Observation of Surface Currents using HF Radar off East Coast of Taiwan: Data Quality Control and Preliminary Results

• Main Authors: Chung-Yaung Lee, 李宗勇
• Other Authors: 楊穎堅
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/85589169471572008192

碩士 === 國立臺灣大學 === 海洋研究所 === 103 === Since east of Taiwan is Kuroshio flow area, we can verify the accuracy of HF radar data by typical flow pattern of the Kuroshio. Signals received were not only from wave backscatter, but from nature as well. Signals that do not originate from waves are labeled “noise”, which can lead to irregular radial velocity. Data quality decreases as distance increases. Outside of distance, there are two major factors that impact data quality. The first is the variation of the earth’s ionosphere. The second is systematic error in bearings of each HF radar site; long-term reverse current direction for instance. As a result, the total velocity would be interfered with, generating anomalies. With this method, differences between first order signals and noises of different ranges are used to determine appropriate radial currents based on each monopole spectrum. Using statistical methods to calculate high quality data with no significant systematic errors in the azimuths of various radial currents, we can acquire more accurate data. The Kuroshio Current is a strong western boundary current, passing through the east of Taiwan. We can cross-reference HF radar data with Sb-ADCP data to analyze for accuracy. After this data selection process, coefficient of determination (R 2 ) between HF radar and Sb-ADCP data could be increased almost 0.25. Finally, combine selected radial velocity into new and accuracy total velocity vector. After these reprocessed progress, discuss tidal variations and seasonal variations of the surface Kuroshio Current.