长江口北支河段潮汐不对称性分析

Analysis on tidal asymmetry in north branch of Yangtze River Estuary

通过对长江口北支连兴港站逐时潮位序列和青龙港站高低潮位序列进行调和分析,从潮汐不对称性方面,寻求出适合描述长江口北支河口形态的参数:变形系数A、G以及振幅参数A2和相位参数P。根据资料所绘制的参数拟合曲线表明,青龙港站、连兴港站均为涨潮占优,且青龙港站潮汐不对称性强于连兴港站,这主要由于长江口北支断面从下游到上游不断缩窄,潮波变形加剧所致;长江口北支从下游连兴港站到上游青龙港站,两站涨潮占优的潮汐不对称性差异在年际变化上总体呈现加强趋势,其主要与青龙港站潮汐不对称性总体减弱、连兴港站基本保持不变有关;北支下泄径流量减少,一定程度上导致了青龙港涨潮优势特性的减弱。

Harmonic analysis is carried out by using hourly tidal data of Lianxinggang Station and the high and low tidal data of Qinglonggang Station in Yangtze Estuary. Some appropriate parameters including deformation coefficient A, G, amplitude parameter A2 and phase parameter P are selected to characterize the geometry of the north branch of Yangtze River Estuary from the perspective of tidal asymmetry. According to the parametric fitting curves, rising tide is dominant at Lianxinggang and Qin- glonggang stations, the tidal asymmetry of the latter station is larger than that at the former one, because the vertical tidal wave becomes strongly distorted as it propagates into the narrowing estuary from downstream to upstream. From Lianxinggang Station to Qinglonggang Station, the difference on flood - dominant tidal asymmetry of two stations overally shows an increasing trend in an inter - annual variation, which is mainly related to the decreasing trend of tidal asymmetry at Qinglonggang Station and basically unchanging trend at Lianxinggang Station. The decrease of runoff of the north branch results in a reduction of rising tide - domi- nant at Qinglonggang Station to some extent.