First global assessment of cloud geometrical thickness from TROPOMI on Sentinel 5P

Kurzfassung

The retrieval of cloud properties from satellite measurements has wide-ranging applications, including light path correction for atmospheric composition, assessment of Earth's radiation budget, studies of aerosol-cloud interactions, and meteorology. One parameter that has received relatively little attention to date is the height of the cloud base and the derived geometrical thickness. This is largely due to the significant attenuation of light when tropospheric clouds are highly opaque at optical wavelengths. After briefly presenting a solution to the radiative transfer problem in the molecular oxygen absorption band measured by the TROPOMI instrument aboard the Sentinel-5P satellite, this study applies three independent algorithms - SACURA, CHROMA, and ROCINN - to the same set of measurements and derives one year of global cloud base altitude, from which the geometrical thickness can be inferred. The validation of the derived cloud parameters, including top and bottom altitude, cloud phase, and optical thickness, sets the stage for the potential creation of a long-term data record for climate research, considering that future missions such as Sentinel-4 on MTG and Sentinel-5 on EPS-SG will provide similar spectral coverage.