MULTI-YEAR SIMULATION OF THE EAST ASIAN MONSOON AND PRECIPITATION IN CHINA USING A REGIONAL CLIMATE MODEL AND EVALUATION

By using regional climate model (NCC/RegCM), East Asian monsoon and precipitation over China during 1998 to 2002 were simulated. Evaluation results show that, the model reproduces the seasonal charact eristics of Asian circulation. It also well reveals the inter-annual variation of Asian monsoon, temperature, wind field and precipitation over the subregions. Deviation of the simulated large-scale features from the analysis generally remains small. Domain-averaged error of the simulated temperature shows a maximum of 2.14 K within the entire troposphere, and specific humidity less than 0.46 g/kg. The simulated winds filed at each layer and wind direction variation in sub domains are consistent with the observation. The seasonal shift of the rainbelt is well reproduced in the model. How ever, there is a discernible systematic bias in the simulated air temperature, which is positive over the land and negative over the ocean in the lower troposphere in summer. The systematic biasexaggerates the summer temperature difference between the land and ocean, which result in the simulated summer monsoon being stronger, the subtropical high being more intensive with north ward shift by 2-3°, so the rain belts shift northward and the rainf all in North China is overest imated. As a result, the model can not well reveal the special rainf all distribution pattern over China in recent years. The deficiency may be mainly contributed to the complex topog raphy and cloud-radiation param eterization scheme. The analyses also indicate it is difficult to simulate the persistent abnormal precipitation pattern over China, and which would be the keyst one for us to improve the model.