Airborne atmospheric carbon dioxide measurement using 1.5 µm laser double-pulse IPDA lidar over a desert area

Abstract

An integrated path differential absorption (IPDA) lidar can accurately measure regional CO2 weighted column average concentrations (XCO2), which are crucial for understanding the carbon cycle in climate change studies. To verify the performance and data inversion methods of space-borne IPDA lidar, in July 2021, we conducted an airborne lidar validation experiment in Dunhuang, Gansu Province, China. An aircraft was equipped with a lidar system developed to measure XCO2 and an in situ greenhouse gas analyzer (GGA). To minimize measurement errors, energy monitoring was optimized. The system bias error of the DAOD was determined by changing the laser output mode from the off/on to the on/on mode. The XCO2 inversion results obtained through comparing the schemes of averaging signals before “log (logarithm)” and averaging after “log” indicate that the former performs better. The IPDA lidar measured XCO2 over the validation site at 405.57 ppm, and both the IPDA lidar and GGA measured sudden changes in the CO2concentration. The assimilation data showed a similar trend according to the altitude to the data measured by the in situ instrument. A comparison of the mean XCO2 derived from the GGA results and assimilation data with the IPDA lidar measurements showed biases of 0.80 and 1.12 ppm, respectively.