Simulation Capability of China Summer Precipitation with a Regional Air-Sea Coupled Model

Based on an OASIS3 (Ocean Atmosphere Sea Ice Soil version 3) coupler, a regional air-sea coupled model is developed by coupling the regional climate model RegCM3 (Regional Climate Model version 3) and the ocean model HYCOM (Hybrid Coordinate Ocean Model). The nesting method is used to properly handle the issue of the ocean lateral boundary conditions. A continuous integration of East Asia, including China, is conducted (1982-2001). The focus point is to verify the simulation capability of the summer precipitation (June-August) over China. The simulation results show that the coupled model can reproduce the spatial distribution of the summer precipitation over China. When compared with the uncoupled experiment, the coupled model shows a better performance in simulating the rainfall amount and the interannual variation over the near-sea regions. The coupled model can also capture the distribution of the first mode of observation with the empirical orthogonal function (EOF) and the corresponding time correlation with the observational EOF1 (the first EOF mode) is enhanced when compared to the uncoupled model. Moreover, combined analysis of the first six modes indicates that there is further improvement for the large temporal scale climate component of the summer precipitation over the mid-low valley of the Yangtze River, Shandong Peninsula, and the Hainan Island after coupling.