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The lifetime of the Luzon Cyclonic Eddy and its Relation upon the Wind Stress Curl
|Authors: ||Chia-Hua Hsieh|
|Contributors: ||NTOU:Department of Marine Environmental Informatics|
sea level anomaly;Luzon cyclonic eddy;lifetime;wind stress curl
|Issue Date: ||2013-10-07T02:53:49Z
|Abstract: ||1992年~2011年的海面高度變異量（SLA）顯示呂宋島西側與西北側會出現中尺度正旋渦（cyclonic eddy），分別命名為「南呂宋正旋渦LCEs與北呂宋正旋渦LCEn」。LCEs生成位置約在17oN,118oE，固定每年出現1~4次，85%在秋冬出現，生命期約3個月；面積約30,000km2，概念上相當於100 km半徑的旋渦。LCEn位置約在19.5oN,120oE，80%每年出現1~2次，90%在冬春出現，生命期2個月，面積20,000 km2，相當於80 km半徑。兩種旋渦相對旋渦邊緣之中心高度差皆約 -6 cm。 1999~2009年呂宋島西側海域之風應力捲度資料的經驗正交函數（EOF）分析顯示，可以啟動正旋渦的正值風應力捲度可能與陽光、季風及呂宋島的地形有關。LCEs向西移動的分量約6 km/day，略低於Rossby Wave應有的8 km/day，可能是常駐性正風捲也有抑制旋渦移動的作用。LCEs向北移的分量則與黑潮入侵北南海的關係應該存在。LCEn的生成與風捲度關係不大，而與呂宋海峽黑潮套流之剝離效應的關係已被數模推斷；其以8 km/day之速向西北西移動，則似乎受Rossby Wave和黑潮入侵的牽引。正旋渦應有冷水或高葉綠素濃度之特性，皆因呂宋附近的衛星影像缺值多而難以判斷。|
Meso-scale cyclonic eddies west or northwest of Luzon are illustrated by the Sea Level Anomaly (SLA) in 1992~2011. They are named the Luzon Cyclonic Eddy south (LCEs) and Luzon Cyclonic Eddy north (LCEn) respectively. The LCEs creates roughly at 17oN, 118oE, and appears 1-4 times a year with about 85% formed during fall to winter. The averaged lifetime is about 3 months. The size is about 30,000 km2, conceptually equivalent to a radius of 100 km eddy. On the other hand, the LCEn generates at 19.5oN, 120oE. The 80% of those eddies appears 1-2 times a year and 90% is formed during winter to spring. The lifetime is about 2 months. The size is about 20,000 km2, equivalent to a radius of 80 km. The altitude difference from center to boundary for two kinds of eddies is the same of about -6 cm. The analysis of the empirical orthogonal functions (EOF) for the wind stress curl of west Luzon in 1999~2009 indicates that the mechanism of positive wind stress curl to initiate a cyclonic eddy could be related to the sun, the monsoon, and the island terrain of Luzon. The westward component of the LCEs migration is about 6 km/day, lower than the Rossby Wave of 8 km/day, possibly a repression for an eddy migration caused by the resident positive wind stress curl. The northward component should be related to the Kuroshio intrusion to north of the South China Sea. On the other hand, the relation of the LCEn creation to the wind stress curl is weak, but to the eddy shedding of Kuroshio loop current in Luzon Strait is modeled. The migration to the west-northwest in a speed of 8 km/day seems to be induced by the Rossby Wave and the Kuroshio intrusion. Cyclonic eddies should be characterized by cold water and high chlorophyll concentration, but not clear for the LCE due to the insufficient coverage of valid satellite data around Luzon.
|Appears in Collections:||[海洋環境資訊系] 博碩士論文|
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