A three-dimensional study of the influence of mountains on a front

Abstract

This study investigates mountain effects on a frontal system in three dimensions. A numerical hydrostatic primitive-equation model is employed. The frontal system is developed in the model from the most unsteady Eady wave in a baroclinic state and is then introduced into a new model domain that contains mountain ridges of difference sizes, shapes and orientations, The cold front experiences a weakening on the upwind slope and strengthening on the downward slope of a mountain. Mountain-induced homogenetic forcing by these winds associated with the front produces frontogenesis/frontolysis at different locations. The deformation and the distortion if the front by a mountain is a superposition effect of the mountain-induced frontogenesis regions and the original front. The front recovers its original horizontal structure after moves away from the mountain. The frotogenetic forcing is dominated mainly by the convergence/divergence associated with the flow over the mountain. Major intensification occurs on the lee side convergence zone. Frontal intensity returns approximately to the original level when the front moves away from the mountain. Mountain orientation is an important factor that determines the frontal distortion..