. and Pittman, J. V. and Stephens, B. B. and Kort, E. A. and Osterman, G. B. and TES Team},
  title = {Comparison of improved Aura Tropospheric Emission Spectrometer CO2 with HIPPO and SGP aircraft profile measurements},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2013},
  volume = {13},
  number = {6},
  pages = {3205--3225},
  doi = {https://doi.org/10.5194/acp-13-3205-2013}
}
Kulawik, S., Wunch, D., O'Dell, C., Frankenberg, C., Reuter, M., Oda, T., Chevallier, F., Sherlock, V., Buchwitz, M., Osterman, G., Miller, C.E., Wennberg, P.O., Griffith, D., Morino, I., Dubey, M.K., Deutscher, N.M., Notholt, J., Hase, F., Warneke, T., Sussmann, R., Robinson, J., Strong, K., Schneider, M., De Maziere, M., Shiomi, K., Feist, D.G., Iraci, L.T. and Wolf, J. Consistent evaluation of ACOS-GOSAT, BESD-SCIAMACHY, CarbonTracker, and MACC through comparisons to TCCON {2016} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {9}({2}), pp. 683-709 
article DOI  
Abstract: Consistent validation of satellite CO2 estimates is a prerequisite for
using multiple satellite CO2 measurements for joint flux inversion, and
for establishing an accurate long-term atmospheric CO2 data record.
Harmonizing satellite CO2 measurements is particularly important since
the differences in instruments, observing geometries, sampling
strategies, etc. imbue different measurement characteristics in the
various satellite CO2 data products. We focus on validating model and
satellite observation attributes that impact flux estimates and CO2
assimilation, including accurate error estimates, correlated and random
errors, overall biases, biases by season and latitude, the impact of
coincidence criteria, validation of seasonal cycle phase and amplitude,
yearly growth, and daily variability. We evaluate dry-air mole fraction
(X-CO2) for Greenhouse gases Observing SATellite (GOSAT) (Atmospheric
CO2 Observations from Space, ACOS b3.5) and SCanning Imaging Absorption
spectroMeter for Atmospheric CHartographY (SCIAMACHY) (Bremen Optimal
Estimation DOAS, BESD v2.00.08) as well as the CarbonTracker (CT2013b)
simulated CO2 mole fraction fields and the Monitoring Atmospheric
Composition and Climate (MACC) CO2 inversion system (v13.1) and compare
these to Total Carbon Column Observing Network (TCCON) observations
(GGG2012/2014). We find standard deviations of 0.9, 0.9, 1.7, and 2.1
ppm vs. TCCON for CT2013b, MACC, GOSAT, and SCIAMACHY, respectively,
with the single observation errors 1.9 and 0.9 times the predicted
errors for GOSAT and SCIAMACHY, respectively. We quantify how satellite
error drops with data averaging by interpreting according to error(2) =
a(2) + b(2) / n (with n being the number of observations averaged, a the
systematic (correlated) errors, and b the random (uncorrelated) errors).
a and b are estimated by satellites, coincidence criteria, and
hemisphere. Biases at individual stations have year-to-year variability
of similar to 0.3 ppm, with biases larger than the TCCON-predicted bias
uncertainty of 0.4 ppm at many stations. We find that GOSAT and CT2013b
underpredict the seasonal cycle amplitude in the Northern Hemisphere
(NH) between 46 and 53 degrees N, MACC overpredicts between 26 and 37
ffi N, and CT2013b underpredicts the seasonal cycle amplitude in the
Southern Hemisphere (SH). The seasonal cycle phase indicates whether a
data set or model lags another data set in time. We find that the GOSAT
measurements improve the seasonal cycle phase substantially over the
prior while SCIAMACHY measurements improve the phase significantly for
just two of seven sites. The models reproduce the measured seasonal
cycle phase well except for at Lauder_125HR (CT2013b) and Darwin
(MACC). We compare the variability within 1 day between TCCON and models
in JJA; there is correlation between 0.2 and 0.8 in the NH, with models
showing 10-50% the variability of TCCON at different stations and
CT2013b showing more variability than MACC. This paper highlights
findings that provide inputs to estimate flux errors in model
assimilations, and places where models and satellites need further
investigation, e.g., the SH for models and 4567 ffi N for GOSAT and
CT2013b.
BibTeX:
@article{kulawik16a,
  author = {Kulawik, Susan and Wunch, Debra and O'Dell, Christopher and Frankenberg, Christian and Reuter, Maximilian and Oda, Tomohiro and Chevallier, Frederic and Sherlock, Vanessa and Buchwitz, Michael and Osterman, Greg and Miller, Charles E. and Wennberg, Paul O. and Griffith, David and Morino, Isamu and Dubey, Manvendra K. and Deutscher, Nicholas M. and Notholt, Justus and Hase, Frank and Warneke, Thorsten and Sussmann, Ralf and Robinson, John and Strong, Kimberly and Schneider, Matthias and De Maziere, Martine and Shiomi, Kei and Feist, Dietrich G. and Iraci, Laura T. and Wolf, Joyce},
  title = {Consistent evaluation of ACOS-GOSAT, BESD-SCIAMACHY, CarbonTracker, and MACC through comparisons to TCCON},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2016},
  volume = {9},
  number = {2},
  pages = {683--709},
  doi = {https://doi.org/10.5194/amt-9-683-2016}
}
Kulawik, S.S., O'Dell, C., Payne, V.H., Kuai, L., Worden, H.M., Biraud, S.C., Sweeney, C., Stephens, B., Iraci, L.T., Yates, E.L. and Tanaka, T. Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations {2017} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {17}({8}), pp. 5407-5438 
article DOI  
Abstract: We present two new products from near-infrared Greenhouse Gases
Observing Satellite (GOSAT) observations: lowermost tropospheric (LMT,
from 0 to 2.5 km) and upper tropospheric-stratospheric (U, above 2.5 km)
carbon dioxide partial column mixing ratios. We compare these new
products to aircraft profiles and remote surface flask measurements and
find that the seasonal and year-to-year variations in the new partial
column mixing ratios significantly improve upon the Atmospheric CO2
Observations from Space (ACOS) and GOSAT (ACOS-GOSAT) initial guess
and/or a priori, with distinct patterns in the LMT and U seasonal cycles
that match validation data. For land monthly averages, we find errors of
1.9, 0.7, and 0.8 ppm for retrieved GOSAT LMT, U, and X CO2; for ocean
monthly averages, we find errors of 0.7, 0.5, and 0.5 ppm for retrieved
GOSAT LMT, U, and X CO2. In the southern hemispheric biomass burning
season, the new partial columns show similar patterns to MODIS fire maps
and MOPITT multispectral CO for both vertical levels, despite a flat
ACOS-GOSAT prior, and a CO-CO2 emission factor comparable to published
values. The difference of LMT and U, useful for evaluation of model
transport error, has also been validated with a monthly average error of
0.8 (1.4) ppm for ocean (land). LMT is more locally influenced than U,
meaning that local fluxes can now be better separated from CO2
transported from far away.
BibTeX:
@article{kulawik17a,
  author = {Kulawik, Susan S. and O'Dell, Chris and Payne, Vivienne H. and Kuai, Le and Worden, Helen M. and Biraud, Sebastien C. and Sweeney, Colm and Stephens, Britton and Iraci, Laura T. and Yates, Emma L. and Tanaka, Tomoaki},
  title = {Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2017},
  volume = {17},
  number = {8},
  pages = {5407--5438},
  doi = {https://doi.org/10.5194/acp-17-5407-2017}
}
Kumar, K.R., Tiwari, Y.K., Valsala, V. and Murtugudde, R. On understanding the land-ocean CO2 contrast over the Bay of Bengal: A case study during 2009 summer monsoon {2014} ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Vol. {21}({7}), pp. 5066-5075 
article DOI  
Abstract: Ship-based observations of atmospheric carbon dioxide (CO2)
concentration over the Bay of Bengal (BoB) between 17 July 2009 and 17
Aug 2009 offered an excellent opportunity to evaluate the land-ocean
contrast of surface CO2 and facilitated its comparison with model
simulated CO2 concentrations. Elevated values of CO2 with large
variability near the coastal region and relatively low values with
correspondingly lower variability over the open ocean suggest that this
observed CO2 variability over the ocean essentially captures the
differences in terrestrial and oceanic CO2 fluxes. Although the region
under investigation is well known for its atmospheric intraseasonal
oscillations of Indian summer monsoon during July and August, the
limited duration of observations performed from a moving ship in a
research cruise, is not able to capture any high-frequency variability
of atmospheric CO2 concentrations. But band-passed sea surface
temperature and wind anomalies do indicate strong intraseasonal
variability over the study region during the observational period. The
synoptic data, albeit quite short in duration, thus offer a clear
benchmark for abrupt variability of CO2 concentration between land and
ocean.
BibTeX:
@article{kumar14a,
  author = {Kumar, K. Ravi and Tiwari, Yogesh K. and Valsala, Vinu and Murtugudde, Raghu},
  title = {On understanding the land-ocean CO2 contrast over the Bay of Bengal: A case study during 2009 summer monsoon},
  journal = {ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH},
  year = {2014},
  volume = {21},
  number = {7},
  pages = {5066--5075},
  doi = {https://doi.org/10.1007/s11356-013-2386-2}
}
Kumar, K.R., Valsala, V., Tiwari, Y.K., Revadekar, J.V., Pillai, P., Chakraborty, S. and Murtugudde, R. Intra-seasonal variability of atmospheric CO2 concentrations over India during summer monsoons {2016} ATMOSPHERIC ENVIRONMENT
Vol. {142}, pp. 229-237 
article DOI  
Abstract: In a study based on a data assimilation product of the terrestrial
biospheric fluxes of CO2 over India, the subcontinent was hypothesized
to be an anomalous source (sink) of CO2 during the active (break) spells
of rain in the summer monsoon from June to September (Valsala et al.,
2013). We test this hypothesis here by investigating intraseasonal
variability in the atmospheric CO2 concentrations over India by
utilizing a combination of ground-based and satellite observations and
model outputs. The results show that the atmospheric CO2 concentration
also varies in synchrony with the active and break spells of rainfall
with amplitude of +/- 2 ppm which is above the instrumental uncertainty
of the present day techniques of atmospheric CO2 measurements. The
result is also consistent with the signs of the Net Ecosystem Exchange
(NEE) flux anomalies estimated in our earlier work. The study thus
offers the first observational affirmation of the above hypothesis
although the data gap in the satellite measurements during monsoon
season and the limited ground-based stations over India still leaves
some uncertainty in the robust assertion of the hypothesis. The study
highlights the need to capture these subtle variabilities and their
responses to climate variability and change since it has implications
for inverse estimates of terrestrial CO2 fluxes. (C) 2016 Elsevier Ltd.
