A CASE-STUDY OF BOUNDARY-LAYER FLOW OVER AN ISOLATED HILL

A 3D linearized model of surface boundary layer flow over complex terr ain, FLOWSTAR, was applied to predict the flow over an isolated hill, Sophienhohe, Julich, Germany. The simulations are analysed in two case s, for winds approaching the hill from 290-degrees and 227-degrees clo ckwise from North, both under slightly stable atmospheric conditions. The model results are in good overall agreement with data. Some discre pancies were found in the individual profiles due both to the limited spatial representation of the local details and to the large variation s in the roughness of the area examined. The analysis of the mean wind speed profiles, observed and calculated, shows that they are approxim ately logarithmic near the surface. Comparison between the apparent ro ughness lengths derived from these profiles is discussed.