Retrievals of atmospheric CO2, CH4 and optical path modifications from the GOSAT observations

Andrey Bril; Sergey Oshchepkov; Tatsuya Yokota; Yukio Yoshida; Isamu Morino; Osamu Uchino; Dmitry Belikov; Shamil Maksyutov

doi:10.1117/12.2028486

17 October 2013 Retrievals of atmospheric CO₂, CH₄ and optical path modifications from the GOSAT observations

Andrey Bril, Sergey Oshchepkov, Tatsuya Yokota, Yukio Yoshida, Isamu Morino, Osamu Uchino, Dmitry Belikov, Shamil Maksyutov

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Proceedings Volume 8890, Remote Sensing of Clouds and the Atmosphere XVIII; and Optics in Atmospheric Propagation and Adaptive Systems XVI; 889008 (2013) https://doi.org/10.1117/12.2028486
Event: SPIE Remote Sensing, 2013, Dresden, Germany

Abstract

We present satellite-based data of the column-averaged dry air mole fraction of atmospheric carbon dioxide (XCO₂) and methane (XCH₄), which were derived from the radiance spectra measured by Greenhouse gases Observing SATellite (GOSAT). We have applied new version of the Photon path-length Probability Density Function (PPDF)-based algorithm to estimate XCO₂ and PPDF parameters. These parameters serve to allow for optical path modification due to atmospheric light scattering and they are retrieved simultaneously with CO2 concentration using radiance spectra from all available GOSAT short wave infrared (SWIR) bands (oxygen A-band, 1.6-μm, and 2.0-μm CO₂ absorption bands). For the methane abundance, retrieved from 1.67-μm absorption band, we applied optical path correction based on PPDF parameters from 1.6-μm CO₂ absorption band. Similarly to widely used CO₂-proxy technique, this correction assumes identical light path modifications in 1.67-μm and 1.6-μm bands. This approach is believed to offer some advantages over the proxy technique since it does not use any prior assumptions on carbon dioxide concentrations. Both carbon dioxide and methane GOSAT retrievals were validated using ground-based Fourier Transform Spectrometer (FTS) measurements provided by the Total Carbon Column Observing Network (TCCON). For XCO₂ retrievals we found subppm station-to-station bias (GOSAT versus TCCON); single-scan precision of mostly below 2 ppm (0.5%); and correlation coefficient for the Northern Hemisphere TCCON stations above 0.8. For XCH4 retrievals over TCCON sites we found single-scan precision below 1 % and correlation coefficient above 0.8.

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Andrey Bril, Sergey Oshchepkov, Tatsuya Yokota, Yukio Yoshida, Isamu Morino, Osamu Uchino, Dmitry Belikov, and Shamil Maksyutov "Retrievals of atmospheric CO₂, CH₄ and optical path modifications from the GOSAT observations", Proc. SPIE 8890, Remote Sensing of Clouds and the Atmosphere XVIII; and Optics in Atmospheric Propagation and Adaptive Systems XVI, 889008 (17 October 2013); https://doi.org/10.1117/12.2028486

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