Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 4 2007 10.5194/acpd-7-10933-2007 http://www.atmos-chem-phys-discuss.net/7/10933/2007/ http://www.atmos-chem-phys-discuss.net/7/10933/2007/acpd-7-10933-2007.html http://www.atmos-chem-phys-discuss.net/7/10933/2007/acpd-7-10933-2007.pdf 10933 10969 2007-07-26 Technical note: a new day- and night-time Meteosat Second Generation Cirrus Detection Algorithm MeCiDA W. Krebs H. Mannstein L. Bugliaro B. Mayer bernhard.mayer@dlr.de Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, 82234 Wessling, Germany A new cirrus detection algorithm for the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) aboard the geostationary Meteosat Second Generation (MSG), MeCiDA, is presented. The algorithm uses the seven infrared channels of SEVIRI and thus provides a consistent scheme for cirrus detection at day and night. MeCiDA combines morphological and multi-spectral threshold tests and detects optically thick and thin ice clouds. The thresholds were determined by a comprehensive theoretical study using radiative transfer simulations for various atmospheric situations as well as by manually evaluating actual satellite observations. The retrieved cirrus masks have been validated by comparison with the Moderate Resolution Imaging Spectroradiometer (MODIS) Cirrus Reflection Flag. To study possible seasonal variations in the performance of the algorithm, one scene per month of the year 2004 was randomly selected and compared with the standard MODIS cirrus product. 81% of the pixels were classified identically by both algorithms. On average, MeCiDA detected 60% of the MODIS cirrus. 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