Retrieval of cloud bottom altitude from TROPOMI on Sentinel-5P

Kurzfassung

Retrieval of cloud properties from satellite measurements has applications in a variety of fields such as light path correction for atmospheric composition, assessment of earth's radiation budget, study of aerosol-cloud interactions, and meteorology. One parameter of particular interest, to which little attention has been paid to date, is the height of the bottom layer of clouds. This is due to the attenuation of light available for passive remote sensing in the case of substantial opacity of tropospheric clouds. In this work it is illustrated a solution to the radiative transfer problem in the molecular oxygen absorption band (the O 2 A-band), measured by TROPOMI aboard Sentinel-5P, leading to the inference of cloud bottom altitude. The concurrent analysis of cloud properties derived with independent algorithmic approaches sheds light on the complementarity of the respective techniques and shows how the retrieval of cloud bottom altitude, together with the characterization of the thermodynamic cloud-top phase, is functional to a more accurate description of clouds. Prospectively, the validation of the derived cloud parameters (top and bottom altitude, cloud-top phase and optical thickness) will provide the constraints for the production of a long-term cloud data record for climate applications.