the Aerosol Optical Thickness (AOT) is estimated from the Dark Dense Vegetation (DDV) pixel method introduced by Kaufmann

Water Vapour content from the L1C image. This algorithm uses a ratio between band B8A and band B09. It is therefore important to have a very good internal resampling that preserves the geolocation accuracy of bands that have different native resolution.

The main output of the Cloud Screening and Scene Classification module consists in a Scene Classification map. Together with the Scene Classification map, two quality indicators are provided: a Cloud confidence map and a Snow confidence map with values ranging from 0 to 100 (%).

source: Müller-Wilm, U., Louis, J., Richter, R., Gascon, F., Niezette, M., 2013. Sentinel-2 Level 2a Prototype Processor : Architecture , Algorithms and First Results. ESA Living Planet Symp. 2013, Edinburgh, UK 2013, 3–10.