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UP: Umweltphysik

UP 21: Aerosol und Messtechnik

UP 21.6: Fachvortrag

Dienstag, 23. März 2004, 17:45–18:00, HS 221

Remote sensing of droplet size distributions from high resolution observations of the glory — •Bernhard Mayer¹, Marc Schröder², Rene Preusker², and Lothar Schüller³ — ¹Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany — ²Institut für Weltraumwissenschaften, Freie Universität Berlin, Germany — ³ESA ESTEC, Nordwijk, The Netherlands

The single scattering properties of clouds are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI) in 180^∘ backscatter geometry, we found that high spatial resolution observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 754 nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution. Applying this technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than previously suggested in the literature which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their evolution.