Cloud Top Pressure Retrieval Using Polarized and Oxygen A-band Measurements from GF5 and PARASOL Satellites

Cloud top pressure (CTP) is one of the critical cloud properties that significantly affects the radiative effect of clouds. Multi-angle polarized sensors can employ polarized bands (490 nm) or O 2 A-bands (763 and 765 nm) to retrieve the CTP. However, the CTP retrieved by the two methods shows inconsistent results in certain cases, and large uncertainties in low and thin cloud retrievals, which may lead to challenges in subsequent applications. This study proposes a synergistic algorithm that considers both O 2 A-bands and polarized bands using a random forest (RF) model. LiDAR CTP data are used as the true values and the polarized and non-polarized measurements are concatenated to train the RF model to determine CTP. Additionally, through analysis, we proposed that the polarized signal becomes saturated as the cloud optical thickness (COT) increases, necessitating a particular treatment for cases where COT < 10 to improve the algorithm’s stability. The synergistic method was then applied to the directional polarized camera (DPC) and Polarized and Directionality of the Earth’s Reflectance (POLDER) measurements for evaluation, and the resulting retrieval accuracy of the POLDER-based measurements (RMSE POLDER = 205.176 hPa, RMSE DPC = 171.141 hPa, R 2 POLDER = 0.636, R 2 DPC = 0.663, respectively) were higher than that of the MODIS and POLDER Rayleigh pressure measurements. The synergistic algorithm also showed good performance with the application of DPC data. This algorithm is expected to provide data support for atmosphere-related fields as an atmospheric remote sensing algorithm within the Cloud Application for Remote Sensing, Atmospheric Radiation, and Updating Energy (CARE) platform.