Diagnostic Analysis of Unbalanced Force of Atmospheric Motion and an Abrupt Heavy Rain during July 1998
An abrupt heavy rain event occurred in Wuhan from 20 to 22 July 1998 is analyzed by using conventional and satellite data. The results show that: (1) The event was caused by a meso βscale convective cloud cluster. (2) The meso β scale system is not related with strong cyclone vorticity or ant cyclone vorticity center in lower or upper troposphere. The divergence strength of the system is higher 101s-1 than that of vorticity. (3) 10 hours before its occurrence, the atmospheric motion was already unbalanced. After the precipitation, its intensity got strongest and it changed into U >0 from U <0. (4) The unbalanced force of lower atmospheric motion and strong divergence in the upper atmosphere are led to the initiation and development of the meso-βscale system as well as the occurrence of heavy rain.