Column-Weighted Carbon Dioxide Concentration Under the Cloud Using Spaceborne IPDA Lidar

In 2022, China launched the world’s first satellite for active lidar CO₂ detection, the Atmospheric Environmental Monitoring Satellite (AEMS, or DQ-1). Its key payload, the Aerosol and Carbon Detection LiDAR (ACDL), provides high-precision CO₂ column concentration (XCO₂) measurements. The system can treat optically thick clouds as hard targets while penetrating thin clouds, enabling separation of above-cloud and whole-column CO₂ signals for below-cloud XCO₂ retrievals. XCO₂ retrievals under the cloud better represent near-surface CO₂ concentrations.