1986年到2006年間美國NOAA/AOML浮標資料庫中南海北部的表層海洋環流有超過505顆的衛星定位浮標的資料，加上本實驗室2006年下半年在澎湖水道與呂宋海峽西側自行施放的十顆浮標資料可供分析。本文以Eulerian法和Lagrangian統計方法來分析經過處理的浮標速度資料，分析表面環流從中尺度到季節性循環的空間結構與暫時性變化。
平均流向量圖、速度變化量橢圓圖和平均流動能圖等都是以0.5°×0.5°網格點來製作。平均流向量圖證實在冬季東北季風時南海北部流場是一個大型的逆時針環流，而在東沙環礁周圍有一股由東北向西南的海流(簡稱東沙海流)，並延伸到越南外海成為一股強勁的海流(簡稱越南海流)，越南海流的最大流速能超過100cm/s。在夏季西南季風的吹拂下，東沙海流變得非常微弱，此時多數浮標在東沙環礁附近徘徊。呂宋海峽進入南海的黑潮水、東沙海流與越南海流有連貫性。
在南海北部海域的南北向擴散率和Lagrangian的時間尺度、空間尺度個別為5.12×107cm2/s、2.56天和64.43公里，而東西向的統計則約為上述值的一半，顯示此區域的時間尺度與空間尺度有很高的不等向性。
東沙海流的平均流速為0.33 m/s。將東沙海流流域區分為十個2°×2°的方塊以分析其空間分佈的Lagrangian統計特性，結果東沙海流在113- 121°E之間的渦動動能均大於平均流動能，顯示此區域的中尺度運動發達，同時由東向西方向，其渦動動能也是逐漸變小，顯示離呂宋海峽越近，其渦動動能越大。
沿著越南東岸外海向南流的浮標資料顯示越南海流的寬度在80到120公里間變化，其平均的核心速度在60-150cm/s之間。冬季時最大的向南海流速度在離岸約38公里處達到130cm/s以上。春季時的向南海流速度較弱，但是最大流速也有100cm/s以上，並集中在離岸距離較近約在18km處，而夏、秋季則缺乏浮標資料。

The surface circulation of the northern South China Sea (NSCS) for the period of 1986-2006 is studied using the data of more than 505 satellite-tracked drifters from NOAA/AOML database and the data from ten drifters which were released by our lab in the Penghu channel and in the Luzon Strait in 2006. In this study, the spatial structure and the temporal variability of the surface currents, at mesoscale to seasonal cycle, are described in terms of Eulerian and Lagrangian statistics from the drifter velocities that have been processed.
Maps of mean currents, velocity variance ellipses and mean kinetic energies were produced in domain of 0.5°×0.5°. The mean flow map confirms that during the winter monsoon, there is a global cyclonic circulation in the NSCS and the southwestward current which passes Dongsha Island and is called the “Dongsha Current”. Its continuation is the southward coastal jet off Vietnam which is called the “Vietnam Current”. Maximum velocities in the Vietnam Current can exceed 100 cm/s. During the summer monsoon, the Dongsha Current became very weak and the drifters looped near Dongsha Island. The drifter data shows that part of Kuroshio water intrudes into South China Sea through Luzon Strait, Dongsha Current and Vietnam Current were coherent flows.
Values of 5.12×107 cm2/s, 2.56 days and 64.43 km were obtained for the diffusivity, Lagrangian time scale and spatial scale in the meridional direction in the NSCS, respectively. In the zonal direction, the statistics are half of the above values which show that the characteristic time and space scale are anisotropic.
The mean velocity in the Dongsha Current is 0.33 m/s. The domain of Dongsha Current is subdivided into ten boxes of size 2°× 2° in order to analyze the spatial structure of Lagrangian statistics. The result shows that the eddy kinetic energy is considerably higher than the mean kinetic energy in the region 113-121°E, indicating that the mesoscale motions are particularly frequent. The eddy kinetic energy gradually decreases toward the west and has a maximum value near the Luzon Strait.
The drifters that flow southward along the east coast of Vietnam shows that the width of the Vietnam Current varies between 80 and 100 km and has a mean core speed of 60-150 cm/s. In winter, Maximum southward velocities could reach 130 cm/s at 38 km off the coast. In spring, a weaker maximum speed (around 100 cm/s) exists at about 18 km off the Vietnam coast. There were not enough drifter data in summer and fall.