All rights reserved.
BibTeX:
@article{kumar16a,
  author = {Kumar, K. Ravi and Valsala, Vinu and Tiwari, Yogesh K. and Revadekar, J. V. and Pillai, Prasanth and Chakraborty, Supriyo and Murtugudde, Raghu},
  title = {Intra-seasonal variability of atmospheric CO2 concentrations over India during summer monsoons},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2016},
  volume = {142},
  pages = {229--237},
  doi = {https://doi.org/10.1016/j.atmosenv.2016.07.023}
}
Kurz, W.A., Shaw, C.H., Boisvenue, C., Stinson, G., Metsaranta, J., Leckie, D., Dyk, A., Smyth, C. and Neilson, E.T. Carbon in Canada's boreal forest - A synthesis {2013} ENVIRONMENTAL REVIEWS
Vol. {21}({4}), pp. 260-292 
article DOI  
Abstract: Canada's managed boreal forest, 54% of the nation's total boreal forest
area, stores 28 Pg carbon (C) in biomass, dead organic matter, and soil
pools. The net C balance is dominated by the difference of two large
continuous fluxes: C uptake (net primary production) and release during
decomposition (heterotrophic respiration). Additional releases of C can
be high in years, or in areas, that experience large anthropogenic or
natural disturbances. From 1990 to 2008, Canada's managed boreal forest
has acted as C sink of 28 Tg C year(-1), removing CO2 from the
atmosphere to replace the 17 Tg of C annually harvested and store an
additional 11 Tg of C year-1 in ecosystem C pools. A large fraction
(similar to 57%) of the C harvested since 1990 remains stored in wood
products and solid waste disposal sites in Canada and abroad, replacing
C emitted from the decay or burning of wood harvested prior to 1990 and
contributing to net increases in product and landfill C pools. Wood
product use has reduced emissions in other sectors by substituting for
emission-intensive products (concrete, steel). The C balance of the
unmanaged boreal forest is currently unknown. The future C balance of
the Canadian boreal forest will affect the global atmospheric C budget
and influence the mitigation efforts required to attain atmospheric CO2
stabilization targets. The single biggest threat to C stocks is
human-caused climate change. Large C stocks have accumulated in the
boreal because decomposition is limited by cold temperatures and often
anoxic environments. Increases in temperatures and disturbance rates
could result in a large net C source during the remainder of this
century and beyond. Uncertainties about the impacts of global change
remain high, but we emphasize the asymmetry of risk: sustained
large-scale increases in productivity are unlikely to be of sufficient
magnitude to offset higher emissions from increased disturbances and
heterotrophic respiration. Reducing the uncertainties of the current and
future C balance of Canada's 270 Mha of boreal forest requires
addressing gaps in monitoring, observation, and quantification of forest
C dynamics, with particular attention to 125 Mha of unmanaged boreal
forest with extensive areas of deep organic soils, peatlands, and
permafrost containing large quantities of C that are vulnerable to
global warming.
BibTeX:
@article{kurz13a,
  author = {Kurz, W. A. and Shaw, C. H. and Boisvenue, C. and Stinson, G. and Metsaranta, J. and Leckie, D. and Dyk, A. and Smyth, C. and Neilson, E. T.},
  title = {Carbon in Canada's boreal forest - A synthesis},
  journal = {ENVIRONMENTAL REVIEWS},
  year = {2013},
  volume = {21},
  number = {4},
  pages = {260--292},
  doi = {https://doi.org/10.1139/er-2013-0041}
}
Kuze, A., Nakamura, Y., Oda, T., Yoshida, J., Kikuchi, N., Kataoka, F., Suto, H. and Shiomi, K. Examining partial-column density retrieval of lower-tropospheric CO2 from GOSAT target observations over global megacities 2022 REMOTE SENSING OF ENVIRONMENT
Vol. 273 
article DOI  
Abstract: We retrieved and examined the partial-column densities of carbon dioxide
(CO2) in the lower (LT, typically 0-4 km) and upper (UT, typically 4-12
km) troposphere (XCO2LT and XCO2UT) collected over six global
megacities: Beijing, New Delhi, New York City, Riyadh, Shanghai, and
Tokyo. The radiance spectra were collected using the Thermal And
Near-infrared Sensor for carbon Observation Fourier-Transform
Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing
SATellite (GOSAT). Our retrieval method uniquely utilizes reflected
sunlight with two orthogonal components of polarization and thermal
emissions. We defined megacity concentration enhancement due to surface
CO2 emissions as XCO2LT minus XCO2UT, allowing us to overcome some of
the challenges in the enhancement analysis using existing column density
data. We examined the relationship between the XCO2LT enhancements from
the time series of intensive target observations over megacities and the
inverse of simulated wind speed, which could be potentially used to
estimate surface emissions. Next, we attempted to estimate the average
emission intensity for each city from the linear regression slope. We
also compared our obtained emission estimates with the Open-Data
Inventory for Anthropogenic CO2 (ODIAC) inventory for evaluation. Our
results demonstrate the potential utility of the new partial-column
density retrievals for estimating megacity CO2 emissions. More frequent
and comprehensive coverage characterizing the spatial distribution of
emissions is necessary to reduce random error and bias associated with
the obtained estimate.
BibTeX:
@article{kuze22a,
  author = {Kuze, A. and Nakamura, Y. and Oda, T. and Yoshida, J. and Kikuchi, N. and Kataoka, F. and Suto, H. and Shiomi, K.},
  title = {Examining partial-column density retrieval of lower-tropospheric CO2 from GOSAT target observations over global megacities},
  journal = {REMOTE SENSING OF ENVIRONMENT},
  year = {2022},
  volume = {273},
  doi = {https://doi.org/10.1016/j.rse.2022.112966}
}
LaFranchi, B.W., McFarlane, K.J., Miller, J.B., Lehman, S.J., Phillips, C.L., Andrews, A.E., Tans, P.P., Chen, H., Liu, Z., Turnbull, J.C., Xu, X. and Guilderson, T.P. Strong regional atmospheric C-14 signature of respired CO2 observed from a tall tower over the midwestern United States {2016} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {121}({8}), pp. 2275-2295 
article DOI  
Abstract: Radiocarbon in CO2 ((CO2)-C-14) measurements can aid in discriminating
between fast (< 1 year) and slower (> 5-10 years) cycling of C between
the atmosphere and the terrestrial biosphere due to the 14C
disequilibrium between atmospheric and terrestrial C. However,
(CO2)-C-14 in the atmosphere is typically much more strongly impacted by
fossil fuel emissions of CO2, and, thus, observations often provide
little additional constraints on respiratory flux estimates at regional
scales. Here we describe a data set of (CO2)-C-14 observations from a
tall tower in northern Wisconsin (USA) where fossil fuel influence is
far enough removed that during the summer months, the biospheric
component of the (CO2)-C-14 budget dominates. We find that the
terrestrial biosphere is responsible for a significant contribution to
(CO2)-C-14 that is 2-3 times higher than predicted by the
Carnegie-Ames-Stanford approach terrestrial ecosystem model for
observations made in 2010. This likely includes a substantial
contribution from the North American boreal ecoregion, but transported
biospheric emissions from outside the model domain cannot be ruled out.
The (CO2)-C-14 enhancement also appears somewhat decreased in
observations made over subsequent years, suggesting that 2010 may be
anomalous. With these caveats acknowledged, we discuss the implications
of the observation/ model comparison in terms of possible systematic
biases in the model versus short-term anomalies in the observations.
Going forward, this isotopic signal could be exploited as an important
indicator to better constrain both the long-term carbon balance of
terrestrial ecosystems and the short-term impact of disturbance-based
loss of carbon to the atmosphere.
BibTeX:
@article{lafranchi16a,
  author = {LaFranchi, B. W. and McFarlane, K. J. and Miller, J. B. and Lehman, S. J. and Phillips, C. L. and Andrews, A. E. and Tans, P. P. and Chen, H. and Liu, Z. and Turnbull, J. C. and Xu, X. and Guilderson, T. P.},
  title = {Strong regional atmospheric C-14 signature of respired CO2 observed from a tall tower over the midwestern United States},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2016},
  volume = {121},
  number = {8},
  pages = {2275--2295},
  doi = {https://doi.org/10.1002/2015JG003271}
}
Lan, X., Tans, P., Sweeney, C., Andrews, A., Jacobson, A., Crotwell, M., Dlugokencky, E., Kofler, J., Lang, P., Thoning, K. and Wolter, S. Gradients of column CO2 across North America from the NOAA Global Greenhouse Gas Reference Network {2017} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {17}({24}), pp. 15151-15165 
article DOI  
Abstract: This study analyzes seasonal and spatial patterns of column carbon
dioxide (CO2) over North America, calculated from aircraft and tall
tower measurements from the NOAA Global Greenhouse Gas Reference Network
from 2004 to 2014. Consistent with expectations, gradients between the
eight regions studied are larger below 2 km than above 5 km. The 11-year
mean CO2 dry mole fraction (XCO2) in the column below similar to 330 hPa
(similar to 8 km above sea level) from NOAA's CO2 data assimilation
model, Carbon-Tracker (CT2015), demonstrates good agreement with those
calculated from calibrated measurements on aircraft and towers. Total
column XCO2 was attained by combining modeled CO2 above 330 hPa from
CT2015 with the measurements. We find large spatial gradients of total
column XCO2 from June to August, with north and northeast regions having
similar to 3 ppm stronger summer drawdown (peak-to-valley amplitude in
seasonal cycle) than the south and southwest regions. The long-term
averaged spatial gradients of total column XCO2 across North America
show a smooth pattern that mainly reflects the large-scale circulation.
