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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/15558

Title: 颱風對西北太平洋上層海洋影響之衛星觀測與數值模擬研究
Satellite Observations and Numerical Simulations of the Impact of Typhoons on the Upper Ocean in the Western North Pacific
Authors: 鄭志文
Contributors: NTOU:Department of Marine Environmental Informatics
國立臺灣海洋大學:海洋環境資訊學系
Keywords: 西北太平洋;颱風;海氣作用;衛星遙測;數值模式
Date: 2009
Issue Date: 2011-06-30T08:14:53Z
Abstract: 本研究目的是利用多衛星遙測、現場觀測資料及三維海洋數值模式對太平洋海域颱風引起之上層海洋響應進行研究分析,以了解颱風引起上層海洋冷卻以及生物響應之主要控制機制。利用微波輻射的海面溫度資料及海洋水色的葉綠素濃度影像,觀測颱風期間之海表冷卻及生物響應之位置及範圍,並以衛星高度計量測之海面高度異常值反映颱風通過前即存在於該海域之中尺度現象。研究結果顯示,2005年行經西北太平洋之海棠颱風,引起一系列海表面降溫現象與預先存在於該海域之氣漩式渦漩呈現高度相關,配合取自Argo浮標之現場實測溫度剖面發現,颱風在特定海域引起較為劇烈之冷卻響應,與氣漩式渦漩所在海域伴隨有較淺之斜溫層,提供冷水較為接近海面之預先存在條件有關。 本研究另使用海洋數值模式Regional Ocean Model System (ROMS)重建海棠颱風引起上層海洋冷卻之動力過程,以進一步了解海棠颱風引起之不連續冷卻響應的成因。藉由不同模式初始條件的使用,量化預先存在的氣漩式渦漩對海棠引起一系列冷卻響應的影響。結果顯示,在缺少預先存在氣漩式渦漩的海洋條件的作用下,海棠颱風引起之冷卻響應只有原本強度的一半,此結果顯示預先存在海洋條件對颱風引起上層海洋冷卻之重要性。 上層海洋熱變化顯示,颱風通過期間混合層中的熱收支平衡,主要受到垂直混合項的影響,而混合層下方水層之熱變化,則主要受控於平流項的影響。預先存在的氣漩式渦漩對颱風經過時之熱變化扮演重要的角色,氣漩式渦漩的作用底下,垂直混合項以及平流項對上層海水溫度的影響皆增強,進而加強颱風經過引起之上層海洋冷卻響應。 除了冷卻響應外,颱風的通過亦會在特定環境條件下產生生物響應, 2008年娜克莉颱風引起生物響應於其移動軌跡左側。模式結果顯示,儘管預先存在海洋條件對該生物響應有所影響,然該生物響應之生成機制,為通過該海域之前一個颱風,在娜克莉颱風形成前對該海域營養鹽進行抬升,配合後續娜克莉颱風通過的作用之合成效應。
The upper ocean responses to the passages of typhoons in the western North Pacific are analyzed using satellite and field observations, as well as a three-dimensional numerical ocean model. The location and magnitude of observed upper ocean responses are characterized by microwave sea surface temperature and chlorophyll-a concentration. Multi-satellite merged sea surface height anomaly (SSHA) data are used to identify meso-scale features existing before the passage of typhoon. A series of cooling responses after Super Typhoon Hai-Tang passage are found to be highly associated with preexisting cyclonic eddies (PCEs) denoted by negative SSHA. Subsurface in-situ temperature profiles from the Argo floats confirm the scenario that shallower thermocline accompanying with cyclonic eddies are the preexisting conditions for intensive cooling following the typhoon passage. Numerical experiments with initial conditions from HYCOM/NCODA system (EXPHYC) and World Ocean Atlas 2001 (EXPWOA) climatology are conducted to quantify the impact of PCEs to subsequent surface cooling induced by typhoon Hai-Tang. The model result shows that the cooling response simulated by EXPHYC fits the satellite observations much better, whereas cooling simulated by EXPWOA is only a half of that by EXPHYC. Meanwhile, results of systematical analysis with a focus on Category 5 typhoons occurring in the region from 2003 to 2008 identify the relationship between PCEs and enhanced surface cooling to majority of intense typhoons, only four exceptional cases coincidentally occurred during El Niño periods. Heat content variations analyses based on model diagnostic outputs derived from two numerical experiments with and without the contribution of PCEs were conducted to explore heat variations in the upper ocean during typhoon Sinlaku’s passage. The results show that vertical mixing dominates the heat content variations within the mixed layer and advection controls the heat variations below the mixed layer. In addition, PCEs are crucial to the upper layer heat content evolution during typhoon’s passage for enhancing the temperature changes contributed by advection and vertical mixing and thus the upper ocean cooling. Typhoon passage also causes biological response under certain circumstances. However, in contrast to rightward bias of surface cooling, Nakri (2008) induced maximum biological response at the left side of its track rather than the right side, whereas the most distinct cooling response occurred. Results of numerical experiments showed that the discrepancy between the physical and biological responses is a result of the advance uplift of nutrient fields by previous typhoon Rammasun.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0D95840004
http://ntour.ntou.edu.tw/ir/handle/987654321/15558
Appears in Collections:[海洋環境資訊系] 博碩士論文

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