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標題: | 台北夜間強降雨_2014年5月20日個案研究 TAIPEI HEAVY RAIN AT NIGHT: A Case Study of 20 May 2014 |
作者: | Shou-Liang Yu 于守良 |
指導教授: | 周仲島(Jong-Dao Jou) |
關鍵字: | 夜間強降雨,冷空氣侵入,沿岸及盆地對流,準滯留對流線,中尺度對流系統, Night time heavy rain event,cold air intrusion,coastal- and basin-originated convection,quasi-stationary convective line,Mesoscale convective systems, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 2014年5月20日深夜22時至5月21日凌晨2時,在台北市僅4個小時就累積了超過200毫米的降雨量,此短延時強降雨事件導致萬華、中正、大安和信義區多處淹水。在統計上台北市夜間發生強降雨機率相當少見。值得注意的是,大雨事件發生時,500 百帕槽伴隨著地面低壓系統剛剛通過台灣北部,本案例大雨的發生時高層的大氣環境並沒有明顯的強降雨發展條件。在中國東南沿岸,準滯留鋒面向東延伸逐漸靠近台灣西海岸,伴隨著鋒面及北方冷空氣,發展形成準滯留對流線。從地面測站溫度分析來看,冷空氣從基隆河口侵入台北盆地南側。從板橋探空資料,最低層顯示出絕對穩定的溫度探空曲線,顯現在台北盆地1公里以下的大氣是穩定的,此時北方侵入的低層冷空氣就像一個移動的地形,與來自南方的溫暖潮濕空氣碰撞後,暖空氣被強迫舉升,變得不穩定並達到飽和。
在本個案研究,雙都合成風場搭配密集地面觀測資料去揭示暴雨低層運動及動力結構。線性結構的中尺度對流系統,在台北市西方形成新生對流胞向東移動與原來台北盆地對流胞合併增強,形成準滯留對流線。上述對流胞發展位置與侵入之北方冷空氣的前緣接近。後續對流發展在台北市西方原來對流位置南側並向東北移動在台北市南側相同位置再次帶來降雨。 數值模式預測到鋒面靠近階段時的暴雨,然而對台北盆地北來冷空氣上方發展之對流,降雨量預測較差。 On the late evening of 20th and early morning of 21th May 2014, more than 200 mm rainfall has been accumulated by rain gauges of Taipei City in just 4 hours. The heavy rain caused severe flash flood over districts in south part of Taipei including Wanhua, Zhongzheng, Daan and Xiny. Occurrence frequency of heavy rain events in Taipei City at night time are relatively rare in statistics. It is noted the heavy rain event occurred while 500 hPa trough accompanied with intensifying surface low pressure system was just passing through the area. No pronounced upper level supported for the development of the heavy rain event. Over the coast of SE China, a quasi-stationary surface front extended eastward and approached to northwest coast of Taiwan gradually. Accompanying with the surface front and northerly cold air, a quasi-stationary convective line formed along with it. From surface temperature analysis, cold air intruded from Kee-Long river into south part of Taipei basin. From Banchiao sounding, the lowest level revealed absolutely-stable temperature profile. The atmosphere below 1 km height in the Taipei basin is stable and is acting like a moving terrain. The warmer and moist air from south was lifted when colliding with the cold air and became unstable after reached saturation. In this study, dual-Doppler synthesized horizontal winds accompanying with intensive surface network are used to reveal the low-level kinematic/dynamic structure associated with the storm. Mesoscale convective systems with linear structure was identified and new cells formed at the west of Taipei City propagated eastward to merge with the basin-originated cells to form quasi-stationary convective line. Cells formed in the basin was closely related to the leading edge of the intrusion cold air from the north. It is noted that new convective line formed at the south rim of the previous line and then propagated north-east and brought rainfall to the same locations. Numerical model predicted the storm rainfall well at the beginning stage while rainfall was associated with the approaching surface front. However, the prediction was poor while the storm development was dominated over the colder air in the basin. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/72075 |
DOI: | 10.6342/NTU201803959 |
全文授權: | 有償授權 |
顯示於系所單位: | 大氣科學系 |
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