Global surface CO2 flux estimates using GOSAT-2 observations

The Greenhouse gases Observing SATellite 2 (GOSAT-2) was launched, as the successor of GOSAT, on 29th October 2018 into a sun-synchronous orbit at an altitude of 613 km with 6-day revisit cycle, then the satellite has been operated with normal mode since 1^st February 2019. GOSAT-2 is designed to measure atmospheric carbon dioxide (CO₂), methane (CH₄) and carbon monoxide (CO) with two instruments: The Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer 2 (TANSO-FTS-2) and the Cloud and Aerosol Imager 2 (TANSO-CAI-2). The GOSAT-2 mission inherits the main objective of the GOSAT that improves our knowledge of spatiotemporal variations of CO₂ and CH₄ in the atmosphere and the process governing their exchange between the atmosphere and the Earth's surface and contributes climate change studies and related environmental policy making. The GOSAT-2 project provides GOSAT-2 products, e.g., Level 1 radiance spectral products of GOSAT-2 observations and FTS-2 shortwave infrared (SWIR) Level 2 atmospheric concentration products. The GOSAT-2 Level 4 products are designed to provide an estimate of monthly global surface fluxes on CO₂ and CH₄ with a spatial resolution of 2.5 ̊ grid using the FTS-2 SWIR Level 2 products. This presentation provides some detail on the GOSAT-2 Level 4 CO₂ product, including the model system based on NICAM-TM 4D-Var and the prior information that are used for estimating global carbon cycle, and comparison with the GOSAT Level 4 CO₂ product, which is the global surface flux estimate based on the GOSAT observations.