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影响重庆的西南涡强降水动态分布特征及成因分析

Analysis of Dynamic Distribution Characteristics and Genesis of the Southwest China Vortex Rainstorms in Chongqing

  • 摘要: 针对西南涡及其强降水落区的移动性,选取2019~2023年影响重庆的25次西南涡强降水过程,采用跟随低涡中心移动的动态合成方法,分析了强降水相对于西南涡中心的动态分布特征与成因。结果表明:西南涡强降水可分为东南型、东部型和多象限型三类。各类西南涡强降水分布和高空急流位置、低槽强度及经向度、低空急流出口区、冷暖平流分布等密切相关,热力、动力特征表现出明显的异同性。东南型为持续时间较短、抬升运动较弱的西南涡影响,低涡垂直方向发展较为浅薄,呈现显著向西北倾斜特征。东部型为持续时间长、抬升运动强的西南涡影响,低涡垂直方向发展较为深厚,低层呈现向西北倾斜特征。多象限型为后部有冷空气持续侵入且抬升运动强的西南涡影响,低涡前后风速具有一定对称性,冷暖气流交汇显著,低涡垂直方向发展最为深厚,低层呈现向北倾斜特征。

     

    Abstract: To investigate the mobility of the Southwest China Vortex (SWV) and its associated rainstorm regions, this study examined 25 SWV-related rainstorm events that affected Chongqing during 2019–2023. A dynamic compositing method that tracks the movement of the vortex center was employed to analyze the circulation structure of the SWV and the distribution of heavy rainfall relative to the vortex center. The conclusions are as follows: SWV rainstorms can be categorized into three types: southeastern, eastern, and multi-quadrant types. The distribution of heavy rainfall for each SWV type is closely related to the position of the upper-level jet, the intensity and meridional extent of the trough, the exit region of low-level jets, and the distribution of warm-air and cold-air advection, while the thermodynamic and dynamic characteristics exhibit distinct similarities and differences. The southeastern type is influenced by the short-lived SWV with weaker upward motion, shallow vertical development, and a pronounced northwestward tilt. The eastern type involves the long-lived, intense SWV with deeper vertical development and a low-level northwestward tilt. The multi-quadrant type is influenced by the SWV with sustained cold-air intrusion from the rear and strong uplift movement. The configuration features symmetric winds in the front and rear, pronounced cold- and warm-air convergence, the deepest vertical development among the three types, and a low-level northward tilt.

     

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