[A-AS11] [JJ] Atmospheric Chemistry

[AAS11-P14] Comparisons of column-averaged dry-air mole fractions of greenhouse gases among GOSAT/TANSO-FTS SWIR, TIR, and NICAM-TM data

*Hiromichi Hatta¹, Naoko Saitoh², Yosuke Niwa³, Ryoichi Imasu⁴, Kei Shiomi⁵, Yukio Yoshida⁶ (1.Chiba university Graduate School of Advanced Integration Science, 2.Center for Environmental Remote Sensing, Chiba University, 3.Meteorologocal Research Institute, 4.Atmosphere and Ocean research Institute, 5.Japan Aerospace Exploration Agency, 6.National Institute for Environmental Studies)

Keywords:GOSAT, XCO2, XCH4

Greenhouse gases Observing SATellite (GOSAT) was launched on 23 January, 2009. Thermal and Near-infrared Sensor for Carbon Observation Fourier Transform Spectrometer (TANSO-FTS) on board the GOSAT has SWIR and TIR bands and can observe column-averaged dry-air mole fractions of CO₂ and CH₄ (XCO₂ and XCH₄) in the SWIR bands [Yoshida et al., 2011] and CO₂ and CH₄ vertical profiles in the TIR band [Saitoh et al., 2009]. In this study, we calculated XCO₂ and XCH₄ values from the TIR CO₂ and CH₄ profiles, and then compared them with XCO₂ and XCH₄ data of the SWIR bands and Nonhydrostatic ICosahedral Atmospheric Model-based Transport Model (NICAM-TM) [Niwa et al., 2011]. Before calculating the TIR XCO₂ values, we applied bias-correction values evaluated based on the comparisons of aircraft CO₂ data.
We compared latitudinal distributions of XCO₂ among TANSO-FTS TIR, SWIR, NICAM-TM, and a priori (NIES-TM05) data [Saeki et al., 2013]. TIR XCO₂ data over the land in the Northern Hemisphere except the Sahara desert were slightly smaller than SWIR XCO₂ data and, in contrast, slightly larger over the land in the Southern Hemisphere. Over the Sahara desert, TIR XCO₂ data in the daytime were considerably smaller than SWIR and NICAM-TM XCO₂ data, which suggests that surface parameters used in the TIR retrieval had some problems. Over Hawaii where there is no strong CO₂ source, TIR XCO₂ data agreed with SWIR XCO₂ data to within 1% on average.