东风带扰动热力特征及其对西太副高东退影响的个例分析

Case Studies on Thermodynamic Characteristics of Vortex in the Easterlies and Its Impact on Eastward Retreat of the Subtropical Anticyclone over the Western Pacific

利用NCEP/NCAR再分析资料,分析了2003年6月22—25日西太平洋副热带高压(下称西太副高)西伸东退时热带东风带扰动附近大气热源的分布和演变特征,以及对西太副高西伸东退的影响和机制。结果表明,高层东风带扰动附近的非绝热效应分布和强度的突变影响西太副高西伸东退,当扰动中心西侧非绝热加热加强,扰动中心东侧西太副高区域冷却加强时,西太副高东退;潜热释放造成的非绝热效应在高层变化最为明显,非绝热变化的主要影响因子是垂直运动。总结了西太副高东退过程与东风带扰动系统热力联系的可能概念模型:东风带扰动处大气热力结构变化引发经向风场异常,使东风带扰动西侧高层有北风发展和强烈的上升运动,扰动东侧有整层的南风发展,有助于西太副高异常东退。因此,西太副高的西伸东退与热带东风带扰动系统的热力作用密切关联。

Using the NCEP/NCAR reanalysis data sets, the characteristics of distribution and evolution of the heating source and sink located in the easterlies vortex（EV） over the tropical region relating to the eastward and westward movement of the subtropical anticyclone over the western Pacific（WPSA） on 22-- 25 June 2003 are analyzed. Their impacts on the eastward and westward movement of the WPSA and the relevant mechanism are discussed as well. The result shows that, the WPSA eastward moving, when the distribution and intensity of the non-adiabatic heating effect nearby the EV vary largely; the characteristic is the enhancement of the heating effect on the west side of the EV and strong cooling to the east side of the EV within the WPSA. The heating source nearby the EV mostly comes from the condensation latent heating. The change of the non-adiabatic heating effect, which is mainly affected by vertical motion, is the most obvious in the upper troposphere. A possible conceptual model is concluded revealing the thermody- namic relationship between the EV and the eastward moving of the WPSA. The modification of thermody- namic structure always causes the change of meridional wind. In the upper troposphere, the enhancements of the north wind and the ascent motion on the west side of the EV, and the development of the south wind in the east side, benefit the abnormal eastward moving of WPSA. Therefore, the eastward and westward movement of the WPSA has a close relation to thermodynamic effect of the EV over the tropical region.