A NEW TENDENCY EQUATION AND ITS APPLICATION TO THE ANALYSIS OF SURFACE PRESSURE CHANGES

Abstract

From a consideration of temperature changes in isobaric surfaces a new pressure-tendency equation is derived which is applicable to mass changes of a layer or pressure changes at any level including the earth's surface. Using this ?isobaric tendency equation? orographically and thermally induced pressure systems are studied with respect to their development and variations in their intensity. An analysis of the terms in the ?isobaric tendency equation? as applied to extratropical cyclones suggests that deepening occurs when one or more of the three following conditions are met: (1) there is strong warm-air advection in the lower strato-sphere, (2) there is a low level of nondivergence permitting subsidence at the level of the tropopause, and (3) there is potentially unstable warm-sector air.