With the increasing temporal and spatial density of CO₂ flux and concentration observations from worldwide tower networks, the importance of interpreting the data is becoming more conspicuous. Previous work shows that tower observations might be able to catch synoptic, regional, and local signals of CO₂ simultaneously. Thus a study that can explain CO₂ transport and the response of the ecosystem to the weather change simultaneously is necessary and will help the development of the regional inverse modeling technique in the future.

Greenhouse gases Observing SATellite (GOSAT) of Japan is planned to be launched in 2008. GOSAT will be equipped with a FTS to monitor CO₂ column density globally. The FTS has three near infrared bands which cover 0.76 µm, 1.6 µm, and 2.0 µm spectral regions, respectively. Retrieval algorithms to estimate CO₂ and CH₄ column densities from these bands data are now being developed. We have investigated retrieval algorithms under the non-clear sky conditions. As one of these cases, a cirrus cloud parameter estimation was researched. The cirrus vertical profile (i.e., existing height) is estimated from the 0.76 µm band data. Strong water vapor absorption area is included in the 2.0 µm spectral band, so that the reflected radiance from a ground surface is absorbed completely by H₂O in this area. Thus the signal in this area is considered as path radiance caused by the cirrus clouds reflection, because there is little water vapor above the cirrus cloud top. By using this signal, the cirrus optical depth can be estimated, and then column densities of CO₂, CH₄ and H₂O are retrieved precisely.

The current WMO CO₂ Mole Fraction Scale consists of a set of fifteen CO₂ –in-air primary standard calibration gases ranging in CO₂ mole fraction from 250 to 520 micromol/mol. Since the WMO CO₂ Expert Group transferred responsibility for maintaining the WMO Scale from the Scripps Institute of Oceanography (SIO) to the Climate Monitoring and Diagnostics Laboratory (CMDL) in 1995, the fifteen WMO primary standards have been calibrated at regular interval, between one and two years, by the CMDL manometric system. From mid-1996 to 2001, the assigned CO₂ values of the WMO Primaries have been jointly based on the SIO and CMDL manometric measurements, and completely on the CMDL manometric measurements alone from 2001 to present. The uncertainty of the 15 primary standards is estimated to be 0.07 micromol/mol in the one-sigma absolute scale. Manometric calibration results indicated that there is no evidence of overall drift of the Primaries from 1996 to 2004. In order to lengthen the useful life of the Primary standards, CMDL has always transferred the WMO Scale to the Secondaries via NDIR analyzers. The uncertainties arising from the analyzer random error and the propagation error due to the uncertainty of the reference gas concentration are discussed. Precision of NDIR transfer calibrations is about 0.01 micromol/mol from 1979 to present. Propagation of the uncertainty is calculated theoretically. In the case of interpolation, the propagation error is estimated to be between 0.05 and 0.07 micromol/mol when the Primaries are used as the reference gases via NDIR transfer calibrations.

CHIOTTO – Continuous HIgh-precisiOn Tall Tower Observations of greenhouse gases – is a European Union-funded project which has as objective to build an infrastructure for the continuous monitoring of greenhouse gas concentrations across Europe above the surface layer using tall towers (~300m height). For this purpose a new analysis system for continuous atmospheric measurements was built and tested at Max Planck Institute for Biogeochemistry, Jena, Germany and was recently installed at a 300 m tower close to Bialystok, Poland (Lat 53°14'N, Long 23°01'E, Alt 180m), as part of the “CHIOTTO” tall tower network. Since July 2005 this system is measuring quasi-continuously the atmospheric concentration of CO₂, CH₄, CO, N₂O, SF₆ and the O₂/N₂ ratio as well as meteorological parameters (atmospheric pressure, temperature, humidity; wind speed and direction) from 5 heights on the tower ranging from 5 to 300 m. The measurement devices are: an Oxzilla O₂ fuel cell analyzer, a LiCor 7000 NDIR CO₂ analyzer, an Agilent gas chromatograph (GC) with flame ionization detector (FID) and electronic capture detector (ECD) for CH₄, CO, N₂O, SF₆. The challenge was to build a reliable automatic system which can run continuously with very little maintenance and to fulfill at the same time the high precision requirements for all the measured species prescribed by the CHIOTTO project goals. The high temporal resolution achieved will capture short term events and diurnal variability. In addition, the system is planned to run for at least several years in order to observe long-term trends as well. We describe the technical setup of the measurement system, the region of influence of the station and present the first months of data if available: correlations between species, observed short term variability patterns and their relation to meteorology and air parcel paths.

To know regional-to-continental scale CO₂ fluxes between atmosphere and terrestrial biosphere using an inverse model, the CO₂ measurements on plural towers situated in a thousand square kilometer area of West Siberia have been carried out since 2002. The CO₂ concentrations at 80m of the tower during daytime afternoon well represents those of PBL with its difference in ±3 ppm, and 90% of them in ±2 ppm, in clear sky day, when no strong inversion is occurred in winter. The tower observation expands to five sites to date, and additional four sites will be established in a year.

Existing instruments for measuring atmospheric profiles of carbon dioxide can be very sensitive, but are all large and bulky and must be flown using aircraft or large, research gondolas.  This work reports on the development of a stand-alone, lightweight CO₂ sensor for use on balloon sondes.  This device will have sub part-per-million (ppm) sensitivity and weigh less than 1 kg.

This presentation describes in-situ atmospheric CO₂ measurements at Waliguan Observatory (WLG, 36°17'N, 100°54'E, 3816m asl) since 1994, together with 5-day isobaric back trajectory analysis.  We also use the Hybrid Single-Particle Lagrangian Integrated Trajectory (Hysplit-4) transport/diffusion model to simulate the CO₂ variation at WLG in January 1999 and compared with observations. A case study for polluted air mass transport event with a short-term elevated CO₂ has been conducted to further investigate the impact of source, sink and long-range transport of atmospheric CO₂.

We analysed the temporal variations of the CO₂ system in the Southern Ocean south of Tasmania and compared the seasonality of the carbon dioxide fugacity (fCO₂) and the air-sea CO₂ flux during spring and summer for two different years: 1996/97 and 2002/03. In summer, the CO₂ flux presents large and contrasting interannual changes in the Permanent Open Ocean Zone (POOZ, 53-61°S): the oceanic CO₂ sink varies from about –0.3 mmol.m^-2.d^-1 in 1997 to –20.6 mmol.m^-2.d^-1 in 2003. This strong sink in February 2003 was related to an increased phytoplankton biomass in this high-nutrient, low-chlorophyll (HNLC) region.

We will present our design of a new autonomous, inexpensive, and robust CO₂ analyzer (AIRCOA), a description of our quality control procedures, and data examples from ongoing deployments.  Our current AIRCOA units require less than $10K (USD) in components, show intercomparability better than 0.1 ppm during laboratory tests, and are designed to run autonomously for months at a time.