Lee Cyclogenesis. Part II: Numerical Studies

Abstract

The effect of topography on the evolution of a disturbance in a baroclinically unstable mean flow is studied using a three-dimensional primitive equation model. A procedure is developed to compare control integrations with no topography with integrations that contain topography. It is found that lee cyclogenesis is caused primarily by the superposition of a growing baroclinic wave with a steady, orographically forced wave of the same scale. Some additional lee growth is found that may be orographically enhanced, or it may be related to certain small problems in the experimental set up. As the disturbances move over the ridge, they are deflected to the north on the upwind side Wore returning to their original latitudes on the lee side. The numerical results in this paper are in general agreement with the authors' previous analytic study.