Orographically induced Rossby wave instabilities.

Abstract

An extension is made to a five-layer, sigma-coordinate, primitive equation model on the sphere, using more degrees of freedom. Taking as the basic state the Northern Hemisphere winter zonal mean flow, orographically unstable modes are found. In all but one case, the associated growth rates are much smaller than those corresponding to baroclinic instability, even for rather larger mountains. -from Authors