PRECISION REQUIREMENTS FOR SPACE-BASED XCO2 DATA
Description:
The Orbiting Carbon
Observatory (OCO) mission will deliver space-based observations of atmospheric
CO2 with the potential to resolve many of the uncertainties in the
spatial and temporal variability of carbon sources and sinks. Our assessments of the measurement
requirements for space-based remote sensing of atmospheric CO2 conclude
that the data must support retrievals of the column-averaged CO2 dry
air mole fraction, XCO2,
with precisions of 3 to 4 ppm to resolve the annually averaged gradients between the Northern and Southern hemispheres, but higher
precision (1 to 2 ppm) will be needed to resolve East-West gradients and
questions like the location and spatial extent of the Northern Hemisphere
terrestrial carbon sink. These
conclusions are derived from the results
of observational system simulation experiments (OSSEs) and synthesis inversion
models [Rayner and O’Brien, 2001; O’Brien and Rayner, 2002; Rayner et al., 2002]. The XCO2 precision
requirements also considered the OCO mission design, the amplitude of XCO2 spatial and temporal gradients, and the relationship between XCO2 data
precision and regional scale surface CO2 flux uncertainties inferred
from XCO2 data.
Author's Names: C. E. Miller, D. Crisp, P. L. DeCola, S. C. Olsen, et al
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PRELIMINARY CONSTRAINTS ON FOSSIL-FUEL CO2: COMPARISON OF TRACERS 14CO2, CO AND SF6
Description: We use the
theoretically ideal tracer 14CO2 to estimate the fossil
fuel CO2 enhancement in boundary layer air at two sites in New
England and Colorado.
Improved D14C measurement
precision of 1.6-2.6‰ provides fossil fuel CO2detection capability
of 0.8-1.5 ppm. Using the tracers CO and SF6, we obtain two
additional independent estimates of the fossil fuel CO2 component,
and we assess the biases in these methods by comparison with the 14CO2-based
estimates. Large differences are observed between the SF6-based
estimates and those from the 14CO2 and CO methods. The
CO-based estimates show seasonally coherent biases, underestimating fossil fuel
CO2 in winter and overestimating in summer.
Author's Names: J.C. Turnbull, J.B. Miller, S.J. Lehman, R.J. Sparks, et al
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Added on: 08-Aug-2005 Downloads: 22
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PROGRESSIVE DECREASE OF THE N. ATLANTIC MIDLATITUDE SINK FOR ATMOSPHERIC CO2
Description: We present monthly means of observations of sea
surface and atmospheric pCO2 and associated variables made on board
commercial vessels operating in the mid-latitude North Atlantic between the UK and the Caribbean.
The measurements were made using automated instrumentation in 1994 -1995, and
again from 2002 - present, allowing the study of changes which have taken place
over a large region of the North Atlantic over
almost a decade. Sea surface pCO2 has increased faster than atmospheric
pCO2 over the whole region, so that ΔpCO2 has decreased,
reducing the mid-latitude North Atlantic sink
from the atmosphere. The change in ΔpCO2 is largest in the north and
east, and smallest in the south and west of the region.
Author's Names: U. Schuster, and A.J. Watson
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Added on: 04-Aug-2005 Downloads: 19
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PROMOTION EFFECTS OF FALLING DROPLETS ON CARBON DIOXIDE ABSORPTION ACROSS THE AIR-WATER INTERFACE
Description: The effect of
rainfall on mass transfer across the air-water interface was investigated
through the CO2 absorption experiments in a turbulent open-channel
flow with the free surface. The results show that the rainfall enhances both
the turbulent mixing near the free surface on the liquid side and the CO2
transfer across the interface. The mass transfer coefficient on the liquid side
is well correlated by both the mean vertical momentum flux of rainfall, M, and the mean kinetic energy of rain
droplets impinging on the unit area of the air-water interface, KEF. However, it was not concluded which
of M and KEF is a better parameter for expressing
the rainfall effects on the mass transfer. The comparison between the mass
transfer coefficient obtained in this study and that obtained in wind-driven
turbulence suggests that it is of great importance to consider the rainfall
effect on the CO2 exchange rate between the atmosphere and ocean in
precisely estimating the global carbon cycle in a climate model.
Author's Names: N. Takagaki1 and S. Komori
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RECENT CO2 FLUX VARIABILITY ESTIMATED FROM ATMOSPHERIC MIXING RATIO MEASUREMENTS – AN UPDATE
Description:
Regular multi-year
measurements of atmospheric CO2 mixing ratios at a network of sites
(Fig. 1) give quantitative spatial and temporal information on surface sources
and sinks [e.g., Conway et al., 1994]. Using a
global atmospheric tracer transport model in a high-resolution (daily, 4x5
degree pixels) inversion setup, we estimate surface-atmosphere CO2 fluxes
that give the best match between modelled and observed CO2 concentrations.
Building on an earlier study [Rödenbeck et al.,
2003], this contribution (1) presents new CO2 flux estimates using
methodological developments, and (2) provides an update on interannual fluxes over
the most recent anomalous time period 2002-2003.
