乐清湾内外潮波变形及不对称性分析

Analysis of deformation and asymmetry of tidal waves inside and outside Yueqing Bay

海湾内外的潮波变形及其不对称性影响海湾内外动力输送和水体交换。利用乐清湾内外共9个测站连续潮位进行调和分析,得到该海湾内外各分潮变化规律,利用潮不对称性偏度计算方法确定湾内外潮汐不对称性时空变化特征,比较了主要分潮组合对潮汐不对称性的贡献度,通过数值研究探讨了湾内偏度比湾外偏度值更小的主要成因,分析了湾内外围垦工程对潮不对称偏度的影响。研究发现:乐清湾内潮汐不对称偏度值为负,表现为落潮占优,同期湾外洞头站偏度值为正,与邻近瓯江、飞云江河口的潮不对称偏度变大、表现涨潮占优的变化规律相反;湾外沿岸各站偏度由东北向西南逐渐增大,由落潮占优向涨潮占优变化;潮汐不对称性偏度呈周期性变化,分析确定M2-M4、M2-S2-MS4分潮组合对潮不对称贡献大,该海域潮汐不对称的强度主要由浅水分潮振幅控制,而相对相位则决定潮汐不对称的方向;数值研究探讨表明,湾内大范围的浅滩地形是其潮汐不对称落潮占优的主要原因,围垦将削弱湾内的落潮占优。

The deformation and asymmetry of tidal waves inside and outside the Yueqing bay affect the dynamic transport and water exchange inside and outside the bay.Harmonic analysis is carried out by using hourly tidal data of 9 stations around the bay,the regularity of tidal constituent variations is obtained,and the temporal and spatial variation characteristics of tidal asymmetry in and out of the bay are determined by calculating tidal asymmetry skewness.The contribution of different tidal constituent combinations to tidal asymmetry is compared.The main causes of smaller skewness inside the bay than those outside the bay are studied by numerical model,and the influence of reclamation project on skewness is analyzed.It is found that the tidal asymmetry skewness in the bay is negative and shows ebb dominance,while that in Dongtou station outside the bay is positive in the same period,which is contrary to the law that the tidal asymmetry skewness increases and shows flood dominance in the adjacent estuary of the Oujiang River and the Feiyunjiang River.The skewness of the coastal stations gradually increases from northeast to southwest,and changes from ebb dominance to flood dominance.Tidal asymmetry has periodic variation characteristic,and it is determined that M2-M4 and M2-S2-MS4 tidal constituent components contribute mostly to the tidal asymmetry,and the intensity of tidal asymmetry in this area is mainly controlled by the amplitude of shallow water tide,while the relative phase determines the direction of tidal asymmetry.The numerical modeling research results show that the large area of bank in the bay is the main reason for its asymmetric ebb tide dominance,and the reclamation will weaken the ebb tide dominance in the bay.