Toward accurate CO2 and CH4 observations from GOSAT

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.