Observations and analysis of Taiwan Strait currents and their applications to maritime search and rescue missions

• Main Authors: Yung-Ting Shen, 沈勇廷
• Other Authors: Ruo-Sen Tseng
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/za96j5

博士 === 國立中山大學 === 海洋生物科技暨資源學系研究所 === 107 === In this study, twelve SVP drifters were deployed in the northern and southern parts of the Taiwan Strait (TS) in February and June 2017, with a sampling interval of 15 minutes to observe the TS flow patterns and water temperature during winter and summer. In addition, long-term observed data from various instruments were analyzed to investigate the temporal and spatial variations of the TS flow field. Based on the trajectories of historical drifters and the 2017 survey, it can be concluded that TS has five flow patterns during wintertime. As the northeastern monsoon intensified, drifters in the northern TS drifted slowly to the south, but then they began to move northward as the winter monsoon relaxed. Some drifters lingered around with strong semidiurnal tidal excursions and amphidromic characteristics off the northern tip of Taiwan and they eventually moved to the seas off northeastern Taiwan and then merged into the Kuroshio. A cyclonic vortex flow and marked water temperature front, with temperature difference up to 7oC, were observed to exist in the seas off northeastern Taiwan, where the Kuroshio intrudes onto the continental shelf of the East China Sea. Combining the AVISO satellite altimeter data with multi-observed data of drifters, high-frequency radars and bottom-mounted Acoustic Doppler Current Profilers (ADCPs), the spatio-temporal characteristics and occurrence statistics of the often-seen anticyclonic eddy off southwestern Taiwan were revealed. Current data observed by the tens of buoy-mounted CWB ADCPs surrounding Taiwan and by the AWCPs near the entrance of three international ports were analyzed to obtain the ocean currents characteristics in the TS. To enhance the immediacy and accuracy of search and rescue missions conducted by Taiwan Coast Guard Administration , this study examines the characteristics of ocean currents and estimates the drifting trajectory of objects for two cases of marine incidents. Two methods are used to predict object’s drift tracks: the first one is simply calculating the advection driven by currents and the second method adopts a Monte Carlo based software, SARMAP. Ocean currents data from a high-frequency radar system comprised of 18 radar units surrounding Taiwan supplemented by bottom-mounted ADCP data and wind data are used as the primary oceanic environment data. The estimated ending points of drifting for both cases of missing persons in water by using both methods are consistent with the actual recovery locations. Our analyses demonstrate that ocean currents data, if properly used, can be very useful for rapid response in marine search and rescue. Finally, a comprehensive marine environmental database could be integrated and constructed based on a vast numbers of long-term observations of ocean currents. The database can be very useful and essential for the prediction and treatment of marine waste dispersal along the coastlines of Taiwan, in addition to the assistance of maritime safety and the search and rescue missions.