The process of tidal currents crossing in and out Shenao Bay

• Main Authors: Chun-Ming Hsu, 許峻銘
• Other Authors: Jian-Hwa Hu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/40971073954369643704

碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 94 === Shenao Bay is a small C-shaped bay in north of Taiwan. The west side of the bay is a protruding peninsula, which makes coastal currents meandering. The thermal plume from the power plant in the bay and the fresh water of Ta-ganlin Creek form the stratification of the bay. The topography and the hy-drography should be factors of the three dimensional interaction of currents in and out of the Bay. Therefore, it becomes the first aim to observe how cur-rents cross over the bay area. Ship-towed Acoustic Doppler Current Profiler（ADP） repeatedly scans the subsurface flows below 2.5m depth and GPS drifters track the surface currents. The time lag problem of scanned data can be eliminated by a synoptic process to obtain those time series of currents fields in horizontal and vertical patterns. The results show that currents at bay mouth are characterized by eddies initiated inside the bay and then moved away offshore. The variation of currents associated with tides starts at bottom and develops upwards gradually. The flood currents from surface to bottom often enter the bay on northwestern side causing a cyclonic motion inside the bay, and then flow out over the southeastern side eventually. In slack time and during the ebb, the opposite motions of the upper and lower layers often appear. The vertical hydrographic structure derived from CTD casts evidences the high temperature and low salinity surface water is as thin as 1m depth. Further-more, the comparison between the ADP observations and GPS drifter tracking indicates that the current stratification of surface 1 m and subsurface 2.5m is remarkable. Key words: Shenao Bay, ADP scans, vertical section, eddies, stratification.