Impacts of Evaporation from Raindrops on Tropical Cyclones. Part I: Evolution and Axisymmetric Structure

Abstract

Cloud-resolving simulations of an ideal tropical cyclone (TC) on an f plane are performed to investigate the effects of evaporative cooling on the evolution and structure of a TC. Evaporative cooling has markedly different impacts on the TC development and structure than melting/sublimation cooling because of the formation of rainbands. Evaporative cooling suppresses the organization of a TC at the early development stage. Evaporative cooling effectively forms convective downdrafts that cool and dry the boundary layer. Stabilizing the TC boundary layer reduces convective available potential energy (CAPE) around the eyewall by about 40% and slows the development. However, at the mature stage evaporative cooling steadily develops the TC for a longer period and enlarges the TC size because of rainbands, which are formed by the cold pool associated with evaporative cooling outside the eyewall. The large amounts of latent heating greatly induce the secondary circulation and transport large absolute angular momentum inward around the midtroposphere, resulting in the steady development of the TC. After a three-day integration, both the area-averaged precipitation and the kinetic energy become greater than when evaporative cooling is excluded.