Numerical Simulation of the 1981 Sichuan Flood. Part I: Evolution of a Mesoscale Southwest Vortex

Abstract

Abstract During the period 11–15 July 1981, heavy rainfall occurred over the Sichuan Basin in China, resulting in severe floods that took a large toll in human life and property damage. Mesoscale analyses by Kuo, Cheng and Anthes have shown that the flood was directly related to the development of a long-lived mesoscale southwest (SW) vortex over the basin. In this paper we present the results of numerical experiments aimed at 1) testing the capability of a limited-area mesoscale model to predict the evolution of the SW vortex and the accompanying heavy precipitation, 2) examining the structure of the simulated vortex using the model data, and 3) elucidating the role of various physical processes in the evolution of the SW vortex. Principal findings are: 1) The control experiment, which utilized an 80-km grid spacing and simple physical parameterizations, was able to simulate the evolution of the mesoscale SW vortex and the accompanying heavy precipitation. The simulation captured many observed features a...