ROLE OF DETAILED WIND TOPOGRAPHY INTERACTION IN OROGRAPHIC RAINFALL

A meso gamma-scale (DELTA-x = 1 km) model for orographic rainfall was used to investigate the dependence of orographic enhancement on wind speed and direction and on detailed topography. Applying the model to cases reported in south Wales, high sensitivity to wind direction and the corresponding upwind topographical cross-sections-factors neglected in some previous studies-was found. This suggests that studies of high-resolution orographical rainfall characteristics (such as orographic enhancement as function of wind speed) or model verification should account for detailed interaction of the wind vector with the high-resolution topography. Comparison with microphysical models illustrates that the effect of detailed wind-topography interaction is at least of similar magnitude to that due to microphysical processes.