Leipzig 2002 – wissenschaftliches Programm

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UP: Umweltphysik

UP 14: Datenauswertung und Modellierung (Atmosphäre) I

UP 14.4: Vortrag

Dienstag, 19. März 2002, 15:30–15:45, HS 16

Semi-analytical cloud retrieval algorithm — •Kokhanovsky Alexander — Institute of Environmental Physics, 1 Kufsteiner Str., D-28334, Bremen

Global cloud cover exceeds 50 water and ice clouds are of considerable importance for atmospheric optics and climate studies. The task of this paper is to present the semi-analytical algorithm for the optical thickness and effective radius of cloud droplets retrieval from space-based platforms, in particularly for the data processing of SCIAMACHY instrument on board of ENVISAT. The algorithm is simple and can be easily incorporated in the modern satellite retrieval software. It is based on the asymptotic radiative transfer theory, which is valid for optically thick clouds only. The local optical characteristics of clouds are calculated in the framework of the geometrical optics approximation (with account for wave corrections). This allows us to avoid complex numerical calculations. Also we do not need to bild up so-called look-up tables, which are usually used in up-to-date cloud retrieval algorithm. Note, that the inverse problem in our case is reduced to the solution of a single transcendent equation. The accuracy of our approximate forward model is found to be better than 5 5. This estimation was obtained using the exact radiative transfer equation solution for optically thick clouds.