The Dynamics of Wave-Induced Downslope Winds

Abstract

A theory for the dynamics of strong surface winds on the lee side of a large mountain range is derived and compared with observations. The strong winds observed near Boulder, Colo., are found to be surface manifestations of standing gravity waves whose wavelength is long compared to typical resonant lee wavelengths. The theory indicates that such waves can become very intense if an inversion is present neat mountain-top level in the upstream environment and if the stability and wind profiles are such that the waves approximately reverse phase between the surface and the tropopause. The theory is extended to the development of a numerical model for estimation of maximum surface winds from upstream sounding data. Comparisons of the model predictions with observations are sufficiently encouraging to suggest the future utilization of such a model for operational forecasting. The differences between the predictions of this theory and those of hydraulic jump models are explored.