STEADY FINITE-AMPLITUDE BAROCLINIC FLOW OVER LONG TOPOGRAPHY IN A ROTATING STRATIFIED ATMOSPHERE.

Abstract

A steady, inviscid, vertically sheared flow past a large mountain ridge in a rotating stratified atmosphere is considered. The Boussinesq approximation is employed and the flow is bounded above by a horizontal rigid lid. Scale analysis indicates that the flow field is nearly balanced in the vertical and cross-topography directions. The Rossby number need not be small but different scale-analyses are required when the radius of deformation is either large or small compared to the geometrical horizontal scale of the topography. A single equation, expressing the conservation of potential vorticity, determines the pressure field induced by the topography. For a given topography the solution depends on the upstream shear parameter and on the Burger number. The zeroth-order far-field behavior is a function only of the shear parameter and the cross-sectional area of the topography. Different topographies are considered in the shear-free case and analytical solutions are obtained. It is found that for sufficiently large Burger numbers the topography exerts its influence over horizontal distances which are large compared to its geometric horizontal extent.