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Abstract:
A physically based model of a snow cover, which has been designed for climate studies, was tested under different conditions (Arctic, midlatitudes, alpine regions). This multi layered model can be used for stand-alone experiments as well as for implementation into sophisticated coupled models. One version of the model, which considers a partial snow coverage of the gr id cells and an albedo masking effect by vegetation, is formulated for the Hamburg climate model ECHAM [Roeckner et al., 1992]. The key parameters of the snow-cover model are snow albedo, description of liquid water (storage capacity, transmission rate), turbulent fluxes at the snow surface, hear; conduction (internal heat conduction and heat exchange with ground), new snow density and density changes due to aging, and the choice of snow layers. Wind drifting processes and an additional form of metamorphism, the wind compaction, have to be considered in areas with high wind speeds. In order to obtain the simulation quality which is necessary for climate studies when using observed forcing data, the precipitation measurements should be corrected and information concerning the precipitation type should be given in the input data sets. A further improvement of the model could be reached by the implementation of a more sophisticated transmission scheme for liquid water, the use of a wind dependent new snow density, and the modification of snow albedo due to different rates of pollution.
