Mesoscale indexing of the distribution of orographic precipitation over high mountains.

A simple analytical expression for indexing the orographic precipitation rate over high mountains is presented. The formula is based upon the assumption that the moisture convergence in the mountainous boundary layer approximately equals the precipitation. Realistic precipitation distributions are obtained when numerical advection is permitted for the Himalayas, Equadorian Andes and the Sierra Nevada Mountains in California. In the latter case the simulated distributions compete well with a fully two-dimensional precipitation model for some unusual stormy events. Following the model results over high mountains, it is suggested that for the distribution of precipitation, particularly over the high mountains, the detailed microphysical processes may play a lesser essential role than that for small to medium size mountains. -from Author