Impacts of Regional Air－Sea Coupling on the Simulation of Summer Precipitation over Eastern China in the RIEMS Model

A regional air－sea coupled model is developed, which consists of the Regional Integrated Environment Model System (RIEMS) and the revised Princeton Ocean Model (POM). Compared with the uncoupled model results and the observations, the role of air－sea interactions in the simulation of summer precipitation in eastern China from 1985 to 2004 is investigated. The results show that the regional air－sea coupled model has a good performance on simulating the mean summer precipitation and the seasonal evolution of the summer rainbelt, and the distribution and intensity of the rainband in the coupled model are more reasonable than those in uncoupled model RIEMS. The improvement of the rainfall simulation is remarkable in North China and South China. Moreover, the coupled model reproduces well the spatial and temporal distributions of summer rainfall in eastern China from 1985 to 2004. The correlation coefficients between the summer rainfalls derived from the coupled model and the observation over North China, the middle and lower reaches of the Yangtze River and South China are higher than those from uncoupled model RIEMS and the observation. Compared with the run with RIEMS, the air－sea feedbacks in the coupled model improve the simulation of the sea surface heat flux, resulting in better agreement with the NCEP/NCAR data in the land－sea thermal contrast over eastern Asia. Therefore, the monsoon circulation and the water vapor transport are better simulated, which improves the rainfall simulation in eastern China.