Sen2Cor Atmospheric Correction with Meteorological Aerosol Optical Thickness

Kurzfassung

Sen2Cor is a Level-2A processor with the main purpose to correct single-date Sentinel-2 Level1C products from the effects of the atmosphere in order to deliver a Level-2A surface reflectance(SR)product. Side products are Cloud Screening and Scene Classification, Aerosol Optical Thickness (AOT) and Water Vapour(WV) maps. The accuracy of the retrieved surface reflectance product is strongly related to the accuracy of the atmospheric Parameters used during the atmospheric correction process, mainly the Aerosol Optical Thickness and the Water Vapour content. The Validation results of Sen2Cor have shown that the retrieval of water vapour is very accurate, whereas the method used to estimate the Aerosol Optical Thickness (AOT)at 550nm, the Dark Dense Vegetation (DDV)Pixel method, faces some limitations. The AOT estimation is not possible when there are no DDV Pixels in the image. The current fallback solution for that case is to perform the atmospheric correction starting with a default AOT value. A novel fallback solution for Sen2Cor is presented. The idea is to use AOT estimates at 550nm from the Copernicus Atmosphere Monitoring Service (CAMS)retrieved from ECMWF. A first Quality assessment of These meteorological AOT data overselected AERONET testsites is presented. Then the method of pre-processing and ingestion of this meteorological data in the Sen2Cor atmospheric correction module is described. Preliminary results are illustrated with an example of L2A surface reflectance product over a specific testsite.