Banner clouds observed at Mount Zugspitze 1Institute for Atmospheric Physics, Johannes Gutenberg-University, Mainz, Germany
17 Apr 2012
2Wetterwarte Garmisch-Partenkirchen/Zugspitze, Garmisch-Partenkirchen, Germany
3Geophysical Institute, University of Bergen, Bergen, Norway
4Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany
We dedicate this paper to the memory of the late Joachim Kuettner, who was our mentor throughout the project.
Received: 19 Sep 2011 – Published in Atmos. Chem. Phys. Discuss.: 31 Oct 2011 Abstract. 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
Revised: 17 Feb 2012 – Accepted: 02 Apr 2012 – Published: 17 Apr 2012
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 a distinct 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 maximize 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.
The two banner cloud events during the campaign have a number of common
features: the windward and the leeward side are characterized by different
wind regimes, 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 increases with altitude. The results are discussed, and it
is argued that they are consistent with previous Large Eddy Simulations using
Citation: Wirth, V., Kristen, M., Leschner, M., Reuder, J., and Schween, J. H.: Banner clouds observed at Mount Zugspitze, Atmos. Chem. Phys., 12, 3611-3625, doi:10.5194/acp-12-3611-2012, 2012.