Author's Names: C. Rödenbeck, T.J. Conway, R. Langenfelds, et al
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Added on: 03-Aug-2005 Downloads: 27
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RECTIFIER EFFECT IN AN ATMOSPHERIC MODEL WITH DAILY BIOSPHERIC FLUXES
Description:
The synoptic scale atmosphere-biosphere interaction
can cause anomalies of ~10 ppm with length scale of ~1000 km in the monthly
averaged surface CO2 concentration. These anomalies may contribute
to the errors and uncertainties of CO2 inversion estimates.
Author's Names: M. Ishizawa, D. Chan, K. Higuchi, S. Maksyutov, et al
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Added on: 28-Jul-2005 Downloads: 27
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REGIONAL AND CONTINENTAL NORTH AMERICAN CARBON EXCHANGE IN 2003 AND 2004 USING AIRCRAFT AND ...
Description:
We quantify atmosphere-biosphere carbon exchange at
the continental scale across North America
during the summers of 2003 and 2004. The 2003 campaign features continental
transects across the northern portion of North America with significant
influence from biomass burning, while the 2004 study focuses on the greater New
England and Quebec
region. We use a Lagrangian, adjoint atmospheric model [Gerbig et al. 2003a,b; Lin et
al. 2003] coupled to a biosphere model derived from the Vegetation
Photosynthesis Model [Xiao et al.,
2004]. Our analysis of the 2004 airborne data demonstrates the progression of
increasing carbon uptake through the boreal zone during the seasonal transition
from early spring to late summer. Data from the coast-to-coast transects of the
2003 campaign allow us to quantify large scale carbon exchange across the
continent.
Author's Names: D.M. Matross, M. Pathmathevan, C. Gerbig, et al
Filesize: 25.12 Kb
Added on: 02-Aug-2005 Downloads: 24
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REGIONAL BOMB-PRODUCED RADIOCARBON INVENTORIES AND THE AIR-SEA GAS TRANSFER VELOCITY
Description: Two major problems in carbon cycle research are that the current
data-based budget of artificially-produced radiocarbon is unbalanced and that
the air-sea gas transfer piston velocity remains uncertain. In this study, the
regional distribution of bomb-produced radiocarbon inventories in the ocean and
their dependencies on the piston velocity is analysed within a seasonal, 3-d
frictional-geostrophic balance ocean model. Model results and data-based reconstructions
are compared to evaluate the consistency between the applied piston velocity
field and data-deduced ocean inventories. Bomb-radiocarbon inventories in the
GEOSECS and WOCE era are predominantly governed by the applied piston velocity.
Here, the piston velocity field provided by the Ocean Carbon Cycle
Intercomparison Project (OCMIP-II) were prescribed and scaled by a globally
constant factor in a range of sensitivity simulations.
Author's Names: S. A. Müller, F. Joos and G.-K. Plattner
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Added on: 29-Jul-2005 Downloads: 19
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REGIONAL CARBON FLUX ESTIMATION USING THE MAXIMUM LIKELIHOOD ENSEMBLE FILTER
Description:
We have developed a
carbon flux inversion method for using a mesoscale meteorological model
(CSU-RAMS) within a Maximum Likelihood Ensemble Filter (MLEF, Zupanski 2005;
Zupanski and Zupanski 2005). The MLEF is a variant of the Ensemble Kalman
Filter, and is used to optimize model state variables and parameters based on
continuous observations of CO2 mixing ratio. The method does not
require the development of a model adjoint, but rather relies on transformation
of variables to efficiently obtain estimates of fluxes with uncertainties and
dynamical model error from an ensemble of forward model simulations. We
demonstrate this method using a mesoscale simulation of weather, transport, and
the surface carbon budget over the continental USA during the summer. The
estimation procedure decomposes the total surface flux into photosynthesis and
respiration (which are assumed to be modeled correctly to first order), plus an
unknown but time-invariant fractional error in each. These residuals are estimated for each model
grid cell over a moving window in time, allowing atmospheric observations to be
integrated over sufficient time to obtain constraint. Model error can also be
estimated by this procedure, and the method can be extended to larger domains
and longer integrations.
Author's Names: A. S. Denning, Dusanka Zupanski, Marek Uliasz, et al
Filesize: 32.10 Kb
Added on: 28-Jul-2005 Downloads: 22
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REGIONAL MULTI-TRACER CO2 CHARACTERISATION BY EVENT FLASK SAMPLING
Description: The
14CO2 analysis of atmospheric samples enables us to
discriminate between biospheric and fossil fuel contributions on top of the
atmospheric CO2 background [e.g. Meijer et al,
1996]. Following, the CO vs. fossil CO2 ratio gives an indication of
the combustion quality and also the possibility to regionally and temporarily
calibrate the CO concentration measurements as a surrogate for fossil CO2
determination by means of (the rather expensive) 14CO2
measurements.
Author's Names: C. Sirignano, R.E.M. Neubert, B. Löscher and H.A.J. Meijer
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Added on: 04-Aug-2005 Downloads: 18
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