Influence of mesoscale orography on idealized cold fronts

Abstract

A three-dimensional numerical model based on the inviscid and adiabatic primitive equations in the Boussinesq approximation is used to investigate the retardation of cold fronts by high two and three-dimensional mountains, approximately the same size as the Alps. Initial and boundary conditions are specified according to an analytical model for an idealized front with constant potential vorticity. The study covers cases with uniform, neutral or stable stratification in both the cold and warm air masses. The model results are compared with previous analytical solutions of a shallow water flow model. A scale analysis and a parameter study identify the conditions under which a front is strongly influenced by mountains. The model explains the magnitude of surface-front deformation for two observed cases where cold fronts are strongly retarded at the Alps. -from Author