教師著作
Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/37078
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Item 臺灣東北海域湧升流之時空變化(2007-11-30) 盧鴻復; 吳朝榮; 李忠潘黑潮為世界重要洋流之一。前人觀測發現黑潮流經臺灣東北海域之時，受到東海陸棚走向之影響，黑潮與複雜的海底地形交互作用，在此處產生湧升流與冷渦現象。過去的研究多以現場觀測為主，難以連貫研究資料的時空變化。因此，本研究以普林斯頓大學所開發之三維海洋數值模式為基礎，採用真實地形與巢狀箝合方法，將較大範圍模式之輸出作為本模式之初始與邊界條件，建構一個水平空間解析度達1/20°之海流模式。本模式可用來模擬臺灣東北海域之海流運動，其結果成功地重建該處之流場與水文型態，藉由分析、研究模式資料，可以瞭解東北海域之流場時空變化。模擬結果顯示，黑潮衝擊陸棚產生湧升流，於表層以冷渦流場表現，此現象受到黑潮運動影響，有季節性的變化，與過去觀測結果一致。除此之外，模式資料更進一步明確表現東北海域冷渦流場在季節尺度內的變化，其資料分析結果反應觀測資料之缺憾，亦指出上層黑潮主軸之擺動週期受到不同機制的作用而有所差異，進而對東北海域之上層流場產生顯著影響。Item Why are there upwellings on the northern shelf of Taiwan under northeasterly winds?(American Meteorological Society, 2010-06-01) Chang, Y.-L.; L.-Y. Oey; C.-R. Wu; H.-F. LuUpwellings are observed on the northern shelf of Taiwan during northeasterly winds. Analytical and realistic numerical models are used to explain how vertical motions are created by divergence and convergence produced by wind acting on the vorticity field of two strong jets: the Kuroshio and the Taiwan Warm Current. The seaward increase in cyclonic vorticity near the Kuroshio’s western edge favors a stronger Ekman transport away from the jet, producing upwelling at the shelfbreak under a northeasterly wind. A similar mechanism for generating vertical motions is found across the Taiwan Warm Current. The numerical model results indicate that the vorticity effects can account for up to 30%–50% of the total variation in the surface Ekman transport. Except during summer’s weak southwesterlies, northeasterly wind is dominant over the East China Sea, suggesting that the vorticity effects may be prominent in the observed shelfbreak upwelling in nonsummer months.