Influence of thin cirrus clouds on the short-wave infrared satellite observation of atmospheric CO2

Abstract

Optically thin cirrus clouds have low solar reflectance but are still efficient at absorbing infrared radiation emitted by the surface and atmosphere, which is one of the important factors for satellite detecting the greenhouse gas CO2. The existence of the cloud greatly reduces the utilization of satellite data. Aiming at improving the utilization effectively of XCO2, the effects of thin cirrus clouds on forward modeling spectra and retrieved results are investigated in this study. The cloud base of 6 km, 8 km, 10 km and the thickness of 0.1 km, 0.2 km, 0.3 km, 0.4 km are simulated to obtain spectra of O2–A (0.76 μm) and CO2 (1.6 μm). The simulation results show that the radiation intensity is reduced due to the existence of thin cirrus clouds for O2–A band, and the radiation intensity is enhanced for the CO2 band. The mean values of spectral residuals for both bands are increased with the increase of cloud base and thickness, and they are nearly zero value. The retrieval results show that the relative errors of O2–A total column concentration are in the range of 0.08 %–0.09 % for all thin cirrus clouds, and the relative errors of CO2 total column concentration are 0.16 %–0.35 %. Therefore, the relative errors of XCO2 are 0.06 %–0.25 %.