A Numerical Study of the Frontal Circulation in the Atmospheric Boundary Layer

Abstract

A diagnostic numerical model was developed for calculating air motion in the atmospheric boundary layer near a front in terms of certain local parameters; namely, the geostrophic wind in the warm air, the densities of the warm and cold air masses, and the slope and speed of the front. The average winds in the cold air calculated on the basis of this model were compared with the average special wind observations made in the vicinity of a particular station when a warm front and a cold front passed that station. Reasonable agreement was found. With this model the dependence of the vertical circulation on the local parameters in a plane normal to the front was studied. Vertical motion in the warm air was found to be related to its horizontal motion relative to the front, and tended to be upward above slow-moving warm fronts and downward above slow-moving cold fronts.