台灣海峽海潮流之研究

Abstract

本論文利用1999年至2001年間以4次底碇式錨碇觀測海流剖面、近海床水溫與水位資料，並收集烏坵嶼和東吉島的風速資料，分析探討台灣海峽內的流場變化。結果顯示台灣海峽內的潮流主要以半日和全日正壓潮流為主。全日正壓潮可用單一凱文行進波沿中國大陸海岸自北向南傳播予以說明，但半日正壓潮則否。 於東北季風期間低頻海流主要是隨著風速強弱而產生變化，當東北風微弱的時候，順沿海峽方向與橫越海峽方向之低頻流速主要分別為逆風向和朝向台灣。當東北風強勁的時候，順沿海峽方向之低頻流速轉為順風向，並驅動低溫的大陸沿岸水南下，在海峽西側形成一道斜壓的流速鋒面。且由於艾克曼效應致使海峽上層海水流向中國大陸方向，下層海水流向台灣方向。計算所得之體積流量時序變化主要也是隨著東北風速強弱而改變，在東北風強盛時為順風向(向南)，東北風微弱時為逆風向(向北)。於1999年9月底至12月中東北風時期所得之順沿海峽方向的低頻體積流量於

The current velocity profiles, bottom water temperature, and sea level were observed to study the spatial and temporal variations of the tidal and subtidal current in the Taiwan Strait from 1999 to 2000. Results indicate both diurnal and semidiurnal tidal currents were primarily barotropic. The barotropic diurnal tide might be explained by a single Kelvin wave propagating along the Mainland China coast from north to south. However, the barotropic semidiurnal tide manifested as a more complicated form in the Taiwan Strait. In the northeast monsoon, the subtidal current generally fluctuated with the northeast winds. When the northeast wind was weak, the along- and cross-strait subtidal current flowed primarily against the wind and toward Taiwan, respectively. As the northeast wind intensified, the along-strait current flowed downwind, brought the cold China coastal water southward, and formed a baroclinic velocity front in the western portion of the Taiwan Strait. The Ekman effect forced the cross-strait current toward Mainland China in the upper water column. Nevertheless, the current in the lower water column remained toward Taiwan. From September 28 to December 14 of 1999, the along-strait volume transport, estimated from interpolated current velocity, varied from -5 to 2 Sv with a mean value of 0.12