大亚湾冬季水位的亚潮变化及其与南海的耦合

Subtidal sea level variability in Daya Bay and its coupling with South China Sea during winter

本文应用常规时间序列谱分析方法和频域的多输入线性模型研究了冬季广东省大亚湾内水位的亚潮变化及其与大亚湾本地和外海、处各种强迫作用因素间的关系。结果表明：冬季大亚湾亚潮水位的能量主要集中在6.4d和3．6d频带，而在10．7d频带还有一较弱谱峰。同期广东沿海风的低频能量也主要集中于2～7d频段。造成冬季亚潮水位变化的原因包含了大亚湾本地气象条件的影响，但主要是远地（外海）因素作用于大亚湾的结果。外海影响一方面是外海气象条件变化造成陆架区和沿岸海域增减水井耦合至大亚湾内的结果。其中，粤东、粤西和大亚湾本地的风场都对6．4d波动有所贡献，而粤西沿海风场则是造成10．7d波动的原因。另一方面，经台湾海峡传播而来的陆架波可能是造成3．6d水位波动的主要原因。

The winter subtidal sea level variability in the Daya Bay and its relations with local andremote forclng are studied using both the time series analyses technique and a multiple-inputlinear system model in the frequency domain. The results show that the winter subtidal energy of sea level in the Daya Bay was concentrated at the 6. 4d and 3. 6d bands with a weakerpeak at 10- 7d. The low-frequency energy of winds along the Guangdong coast for the sameperiod also concentrated at 2~ 7d bands. Although the results show certain coherence ofsubtidal sea level in the Daya Bay with local meteorological conditions, it is concluded thatforcing mainly came from the far field (the open sea). It is found that remote forcing interacts with the Bay through two kinds of mechanism: surges caused by fluctuating meteorological conditions in the open waters along the shelf ; and shelf waves propagating westwardalong the South China Coast. It is suggested that the 6. 4d sea level fluctuation is caused bycombined effects of both remote wind forcing (those from upwind' direction off the easternGuangdong and from 'downwind' direction of f the western Guangdong) and local wind forcing ; and that the 10. 7d fluctuation mainly caused by winds off the western Guangdong. It isfurther suggested that shelf waves which propagate southwestward along the coast throughthe Taiwan Strait are responsible for the 3. 6d sea level fluctuation observed in the Daya Bay.