First Global Xco2 Products from Spaceborne Lidar: Methodology, Results and Potentials

Abstract

The Aerosols and Carbon Dioxide Lidar (ACDL) onboard the DQ-1 satellite represents a transformative advancement in global atmospheric CO2 monitoring. This study evaluates a year of ACDL XCO2 observations from June 2022 to April 2023, focusing on retrieval methodology, validation, and spatial distribution characteristics. The ACDL system uniquely captures global CO2 concentrations, including regions previously underrepresented by passive satellites, such as polar areas, cloud-covered zones, and nighttime conditions. The ACDL XCO2 product achieves a global accuracy of 0.09 ± 2.6 ppm, initially validated via TCCON data, and demonstrates substantial spatial coverage, with valid observations in 87.6% of the global 0.5° grid for monthly products. The comparison between the total column XCO2 and the partial XCO2 above the cloud has been shown for the first time. As an example, XCO2 observations in December 2022 show that the difference between the total column XCO2 and the partial XCO2 is about 0.4 ppm. High-latitude measurements reveal minimal seasonal variability in polar regions, while tropical rainforest regions exhibit pronounced diurnal differences. Additionally, observations over industrial zones in the Northern Hemisphere highlight peak XCO2 levels of approximately 424 ppm. These findings demonstrate ACDL's ability to capture critical carbon dynamics and provide high-resolution insights into global carbon cycles. Despite its achievements, challenges such as dependency on reanalysis data, and spectral parameter uncertainties still remain. We anticipate that by mid-2025, the complete ACDL XCO2 dataset, encompassing two and a half years of observations since June 2022, will be publicly released. This work aims to facilitate a deeper understanding and more effective utilization of this novel dataset by the scientific community and other stakeholders.

Keywords: Greenhouse Gases；Satellite Remote Sensing；IPDA LiDAR；ACDL