区域气候模式对我国中、东部夏季气候的数值模拟

NUMERICAL SIMULATION OF SUMMER CLIMATE OVER CENTER AND EAST CHINA USING A REGIONAL CLIMATE MODEL

关键词:  区域气候模式  中国  夏季气候  数值模拟  位势高度  气温  降水

Key words:  regional climate model  China  summer climate  numerical simulation  geopotential height  temperature  precipitation

摘要:

利用高分辨率的区域气候模式RegCM3(ICTP,2004年)对1994、1997、1998年我国夏季(6～8月)气候进行了数值模拟试验,并对比分析了不同积云对流方案对降水场模拟结果的影响。结果表明:该模式能够较真实地描述出我国夏季温度场的主要高、低温中心及月际变化,但模拟的气温场偏低;选择不同的积云对流方案对降水的模拟结果影响很大,采用Grell积云对流方案模拟出的我国夏季降水场最接近观测场,较好地模拟出我国东部地区夏季主要雨带的大致位置及变化,但雨带的位置偏南、中心降水量值偏大;500 hPa位势高度场的模拟结果和实际观测场较为一致,但西风带的位置偏南,相应地副热带高压588位势什米线位置较观测场向东南偏移。

Abstract:

RegCM3 (Giorgi et al, 2004) is a higher resolution regional climate model which is a modified versionof the NCAR/ RegCM2 (Giorgi et al, 1993). In this paper RegCM3 is used to simulate the central and easternChina summer climate (June, July and August) for 1994, 1997 and 1998. The domain of the simulated experimentcovers the central and eastern China with the center at 110°E, 37°N. Horizontal resolution of the model is 60 km×60 km and the vertical resolution is 18 layers. Numbers of grid points are 80 in the north-south direction and 82in the east-west direction. The results are as follows (1) The patterns of the simulated surface air temperature,precipitation and the 500 hPa geopotential height fields are consistent with the patterns of observation fields. (2)The inter-monthly temperature variation, the high temperature and low temperature areas were well described bythe model. However, compared to the observation, the area of low temperature in North China is larger while thearea of high temperature in East China is smaller, and the central values are lower than the observation, whichresults from the bias of the simulated geopotential height field. (3) The rain belts were well reproduced in themodel, but the values are greater than the observation, especially in northeast China, and the rain belt in SouthChina shifted southward. This deficiency may be mainly contributed to the complex topography and convectiveprecipitation schemes. From the result of a comparative study of convective precipitation schemes, the Grellscheme (Grell, 1993) is the best. (4) The model also well reveals the patterns of polar vortex, westerly wave andsubtropical high in the 500 hPa geopotential height field and a weaker simulated subtropical high withsoutheastward shift. In summary, RegCM3 can be used to research the regional climate change over China butwith bias. Although the simulated temperature field is the closest to the observation, it is the keystone for us toimprove the model because it may be an important cause producing the bias of height field and further resulting inthe bias of simulated precipitation field.