A New Aerosol Retrieval Algorithm for Sentinel-2 Images Over Urban Surfaces

Operational aerosol optical depth (AOD) products are limited to coarse resolution (kilometers or hundreds of meters). In this study, the Sentinel-2 images were used to generate high-resolution (60 m) AODs over urban surfaces. Compared with traditional aerosol retrieval algorithm, the proposed algorithm has three major improvements including: 1) taking advantage of the aerosol-sensitive coastal band in aerosol retrieval; 2) no estimation of surface reflectance; and 3) not using of the shortwave infrared (SWIR) band. For validation, measurements from four Aerosol Robotic Network (AERONET) sites located in Beijing covering 2018 to 2021 were collected. The validation results show that the retrieved Sentinel-2 AODs highly correlate with AERONET measurements, with overall correlation coefficient for all four sites of 0.927, expected error (EE) of 68.75%, mean absolute error (MAE) of 0.082, and root-mean-square error (RMSE) of 0.108. The proposed algorithm can provide reliable AODs at 60 m resolution over urban surfaces.