We have conducted a CarbonTracker experiment to investigate the impact
of Eurasian long-range transport. The result suggests that the large
summertime Eurasian boreal flux contributes about half of the
north-south column XCO2 gradient across North America. Our results
confirm that continental-scale total column XCO2 gradients simulated by
CarbonTracker are realistic and can be used to evaluate the credibility
of some spatial patterns from satellite retrievals, such as the
long-term average of growing-season spatial patterns from satellite
retrievals reported for Europe which show a larger spatial difference
(similar to 6 ppm) and scattered hot spots.
BibTeX:
@article{lan17a,
  author = {Lan, Xin and Tans, Pieter and Sweeney, Colm and Andrews, Arlyn and Jacobson, Andrew and Crotwell, Molly and Dlugokencky, Edward and Kofler, Jonathan and Lang, Patricia and Thoning, Kirk and Wolter, Sonja},
  title = {Gradients of column CO2 across North America from the NOAA Global Greenhouse Gas Reference Network},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2017},
  volume = {17},
  number = {24},
  pages = {15151--15165},
  doi = {https://doi.org/10.5194/acp-17-15151-2017}
}
de lange , A. and Landgraf, J. Methane profiles from GOSAT thermal infrared spectra {2018} ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. {11}({6}), pp. {3815-3828} 
article DOI  
Abstract: This paper discusses the retrieval of atmospheric methane profiles from
the thermal infrared band of the Japanese Greenhouse Gases Observing
Satellite (GOSAT) between 1210 and 1310 cm(-1), using the RemoTeC
analysis software. Approximately one degree of information on the
vertical methane distribution is inferred from the measurements, with
the main sensitivity at about 9 km altitude but little sensitivity to
methane in the lower troposphere. For verification, we compare the
GOSAT-TIR methane profile retrieval results with profiles from model
fields provided by the Monitoring Atmospheric Composition and Climate
(MACC) project, scaled to the total column measurements of the Total
Carbon Column Observing Network (TCCON) at ground-based measurement
sites. Without any radiometric corrections of GOSAT observations,
differences between both data sets can be as large as 10 %. To mitigate
these differences, we developed a correction scheme using a principal
component analysis of spectral fit residuals and airborne observations
of methane during the HIAPER pole-to-pole observations (HIPPO) campaign
II and III. When the correction scheme is applied, the bias in the
methane profile can be reduced to less than 2% over the whole altitude
range with respect to MACC model methane fields. Furthermore, we show
that, with this correction, the retrievals result in smooth methane
fields over land and ocean crossings and no differences can be discerned
between daytime and night-time measurements. Finally, a cloud filter is
developed for the nighttime and ocean measurements. This filter is
rooted in the GOSAT-TIR (thermal infrared) measurements and its
performance, in terms of biases, is consistent with the cloud filter
based on the GOSAT-SWIR (shortwave infrared) measurements. The TIR
filter shows a higher acceptance rate of observations than the SWIR
filter, at the cost of a higher uncertainty in the retrieved methane
profiles.
BibTeX:
@article{lange18a,
  author = {de lange, Arno and Landgraf, Jochen},
  title = {Methane profiles from GOSAT thermal infrared spectra},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES},
  year = {2018},
  volume = {11},
  number = {6},
  pages = {3815-3828},
  doi = {https://doi.org/10.5194/amt-11-3815-2018}
}
Langley, B. Modelling urban forest structure and services using the urban forest effects (UFORE) model 2012 School: University of British Columbia  jurthesis URL 
BibTeX:
@jurthesis{langley12a,
  author = {Langley, Benjamin},
  title = {Modelling urban forest structure and services using the urban forest effects (UFORE) model},
  school = {University of British Columbia},
  year = {2012},
  url = {https://open.library.ubc.ca/collections/undergraduateresearch/52966/items/1.0075544}
}
Lanso, A.S., Bendtsen, J., Christensen, J.H., Sorensen, L.L., Chen, H., Meijer, H.A.J. and Geels, C. Sensitivity of the air-sea CO2 exchange in the Baltic Sea and Danish inner waters to atmospheric short-term variability {2015} BIOGEOSCIENCES
Vol. {12}({9}), pp. 2753-2772 
article DOI  
Abstract: Minimising the uncertainties in estimates of air-sea CO2 exchange is an
important step toward increasing the confidence in assessments of the
CO2 cycle. Using an atmospheric transport model makes it possible to
investigate the direct impact of atmospheric parameters on the air-sea
CO2 flux along with its sensitivity to, for example, short-term temporal
variability in wind speed, atmospheric mixing height and atmospheric CO2
concentration. With this study, the importance of high spatiotemporal
resolution of atmospheric parameters for the air-sea CO2 flux is
assessed for six sub-basins within the Baltic Sea and Danish inner
waters. A new climatology of surface water partial pressure of CO2
(pCO(2)(w)) has been developed for this coastal area based on available
data from monitoring stations and on-board pCO(2)(w) measuring systems.
Parameterisations depending on wind speed were applied for the transfer
velocity to calculate the air-sea CO2 flux. Two model simulations were
conducted - one including short-term variability in atmospheric CO2
(VAT), and one where it was not included (CAT).
A seasonal cycle in the air-sea CO2 flux was found for both simulations
for all sub-basins with uptake of CO2 in summer and release of CO2 to
the atmosphere in winter. During the simulated period 2005-2010, the
average annual net uptake of atmospheric CO2 for the Baltic Sea, Danish
straits and Kattegat was 287 and 471 Gg C yr(-1) for the VAT and CAT
simulations, respectively. The obtained difference of 184 Gg C yr(-1)
was found to be significant, and thus ignoring short-term variability in
atmospheric CO2 does have a sizeable effect on the air-sea CO2 exchange.
The combination of the atmospheric model and the new pCO(2)(w) fields
has also made it possible to make an estimate of the marine part of the
Danish CO2 budget for the first time. A net annual uptake of 2613 Gg C
yr(-1) was found for the Danish waters.
A large uncertainty is connected to the air-sea CO2 flux in particular
caused by the transfer velocity parameterisation and the applied
pCO(2)(w) climatology. However, as a significant difference of 184 Gg C
yr(-1) is obtained between the VAT and CAT simulations, the present
study underlines the importance of including short-term variability in
atmospheric CO2 concentration in future model studies of the air-sea
exchange in order to minimise the uncertainty.
BibTeX:
@article{lanso15a,
  author = {Lanso, A. S. and Bendtsen, J. and Christensen, J. H. and Sorensen, L. L. and Chen, H. and Meijer, H. A. J. and Geels, C.},
  title = {Sensitivity of the air-sea CO2 exchange in the Baltic Sea and Danish inner waters to atmospheric short-term variability},
  journal = {BIOGEOSCIENCES},
  year = {2015},
  volume = {12},
  number = {9},
  pages = {2753--2772},
  doi = {https://doi.org/10.5194/bg-12-2753-2015}
}
Lanso, A.S., Sorensen, L.L., Christensen, J.H., Rutgersson, A. and Geels, C. The influence of short-term variability in surface water pCO(2) on modelled air-sea CO2 exchange {2017} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {69} 
article DOI  
Abstract: Coastal seas and estuarine systems are highly variable in both time and
space and with their heterogeneity difficult to capture with
measurements. Models are useful tools in obtaining a better
spatiotemporal coverage or, at least, a better understanding of the
impacts such heterogeneity has in driving variability in coastal oceans
and estuaries. A model-based sensitivity study is constructed in this
study in order to examine the effects of short-term variability in
surface water pCO(2) on the annual air-sea CO2 exchange in coastal
regions. An atmospheric transport model formed the basis of the
modelling framework for the study of the Baltic Sea and the Danish inner
waters. Several maps of surface water pCO(2) were employed in the
modelling framework. While a monthly Baltic Sea climatology (BSC) had
already been developed, the current study further extended this with the
addition of an improved near-coastal climatology for the Danish inner
waters. Furthermore, daily surface fields of pCO(2) were obtained from a
mixed layer scheme constrained by surface measurements of pCO(2) (JENA).
Short-term variability in surface water pCO(2) was assessed by
calculating monthly mean diurnal cycles from continuous measurements of
surface water pCO(2), observed at stationary sites within the Baltic
Sea. No apparent diurnal cycle was evident in winter, but diurnal cycles
(with amplitudes up to 27 mu atm) were found from April to October. The
present study showed that the temporal resolution of surface water
pCO(2) played an influential role on the annual air-sea CO2 exchange for
the coastal study region. Hence, annual estimates of CO2 exchanges are
sensitive to variation on much shorter time scales, and this variability
should be included for any model study investigating the exchange of CO2
across the air-sea interface. Furthermore, the choice of surface pCO(2)
maps also had a crucial influence on the simulated air-sea CO2 exchange.