謝誌…………………………………………………………………… Ⅰ
中文摘要……………………………………………………………… Ⅱ
英文摘要……………………………………………………………… Ⅳ
目錄…………………………………………………………………… Ⅵ
圖目錄………………………………………………………………… Ⅷ
表目錄………………………………………………………………… Ⅹ
ㄧ、 前言……………………………………………………………… 1
1.1 研究區域………………………………………………………1
1.2 前人研究………………………………………………………1
1.3 研究目的………………………………………………………4
二、 實驗方法與資料來源…………………………………………… 6
2.1 浮標資料來源…………………………………………………6
2.2 WOCE-SVP………………………………………………………7
2.3 浮標系統與資料處理過程……………………………………8
2.4 海岸線與水深資料……………………………………………9
三、 分析方法…………………………………………………………20
3.1 Eulerian統計方法………………………………………… 20
3.2 Lagrangian統計方法……………………………………… 22
四、 平均環流、速度變化量和擴散率……………………………… 26
4.1 Eulerian統計……………………………………………… 26
4.1.1 平均環流…………………………………………… 26
4.1.2 速度變化量………………………………………… 27
4.1.3 平均流動能(MKE)、渦動動能(EKE)……………… 28
4.2 Lagrangian統計…………………………………………… 29
4.2.1 時間尺度與空間尺度……………………………… 29
4.2.2擴散率…………………………………………………31
五、 季節性與空間性的變化………………………………………… 48
5.1 南海北部海域Eulerian統計……………………………… 48
5.2越南海流隨離岸距離的變化…………………………………50
5.3 Lagrangian特性的時空分佈……………………………… 51
5.4 東沙海流的空間分佈統計………………………………… 52
六、 結論………………………………………………………………74
參考文獻……………………………………………………………… 76


圖目錄
圖1-1. 南海北部海底地形水深圖…………………………………… 5
圖2-1. 南海海域浮標軌跡圖(1982-2006)………………………… 11
圖2-2. 南海北部1986-2006浮標資料數目年月分佈圖…………… 12
圖2-3. 東沙海流1986-2006浮標資料數目年月分佈圖…………… 13
圖2-4. 越南東岸外海1986-2006浮標資料數目年月分佈圖………14
圖2-5. 南海北部海域浮標資料數目密度圖(1982-2006)………… 15
圖2-6. 本研究流入東沙海流的浮標軌跡圖…………………………16
圖2-7. Argos浮標之迷你型洞襪式浮標照片圖…………………… 17
圖2-8. Argos浮標之原型與迷你型洞襪式浮標示意圖(摘自NOAA/
AOML網站) ……………………………………………………18
圖3-1. No.56662浮標的自相關函數…………………………………25
圖4-1. 水深15m平均流速向量圖(1982-2006)…………………… 33
圖4-2. 南海海域浮標流速大於40cm/s的軌跡圖(1982-2006)…… 34
圖4-3. 南海海域浮標流速大於60cm/s的軌跡圖(1982-2006)…… 35
圖4-4. 南海海域浮標大於80cm/s的軌跡圖(1982-2006) …………36
圖4-5. 南海海域浮標流速大於100cm/s的軌跡圖(1982-2006)… 37
圖4-6. 冬季水深15m平均流速分佈圖(1982-2006)……………… 38
圖4-7. 夏季水深15m平均流速分佈圖(1982-2006)……………… 39
圖4-8. 水深15m平均流向量與速度變化量橢圓圖(1982-2006)… 40
圖4-9. 水深15m平均流向量與平均流動能圖(1982-2006)……… 41
圖4-10. 水深15mn速度變化量橢圓與平均渦動動能(1982-2006) 42
圖4-11. 水深15m EKE/MKE圖(1982-2006)………………………… 43
圖4-12. 以Lagrangian統計法計算南海北部海域浮標軌跡資料中流
速移除平均流速後的擴散率(diffusivity)對10天的時間
延遲圖……………………………………………………… 44
圖5-1. 南海北部浮標軌跡的四季分佈圖……………………………55
圖5-2. 秋季水深15m平均流速分佈圖(1982-2006) ………………56
圖5-3. 春季水深15m平均流速分佈圖(1982-2006)……………… 57
圖5-4. 水深15m四季渦漩動能圖(1982-2006)…………………… 58
圖5-5. 冬季水深15m平均流向量與平均流動能圖(1982-2006)… 59
圖5-6. 冬季水深15mn速度變化量橢圓與平均渦動動能圖……… 60
圖5-7. 冬季水深15m EKE/MKE圖(1982-2006)…………………… 61
圖5-8. 夏季水深15m平均流向量與平均流動能圖(1982-2006)… 62
圖5-9. 夏季水深15mn速度變化量橢圓與平均渦動動能圖……… 63
圖5-10. 夏季水深15m EKE/MKE圖(1982-2006)…………………… 64
圖5-11. 朝南流的越南海流向南流速統計圖……………………… 65
圖5-12. 南海北部四季浮標單質點位移量的吐煙圖……………… 66
圖5-13. 東沙海流四季浮標單質點位移量的吐煙圖……………… 67
圖5-14. 越南東岸外海全年與冬季浮標位移量的吐煙圖………… 68
圖5-15. 東沙海流水深15m平均流速向量圖(1982-2006) ……… 69
圖5-16. 水深15m平均流向量與速度變化量橢圓圖(1982-2006)… 70
圖5-17. 東沙海流的Lagrangian空間尺度、時間尺度與擴散率對
2°×2°速度變化量圖……………………………………… 71
表目錄
表2-1. 本研究以海研三號施放Argos浮標紀錄…………………… 19
表4-1. 南海北部浮標Lagrangian統計摘要……………………… 45
表4-2. 東沙海流浮標Lagrangian統計摘要……………………… 46
表4-3. 越南東岸外海浮標Lagrangian統計摘要………………… 47
表5-1. 東沙海流浮標Lagrangian統計的空間變化摘要………… 72

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