东亚副热带西风急流与地表加热场的耦合变化特征

利用NCEP/NCAR月平均再分析资料，采用奇异值分解方法分析200 hPa纬向风场与东亚地表加热场的空间耦合变化特征，揭示影响东亚副热带西风急流位置及强度变化的加热关键区域。研究结果表明，冬季西太平洋黑潮暖流区是表面感热、潜热通量场的大值区，其加热强度主要影响东亚副热带西风急流的强度变化，当加热增强（减弱）时，急流加强（减弱）。热带和副热带地区地表加热的反相变化对应纬向风的整体一致变化，且影响关键区在热带地区， 这种耦合分布型主要体现为年代际的变化特征。夏季，海陆感热加热差异主要影响中低纬纬向风的变化，而影响急流位置南北移动的加热关键区位于阿拉伯海及印度半岛北部，这种加热分布体现感热的局地性变化，可能与高原大地形分布有关。由于夏季降水的不均匀性，潜热加热与200 hPa纬向风场的耦合关系较为复杂。通过分析加热异常年的环流形势差异发现，对流层中上层经向温差对地表加热场异常变化的响应是导致高层纬向风变化的原因，这种地面加热变化导致高层温度场及流场的响应可通过热力适应理论得到较好的解释。

The Characteristics of the Coupling Variation Between the Subtropical Westerly Jet and the Surface Heating Fields over East Asia

The significant impact of heating fields on the upper-tropospheric westerly jet has been revealed in much previous research,but little effort has been paid on differentiating the relative contribution of various heating fields over tropical and subtropical regions.It is meaningful to objectively investigate the key areas of heating fields and their association with the westerly jet and further study the relative contribution of heating fields between tropical and subtropical regions to the variations of the westerly jet,which is helpful for understanding the mechanism of westerly jet activity and valuable for climate prediction of East Asia.In this paper the characteristics of coupling spatial patterns and their temporal variations of the surface heating fields and zonal winds at 200 hPa over East Asia are investigated by using the diagnosis method of singular value decomposition(SVD) for the NCEP/NCAR monthly reanalysis data.The results indicate as follows: In winter,the heating intensity in the Kuroshio Current area of the western Pacific Ocean shows significant correlation with the westerly jet in the upper troposphere with the stronger(weaker) surface heating corresponding to the stronger(weaker) jet intensity,and this coupling pattern shows evident interannual oscillation.On the other hand,the out-phase changes of surface heating between tropical and subtropical regions is closely associated with the uniform change of the westerlies and the key heating areas are mainly located in tropical regions.Moreover,this coupling pattern exhibits obvious decadal variability.In summer,the abnormally opposite variation of the heating between the land and the sea is mainly responsible for the variation of zonal wind at mid-low latitudes,whereas the Arab sea and the northern India Peninsula are the key areas for the meridional migration of the westerly jet,which mainly reflects the local variation of heating fields related to the existence of the Tibetan Plateau.The correlative mechanism of the surface heating fields and upper-tropospheric westerly jet can be explained by using the thermal adaptation exoterica that the vertical structure of atmosphere is determined by the distribution of the heat-source and the wind field always adjusts to the temperature(pressure) variations in large-scale circulation.Comparison of the atmospheric circulation differences in the anomalous years of surface heating further indicates that the response of the meridional differences of midupper air temperature to the anomalous heating is the basic reason for the zonal wind interannual variations in the upper troposphere.