A regional climate model simulation of summer monsoon over east asia: a case study of 1991 flood in yangtze-huai river valley

Abstract

The evolution of summer monsoon over East Asia is the result of multi-scale interactions, including the large-scale subtropical high, upper level jet and regional-scale Meiyu front, vortex, and thermal heating. Regional Climate Models should be a better way to simulate the summer monsoon evolution, because not only they can reflect the large-scale forcing through boundary condition, theirs high resolution can also catch regional-scale forcing in detail. To evaluate the ability of SUNYA-ReCM to simulate the evolution of the summer monsoon over East Asia especially in the extreme climate, a simulation of the East Asian flood that occurred during 1991 summer was performed. This simulation was driven by large-scale atmospheric background derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Tropic Ocean Global Atmospheric (TOGA) analysis. The model is capable of reproducing the major features of the monthly mean monsoon circulation, anomalous rainfall in the Yangtze-Huai River Valley and the two northward jumps of rainfall belt as well as the other large-scale components of the monsoon. The changes of the large-scale circulation during the evolution of summer monsoon are also well simulated, which include: (1) the wind direction changes from southeasterly to southwesterly in the South China Sea. (2) The northward shift of the upper westerly over East China and the Tibetan Plateau. (3) The northward shift of the western Pacific subtropic high at 500 hPa. The model also has a good simulation on the evolution of the regional-scale components of the monsoon, including Meiyu front and southwest (SW) vortex in Sichuan Basin.