Simulation of Summer Monsoon Climate over East Asia with an NCAR Regional Climate Model

Abstract

A summertime season climate over east Asia is simulated with a regional climate model (RegCM) developed at the National Center for Atmospheric Research (NCAR) to validate the model's capability to produce the basic characteristics of monsoon climate over the region. The RegCM used here is a modified version of the NCAR-Pennsylvania State University Mesoscale Model (MM4), in which the Biosphere-Atmosphere Transfer Scheme and a detailed radiative transfer package have been implemented for climate application. The model horizontal resolution is 50 km, and the domain covers a 5200 km ? 4700 km area encompassing eastern Asia and adjacent ocean regions. The simulation period is June?August 1990, and the model-driving initial and lateral boundary conditions are from European Centre for Medium-Range Weather Forecasts analyses of observations. The simulated patterns of the monsoon circulation, precipitation, and land-surface temperature are in general agreement with observations, although the model is somewhat too dry and cool. Furthermore, the RegCM captures terrain-induced local rain maxima and temperature centers. Three special aspects of the model results are examined for assessment of model performance: 1) the RegCM reproduces the entire progress of a summer monsoon and the accompanying rain belt, including different 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 moisture are simulated.