Degradation of the FY-3D MERSI-II: Cross-Calibration With MODIS and Its Impact on Aerosol Retrieval

The Medium Resolution Spectral Imager II (MERSI-II) onboard the Chinese Fengyun-3D satellite has experienced radiometric degradation in its reflective solar bands since its launch, leading to biases in quantitative retrievals. This study uses high-accuracy MODIS observations as a reference to improve the radiometric calibration performance of MERSI-II and quantifies its impact on aerosol retrieval. First, the ratio of MERSI-II observed top-of-atmosphere (TOA) reflectance to MODIS-simulated MERSI-II reflectance, after angular and spectral matching, is used to evaluate calibration uncertainty and degradation trends based on three pseudo-invariant targets: the Dunhuang desert, DomeC in Antarctica, and deep convective clouds. The evaluation results from 2019 to 2023 show the 550, 650, and 865 nm bands are stable (1000 nm) degrade significantly (>1.26%/yr, p-value