Ground return signal simulation and retrieval algorithm of spaceborne integrated path DIAL for CO_2 measurements

摘要

Spacebome integrated path differential absorption (IPDA) lidar is an active-detection system which is able to perform global CO_2 measurement with high accuracy of lppmv at day and night over ground and clouds. To evaluate the detection performance of the system, simulation of the ground return signal and retrieval algorithm for CO_2 concentration are presented in this paper. Ground return signals of spaceborne IPDA lidar under various ground surface reflectivity and atmospheric aerosol optical depths are simulated using given system parameters, standard atmosphere profiles and HITRAN database, which can be used as reference for determining system parameters. The simulated signals are further applied to the research on retrieval algorithm for CO_2 concentration. The column-weighted dry air mixing ratio of CO_2 denoted by XCO_2 is obtained. As the deviations of XCO_2 between the initial values for simulation and the results from retrieval algorithm are within the expected error ranges, it is proved that the simulation and retrieval algorithm are reliable.