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 CO(2 )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 (R-2) 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.