ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-29407-2011 Bannerclouds observed at Mount Zugspitze Wirth V. 1 Kristen M. 2 Leschner M. 1 Reuder J. 3 Schween J. H. 4 Institute for Atmospheric Physics, Johannes Gutenberg-University, Mainz, Germany Wetterwarte Garmisch-Partenkirchen/Zugspitze, Garmisch-Partenkirchen, Germany Geophysical Institute, University of Bergen, Bergen, Norway Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany <br></br> <i>We dedicate this paper to the memory of the late Joachim Kuettner, who was our mentor throughout the project.</i><br></br> 31 10 2011 11 10 29407 29439 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/29407/2011/acpd-11-29407-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/29407/2011/acpd-11-29407-2011.pdf

Systematic observations of banner clouds at Mount Zugspitze in the Bavarian Alps are presented and discussed. One set of observations draws on daily time lapse movies, which were taken over several years at this mountain. Identifying banner clouds with the help of these movies and using simultaneous observations of standard variables at the summit of the mountain provides climatological information regarding the banner clouds. In addition, a week-long measurement campaign with an entire suite of instruments was carried through yielding a comprehensive set of data for two specific banner cloud events. <br></br> The duration of banner cloud events has a long-tailed distribution with a mean of about 40 min. The probability of occurrence has both a distinct diurnal and seasonal cycle, with a maximum in the afternoon and in the warm season, respectively. These cycles appear to correspond closely to analogous cycles of relative humidity, which maximizes in the late afternoon and during the warm season. In addition, the dependence of banner cloud occurrence on wind speed is weak. Both results suggest that moisture conditions are a key factor for banner cloud occurrence. The distribution of wind direction during banner cloud events slightly deviates from climatology, suggesting an influence from the specific Zugspitz orography. <br></br> The two banner cloud events during the campaign have a number of common features: the windward and the leeward side are characterized by a different wind regime, however, with mean upward flow on both sides; the leeward air is both moister and warmer than the windward air; the background atmosphere has an inversion just above the summit of Mt. Zugspitze; the lifting condensation level is an increasing function with altitude. The results are discussed, and it is argued that they are consistent with previous Large Eddy Simulations using idealized orography.

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