Simulations of summer monsoon climate over East Asia with a Regional Climate Model (RegCM) using Tiedtke convective parameterization scheme (CPS)

Abstract

In this study, we implemented the Tiedtke convective parameterization scheme (CPS) into the Abdus Salam International Centre for Theoretical Physics (ICTP) Regional Climate Model version 3 (RegCM3) and simulated the East Asian Summer Monsoon (EASM) climate. A 6-year experiment was completed, from September 1996 through August 2002, and compared with an analogous experiment employing the Grell CPS option available in RegCM3. The ability of the model to represent the average climatology was investigated. Our results indicate that the Tiedtke CPS shows a generally good performance in describing surface climate and large-scale circulation throughout the summer monsoon period. Compared to the simulation with Grell CPS, the simulation with Tiedtke scheme shows a number of improvements, including a better distribution of summer monsoon precipitation due to a better positioning of the Western Pacific Subtropical High (WPSH) in the middle troposphere and the southwesterly jet in the lower troposphere, and more realistic seasonal evolution of the monsoon precipitation. The cold surface air temperature bias characteristic frequently seen in Grell scheme over this region is also reduced. Generally, the Tiedtke scheme simulates warm and wet atmospheric conditions in the middle and lower tropospheres, a result more in agreement with the European Centre for Medium-Range Weather Forecasts (ECMWF) 40Years analysis (ERA-40). The Tiedtke scheme is more prone to activate convection in the lower troposphere than the Grell scheme due to more moist static energy available for activating and supporting the development of convection systems.