BibTeX:
@article{lanso17a,
  author = {Lanso, Anne Sofie and Sorensen, Lise Lotte and Christensen, Jesper H. and Rutgersson, Anna and Geels, Camilla},
  title = {The influence of short-term variability in surface water pCO(2) on modelled air-sea CO2 exchange},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2017},
  volume = {69},
  doi = {https://doi.org/10.1080/16000889.2017.1302670}
}
Lanso, A.S., Smallman, T.L., Christensen, J.H., Williams, M., Pilegaard, K., Sorensen, L.-L. and Geels, C. Simulating the atmospheric CO2 concentration across the heterogeneous landscape of Denmark using a coupled atmosphere-biosphere mesoscale model system {2019} BIOGEOSCIENCES
Vol. {16}({7}), pp. {1505-1524} 
article DOI URL 
Abstract: Although coastal regions only amount to 7% of the global oceans, their contribution to the global oceanic air-sea CO2 exchange is proportionally larger, with fluxes in some estuaries being similar in magnitude to terrestrial surface fluxes of CO2. Across a heterogeneous surface consisting of a coastal marginal sea with estuarine properties and varied land mosaics, the surface fluxes of CO2 from both marine areas and terrestrial surfaces were investigated in this study together with their impact in atmospheric CO2 concentrations by the usage of a high-resolution modelling framework. The simulated terrestrial fluxes across the study region of Denmark experienced an east-west gradient corresponding to the distribution of the land cover classification, their biological activity and the urbanised areas. Annually, the Danish terrestrial surface had an uptake of approximately -7000 GgC yr(-1). While the marine fluxes from the North Sea and the Danish inner waters were smaller annually, with about -1800 and 1300 GgC yr(-1), their sizes are comparable to annual terrestrial fluxes from individual land cover classifications in the study region and hence are not negligible. The contribution of terrestrial surfaces fluxes was easily detectable in both simulated and measured concentrations of atmospheric CO2 at the only tall tower site in the study region. Although, the tower is positioned next to Roskilde Fjord, the local marine impact was not distinguishable in the simulated concentrations. But the regional impact from the Danish inner waters and the Baltic Sea increased the atmospheric concentration by up to 0.5 ppm during the winter months.
BibTeX:
@article{lanso19a,
  author = {Lanso, Anne Sofie and Smallman, Thomas Luke and Christensen, Jesper Heile and Williams, Mathew and Pilegaard, Kim and Sorensen, Lise-Lotte and Geels, Camilla},
  title = {Simulating the atmospheric CO2 concentration across the heterogeneous landscape of Denmark using a coupled atmosphere-biosphere mesoscale model system},
  journal = {BIOGEOSCIENCES},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {16},
  number = {7},
  pages = {1505--1524},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://bg.copernicus.org/articles/16/1505/2019/},
  doi = {https://doi.org/10.5194/bg-16-1505-2019}
}
Laskar, A.H., Lin, L.-C., Jiang, X. and Liang, M.-C. Distribution of CO2 in Western Pacific, Studied Using Isotope Data Made in Taiwan, OCO‐2 Satellite Retrievals, and CarbonTracker Products 2018 Earth and Space Science  article URL 
BibTeX:
@article{laskar18a,
  author = {Amzad H. Laskar and Li-Ching Lin and Xun Jiang and Mao-Chang Liang},
  title = {Distribution of CO2 in Western Pacific, Studied Using Isotope Data Made in Taiwan, OCO‐2 Satellite Retrievals, and CarbonTracker Products},
  journal = {Earth and Space Science},
  year = {2018},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018EA000415}
}
Lauvaux, T., Schuh, A.E., Uliasz, M., Richardson, S., Miles, N., Andrews, A.E., Sweeney, C., Diaz, L.I., Martins, D., Shepson, P.B. and Davis, K.J. Constraining the CO2 budget of the corn belt: exploring uncertainties from the assumptions in a mesoscale inverse system {2012} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {12}({1}), pp. 337-354 
article DOI  
Abstract: We performed an atmospheric inversion of the CO2 fluxes over Iowa and
the surrounding states, from June to December 2007, at 20 km resolution
and weekly timescale. Eight concentration towers were used to constrain
the carbon balance in a 1000x1000 km(2) domain in this agricultural
region of the US upper midwest. The CO2 concentrations of the boundaries
derived from CarbonTracker were adjusted to match direct observations
from aircraft profiles around the domain. The regional carbon balance
ends up with a sink of 183 Tg C +/- 35 Tg C over the area for the period
June-December, 2007. Potential bias from incorrect boundary conditions
of about 0.55 ppm over the 7 months was corrected using mixing ratios
from four different aircraft profile sites operated at a weekly time
scale, acting as an additional source of uncertainty of 24 Tg C. We used
two different prior flux estimates, the SiBCrop model and the inverse
flux product from the CarbonTracker system. We show that inverse flux
estimates using both priors converge to similar posterior estimates (20
Tg C difference), in our reference inversion, but some spatial
structures from the prior fluxes remain in the posterior fluxes,
revealing the importance of the prior flux resolution and distribution
despite the large amount of atmospheric data available. The retrieved
fluxes were compared to eddy flux towers in the corn and grassland
areas, revealing an improvement in the seasonal cycles between the two
compared to the prior fluxes, despite large absolute differences due to
representation errors. The uncertainty of 34 Tg C (or 34 g C m(2)) was
derived from the posterior uncertainty obtained with our reference
inversion of about 25 to 30 Tg C and from sensitivity tests of the
assumptions made in the inverse system, for a mean carbon balance over
the region of -183 Tg C, slightly weaker than the reference. Because of
the potential large bias (similar to 24 Tg C in this case) due to choice
of background conditions, proportional to the surface but not to the
regional flux, this methodology seems limited to regions with a large
signal (sink or source), unless additional observations can be used to
constrain the boundary inflow.
BibTeX:
@article{lauvaux12a,
  author = {Lauvaux, T. and Schuh, A. E. and Uliasz, M. and Richardson, S. and Miles, N. and Andrews, A. E. and Sweeney, C. and Diaz, L. I. and Martins, D. and Shepson, P. B. and Davis, K. J.},
  title = {Constraining the CO2 budget of the corn belt: exploring uncertainties from the assumptions in a mesoscale inverse system},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  year = {2012},
  volume = {12},
  number = {1},
  pages = {337--354},
  doi = {https://doi.org/10.5194/acp-12-337-2012}
}
Lauvaux, T., Schuh, A.E., Bocquet, M., Wu, L., Richardson, S., Miles, N. and Davis, K.J. Network design for mesoscale inversions of CO2 sources and sinks {2012} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {64} 
article DOI  
Abstract: Recent instrumental deployments of regional observation networks of
atmospheric CO2 mixing ratios have been used to constrain carbon sources
and sinks using inversion methodologies. In this study, we performed
sensitivity experiments using observation sites from the Mid Continent
Intensive experiment to evaluate the required spatial density and
locations of CO2 concentration towers based on flux corrections and
error reduction analysis. In addition, we investigated the impact of
prior flux error structures with different correlation lengths and biome
information. We show here that, while the regional carbon balance
converged to similar annual estimates using only two concentration
towers over the region, additional sites were necessary to retrieve the
spatial flux distribution of our reference case (using the entire
network of eight towers). Local flux corrections required the presence
of observation sites in their vicinity, suggesting that each tower was
only able to retrieve major corrections within a hundred of kilometres
around, despite the introduction of spatial correlation lengths (similar
to 100 to 300 km) in the prior flux errors. We then quantified and
evaluated the impact of the spatial correlations in the prior flux
errors by estimating the improvement in the CO2 model-data mismatch of
the towers not included in the inversion. The overall gain across the
domain increased with the correlation length, up to 300 km, including
both biome-related and non-biome-related structures. However, the
spatial variability at smaller scales was not improved. We conclude that
the placement of observation towers around major sources and sinks is
critical for regional-scale inversions in order to obtain reliable flux
distributions in space. Sparser networks seem sufficient to assess the
overall regional carbon budget with the support of flux error
correlations, indicating that regional signals can be recovered using
hourly mixing ratios. However, the smaller spatial structures in the
posterior fluxes are highly constrained by assumed prior flux error
correlation lengths, with no significant improvement at only a few
hundreds of kilometres away from the observation sites.
BibTeX:
@article{lauvaux12b,
  author = {Lauvaux, T. and Schuh, A. E. and Bocquet, M. and Wu, L. and Richardson, S. and Miles, N. and Davis, K. J.},
  title = {Network design for mesoscale inversions of CO2 sources and sinks},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2012},
  volume = {64},
  doi = {https://doi.org/10.3402/tellusb.v64i0.17980}
}
Lauvaux, T., Miles, N.L., Richardson, S.J., Deng, A., Stauffer, D.R., Davis, K.J., Jacobson, G., Rella, C., Calonder, G.-P. and DeCola, P.L. Urban Emissions of CO2 from Davos, Switzerland: The First Real-Time Monitoring System Using an Atmospheric Inversion Technique {2013} JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY
Vol. {52}({12}), pp. 2654-2668 
article DOI  
Abstract: Anthropogenic emissions from urban areas represent 70% of the fossil
fuel carbon emitted globally according to carbon emission inventories.
The authors present here the first operational system able to monitor in
near-real time daily emission estimates, using a mesoscale atmospheric
inversion framework over the city of Davos, Switzerland, before, during,
and after the World Economic Forum 2012 Meeting (WEF-2012). Two
instruments that continuously measured atmospheric mixing ratios of
greenhouse gases (GHGs) were deployed at two locations from 23 December
2011 to 3 March 2012: one site was located in the urban area and the
other was out of the valley in the surrounding mountains. Carbon
dioxide, methane, and carbon monoxide were measured continuously at both
sites. The Weather Research and Forecasting mesoscale atmospheric model
(WRF), in four-dimensional data assimilation mode, was used to simulate
the transport of GHGs over the valley of Davos at 1.3-km resolution.
