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Mesoskalige numerische Simulation von Wolken- und Niederschlagsprozessen über strukturiertem Gelände

Mesoskalige numerische Simulation von Wolken- und Niederschlagsprozessen über strukturiertem Gelände
Research Topic:Mesoskalige numerische Simulation von Wolken- und Niederschlagsprozessen über strukturiertem Gelände
type:Thesis
time:7/1999
tutor:Beheng, K.D.
person in charge:

Dotzek, Nikolai 

 

links:Volltext (PDF)

Abstract

This dissertation thesis deals with numerical simulation of cloud- and precipitation processes over highly structured terrain. For typical domain sizes of 50 to 400 km horizontally, these phenomena group into the mesoscale being the intermediate range between the large–scale synoptic weather situations and very small–range local processes. To directly simulate clouds and precipitation complexes with the model KAMM2 in this range of scales and to realistically describe the interaction of atmospheric processes with complex mountainous terrain of highly variable orography and land–use requires an extensive revision and development of the model equations. Therefore not only are purely cloud–microphysical questions addressed, but hydrological as well as climatological and radar–meteorological aspects have to be considered. Last but not least the amount of numerical work is also quite substantial.

This work is based on the step–by–step modification of the mesoscale model KAMM up to a state allowing for the description of deep moist convection including the ice phase. In addition to the cloud model development also the necessary changes in other parts of the model are being described, such as the interaction of soil, vegetation and atmospheric boundary layer. Another major point in setting up the model was the generation of typical radar products and -images which facilitate comparison of the model output to the experimental findings at the Institute for Meteorology and Climate Research and allow for an easier general evaluation of the cloud model.

The modified version of the model is then tested using exemplary cases with idealized topography, before simulations are being performed for the Upper Rhine valley area with its real topography. The results obtained for a typical synoptic situation are being compared to experimental data from the Karlsruhe C–band Doppler precipitation radar. This kind of comparison allows for an evaluation of the model’s skill and the quality of the simulation data. The synopsis of both model results and radar observations enables to explain orogenic maxima of strong convection in the Upper Rhine valley region by identification of their generation mechanisms.