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Tidal asymmetry in a funnel-shaped estuary with mixed semidiurnal tides

机译：混合半日潮的漏斗形河口中的潮汐不对称

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摘要

Different types of tidal asymmetry (see review of de Swart and Zimmerman Annu Rev Fluid Mech 41: 203-229, 2009) are examined in this study. We distinguish three types of tidal asymmetry: duration and magnitude differences between flood and ebb tidal flow, duration difference between the rising and falling tides. For waterborne substance transport, the first two asymmetries are important while the last one is not. In this study, we take the Huangmaohai Estuary (HE), Pearl River Delta, China as an example to examine the spatio-temporal variations of the tidal asymmetry in a mixed semidiurnal tidal regime and to explain them by investigating the associated mechanisms. The methodology defining the tidal duration asymmetry and velocity skewness, proposed by Nidzieko (J Geophys Res 115: C08006. doi: 10.1029/2009JC005864, 2010) and synthesized by Song et al. (J Geophys Res 116: C12007. doi: 10.1029/2011JC007270 2011), is utilized here and referred to as tidal duration asymmetry (TDA) and flow velocity asymmetry (FVA), respectively. The methodology is further used to quantify the flow duration asymmetry (FDA). A positive asymmetry means a shorter duration of low water slack for FDA, a shorter duration of the rising tide for TDA, and a flood dominance for FVA and vice versa. The Regional Ocean Modeling System (ROMS) model is used to provide relatively long-term water elevation and velocity data and to conduct diagnostic experiments. In the HE, the main tidal constituents are diurnal tides K (1), O (1) and semidiurnal tides M (2) and S (2). The interaction among the diurnal and semidiurnal tides generates a negative tidal asymmetry, while the interactions among semidiurnal tides and their overtides or compound tides result in a positive tidal asymmetry. The competition among the above interactions determines the FDA and TDA, whereas for the FVA, aside from the interaction among different tidal constituents, an extra component, the residual flow, plays an important role. The results show that the FDA exhibits a predominant tendency of shorter duration of low water slack, favoring the landward transport of fine sediment. The FVA demonstrates prevailing ebb dominance in the study period, favoring the seaward transport of coarse sediment. This ebb dominance is primarily induced by the interaction among the residual flow and the tidal constituents. The external TDA in the ocean experiences distinct cyclic variations with positive asymmetry when semidiurnal tides dominate and negative asymmetry during the periods when diurnal tides dominate. The funnel shape of the HE is advantageous for the development of positive tidal asymmetry as the semidiurnal tides are more amplified than the diurnal tides. The effect of river flow can enhance the ebb dominance, while the baroclinic effect is more complex. The existence of channel and shoals favors the development of residual pattern with seaward flow (ebb dominance) in the channel and landward flow (flood dominance) at the shoal when the tides are strong (semidiurnal tides dominate) and the residual pattern with landward flow (flood dominance) in the channel and seaward flow (ebb dominance) at the shoal when the baroclinic effect is dominant (diurnal tides dominate).
机译：在这项研究中检查了不同类型的潮汐不对称性（请参见de Swart和Zimmerman Annu Rev Fluid Mech 41：203-229，2009年的评论）。我们区分了三种潮汐不对称类型：潮汐和潮汐流之间的持续时间和幅度差异，潮汐涨落之间的持续时间差异。对于水性物质运输，前两个不对称很重要，而后一个不重要。在这项研究中，我们以中国珠江三角洲的黄ma海河口（HE）为例，研究了混合半日潮模式下潮汐不对称性的时空变化，并通过研究相关机制来解释它们。由Nidzieko（J Geophys Res 115：C08006。doi：10.1029 / 2009JC005864，2010）提出并由Song等人合成的定义潮汐持续时间不对称和速度偏斜的方法。 （J Geophys Res 116：C12007。doi：10.1029 / 2011JC007270 2011）在这里被利用，并且分别称为潮汐持续时间不对称性（TDA）和流速不对称性（FVA）。该方法还用于量化流动持续时间不对称性（FDA）。正的不对称性意味着FDA的低耗水量持续时间较短，TDA的涨潮持续时间较短，FVA占主导地位，反之亦然。区域海洋建模系统（ROMS）模型用于提供相对长期的水位和速度数据并进行诊断实验。在HE中，主要的潮汐成分是日潮K（1），O（1）和半日潮M（2）和S（2）。日潮和半日潮之间的相互作用产生负的潮汐不对称性，而半日潮及其超潮或复合潮汐之间的相互作用导致正潮汐不对称。上述相互作用之间的竞争决定了FDA和TDA，而对于FVA，除了不同潮汐成分之间的相互作用之外，额外的组分（残留流量）也起着重要的作用。结果表明，FDA表现出较短的低水松弛持续时间的主要趋势，有利于精细沉积物的陆上运输。 FVA在研究期间显示出主要的退潮优势，有利于粗泥沙的向海运输。这种退潮优势主要是由残余流量和潮汐成分之间的相互作用引起的。海洋中的TDA经历明显的周期性变化，半日潮主导时为正不对称，而日潮主导时则为负不对称。 HE的漏斗形有利于发展正潮汐不对称性，因为半日潮比日潮更放大。河流流量的影响可以增强潮汐优势，而斜压作用则更为复杂。河道和浅滩的存在有利于在潮汐较强时（半日潮占主导地位）在河道中向海流动（退潮优势）和在岸滩向陆流（洪潮优势）形成残留模式，而有利于陆上流动（当斜压作用占主导地位（昼夜潮占主导地位）时，河道中的洪流优势和浅滩的海流（退潮优势）。

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  • 来源
    《Ocean Dynamics》 |2016年第5期|637-658|共22页
  • 作者

    Gong Wenping; Schuttelaars Henk; Zhang Heng;

  • 作者单位

    Sun Yat Sen Univ, Sch Marine Sci, Ctr Coastal Ocean Sci & Technol Res, 135 Xingangxi Rd, Guangzhou 510275, Guangdong, Peoples R China|Guangdong Prov Key Lab Marine Resources & Coastal, Guangzhou 510275, Guangdong, Peoples R China;

    Delft Univ Technol, Delft Inst Appl Math, Mekelweg 4, NL-2628 CD Delft, Netherlands;

    Sun Yat Sen Univ, Sch Marine Sci, Ctr Coastal Ocean Sci & Technol Res, 135 Xingangxi Rd, Guangzhou 510275, Guangdong, Peoples R China|Guangdong Prov Key Lab Marine Resources & Coastal, Guangzhou 510275, Guangdong, Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    Tidal asymmetry; Funnel-shaped estuary; Mixed tidal regime; China; Pearl River Delta;

    机译：潮汐不对称漏斗形河口混合潮汐状态中国珠江三角洲;

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