SIMULATION OF SUMMER MONSOON CLIMATE OVER EAST-ASIA WITH AN NCAR REGIONAL CLIMATE MODEL

A summertime season climate over east Asia is simulated with a regiona l climate model (RegCM) developed at the National Center for Atmospher ic Research (NCAR) to validate the model's capability to produce the b asic characteristics of monsoon climate over the region- The RegCM use d here is a modified version of the NCAR-Pennsylvania State University Mesoscale Model (MM4), in which the Biosphere-Atmosphere Transfer Sch eme and a detailed radiative transfer package have been implemented fo r climate application. The model horizontal resolution is 50 km, and t he domain covers a 5200 km x 4700 km area encompassing eastern Asia an d adjacent ocean regions. The simulation period is June-August 1990, a nd the model-driving initial and lateral boundary conditions are from European Centre for Medium-Range Weather Forecasts analyses of observa tions. The simulated patterns of the monsoon circulation, precipitatio n, and land-surface temperature are in general agreement with observat ions, although the model is somewhat too dry and cool. Furthermore, th e RegCM captures terrain-induced local rain maxima and temperature cen ters. Three special aspects of the model results are examined for asse ssment of model performance: 1) the RegCM reproduces the entire progre ss of a summer monsoon and the accompanying rain belt, including diffe rent steady phases and sudden transitions between two adjacent phases; 2) the paths of tropical storms occurring during the simulated period are. closely traced by the model; and 3) realistic patterns of soil m oisture are simulated.