Global Terrestrial Ecosystem Carbon Flux Inferred from TanSat XCO2 Retrievals

TanSat is China’s first greenhouse gases observing satellite. In recent years, substantial progresses have been achieved on retrieving column-averaged CO₂ dry air mole fraction (XCO₂). However, relatively few attempts have been made to estimate terrestrial net ecosystem exchange (NEE) using TanSat XCO₂ retrievals. In this study, based on the GEOS-Chem 4D-Var data assimilation system, we infer the global NEE from April 2017 to March 2018 using TanSat XCO₂. Evaluations against independent CO₂ observations and comparison with previous estimates indicate that the inverted land sinks in the northern middle latitudes and southern temperate regions are improved to a certain extent, however, they are obviously overestimated in northern high latitudes and underestimated in tropical lands (mainly northern Africa), respectively. There are 4 monthly mean variables in this dataset, including prior NEE, posterior NEE, prior ocean flux, and posterior ocean flux, which are all in a spatial resolution of 5 deg by 4 deg.