The Effects of Evaporation on Frontal Circulations

Abstract

The condensation of water vapor in the ascent region of frontal zones has been shown by many studies to increase substantially the rate of frontogenesis. Phase change of water substance in the downdraft has, however, received comparatively little attention. Here we add evaporation of falling rain to a semigeostrophic model of frontogenesis that also allows for condensation heating in the updraft, as in previous work. Evaporation of rain significantly increases the rate of frontogenesis and, more dramatically, leads to a strong, concentrated sloping downdraft just beneath the narrow sheet of saturated ascent.