On Mountain Upslope Winds

Abstract

Equations developed by Ogura (1962) for a two dimensional axially symmetric thermal initiation problem are adjusted to two rectilinear dimensions and used in a numerical study of mountain upslope winds. The winds are initiated by an assumed potential temperature change at the surface of a mountain 1 km high with a 45° slope. A level plain 2 km long extends from the base of the mountain. Two cases are considered, one in a neutral environment, the second in a slightly stable environment to approximate conditions over the Santa Catalina Mountains near Tucson, Arizona. A neutral environment leads to formation of a bubble which moves up and away from the slope. As the bubble rises above the ridge line, some similarities with previous initial-bubble numerical studies are seen. A stable environment slows the development of the upslope winds and causes columnar shaped convection over the mountain slope. The results of the two cases are compared with each other, with previous numerical studies on isolated thermal bubbles and with a few observational studies on upslope winds. Pressure deviations for the model are computed and appear reasonable. Many of the features of the upslope wind are reproduced in the model.