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VIEWS: 14 PAGES: 1

									                              Bannerclouds at Mount Zugspitze in Germany
                                                                                                                                      Jan H. Schween1, Jochen Reuder2
Universität zu Köln
                                                                          1Meteorological        Inst. Univ. Munich, currently at Institute for Geophysics and Meteorology University of Cologne, Germany , jschween@uni-koeln.de
                                                                                                                                      2currently      at Geophysical Institute, University of Bergen, Norway

                                                                                                                                                                                                                                                                                                            air inside cloud is warmer
Intro                                                                               Continous Measurements                                                                 S-Mast                                         6.10.2005 16:41                                             N-Mast                than windward air
Banner clouds are clouds resembling a banner or                                     • The cable cars on the northern side
flag which form on the leeward side of ridges or                                      (Eibseebahn) and on the southern side
peaked mountains. While the windward side of                                          (Gletscherbahn) of the mountain were each
the mountain remains cloud free the cloud forms                                       equipped with temperature (T), humidity (rH)
only on the leeward side.                                                             and pressure (P) sensors. The cable cars make
Mount Zugspitze (2962m asl) in the german alps                                        every day between 18 and 70 rides giving
is served from three sides with cable cars. This                                      nearly continous measurements. Measures are
and the infrastructure on the top of the montain                                      corrected for the inertia of the sensors with the                                              Banner cloud present                                                                                                             Banner cloud present

gave us the opportunity to perform continous                                          method described in Poster EGU2007-A-10058;
measurements.                                                                       • Two masts were set up at the ridge west of the
                                                                                      summit and equipped with wind (v), T and rH                                                                                       4000
                                                                                                                                                                                                                                      θ
                         cold dry air                                                                                                                                                                                                θD
        windward side
                                                           turbulence
                                                                                      sensors to measure the conditions close to the                                                                                    3500      TD ref
                                                           warm humid air                                                                                                                                                         ΔzLCL
                                          low
                                        pressure
                                                                                      point of confluence of windward and leeward
                                                   cloud                                                                                                                                                                3000

                                                           leeward side
                                                                                      air.
    strong wind                              horizontal




                                                                                                                                                                                                            z (m asl)
                                                                                                                                                                                                                        2500
                                             convergence
                                                                                    • A webcam at the DWD Station at the summit
                                                                                                                                                                                                                        2000
                                                                                      takes every 5s an image. Images are cut to
                                                                                      movies giving information about formation                                                                                         1500

                                                                                      and development of banner clouds. These                                                                                           1000

                                                                                      movies were used to derive a definition of                                                                                         500
                                                                                                                                                                                                                            270            280   290           300        310        320
                                                                                      banner clouds (Schween et al. 2006)                                                                                                                              θ (K)               Lifting condensation levels
                                               valley station Eibseebahn                                      N-Mast                   S-Mast                                                                                                                              (LCL) from radiosounding
                          pier 1                        990m asl
                                                                                                                                               9m
                                                                                                                                                                       Results
                                                                                                                                                                       • Banner clouds do not form only on peaked mountains                                          References
                                                                                                                                                                         like the Matterhorn but also on ridges as the one at
                  N       pier 2
                                                                                                                                                                         mount Zugspitze shown here.
                                                                                                                                                                                                                                                                     Schween J.H., Küttner J., Reinert D., Reuder J., Wirth V.
                                                                                                                                                                                                                                                                     2006 Defintion of "banner clouds" based on time lapse
                                           Eibseebahn 1970 m alt.diff.                                                                         3.7m                                                                                                                  movies, ACPD 6 vol.5, pp 9995-10019,
                                                                                                                                                                       • Banner clouds occur mostly during postfrontal
                                                                                                                                                                                                                                                                     www.copernicus.org/EGU/acp/acpd/6/9995/acpd-6-
                                                                                                                                             2.6m                        situations with slightly stable stratification.                                             9995.pdf
                                                                                                                                                                       • The cloud forms due to forced lifting.                                                      Schween, J.H. 2007, A method to overcome the problem of
                                                                                                 3000                                               700                                                                                                              ’slow’ sensors, Poster EGU2007-A-10058 at the EGU
                      masts               Zugspitze summit 2962 m asl                                                                    S side                        • Windspeeds at the ridge were during banner cloud
                                                                                                                                                                                                                                                                     general assembly 2007
                                                                                                 2500                                               750
                                                                                                                                                                         episodes at minimum 3 m/s
                                    Gletscherbahn 384 m alt. diff.
                                                                                                                                                                       • Vertical and horizontal extent of the cloud seem to
                                                                                                                                                          PISA (hPa)
                                                                                     z (m ASL)




                                Sonn Alpin 2576 m asl.                                           2000                                               800                  depend strongly on wind speed, stratification and                                           Acknowledgements
                                                                                                            N side                                                       humidity distribution.                                                                      We thank the Bayerische Zugspitzbahn (BZB) for the possibility to equip the
                                                                                                 1500                                                                                                                                                                cable cars with our instruments.
                                                                                                                                                    850
                                                                                                                                                                       • The air inside the cloud is by several K warmer than                                        The personnel of the meteorological station Zugspitze of the German
                                                                                                                                                                                                                                                                     Meteorological Service (DWD) supports us with observations.
                                                                                                 1000                                               900                  the air from the windward side flowing above the
                                                                                                                                                                                                                                                                     The project is granted by the German Research Foundation (DFG)
                                                                                                        0       1000   2000    3000   4000     5000                      cloud.
                                                                                                                          x (m)

								
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