Wintertime emissions prior to the WEF-2012 were about 40% higher than
the initial annual inventory estimate, corresponding to the use of
heating fuel in the winter. Daily inverse fluxes were highly correlated
with the local climate, especially during the severe cold wave that
affected most of Europe in early February 2012. During the WEF-2012,
emissions dropped by 35% relative to the first month of the deployment,
despite similar temperatures and the presence of several thousand
participants at the meeting. On the basis of composite diurnal cycles of
hourly CO/CO2 ratios, the absence of traffic peaks during the WEF-2012
meeting indicated that change in road emissions is potentially
responsible for the observed decrease in the city emissions during the
meeting.
BibTeX:
@article{lauvaux13a,
  author = {Lauvaux, Thomas and Miles, Natasha L. and Richardson, Scott J. and Deng, Aijun and Stauffer, David R. and Davis, Kenneth J. and Jacobson, Gloria and Rella, Chris and Calonder, Gian-Paul and DeCola, Philip L.},
  title = {Urban Emissions of CO2 from Davos, Switzerland: The First Real-Time Monitoring System Using an Atmospheric Inversion Technique},
  journal = {JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY},
  year = {2013},
  volume = {52},
  number = {12},
  pages = {2654--2668},
  doi = {https://doi.org/10.1175/JAMC-D-13-038.1}
}
Lauvaux, T., Miles, N.L., Deng, A., Richardson, S.J., Cambaliza, M.O., Davis, K.J., Gaudet, B., Gurney, K.R., Huang, J., O'Keefe, D., Song, Y., Karion, A., Oda, T., Patarasuk, R., Razlivanov, I., Sarmiento, D., Shepson, P., Sweeney, C., Turnbull, J. and Wu, K. High-resolution atmospheric inversion of urban CO2 emissions during the dormant season of the Indianapolis Flux Experiment (INFLUX) {2016} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {121}({10}), pp. 5213-5236 
article DOI  
Abstract: Based on a uniquely dense network of surface towers measuring
continuously the atmospheric concentrations of greenhouse gases (GHGs),
we developed the first comprehensive monitoring systems of CO2 emissions
at high resolution over the city of Indianapolis. The urban inversion
evaluated over the 2012-2013 dormant season showed a statistically
significant increase of about 20% (from 4.5 to 5.7 MtC +/- 0.23 MtC)
compared to the Hestia CO2 emission estimate, a state-of-the-art
building-level emission product. Spatial structures in prior emission
errors, mostly undetermined, appeared to affect the spatial pattern in
the inverse solution and the total carbon budget over the entire area by
up to 15%, while the inverse solution remains fairly insensitive to the
CO2 boundary inflow and to the different prior emissions (i.e., ODIAC).
Preceding the surface emission optimization, we improved the atmospheric
simulations using a meteorological data assimilation system also
informing our Bayesian inversion system through updated observations
error variances. Finally, we estimated the uncertainties associated with
undetermined parameters using an ensemble of inversions. The total CO2
emissions based on the ensemble mean and quartiles (5.26-5.91 MtC) were
statistically different compared to the prior total emissions (4.1 to
4.5 MtC). Considering the relatively small sensitivity to the different
parameters, we conclude that atmospheric inversions are potentially able
to constrain the carbon budget of the city, assuming sufficient data to
measure the inflow of GHG over the city, but additional information on
prior emission error structures are required to determine the spatial
structures of urban emissions at high resolution.
BibTeX:
@article{lauvaux16a,
  author = {Lauvaux, Thomas and Miles, Natasha L. and Deng, Aijun and Richardson, Scott J. and Cambaliza, Maria O. and Davis, Kenneth J. and Gaudet, Brian and Gurney, Kevin R. and Huang, Jianhua and O'Keefe, Darragh and Song, Yang and Karion, Anna and Oda, Tomohiro and Patarasuk, Risa and Razlivanov, Igor and Sarmiento, Daniel and Shepson, Paul and Sweeney, Colm and Turnbull, Jocelyn and Wu, Kai},
  title = {High-resolution atmospheric inversion of urban CO2 emissions during the dormant season of the Indianapolis Flux Experiment (INFLUX)},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
  year = {2016},
  volume = {121},
  number = {10},
  pages = {5213--5236},
  doi = {https://doi.org/10.1002/2015JD024473}
}
Lauvaux, T., Diaz-Isaac, L.I., Bocquet, M. and Bousserez, N. Diagnosing spatial error structures in CO2 mole fractions and XCO2 column mole fractions from atmospheric transport {2019} ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. {19}({18}), pp. {12007-12024} 
article DOI URL 
Abstract: Atmospheric inversions inform us about the magnitude and variations of greenhouse gas (GHG) sources and sinks from global to local scales. Deployment of observing systems such as spaceborne sensors and ground-based instruments distributed around the globe has started to offer an unprecedented amount of information to estimate surface exchanges of GHG at finer spatial and temporal scales. However, all inversion methods still rely on imperfect atmospheric transport models whose error structures directly affect the inverse estimates of GHG fluxes. The impact of spatial error structures on the retrieved fluxes increase concurrently with the density of the available measurements. In this study, we diagnose the spatial structures due to transport model errors affecting modeled in situ carbon dioxide (CO2) mole fractions and total-column dry air mole fractions of CO2 (XCO2). We implement a cost-effective filtering technique recently developed in the meteorological data assimilation community to describe spatial error structures using a small-size ensemble. This technique can enable ensemble-based error analysis for multiyear inversions of sources and sinks. The removal of noisy structures due to sampling errors in our small-size ensembles is evaluated by comparison with larger-size ensembles. A second filtering approach for error covariances is proposed (Wiener filter), producing similar results over the 1-month simulation period compared to a Schur filter. Based on a comparison to a reference 25-member calibrated ensemble, we demonstrate that error variances and spatial error correlation structures are recoverable from small-size ensembles of about 8 to 10 members, improving the representation of transport errors in mesoscale inversions of CO2 fluxes. Moreover, error variances of in situ near-surface and free-tropospheric CO2 mole fractions differ significantly from total-column XCO2 error variances. We conclude that error variances for remote-sensing observations need to be quantified independently of in situ CO2 mole fractions due to the complexity of spatial error structures at different altitudes. However, we show the potential use of meteorological error structures such as the mean horizontal wind speed, directly available from ensemble prediction systems, to approximate spatial error correlations of in situ CO2 mole fractions, with similarities in seasonal variations and characteristic error length scales.
BibTeX:
@article{lauvaux19a,
  author = {Lauvaux, Thomas and Diaz-Isaac, Liza I. and Bocquet, Marc and Bousserez, Nicolas},
  title = {Diagnosing spatial error structures in CO2 mole fractions and XCO2 column mole fractions from atmospheric transport},
  journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2019},
  volume = {19},
  number = {18},
  pages = {12007--12024},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://acp.copernicus.org/articles/19/12007/2019/},
  doi = {https://doi.org/10.5194/acp-19-12007-2019}
}
Law, R.M., Steele, L.P., Krummel, P.B. and Zahorowski, W. Synoptic variations in atmospheric CO2 at Cape Grim: a model intercomparison {2010} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {62}({5, SI}), pp. 810-820 
article DOI  
Abstract: A `TransCom' model intercomparison is used to assess how well synoptic
and diurnal variations of carbon dioxide (CO2) and 222Rn (radon) can be
modelled at the coastal site, Cape Grim, Australia. Each model was run
with prescribed fluxes and forced with analysed meteorology for
2000-2003. Twelve models were chosen for analysis based on each model's
ability to differentiate baseline CO2 concentrations from non-baseline
CO2 (influenced by regional land fluxes). Analysis focused on
non-baseline events during 2002-2003. Radon was better simulated than
CO2, indicating that a spatially uniform radon land flux is a reasonable
assumption and that regional-scale transport was adequately captured by
the models. For both radon and CO2, the ensemble model mean generally
performed better than any individual model. Two case studies highlight
common problems with the simulations. First, in summer and autumn the
Cape Grim observations are sometimes influenced by Tasmanian rather than
mainland Australian fluxes. These periods are poorly simulated.
Secondly, an event with an urban plume demonstrates how the relatively
low spatial resolution of the input CO2 fluxes limits the quality of the
simulations. Analysis of periods with below baseline concentration
indicates the possible influence of carbon uptake by winter crops in
southern mainland Australia.
BibTeX:
@article{law10a,
  author = {Law, Rachel M. and Steele, L. Paul and Krummel, Paul B. and Zahorowski, Wlodek},
  title = {Synoptic variations in atmospheric CO2 at Cape Grim: a model intercomparison},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2010},
  volume = {62},
  number = {5, SI},
  pages = {810--820},
  doi = {https://doi.org/10.1111/j.1600-0889.2010.00470.x}
}
Lee, T.R., De Wekker, S.F.J., Andrews, A.E., Kofler, J. and Williams, J. Carbon dioxide variability during cold front passages and fair weather days at a forested mountaintop site {2012} ATMOSPHERIC ENVIRONMENT
Vol. {46}, pp. 405-416 
article DOI  
Abstract: This study describes temporal carbon dioxide (CO2) changes at a new
meteorological site on a mountaintop in the Virginia Blue Ridge
Mountains during the first year of measurements. Continental mountaintop
locations are increasingly being used for CO2 monitoring, and
investigations are needed to better understand measurements made at
these locations. We focus on CO2 mixing ratio changes on days with cold
front passages and on fair weather days. Changes in CO2 mixing ratios
are largest during cold front passages outside the growing season and on
clear, fair weather days in the growing season. 67% (60%) of the
frontal passages during the non-growing (growing) season have larger
postfrontal than prefrontal CO2 mixing ratios. The increase in CO2
mixing ratio around the frontal passage is short-lived and coincides
with changes in CO and O-3. The CO2 increase can therefore be used as an
additional criterion to determine the timing of frontal passages at the
mountaintop station. The CO2 increase can be explained by an
accumulation of trace gases along frontal boundaries. The magnitude and
duration of the CO2 increase is affected by the wind speed and direction
that determine the source region of the postfrontal air.
