Multi‐scale topographic control of southwest vortex formation in Tibetan Plateau region in an idealized simulation
Multi‐scale topographic control of southwest vortex formation in Tibetan Plateau region in an idealized simulation
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DOI：
10.1002/2014jd021898
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发表时间：
2014-10
期刊：
影响因子：
--
通讯作者：
Qiwei Wang;Z. Tan
中科院分区：
文献类型：
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作者：
Qiwei Wang;Z. Tan
西南涡（SWV）是发生在中国西南部青藏高原背风面的背风涡，受青藏高原、横断山脉和四川盆地不同尺度地形的强烈影响。通过在理想化背景流中进行干动力学模拟，研究了这些地形特征在 SWV 形成中的作用。两个浅层地形引起的涡流被发现是 SWV 形成的主要贡献者。第一个涡流从横断山脉东南部延伸出来，第二个涡流从青藏高原东侧与横断山脉和四川盆地相连。拉伸、倾斜和摩擦在沿两条涡流的垂直涡度产生中发挥着不同的作用，其中行星涡的拉伸在第一涡流的上层主导其他垂直涡源。 SWV是由于地形特征的综合作用而形成的。横断山脉使青藏高原周围的西南气流转向，诱发第一个涡流，四川盆地增强第二个涡流，这与青藏高原顶部气流的拉伸和倾斜有关。此外，四川盆地为两股涡流汇合、促进SWV形成提供了有利的天然场所。敏感性实验表明，西南风的位置和规模主要受青藏高原和横断山脉控制，四川盆地起次要作用。
The southwest vortex (SWV) is a lee vortex occurring on the leeside of the Tibetan Plateau in southwestern China, which is strongly affected by the different scale topography of the Tibetan Plateau, Hengduan Cordillera, and Sichuan Basin. The roles of these topographic features in SWV formation were investigated by conducting simulations with dry dynamics in an idealized background flow. Two shallow topographically induced vorticity streams are found to be the main contributors to SWV formation. The first vorticity stream extends out from the southeastern Hengduan Cordillera and the second from the east side of the Tibetan Plateau conjoint with the Hengduan Cordillera and Sichuan Basin. The stretching, tilting, and friction play different roles in vertical vorticity generation along the two vorticity streams, in which the stretching of the planetary vorticity dominates other vertical vorticity sources at the upper level of the first vorticity stream. The SWV forms due to the combined effects of the topographic features. The Hengduan Cordillera turns the southwesterly airflow around the Tibetan Plateau to induce the first vorticity stream, and the Sichuan Basin enhances the second one, which is associated with the stretching and tilting of airflow from the top of the Tibetan Plateau. Moreover, the Sichuan Basin provides a natural site favorable for the merging of the two vorticity streams and then promoting SWV formation. The sensitivity experiments show that the location and scale of the SWV are controlled mainly by the Tibetan Plateau and Hengduan Cordillera, and the Sichuan Basin plays a secondary role.