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標題: | 莫拉克颱風引起台灣東南海域黑潮之逆風流反應 The head-wind Kuroshio southeast of Taiwan during typhoon Morakot |
作者: | Ying-Han Liao 廖浧涵 |
指導教授: | 唐存勇 |
關鍵字: | 颱風,莫拉克,台灣東南,黑潮,冷心渦漩, typhoon,Morakot,southeast of Taiwan,Kuroshio,cold eddy, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 本研究藉由分析佈放於臺灣東岸與綠島間海域之錨錠海流觀測資料與中央氣象局綠島測站之風速資料,探討當地海流與風場之變化。錨錠點之海流流向於觀測期間(2009年4月27日至9月13日)主要為東北偏北,約於2009年8月7日莫拉克(Morakot)颱風影響錨錠點海流期間,海流流速與次表層海水溫度皆有顯著之變化。水深320公尺以上整層海流於8月7日出現持續約24小時與風向反向之逆風流(西流),表面之北向流速於西流出現後12小時開始降低,並於西流消失後增強且向下延伸至320公尺,約於24小時後恢復原來之北向流速。伴隨海流之變化,水深343公尺之海水溫度於颱風期間驟升約1°C,旋即持續降溫4°C。
由於錨錠觀測僅限空間一點,故援用美國海軍實驗室(Naval Research Laboratory, NRL)發展之東亞海域現報預報系統模式(East Asian Seas Nowcast /Forecast System, EASNFS)結果以瞭解海流於水平空間上之變化,首先將模式資料與錨錠觀測資料比對以確認模式於本研究之適用性。模式資料顯示,黑潮於一般情況下靠近台灣東南岸;於莫拉克颱風登陸台灣數日前,台灣東南海域出現一範圍較小之冷心渦漩,此小範圍渦旋受熱帶性低氣壓柯尼(Goni)影響,柯尼造成南海北部之黑潮套流幅度增加,使台灣東南黑潮路徑向東偏移,而後冷心渦漩開始發展;莫拉克颱風期間,西風使黑潮之東偏幅度增加,冷心渦漩發展空間隨之增大及綠島,錨錠之逆風流現象應為冷心渦漩流場所貢獻。因此,錨錠觀測之逆風流現象受到熱帶性低氣壓柯尼影響而開始發展,主要於第二階段受莫拉克颱風影響而範圍增大。 The current velocity obtained from an Acoustic Doppler Current Profiler (ADCP) subsurface mooring in between east coast of Taiwan and Green Island was studied. The wind at Green Island was also used to assist the study. The Kuroshio was NNE primarily during the deployment, April 27 to September 13, 2009, except when the typhoon Morakot hit the mooring site around August 7, 2009. The head-wind current (westward current) was observed on 7th August and lasted for 24 hours when the Morakot passed through the mooring site. The northward current decreased or even disappeared in upper 50m ocean 12 hours after the westward current. It re-appeared in accompanying with a downward extension for about 24 hours. The temperature at 343m also went through an increase (1°C)/decrease (4°C) variation. The output of model, East Asian Sea Nowcast / Forecast System (EASNFS), was used to assist the interpretation for the single mooring observation in horizontal space. Model validation was done and confirmed. The model output indicates that the Kuroshio was close to southeast coast of Taiwan, in general. A small cold eddy was found southwest of the mooring site a few days before Morakot landed on Taiwan. It could be produced by the tropical depression Goni. Goni enlarged the Kuroshio loop in northern South China Sea. Kuroshio path shifted eastward off southeast Taiwan and then the cold eddy was appeared. The westerly wind pushed the Kuroshio further eastward and left more room for the development of cold eddy, which northern tip could reach Green Island and represented the westward current around mooring site. Therefore, the emergence of observed head-wind current could due to tropical depression Goni and typhoon Morakot. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/44986 |
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顯示於系所單位: | 海洋研究所 |
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