An index reflecting mesoscale vortex–vortex interaction and its diagnostic applications for rainstorm area. (26th April 2019)

• Record Type: Journal Article
• Authors: Chen, Yongren; Li, Yueqing; Kang, Lan
• Is Part Of: Atmospheric science letters. Volume 20:Number 6(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-04-26
• Subjects: positive vorticity column -- Southwest China vortex -- Tibetan Plateau vortex; Atmospheric physics -- Periodicals; 551
• DOI: 10.1002/asl.902
• Languages: English
• ISSNs: 1530-261X

Abstract

Abstract: The Tibetan Plateau Vortex (TPV) and Southwest China Vortex (SWCV) are important precipitation systems of the upper reaches of the Yangtze River in China in the warm half year (May–October). Sometimes, the vortices both move towards the Sichuan Basin, and encounter one other to merge into a deep vortex that induces mesoscale convective systems (MCSs) and heavy rainfall. In this paper, a formula for the depth of the positive vorticity column (PVC) in two extreme rainstorm events was constructed to reveal the dynamical characteristics of TPV–SWCV interaction. The results showed that: (a) One feature of TPV–SWCV interaction was to form a deep vortex with very deep positive vorticity in the vertical direction, and the occurrence of extreme rainstorms was closely related to the deep vortex. (b) The PVC depth can describe the thickness features of the deep vortex well: MCSs with low brightness temperature were observed in the area of >2 × 10 2 hPa PVC depth, and their frequent activities were the direct reason for the occurrence of extreme rainstorms. (c) The rainstorm areas were basically consistent with the area of large PVC depth, especially the area of 5–7 × 10 2 hPa PVC depth where 24‐hr accumulated precipitation reached 100 mm or more. The study indicates that the PVC depth can reflect the development of vortices in the vertical direction, and has the potential to be a valuable index for diagnosing heavy rainfall area. Abstract : In this paper, we constructed a formula for the length of positive vorticity column to reveal the characteristic of Tibetan Plateau Vortex–Southwest China Vortex interaction. The result showed that PVC index was a valued index to diagnose the heavy rain area. MCSs were observed in an area with large PVC values of >2 × 10 2 hPa, and rainstorm areas were basically consistent with the area of large PVC's length, especially in the areas of PVC's length of 5–7 × 10 2 hPa. The moving path (a) of the TPV and SWCV every 12 hr (shaded area: Terrain) during 15–July 19, 2007 (TPV [ ]; SWCV [ ]) and during June 29 to July 1, 2013 (TPV [ ]; SWCV [ ]); the 500‐hPa (black) and 850‐hPa (gray) observational wind field (m/s), geopotential height (dam), and total accumulated precipitation (shaded, mm): (b) 850‐hPa wind field, 500‐hPa geopotential height and wind field at 0000 UTC July 18, 2007 and 72‐hr accumulated precipitation from 0000 UTC July 16, 2007 to 0000 UTC July 19, 2007; (c) 850‐hPa wind field, 500‐hPa geopotential height and wind field at 0000 UTC July 1, 2013 and 72‐hr accumulated precipitation from 0000 UTC June 29, 2013 to 0000 UTC July 2, 2013.