Southward-moving fronts result in the largest prolonged period of
elevated CO2, consistent with the postfrontal advection of air from the
Northeastern United States where anthropogenic contributions are
relatively large compared to other areas in the footprint of the
mountaintop station. These anthropogenic contributions to the CO2
changes are confirmed through concurrent CO measurements and output from
NOAA's CarbonTracker model. (C) 2011 Elsevier Ltd. All rights reserved.
BibTeX:
@article{lee12a,
  author = {Lee, Temple R. and De Wekker, Stephan F. J. and Andrews, Arlyn E. and Kofler, Jonathan and Williams, Jonathan},
  title = {Carbon dioxide variability during cold front passages and fair weather days at a forested mountaintop site},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2012},
  volume = {46},
  pages = {405--416},
  doi = {https://doi.org/10.1016/j.atmosenv.2011.09.068}
}
Lee, T.R., De Wekker, S.F.J., Pal, S., Andrews, A.E. and Kofler, J. Meteorological controls on the diurnal variability of carbon monoxide mixing ratio at a mountaintop monitoring site in the Appalachian Mountains {2015} TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. {67} 
article DOI  
Abstract: The variability of trace gases such as carbon monoxide (CO) at surface
monitoring stations is affected by meteorological forcings that are
particularly complicated over mountainous terrain. A detailed
understanding of the impact of meteorological forcings on trace gas
variability is challenging, but is vital to distinguish trace gas
measurements affected by local pollutant sources from measurements
representative of background mixing ratios. In the present study, we
investigate the meteorological and CO characteristics at Pinnacles
(38.61 N, 78.35 W, 1017m above mean sea level), a mountaintop monitoring
site in northwestern Virginia, USA, in the Appalachian Mountains, from
2009 to 2012, and focus on understanding the dominant meteorological
forcings affecting the CO variability on diurnal timescales. The annual
mean diurnal CO cycle shows a minimum in the morning between 0700 and
0900 LST and a maximum in the late afternoon between 1600 and 2000 LST,
with a mean (median) daily CO amplitude of 39.2 +/- 23.7 ppb (33.2 ppb).
CO amplitudes show large day-to-day variability. The largest CO
amplitudes, in which CO mixing ratios can change >100 ppb in >3 h, occur
in the presence of synoptic disturbances. Under fair weather conditions,
local-to regional-scale transport processes are found to be more
important drivers of the diurnal CO variability. On fair weather days
with northwesterly winds, boundary layer dilution causes a daytime CO
decrease, resembling the variability observed atop tall towers in flat
terrain. Fair weather days with a wind shift from the northwest to the
south are characterised by an afternoon CO increase and resemble the
variability observed at mountaintops influenced by the vertical
transport of polluted air from adjacent valleys.
BibTeX:
@article{lee15a,
  author = {Lee, Temple R. and De Wekker, Stephan F. J. and Pal, Sandip and Andrews, Arlyn E. and Kofler, Jonathan},
  title = {Meteorological controls on the diurnal variability of carbon monoxide mixing ratio at a mountaintop monitoring site in the Appalachian Mountains},
  journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY},
  year = {2015},
  volume = {67},
  doi = {https://doi.org/10.3402/tellusb.v67.25659}
}
Lee, S., Kim, D., Im, J., Lee, M.-I. and Park, Y.-G. CO2 concentration and its spatiotemporal variation in the troposphere using multi-sensor satellite data, carbon tracker, and aircraft observations {2017} GISCIENCE & REMOTE SENSING
Vol. {54}({4}), pp. 592-613 
article DOI  
Abstract: Satellite-based atmospheric CO2 observations have provided a great
opportunity to improve our understanding of the global carbon cycle.
However, thermal infrared (TIR)-based satellite observations, which are
useful for the investigation of vertical distribution and the transport
of CO2, have not yet been studied as much as the column amount products
derived from shortwave infrared data. In this study, TIR-based satellite
CO2 products - from Atmospheric Infrared Sounder, Tropospheric Emission
Spectrometer (TES), and Thermal And Near infrared Sensor for carbon
Observation - and carbon tracker mole fraction data were compared with
in situ Comprehensive Observation Network for Trace gases by AIrLiner
(CONTRAIL) data for different locations. The TES CO2 product showed the
best agreement with CONTRAIL CO2 data resulting in R-2 similar to 0.87
and root-mean-square error similar to 0.9. The vertical distribution of
CO2 derived by TES strongly depends on the geophysical characteristics
of an area. Two different climate regions (i.e., southeastern Japan and
southeastern Australia) were examined in terms of the vertical
distribution and transport of CO2. Results show that while vertical
distribution of CO2 around southeastern Japan was mainly controlled by
horizontal and vertical winds, horizontal wind might be a major factor
to control the CO2 transport around southeastern Australia. In addition,
the vertical transport of CO2 also varies by region, which is mainly
controlled by anthropogenic CO2, and horizontal and omega winds. This
study improves our understanding of vertical distribution and the
transport of CO2, both of which vary by region, using TIR-based
satellite CO2 observations and meteorological variables.
BibTeX:
@article{lee17a,
  author = {Lee, Sanggyun and Kim, Dongmin and Im, Jungho and Lee, Myong-In and Park, Young-Gyu},
  title = {CO2 concentration and its spatiotemporal variation in the troposphere using multi-sensor satellite data, carbon tracker, and aircraft observations},
  journal = {GISCIENCE & REMOTE SENSING},
  year = {2017},
  volume = {54},
  number = {4},
  pages = {592--613},
  doi = {https://doi.org/10.1080/15481603.2017.1317120}
}
Lee, T.R., De Wekker, S.F.J. and Pal, S. The Impact of the Afternoon Planetary Boundary-Layer Height on the Diurnal Cycle of CO and Mixing Ratios at a Low-Altitude Mountaintop {2018} BOUNDARY-LAYER METEOROLOGY
Vol. {168}({1}), pp. {81-102} 
article DOI  
Abstract: Mountaintop trace-gas mixing ratios are often assumed to represent free
atmospheric values, but are affected by valley planetary boundary-layer
(PBL) air at certain times. We hypothesize that the afternoon valley-PBL
height relative to the ridgetop is important in the diurnal cycle of
mountaintop trace-gas mixing ratios. To investigate this, we use, (1)
4-years (1 January 2009-31 December 2012) of CO and mixing-ratio
measurements and supporting meteorological observations from Pinnacles
(, , 1017 m a.s.l.), which is a monitoring site in the Appalachian
Mountains, (2) regional mixing-ratio measurements, and (3) PBL heights
determined from a nearby sounding station. Results reveal that the
amplitudes of the diurnal cycles of CO and mixing ratios vary as a
function of the daytime maximum valley-PBL height relative to the
ridgetop. The mean diurnal cycle for the subset of days when the
afternoon valley-PBL height is at least 400 m below the ridgetop shows a
daytime CO mixing-ratio increase, implying the transport of PBL air from
the valley to the mountaintop. During the daytime, on days when the PBL
heights exceed the mountaintop, PBL dilution and entrainment cause CO
mixing ratios to decrease. This decrease in CO mixing ratio, especially
on days when PBL heights are at least 400 m above the ridgetop, suggests
that measurements from these days can be used as with afternoon
measurements from flat terrain in applications requiring
regionally-representative measurements.
BibTeX:
@article{lee18a,
  author = {Lee, Temple R. and De Wekker, Stephan F. J. and Pal, Sandip},
  title = {The Impact of the Afternoon Planetary Boundary-Layer Height on the Diurnal Cycle of CO and Mixing Ratios at a Low-Altitude Mountaintop},
  journal = {BOUNDARY-LAYER METEOROLOGY},
  year = {2018},
  volume = {168},
  number = {1},
  pages = {81-102},
  doi = {https://doi.org/10.1007/s10546-018-0343-9}
}
Lee, E., Zeng, F.-W., Koster, R.D., Weir, B., Ott, L.E. and Poulter, B. The impact of spatiotemporal variability in atmospheric CO2 concentration on global terrestrial carbon fluxes {2018} BIOGEOSCIENCES
Vol. {15}({18}), pp. {5635-5652} 
article DOI  
Abstract: Land carbon fluxes, e.g., gross primary production (GPP) and net biome production (NBP), are controlled in part by the responses of terrestrial ecosystems to atmospheric conditions near the Earth's surface. The Coupled Model Intercomparison Project Phase 6 (CMIP6) has recently proposed increased spatial and temporal resolutions for the surface CO2 concentrations used to calculate GPP, and yet a comprehensive evaluation of the consequences of this increased resolution for carbon cycle dynamics is missing. Here, using global offline simulations with a terrestrial biosphere model, the sensitivity of terrestrial carbon cycle fluxes to multiple facets of the spatiotemporal variability in atmospheric CO2 is quantified. Globally, the spatial variability in CO2 is found to increase the mean global GPP by a maximum of 0.05 Pg C year(-1), as more vegetated land areas benefit from higher CO2 concentrations induced by the inter-hemispheric gradient. The temporal variability in CO2, however, compensates for this increase, acting to reduce overall global GPP; in particular, consideration of the diurnal variability in atmospheric CO2 reduces multi-year mean global annual GPP by 0.5 Pg C year(-1) and net land carbon uptake by 0.1 Pg C year(-1). The relative contributions of the different facets of CO2 variability to GPP are found to vary regionally and seasonally, with the seasonal variation in atmospheric CO2, for example, having a notable impact on GPP in boreal regions during fall. Overall, in terms of estimating global GPP, the magnitudes of the sensitivities found here are minor, indicating that the common practice of applying spatially uniform and annually increasing CO2 (without higher-frequency temporal variability) in offline studies is a reasonable approach - the small errors induced by ignoring CO2 variability are undoubtedly swamped by other uncertainties in the offline calculations. Still, for certain regional-and seasonal-scale GPP estimations, the proper treatment of spatiotemporal CO2 variability appears important.
