INCORPORATION OF AN EVAPORATIVE COOLING SCHEME INTO A DYNAMIC-MODEL OF OROGRAPHIC PRECIPITATION

A simple evaporative cooling scheme was incorporated into a dynamic mo del to estimate orographic precipitation in mountainous regions. The o rographic precipitation model is based on the transport of atmospheric moisture and the quantification of precipitable water across a 3D rep resentation of the terrain from the surface up to 250 hPa. Advective w ind fields are computed independently and boundary conditions are extr acted from radiosonde data. Precipitation rates are obtained through c alibration of a spatially distributed precipitation efficiency paramet er. The model was applied to the central Sierra Nevada. Results show a gain of the order of 20% in threat-score coefficients designed to mea sure the forecast ability of the model. Accuracy gains are largest at high elevations and during intense storms associated with warm air mas ses.