Simulating orographic rainfall with a limited-area, non-hydrostatic atmospheric model under idealized forcing

[摘要] A modified version of an operational 3-dimensional, non-hydrostatic, limited-areaatmospheric model (MM5) was used to perform high-resolution, idealized simulations of theinteraction of an infinitely long single ridge with a steady, lateral large-scale windfield. The effect of different mountain ridge dimensions, wind speeds and patterns andmoisture profiles on the quantity and distribution of orographic rainfall wasinvestigated. The simulations demonstrated a number of commonly observed mountain flowfeatures like formation of cap clouds, foehn wall, convective break-out associated withmountain topography, interaction of downslope winds withsea breeze, and different stagesof cumulus development. It was found that the rainfall maxima associated with the mountainalways occur upstream of the ridge peak. Changing mountain dimensions, wind speeds andpatterns and moisture profile had clear effects on amount and pattern of accumulatedrainfall. Low wind speeds resulted the maximum accumulated rainfall to occur considerabledistance upstream of ridge peak. Reversal of wind directions in upper atmosphere causedrainfall to be largely restricted to the wind-side of the peak. The observed rainfallpatterns are explained by the different flow patterns observed in the model output.

[学科分类] 大气科学