A direct measurement technique of satellite-based CO₂ flux

At present, the mainstream of global carbon flux monitoring is realized through assimilation algorithms by integrating ground-based greenhouse gas flux network and concentration measurement, satellite-based remote sensing greenhouse gas concentration and other data sources. Considering the limited coverage of in-situ measurement, a direct carbon flux measurement method was proposed. The method was based on the first order closure theory of turbulence, adopted the horizontal wind profile and CO2 concentration profile and combined with Monin-Obukhov similarity theory to directly calculate CO2 flux. The horizontal wind profile was retrieved by the dual looking lidar using the coherent Doppler wind measurement method, and the CO2 concentration profile was detected based on the differential absorption principle of the lidar. The method could achieve the current international wind measurement accuracy of 1 m/s and the detection accuracy of 10(-6) CO2 concentration based on the satellite platform. Through preliminary analysis of the flux model, it is found that under neutral atmospheric condition with strong carbon sources (such as near ground CO2 concentration difference>10(-5)), the accuracy of the CO2 flux can meet the requirements of scientific application, that is, the uncertainty of CO2 flux measurement within 25% can be achieved. In general, this method can provide large-scale CO2 flux observation data as a meaningful supplement to the in-situ measurement of ground-based carbon flux.