Measurement of CO2 Column Concentration Above Cloud Tops With a Spaceborne IPDA Lidar.

The Atmospheric Environment Monitoring Satellite (AEMS), launched by China in 2022, was equipped with active remote sensing lidar for carbon monitoring. It adopts the Integrated Path Differential Absorption (IPDA) technology to monitor global CO2 column concentration (XCO2). The calculation of cloud top XCO2 requires cloud height data. A comparison between SRTM global elevation data and 1,572 nm channel elevation data reveals a coefficient of determination (R2) of 0.998, with an average deviation of 1.24 m. The cloud top XCO2 observations are consistent with the OCO‐2 and CarbonTracker trends. The ocean carbon uptake rate, assessed by the difference in CO2 concentration between cloud top and sea surface, is −0.319 mmol/m2/h, which is in good agreement with the associated carbon flux data. This demonstrates the great potential of IPDA lidar for remote sensing of cloud top CO2 and quantifying ocean carbon uptake. Plain Language Summary: For global greenhouse gas monitoring, passive remote sensing technology has consistently struggled to balance the reliability and usability of monitoring data in cloudy regions. The AEMS employs 1,572 nm IPDA lidar technology for active remote sensing of global XCO2, enabling effective processing and utilization of cloud echo data. In this study, we focused on the concentrations of CO2 columns using cloud top echoes and performed a preliminary comparison of cloud top XCO2 results with related data products from the passive satellite OCO‐2 and CarbonTracker. By quantifying the difference in CO2 concentration between two altitude layers above the sea surface, we assessed ocean carbon absorption capacity, and the results demonstrated high reliability. This work highlights the significant advantages of spaceborne IPDA lidar in global CO2 measurement, cloud echo data processing, and ocean carbon flux assessment, providing valuable data support for climate change research. Key Points: Inverting cloud top XCO2 using lidar reflection signals above the cloud enhances the utilization of satellite observation dataBased on passive satellite and model data, the accuracy of atmospheric environment monitoring satellite data inversion is demonstratedFirst use of active remote sensing satellites for assessment of marine carbon uptake [ABSTRACT FROM AUTHOR]