Inverse modeling of CO sub(2) sources and sinks using satellite observations of CO sub(2) from TES and surface flask measurements

• Published in: Atmospheric chemistry and physics discussions 2011-02, Vol.11 (2), p.4263-4311
• Main Authors: Nassar, R, Jones, DBA, Kulawik, S S, Worden, J R, Bowman, K W, Andres, R J, Suntharalingam, P, Chen, J M, Brenninkmeijer, CAM, Schuck, T J
• Format: Article
• Language: English
• ISSN: 1680-7367; 1680-7375

We infer CO sub(2) surface fluxes using satellite observations of mid-tropospheric CO sub(2) from the Tropospheric Emission Spectrometer (TES) and measurements of CO sub(2) from surface flasks in a time-independent inversion analysis based on the GEOS-Chem model. Using TES CO sub(2) observations over oceans, spanning 40 degree S-40 degree N, we find that the horizontal and vertical coverage of the TES and flask data are complementary. This complementarity is demonstrated by combining the datasets in a joint inversion, which provides better constraints than from either dataset alone, when a posteriori CO sub(2) distributions are evaluated against independent ship and aircraft CO sub(2) data. In particular, the joint inversion offers improved constraints in the tropics where surface measurements are sparse, such as the tropical forests of South America, which the joint inversion suggests was a weak sink of -0.17 plus or minus 0.20 Pg C in 2006. Aggregating the annual surface-to-atmosphere fluxes from the joint inversion yields -1.13 plus or minus 0.21 Pg C for the global ocean, -2.77 plus or minus 0.20 Pg C for the global land biosphere and -3.90 plus or minus 0.29 Pg C for the total global natural flux (defined as the sum of all biospheric, oceanic, and biomass burning contributions but excluding CO sub(2) emissions from fossil fuel combustion). These global ocean, global land and total global fluxes are shown to be in the range of other inversion results for 2006. To achieve these results, a latitude dependent bias in TES CO sub(2) in the Southern Hemisphere was assessed and corrected using aircraft flask data, and we demonstrate that our results have low sensitivity to variations in the bias correction approach. Overall, this analysis suggests that future carbon data assimilation systems can benefit by integrating in situ and satellite observations of CO sub(2) and that the vertical information provided by satellite observations of mid-tropospheric CO sub(2) combined with measurements of surface CO sub(2), provides an important additional constraint for flux inversions.