Intercomparison of Carbon Dioxide Products Retrieved from GOSAT Short-Wavelength Infrared Spectra for Three Years (2010–2012)

This paper presents the comparison of two CO2 datasets from the National Institute for Environmental Studies (NIES) of Japan and the Atmospheric CO2 Observations from Space (ACOS) of NASA for three years (2010 to 2012). Both CO2 datasets are retrieved from the Greenhouse gases Observing SATellite (GOSAT) short-wavelength infrared spectra over High gain surface land. In this three-year period, the yield of the NIES CO2 column averaged dry air mole fractions (XCO2) is about 71% of ACOS retrievals. The overall bias is 0.21 ± 1.85 ppm and −0.69 ± 2.13 ppm for ACOS and NIES XCO2, respectively, when compared with ground-based Fourier Transform Spectrometer (FTS) observations from twelve Total Carbon Column Observing Network (TCCON) sites. The differences in XCO2 three-year means and seasonal means are within about 1 to 2 ppm. Strong consistency is obtained for the ACOS and NIES XCO2 monthly averages time series over different regions, with the greatest mean difference of ACOS to NIES monthly means over China (1.43 ± 0.60 ppm) and the least over Brazil (−0.03 ± 0.64 ppm). The intercomparison between the two XCO2 datasets indicates that the ACOS XCO2 is globally higher than NIES by about 1 ppm and has smaller bias and better consistency than NIES data.