Definition of "banner clouds" based on time lapse movies J. H. Schween1, J. Kuettner2, D. Reinert3, J. Reuder4, and V. Wirth3 1currently at: Institute for Geophysics and Meteorology, University of Cologne, Germany 2National Center for Atmospheric Research, Boulder, CO, USA 3Institute for Atmospheric Physics, Johannes Gutenberg-University, Mainz, Germany 4Geophysical Institute, University of Bergen, Norway
Abstract. Banner clouds appear on the leeward side of a mountain and resemble a banner or
a flag. This article provides a comprehensive definition of "banner clouds". It
is based primarily on an extensive collection of time lapse movies, but
previous attempts at an explanation of this phenomenon are also taken into
account. The following ingredients are considered essential: the cloud must
be attached to the mountain but not appear on the windward side; the cloud must
originate from condensation of water vapour contained in the air (rather than
consist of blowing snow); the cloud must be persistent; and the cloud must not
be of convective nature.
The definition is illustrated and discussed with the
help of still images and time lapse movies taken at Mount Zugspitze in the
Citation: Schween, J. H., Kuettner, J., Reinert, D., Reuder, J., and Wirth, V.: Definition of "banner clouds" based on time lapse movies, Atmos. Chem. Phys., 7, 2047-2055, doi:10.5194/acp-7-2047-2007, 2007.