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The inspection and modification of CODAR observations in Kuroshio
|Authors: ||Cheng-Han Jiang|
|Contributors: ||NTOU:Department of Marine Environmental Informatics|
|Issue Date: ||2013-10-07T02:53:50Z
|Abstract: ||台灣海洋科技研究中心（TORI）在台灣四周架設了岸基雷達測流系統CODAR，並於2010年開始觀測黑潮。遙測的流場有數百個網格點，點距10x10公里，時距每小時，但偶然會發生網格上的資料空缺，可採用經驗正交函數EOF的方法加以補全，也同時修飾了若干不合理的資料。這些遙測的流場必須跟實地真值比較，6個GPS浮標的結果顯示，在黑潮主流區，CODAR「流向」平均偏在浮標左方約10°，RMS約為30°，顯示CODAR流場的可信度還不錯；CODAR「流速」則普遍低於浮標所測，且流場之流速越快，流速低估的現象越明顯。在黑潮主流區之外的低流速或渦旋區，流向的平均偏差擴大一倍，且RMS增至80°。 近兩年的CODAR空間流場資料初步提供不同時間尺度的分析，細緻地看到黑潮表面流與周邊流場的互動，特別是台灣東南方中尺度順時鐘渦旋的消長，應該是黑潮變化的共伴現象。|
The CODAR (coastal ocean dynamics applications radar) system around Taiwan has been set up by the Taiwan Ocean Research Institute (TORI) and begun observing the Kuroshio since 2010. There are hundreds of data grids in a resolution of 10 km in space and an hour in time. Occasionally, data of some grids might be missing, which could be complemented by the empirical orthogonal functions (EOF) method. By doing so, unreasonable data are modified as well. The remotely sensed current field is compared with the ground truth of six GPS drifters. The result shows that, in the Kuroshio main stream, the current direction of CODAR observations is in average on the left of drifters about 10°with the RMS of about 30°, illustrating the acceptability of the CODAR system. On the other hand, the magnitude of speeds of the CODAR system is generally lower than the drifters. Such underestimate becomes significant while the current gets fast. Outside the Kuroshio where the speeds are usually low with eddies, the bias in direction enlarge twice with the RMS up to 80°. Nearly two-years CODAR observations provide preliminary studies of different time scales. The interaction of Kuroshio surface flow with the current field in the neighborhood can be examined with care. Especially, the growth and decline of the meso-scale anti-cyclonic eddy southeast of Taiwan should be an accompanying phenomenon along with the Kuroshio variation.
|Appears in Collections:||[海洋環境資訊系] 博碩士論文|
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