BibTeX:
@article{lee18b,
  author = {Lee, Eunjee and Zeng, Fan-Wei and Koster, Randal D. and Weir, Brad and Ott, Lesley E. and Poulter, Benjamin},
  title = {The impact of spatiotemporal variability in atmospheric CO2 concentration on global terrestrial carbon fluxes},
  journal = {BIOGEOSCIENCES},
  publisher = {COPERNICUS GESELLSCHAFT MBH},
  year = {2018},
  volume = {15},
  number = {18},
  pages = {5635--5652},
  doi = {https://doi.org/10.5194/bg-15-5635-2018}
}
Lee, E., Zeng, F.-W., Koster, R.D., Ott, L.E., Mahanama, S., Weir, B., Poulter, B. and Oda, T. Impact of a Regional US Drought on Land and Atmospheric Carbon {2020} JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. {125}({8}) 
article DOI URL 
Abstract: The impacts of drought on regional land and atmospheric carbon are still poorly understood. Here we quantify the impact of a regional U.S. drought on land carbon fluxes (gross primary production, or GPP, and net biosphere production) and atmospheric carbon (CO2) by imposing an idealized 3-month meteorological drought in an ensemble of coupled land-atmosphere climate simulations. The imposed drought, applied to the lower Mississippi River Valley (similar to 500,000 km(2)), leads to a 23% GPP reduction in the drought area in the month immediately following the drought's termination. The drought also caused GPP reductions in some remote areas through drought-induced impacts on remote meteorology, particularly the areas adjacent to the imposed drought. In the remote areas, the induced precipitation changes are responsible for most of the anomalous land productivity. The impact of the drought-induced meteorological anomalies on GPP is greater than that of the CO2 anomalies by at least an order of magnitude. While their impact on GPP is secondary, the drought-induced atmospheric CO2 anomalies near the land surface can be as large as 3.57 ppm. The significant CO2 anomalies cover an area up to three times of that of the imposed drought, suggesting that atmospheric transport needs to be considered in the interpretation of drought-induced CO2 anomalies in the atmosphere. The imposed drought also leads to column-averaged CO2 increases of up to 0.78 ppm, which is at the edge of the uncertainty from single soundings of current greenhouse gas observing satellites. Plain Language Summary During a regional drought, a deficiency of precipitation affects vegetation productivity, which can alter net carbon exchange between the land and the atmosphere and, in turn, the CO2 concentration in the atmosphere. Moreover, the anomalous heat and moisture fluxes at the land surface caused by the drought can generate changes in meteorology, affecting areas beyond the original drought area. Using a version of the NASA Goddard Earth Observing System Earth System Model that allows full characterization of the carbon-water-energy feedback processes, we imposed an idealized spring drought over the lower Mississippi River Valley (similar to 500,000 km(2)) and quantified the resulting changes in vegetation productivity, net carbon exchange flux, and atmospheric CO2 concentration. We found that the productivity in the drought area decreases by 23% and that the productivities in some remote areas, particularly areas adjacent to the imposed drought, are also affected through impacts on remote meteorology. The anomalous atmospheric CO2 caused by the idealized spring drought is at the edge of the measurement uncertainty of current greenhouse gas observing satellites. Due to atmospheric transport (e.g., wind), it covers an area up to three times of that of the imposed drought.
BibTeX:
@article{lee20a,
  author = {Lee, Eunjee and Zeng, Fan-Wei and Koster, Randal D. and Ott, Lesley E. and Mahanama, Sarith and Weir, Brad and Poulter, Benjamin and Oda, Tomohiro},
  title = {Impact of a Regional US Drought on Land and Atmospheric Carbon},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  publisher = {AMER GEOPHYSICAL UNION},
  year = {2020},
  volume = {125},
  number = {8},
  note = {Query date: 2021-04-02 15:20:04},
  url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005599},
  doi = {https://doi.org/10.1029/2019JG005599}
}
Lefrançois, E. Revegetation and reclamation of oil sands process-affected material using Frankia-inoculated alders: Field and greenhouse trials 2009 School: McGill University  mastersthesis URL 
BibTeX:
@mastersthesis{lefrancois09a,
  author = {Lefrançois, Elisabeth},
  title = {Revegetation and reclamation of oil sands process-affected material using Frankia-inoculated alders: Field and greenhouse trials},
  school = {McGill University},
  year = {2009},
  url = {http://digitool.library.mcgill.ca/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&forebear_coll=&user=GUEST&pds_handle=&pid=66758&con_lng=ENG&search_terms=&divType=&adjacency=N&rd_session=http://digitool.Library.McGill.CA:80/R/FT8AIQ9EGIVNJ1RIEL1L3JBY3VJSPXGBFKD2RGI227CGSACT1A-00024}
}
Lenton, A., Tilbrook, B., Law, R.M., Bakker, D., Doney, S.C., Gruber, N., Ishii, M., Hoppema, M., Lovenduski, N.S., Matear, R.J., McNeil, B.I., Metzl, N., Fletcher, S.E.M., Monteiro, P.M.S., Roedenbeck, C., Sweeney, C. and Takahashi, T. Sea-air CO2 fluxes in the Southern Ocean for the period 1990-2009 {2013} BIOGEOSCIENCES
Vol. {10}({6}), pp. 4037-4054 
article DOI  
Abstract: The Southern Ocean (44-75 degrees S) plays a critical role in the global
carbon cycle, yet remains one of the most poorly sampled ocean regions.
Different approaches have been used to estimate sea-air CO2 fluxes in
this region: synthesis of surface ocean observations, ocean
biogeochemical models, and atmospheric and ocean inversions. As part of
the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we
combine these different approaches to quantify and assess the magnitude
and variability in Southern Ocean sea-air CO2 fluxes between 1990-2009.
Using all models and inversions (26), the integrated median annual
sea-air CO2 flux of -0.42+/-0.07 Pg C yr(-1) for the 44-75 degrees S
region, is consistent with the -0.27+/-0.13 Pg C yr(-1) calculated using
surface observations. The circumpolar region south of 58 degrees S has a
small net annual flux (model and inversion median: -0.04+/-0.07 Pg C
yr(-1) and observations: +0.04+/-0.02 Pg C yr(-1)), with most of the net
annual flux located in the 44 to 58 degrees S circumpolar band (model
and inversion median: -0.36+/-0.09 Pg C yr(-1) and observations:
-0.35+/-0.09 Pg C yr(-1)). Seasonally, in the 44-58 degrees S region,
the median of 5 ocean biogeochemical models captures the observed
sea-air CO2 flux seasonal cycle, while the median of 11 atmospheric
inversions shows little seasonal change in the net flux. South of 58
degrees S, neither atmospheric inversions nor ocean biogeochemical
models reproduce the phase and amplitude of the observed seasonal
sea-air CO2 flux, particularly in the Austral Winter. Importantly, no
individual atmospheric inversion or ocean biogeochemical model is
capable of reproducing both the observed annual mean uptake and the
observed seasonal cycle. This raises concerns about projecting future
changes in Southern Ocean CO2 fluxes. The median interannual variability
from atmospheric inversions and ocean biogeochemical models is
substantial in the Southern Ocean; up to 25% of the annual mean flux,
with 25% of this interannual variability attributed to the region south
of 58 degrees S. Resolving long-term trends is difficult due to the
large interannual variability and short time frame (1990-2009) of this
study; this is particularly evident from the large spread in trends from
inversions and ocean biogeochemical models. Nevertheless, in the period
1990-2009 ocean biogeochemical models do show increasing oceanic uptake
consistent with the expected increase of -0.05 Pg C yr(-1) decade(-1).
In contrast, atmospheric inversions suggest little change in the
strength of the CO2 sink broadly consistent with the results of Le Quere
et al. (2007).
BibTeX:
@article{lenton13a,
  author = {Lenton, A. and Tilbrook, B. and Law, R. M. and Bakker, D. and Doney, S. C. and Gruber, N. and Ishii, M. and Hoppema, M. and Lovenduski, N. S. and Matear, R. J. and McNeil, B. I. and Metzl, N. and Fletcher, S. E. Mikaloff and Monteiro, P. M. S. and Roedenbeck, C. and Sweeney, C. and Takahashi, T.},
  title = {Sea-air CO2 fluxes in the Southern Ocean for the period 1990-2009},
  journal = {BIOGEOSCIENCES},
  year = {2013},
  volume = {10},
  number = {6},
  pages = {4037--4054},
  doi = {https://doi.org/10.5194/bg-10-4037-2013}
}
Levinson, D.H. and Lawrimore, J.H. State of the climate in 2007 {2008} BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
Vol. {89}({7, S}), pp. {10+} 
article DOI  
Abstract: The combined land and ocean surface temperature in 2007 fell within the
10 highest on record while the average land temperature was the warmest
since global records began in 1880. In the low to midtroposphere, the
annual global mean temperature was among the five warmest since reliable
global records began in 1958, but still cooler than the record warmest
year of 1998. For the fourth consecutive year, the annual precipitation
averaged over global land surfaces was above the long-term mean,
although the anomaly was significantly less than in 2006 when the annual
value was the eighth wettest since 1901.
The globally averaged concentration of carbon dioxide (CO2) continued to
increase in 2007, having risen to 382.7 ppm at the Mauna Loa Observatory
in Hawaii. The average rate of rise of CO2 has been 1.6 ppm yr(-1) since
1980; however, since 2000 this has increased to 1.9 ppm yr(-1). In
addition, both methane (CH4) and carbon monoxide (CO) concentrations
were also higher in 2007.
Over the oceans, global SST during 2007 showed significant departures
from the 1971-2000 climatology. Annual average upper-ocean heat content
anomalies declined between 2006 and 2007 in the eastern equatorial
Pacific and increased in off-equatorial bands in that ocean basin. These
changes were consistent with the transition from an El Nino in 2006 to a
La Nina in 2007. The global mean see level anomaly (SLA) in 2007 was 1.1
mm higher than in 2006, which is about one standard deviation below what
would be excepted from the 15-yr trend value of 3.4 mm yr(-1).
