区域气候模式对东亚季风和中国降水的多年模拟与性能检验

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

利用高分辨率区域气候模式 (NCC/RegCM)对 1998～ 2 0 0 2年的东亚环流及中国区域降水进行了数值模拟。对模拟结果的检验表明 ,模式能较真实地模拟出东亚地区多年平均的月季环流特征、季风的年变化、中国各主要气候区温度、降水的季节变化及中国主要雨带的季节性进退。但模拟的气温场在夏季对流层中、低层海洋偏暖、陆地偏冷 ,由于温度场的这种系统性误差加大了夏季海、陆温差 ,导致模拟的东亚夏季风偏强 ,使夏季雨带位置向北偏移 ,从而使华北地区降水估计偏高 ,没能很好地反映最近 5a来中国降水呈南涝北旱的气候特征。模式中地形的作用及云 辐射参数化方案等的处理可能是模拟误差的主要来源 ,这也反映了模式对于准确模拟中国区域降水的长期异常分布还比较困难 ,今后应进一步改进模式的模拟能力。

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 characteristics of Asian circulation. It also well reveals the inter-annual variation of Asian monsoon, temperature, wind field and precipitation over the sub regions. 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 rain belt is well reproduced in the model. However, 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 bias exaggerates 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 northward shift by 2—3°, so the rain belts shift northward and the rainfall in North China is overestimated. As a result, the model can not well reveal the special rainfall distribution pattern over China in recent years. The deficiency may be mainly contributed to the complex topography and cloud-radiation parameterization scheme. The analyses also indicate it is difficult to simulate the persistent abnormal precipitation pattern over China, and which would be the keystone for us to improve the model.