中文摘要：

为评估P-σ九层区域气候模式模拟对流层上层东亚副热带西风急流季节变化的能力，比较模式模拟的东亚副热带西风急流季节变化与NCEP／NCAR再分析资料之间的差异及其与对流层中上层大气南北温度差异的关系。结果表明，模式模拟东亚副热带西风急流的能力在洋面上空强于大陆上空，模拟低纬度急流的能力好于高纬度。模拟的东亚副热带西风急流垂直结构、水平结构和季节变化等的主要特征与NCEP／NCAR再分析资料基本一致，但模拟的急流强度全年偏弱。分析急流与对流层中上层经向温度梯度的季节变化发现，急流出现的位置总是对应着经向温度梯度较大区域，急流中心有随气温南北差异大值中心移动的趋势，急流中心与最大温差中心相对应，表明急流中心的位置变化是对气温南北差异季节变化的响应。与再分析资料相比，模拟的经向温度梯度比再分析资料偏小约2K／10纬距，与此相对应的模拟的急流中心风速偏小约10m·s^-1。由于大气温度变化与非绝热加热有关，进一步分析发现，模式模拟的夏季副热带急流偏差与东亚地区的地面感热及潜热等非绝热加热的模拟偏差具有密切的关系。

英文摘要：

The performance of a regional climate model with P-σ incorporated coordinate in simulating the seasonal variation of the East Asian subtropical westerly jet （EAWJ） in the upper troposphere has been evaluated by analyzing the differences between the model results and the NCEP/NCAR reanalysis data, and the relationship between the EAWJ seasonal variation and the meridional atmospheric temperature difference in the mid-upper troposphere has also been analyzed in this paper. The results show that the model can reproduce the major features of the EAWJ horizontal and vertical structures and seasonal evolution, in comparison with NCEP/NCAR reanalysis. The ability of model to simulate EAWJ is better over the ocean than over the continent, in lower latitude than in higher latitude. There also exist considerable biases in EAWJ intensity and location simulations. The model underestimates the EAWJ intensity throughout the year. Analyses of the EAWJ seasonal variation and the atmospheric meridional temperature gradient in the mid-upper troposphere indicate that the EAWJ center always corresponds to the largest meridional temperature gradient in the mid-upper troposphere, suggesting that the seasonal variation of EAWJ is a response to the meridional temperature difference. Comparing with the NCEP/NCAR reanalysis, the model reproduces weaker meridional temperature gradient with a value of about 2K/10-latitude, leading to the EAWJ intensity 10 m · s^-1 weaker than the reanalysis. According to the thermodynamic equation, the atmospheric temperature change results from the diabatic or adiabatic heating. Comparison of the simulated surface sensible and latent heat flux with the NCEP/NCAR reanalysis data indicates that the discrepancies of surface heat flux are related to the location and intensity biases in the EAWJ simulation.