APDA Water Vapor Retrieval Validation for Sentinel-2 Imagery

Water vapor is one of the main parameters for the atmospheric correction of Sentinel-2 imagery. Together with the aerosol retrieval, it determines the accuracy of the surface reflectance product. Since Sentinel-2A and soon Sentinel-2B are operational satellites with a free data policy, there is great interest in processing these data and using them for environmental studies. This letter performs a validation of Sentinel-2 retrieved water vapor over land by comparing the scene-derived water vapor column with the Aerosol Robotic Network (AERONET) measurement as an independent source. The validation is performed for a large range of AERONET site elevations and solar zenith angles using the atmospheric precorrected differential absorption technique. Results show a high correlation with a low root-mean-square error of about 0.1 cm for water vapor values from 0.2 to 5 cm.