碩士 / 國立臺灣大學 / 大氣科學研究所 / 103 / During 13-14 June 2012, a low pressure system developed over northern South China Sea (SCS). It propagated northeastward and entered the Taiwan Strait with its trough extending through the northeast of Taiwan. Affected by this trough, the Mei-Yu front which originally travelled southeastward turned to move northward after 1200 UTC 13 June and until 0000 UTC 15 June. Meanwhile, organized convection developed along the retreating front and produced heavy rainfalls over Taiwan. The purpose of the present study is to better understand the dynamical mechanism of the retreat of the Mei-Yu front and the relationship between the low over northern SCS and the retrogression of the front.
Synoptic evolution at 850 hPa revealed that the Mei-Yu front started its northward movement when southerly wind components appeared to the north of the front at 1200 UTC 13 June. Diagnosis on vorticity budget and frontogenetical function showed that the horizontal advection of positive vorticity and the horizontal gradient of equivalent potential temperature to the north of the Mei-Yu front was responsible for the northward movement of the front. In addition, results of piecewise potential vorticity (PV) inversion showed that the southerly wind component over the region north of the front was due to the low development over northern SCS. When cyclonic circulation associated with low affected the Mei-Yu front, winds north of the front veered from northeasterly to southeasterly, and caused the cold and dry air to retreat over the same area. Therefore, the area of maximum gradient of equivalent potential temperature associated with the Mei-Yu front was shifted northward, and the front retrogressed.
Piecewise PV inversion technique also illustrated that the low system over northern SCS developed through conditional instability of the second kind (CISK) mechanism. The low developed vertically with a quasi-barotropic structure and its development was related to the latent heat release from the deep convection.
| Identifer | oai:union.ndltd.org:TW/103NTU05022037 |
| Date | January 2015 |
| Creators | Kuok-Hou Ho, 何國豪 |
| Contributors | Tai-Jen Chen, 陳泰然 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 90 |
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