Development of Level 2 aerosol and surface products from cross-Track scanning polarimeter POSP on board the GF-5(02) satellite

Abstract

The development of long-Term, continuous, consistent, and high-quality satellite remote sensing aerosol and surface products is crucial to constrain climate models and improve our understanding of climate change. Particulate Observing Scanning Polarization (POSP) is the first space-borne multi-spectral (UV-VIS-NIR-SWIR) cross-Track scanning polarimeter dedicated to complementing the Directional Polarimetric Camera (DPC) multi-Angle polarimetric measurements and performing synergistic observations, namely the polarization crossfire (PCF) suite on board the Chinese GF-5(02) (Gaofen-5 series) satellite. The POSP's unique single-view spectral (UV-VIS-NIR-SWIR) high-precision polarimetric measurements provide rich information for atmospheric aerosol and surface characterization. Here, we developed aerosol and surface products from POSP/GF-5(02) based on the Generalized Retrieval of Atmosphere and Surface Properties (GRASP)/Models approach. The detailed retrieval approach and processing scheme are provided. The baseline Level 2 product was generated for the first 18 months of POSP measurements from December 2021 to May 2023 and is publicly available and registered at 10.57760/sciencedb.14748 (Chen et al., 2024c). The obtained POSP/GF-5(02) aerosol and surface products are validated and intercompared with the ground-based AERONET reference aerosol dataset and other independent satellite products, such as the NOAA-20 VIIRS/DB aerosol product and the MODIS MCD43 surface product. The results show generally good consistency of POSP products with AERONET, the VIIRS/NOAA-20 aerosol dataset, and the MODIS surface product. Moreover, the developed POSP product includes not only total aerosol optical depth (AOD) but also detailed properties of aerosols (aerosol size, absorption, layer height, type, etc.), along with full-surface bidirectional reflectance distribution function (BRDF), bidirectional polarization distribution function (BPDF), black-sky albedo, white-sky albedo, and normalized difference vegetation index (NDVI). These parameters are of high importance to constrain the Earth-Atmosphere radiation budget. The retrieval of these properties seems to be possible due to the polarimetric capabilities and wide UV-VIS-NIR-SWIR spectral range of POSP observations and advances of the used GRASP/Models retrieval approach. Finally, some potential improvements for the POSP Level 1-Level 2 processing chain are identified, and the limitations and lessons learned are discussed.