Mesoscale Characteristics of Monsoonal Convection and Associated Stratiform Precipitation

Abstract

Observations undertaken on 12 January 1990 at Darwin, Australia (12°S, 130°E), are used to document the structure of a monsoonal rainband in a low-CAPE, low-shear tropical environment. Dual-Doppler radar analyses are employed to investigate the structure and kinematics of the convective and stratiform regions. A system with the characteristics of a relatively short-lived squall line in which warm rain processes play a significant role in the production of precipitation is evident. Planetary boundary layer cold-pool production is important in the organization and motion of the system. A trailing stratiform region is evident with a mean updraft-downdraft circulation, but is composed of in situ decaying convective cells. A storm-relative mesoscale cyclonic circulation is also observed within the stratiform cloud. This vortex was maintained by thermodynamically induced midlevel convergence, convectively generated storm-scale circulations, and their interaction with the background monsoon now.