AN INVESTIGATION OF THE STRUCTURE AND DYNAMICS OF AN INTENSE SURFACE FRONTAL ZONE

Abstract

Intensive analysis of a pronounced surface frontal zone indicates that the associated horizontal temperature gradient, horizontal wind shear and horizontal divergence are most extreme near the ground and become much more diffuse above the lowest few thousand feet. In an endeavor to account for these structural characteristics, measurements are made of the frontogenetical and frontolytical effects in the fields of temperature and wind, following the motion of the air. In the vicinity of the frontal zone in the lowest levels, these effects are found to be one or two orders of magnitude larger than those generally observed in the free atmosphere. It is indicated that the frontal zone itself is composed of air initially in the warm sector which has been first effectively entrained into the zone through the operation of intense frontogenetical effects and is then subjected to intense frontolysis as it rises within the zone, thus accounting for the observed maximum intensity of the frontal characteristics near the ground. It appears, furthermore, that the motion of this type of frontal zone at the surface is controlled by the motion of the adjacent cold air.