高原南侧地形槽与孟湾槽的形成演变特征及其与南海夏季风建立的关系  

Characteristics of Topographic Trough on South Side of TP and BB Trough and Relationship between Them and SCSSM Onset

作　　者：韦晋[1,2] 何金海[2] 钟珊珊[2] 温敏[3] 

机构地区：[1]厦门市气象局,福建厦门361016 [2]南京信息工程大学江苏省气象灾害重点实验室,江苏南京210044 [3]中国气象局中国气象科学研究院,北京100081

出　　处：《高原气象》2008年第4期764-771,共8页Plateau Meteorology

基　　金：国家自然科学基金项目(40633018);国家基础研究发展规划项目"973"(2006CB403607);国家自然科学基金项目(40475029)共同资助

摘　　要：用1981-2000年NECP／NCAR再分析数据集资料，分析了全年各月大气环流特征，发现青藏高原（下称高原）南侧低空基本上存在一个常年正涡度带，这是高原近地面西风与其外围自由大气西风之间的气旋性切变的表现。特别是在90°E附近有一明显的地形槽，我们选取80°～90°E，25°N关键区域内的涡度作为表征该地形槽的指数，分析了高原南侧地形槽与孟加拉湾（下称孟湾）槽形成和演变特征的异同，并探讨其与南海夏季风建立的关系。结果表明，高原南侧地形槽的季节性演变与高原热源联系非常密切，其显著的4月突变和6月突变与高原热源发生跳跃性变化相联系。冬季高原冷却作用形成低空反气旋环流，叠加在原本增强的大尺度西风绕流上，促使高原地形槽减弱；由春入夏，高原加热作用形成低空气旋性环流，增大西风绕流作用，促使高原地形槽加深。高原地形槽加强南伸和斯里兰卡低涡持续北移直至二者相互打通是亚洲低纬度副热带高压带在孟湾上空最先断裂和孟湾槽形成的一种触发机制，此后槽前西南气流加强，副热带高压东撤，南海夏季风进一步东扩，最后导致南海夏季风建立。Utilizing the NECP/NCAR reanalysis data, the annual atmospheric circulation over East Asia from 1981 to 2000 is investigated. It is discovered that a zonal positive vorticity belt maintains on the south side of Tibetan Plateau（TP）, due to the interaction of the Plateau boundary layer and its neighboring free atmosphere. Particularly, there is an obvious topographic trough related to the positive vorticity near 90°E. In light of this, a Tibetan Plateau Topographic Trough Index （TPTTI） is defined in the paper over the key areas （80°～90°E, 23°～26°N ）. The index is proved to be effective in distinguishing between the characteristic of the （TPTT） and that of the Bay of Bengal Trough （BBT）. The annual variation of the TPTT is closely related to the Plateau heating source, and the former significant abrupt changes during April and June might be primarily induced by the seasonal sudden jump of the latter. In winter, the low-level anticyclone caused by the Tibetan Plateau cooling is strengthened and superimposes the westerly wind that should have been strengthened by dynamic effect, which weakens the TPTT. However, in summer, the low-level cyclone resulting from the TP heating strengthens the circumferential westerly and deepens the TPTT. Further investigations indicate that there is a considerable relationship between the South China Sea summer monsoon（SCSSM） onset and the evolution of the TPTT and the BBT. The TPTT propagates southward and the vortex near Sir Lanka moves northward continuously, till they meet and interact over the Bay of Bengal（BB）. This is the direct process of the subtropical high belt splitting initially over BB and the establishment of the BBT. Subsequently, the southwesterly wind becomes stronger and promotes the eastward retreat of subtropical high, causing the SCSSM bursts over the whole South China Sea.

关 键 词：高原南侧地形槽 孟湾槽 季风爆发 

分 类 号：P462[天文地球—大气科学及气象学]