In the tropics, the Atlantic hurricane season was near normal in 2007,
although slightly more active than in 2006. In the north and south
Indian Ocean Basins, both the seasonal totals and intensity of tropical
cyclones (TC) were significantly above average, and included two
Saffir-Simpson category 5 TCs in the north Indian Ocean and a world
record rainfall amount of 5510 mm over a 3-8 day period on the island of
Reunion in the south Indian Ocean.
In the polar regions 2007 was the warmest on record for the Arctic, and
continued a general, Arctic-wide warming trend that began in the
mid-1960s. An unusually strong high pressure region in the Beaufort Sea
during summer contributed to a record minimum Arctic sea ice cover in
September. Measurements of the mass balance of glaciers and ice caps
indicate that in most of the world, glaciers and ice caps indicate that
in most of the world, glaciers are shrinking in mass. The Greenland ice
sheet experienced records in both the duration and extent of the summer
surface melt. From the continental scale as a whole the Antarctic was
warmer than average in 2007, although the Antarctic Peninsula was
considerably cooler than average. The size of the ozone hole was below
the record levels of 2006, and near the average of the past 15 yr, due
to warmer springtime temperatures in the Antarctic stratosphere.
BibTeX:
@article{levinson08a,
  author = {Levinson, D. H. and Lawrimore, J. H.},
  title = {State of the climate in 2007},
  journal = {BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY},
  year = {2008},
  volume = {89},
  number = {7, S},
  pages = {10+},
  doi = {https://doi.org/10.1175/BAMS-89-7-StateoftheClimate}
}
Li, Z.Q., Xie, Y.S., Gu, X.F., Li, D.H., Li, K.T., Zhang, X.Y., Wu, J. and Xiong, W. Atmospheric column CO2 measurement from a new automatic ground-based sun photometer in Beijing from 2010 to 2012 2012 ATMOSPHERIC MEASUREMENT TECHNIQUES DISCUSSION  article  
Abstract: Carbon dioxide is generally regarded as the most important greenhouse gas affecting global warming. Many researches have been conducted to measure atmospheric CO 2 concentration, analyze CO 2 variation on both seasonal and interannual scales and predict …
BibTeX:
@article{li12a,
  author = {Z. Q. Li and Y. S. Xie and X. F. Gu and D. H. Li and K. T. Li and X. Y. Zhang and J. Wu and W. Xiong},
  title = {Atmospheric column CO2 measurement from a new automatic ground-based sun photometer in Beijing from 2010 to 2012},
  journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES DISCUSSION},
  year = {2012}
}
Li, C., Zhou, L., Qin, D., Liu, L., Qin, X., Wang, Z. and Ren, J. Preliminary study of atmospheric carbon dioxide in a glacial area of the Qilian Mountains, west China {2014} ATMOSPHERIC ENVIRONMENT
Vol. {99}, pp. 485-490 
article DOI  
Abstract: Carbon dioxide represents the most important contribution to increased
radiative forcing. The preliminary results of the atmospheric carbon
dioxide mole fraction from the glacial region in the Qilian Mountains
area, in the northeast of the Qinghai-Xizang (Tibetan) Plateau during
July, 2009 to October, 2012 are presented. The annual mean CO2 mole
fractions in 2010 and 2011 were 388.4 +/- 2.7 ppm and 392.7 +/- 2.6 ppm,
respectively. These values were consistent with the CO2 mole fractions
from the WMO/GAW stations located at high altitudes. However, both the
concentration and seasonal variation were significantly lower than
stations located adjacent to megacities or economic centers at low
latitudes in eastern China. Shorter durations of photosynthesis of the
alpine vegetation system that exceeded respiration were detected at the
Qilian Mountains glacial area. The annual mean increase during the
sampling period was 2.9 ppm yr(-1) and this value was higher than the
global mean values. Anthropogenic activities in the cities adjacent to
the Qilian Mountains may have important influences on the CO2 mole
fractions, especially in summer, when north and north-north-west winds
are typical. (C) 2014 Elsevier Ltd. All rights reserved.
BibTeX:
@article{li14a,
  author = {Li, Chuanjin and Zhou, Lingxi and Qin, Dahe and Liu, Lixin and Qin, Xiang and Wang, Zebin and Ren, Jiawen},
  title = {Preliminary study of atmospheric carbon dioxide in a glacial area of the Qilian Mountains, west China},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2014},
  volume = {99},
  pages = {485--490},
  doi = {https://doi.org/10.1016/j.atmosenv.2014.10.020}
}
Li, R., Zhang, M., Chen, L., Kou, X. and Skorokhod, A. CMAQ simulation of atmospheric CO2 concentration in East Asia: Comparison with GOSAT observations and ground measurements {2017} ATMOSPHERIC ENVIRONMENT
Vol. {160}, pp. 176-185 
article DOI  
Abstract: Satellite observations are widely used in global CO2 assimilations, but
their quality for use in regional assimilation systems has not yet been
thoroughly determined. Validation of satellite observations and model
simulations of CO2 is crucial for carbon flux inversions. In this study,
we focus on evaluating the uncertainties of model simulations and
satellite observations. The atmospheric CO2 distribution in East Asia
during 2012 was simulated using a regional chemical transport model
(RAMS-CMAQ) and compared with both CO2 column density (XCO2) from the
Gases Observing SATellite (GOSAT) and CO2 concentrations from the World
Data Centre for Greenhouse Gases (WDCGG). The results indicate that
simulated XCO2 is generally lower than GOSAT XCO2 by 1.19 ppm on
average, and their monthly differences vary from 0.05 to 2.84 ppm, with
the corresponding correlation coefficients ranging between 0.1 and 0.67.
CMAQ simulations are good to capture the CO2 variation as ground-based
observations, and their correlation coefficients are from 0.62 to 0.93,
but the average value of CMAQ simulation is 2.4 ppm higher than
ground-based observation. Thus, we inferred that the GOSAT retrievals
may overestimate XCO2, which is consistent with the validation of GOSAT
XCO2 using Total Carbon Column Observing Network measurements. The
near-surface CO2 concentration was obviously overestimated in GOSAT
XCO2. Compared with the relatively small difference between CMAQ and
GOSAT XCO2, the large difference in CO2 near surface or their vertical
profiles indicates more improvements are needed to reduce the
uncertainties in both satellite observations and model simulations. (C)
2017 Elsevier Ltd. All rights reserved.
BibTeX:
@article{li17a,
  author = {Li, Rong and Zhang, Meigen and Chen, Liangfu and Kou, Xingxia and Skorokhod, Andrei},
  title = {CMAQ simulation of atmospheric CO2 concentration in East Asia: Comparison with GOSAT observations and ground measurements},
  journal = {ATMOSPHERIC ENVIRONMENT},
  year = {2017},
  volume = {160},
  pages = {176--185},
  doi = {https://doi.org/10.1016/j.atmosenv.2017.03.056}
}
Li, X., Hu, X.-M., Ma, Y., Wang, Y., Li, L. and Zhao, Z. Impact of planetary boundary layer structure on the formation and evolution of air-pollution episodes in Shenyang, Northeast China {2019} ATMOSPHERIC ENVIRONMENT
Vol. {214} 
article DOI  
Abstract: The impact of the planetary boundary layer (PBL) structure on air pollution in Northeast China, where frequently experiences air pollution episodes in autumn and winter, is not well understood due to a lack of observations. In this study, four pollution episodes during autumn and winter of 2016 at Shenyang, a provincial capital city in Northeast China, were examined to investigate the linkage between the PBL structure and air pollution using meteorological sounding data and LiDAR-retrieved profiles of aerosol extinction coefficients. We also conducted a tracer simulation using the Weather Research and Forecasting model with Chemistry (WRF-Chem) to demonstrate the transport and vertical mixing of air pollutants in the PBL. The results indicated that a stable, moist and shallow surface layer (< 400 m) formed and remained at night due to strong surface radiative cooling after a steep decline of temperature during the first air-pollution episode (EP1, from 12:00 Local Time (LT) on November 26 to 07:00 LT on November 27). Stable stratification and stagnant winds contributed to the increase of surface pollutant concentrations in EP1. Strong surface potential temperature inversion and enhanced local emissions during evening rush hour resulted in the formation of EP2 (13:00-23:00 LT on December 2). Observations and modelling results revealed that large amount of pollutants were transported by the southerly nocturnal low-level jets from the North China Plain to Shenyang after EP2. These pollutants were trapped in the residue layer at night and then mixed to the surface after sunrise due to convective turbulence, leading to the formation of EP3 (06:00-23:00 LT on December 3). EP4 (03:00-14:00 LT on December 4) occurred in the convergence zone ahead of an approaching trough. Low wind speed (< 6 m s(-1)) and high relative humidity (> 80%) in the PBL enhanced the deterioration of air quality near the surface.
BibTeX:
@article{li19a,
  author = {Li, Xiaolan and Hu, Xiao-Ming and Ma, Yanjun and Wang, Yangfeng and Li, Liguang and Zhao, Ziqi},
  title = {Impact of planetary boundary layer structure on the formation and evolution of air-pollution episodes in Shenyang, Northeast China},
  journal = {ATMOSPHERIC ENVIRONMENT},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  year = {2019},
  volume = {214},
  doi = {https://doi.org/10.1016/j.atmosenv.2019.116850}
}
Li, X., Hu, X.-M., Cai, C., Jia, Q., Zhang, Y., Liu, J., Xue, M., Xu, J., Wen, R. and Crowell, S.M.R. Terrestrial CO2 Fluxes, Concentrations, Sources and Budget in Northeast China: Observational and Modeling Studies {2020} JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. {125}({6