[A-CG37] 衛星による地球環境観測

[ACG37-02] Global CO₂ and CH₄ flux extimates based on satellite observations by GOSAT and GOSAT-2

*齊藤 誠¹、丹羽 洋介¹、高木 宏志¹、亀井 秋秀¹、佐伯 田鶴¹、白石 知宏¹、野田 響¹、平田 竜一¹、村上 和隆¹、森野 勇¹、八代 尚¹、吉田 幸生¹、Maksyutov Shamil¹、松永 恒雄¹ (1.国立環境研究所)

キーワード：衛星観測、温室効果ガス、大気逆解法

Understanding changes in the Earth system and the impact of human activity is significant scientific challenge. Earth explorer satellite missions provide essential observational data to study the scientific issues in local, regional, and global scales. Greenhouse gases Observing SATellite (GOSAT) and the successor GOSAT-2 are Japanese Earth explore satellite missions for monitoring global distribution of greenhouse gases. This study describes overviews of global surface carbon dioxide (CO₂) and methane (CH₄) flux estimates based on respective TANSO-FTS and TANSO-FTS-2 Column-averaged Dry-air Mole Fraction Products (GOSAT and GOSAT-2 SWIR Level 2 Products) being retrieved from the spectral data acquired by GOSAT and GOSAT-2 satellites. The flux estimates derived from GOSAT SWIR Level 2 Products have been released as GOSAT Level 4 Products, whose latest versions cover variability of global CO₂ and CH₄ fluxes for 2009 and 2020. We show that the GOSAT Level 4 Products using a fixed-lag Kalman smoother built on an atmospheric tracer transport model NIES-TM can provide an information to infer carbon cycle over regional scale. As a case study of surface flux estimate over the blank region of surface observational stations, an insight regarding relationship between CH₄ emissions and reginal meteorological conditions in central South America is given in this study by using the satellite observations effectively. New global surface flux estimates derived from GOSAT-2 SWIR Level 2 Products are developed using a global circulation mode NICAM-based Inverse Simulation for Monitoring CO₂ and CH₄ (NISMON) system. In the estimate uncertainties being inherent in the GOSAT-2 SWIR Level 2 Products results in erroneous distributions of flux estimates, especially over the African continent. We demonstrate latest results of GOSAT-2 Level 4 product using updated GOSAT-2 SWIR Level 2 Products and their comparison with other observational and model estimate results.