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

A regional air-sea coupled model based on the regional climate model (RegCM3) and the regional oceanic model POM (Princeton Ocean Model) is developed and a series of experiments are performed to verify the ability of the coupled model in simulating the summer precipitation over China from 1963 to 2002. The results show that the space correlation coefficients between the GISST (Global Ice and Sea Surface Temperature)data and the simulated SST by RegCM3-POM exceed 0.9. Compared with the uncoupled experiments, the coupled model RegCM3-POM has a better performance in simulating the mean summer (June to August)precipitation over China, and the distribution of the rainband in the coupled model is more accurate. The improvement of the rainfall simulation is significant over the Yangtze River Valley and in South China.The rainbelt intraseasonal evolution over eastern China in summer indicates that the simulation ability of RegCM3-POM is improved in comparison with the uncoupled model. The interannual summer rainfall variation over eastern China simulated by RegCM3-POM is in accordance with observation, while the spatial pattern of the interannual summer rainfall variation in the uncoupled model is inaccurate. The simulated correlation coefficient between the summer rainfall in the uncoupled model RegCM3 and observation is 0.30 over the Yangtze River Valley and 0.29 in South China. The coefficient between the rainfall in the coupled RegCM3-POM and observation is 0.48 over the Yangtze River Valley and 0.61 in South China. The RegCM3-POM has successfully simulated the correlation coefficients between summer rainfall in the Yangtze River Valley and SST anomalies of the Bay of Bengal, South China Sea, and the Kuroshio area, whereas the uncoupled model RegCM3 fails to reproduce this relationship. The study further shows that the monsoon circulation and the path of the moisture transport flux simulated by RegCM3-POM are in good agreement with the NCEP/NCAR data.