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首页> 外文期刊>Journal of marine systems: journal of the European Association of Marine Sciences and Techniques >Circulation and mixing along the North Passage in the Changjiang River estuary, China
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Circulation and mixing along the North Passage in the Changjiang River estuary, China

机译：长江口北通道的环流和混合

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Simultaneous field observations were made of time series of water level, current velocity, salinity and suspended sediment concentration at ten hydrological gauging stations along the North Passage in the Changjiang River estuary on 17 to 24 February (dry season) and 12 to 18 August 2012 (wet season), respectively. Quantitative analyses of those data are attempted to understand circulation and mixing along the Deepwater Navigational Channel in this estuary. Landward subtidal flow only appears during the neap tide. The maximum bottom landward velocity is in the order of 0.05-0.1 m.s(-1) in the dry season and 0.15-02 m.s(-1) in the wet season, respectively. In both dry and wet seasons, calculated mixing parameter (M), which is the ratio of the tidal timescale to the vertical mixing timescale, is below the critical value (1.0) on a neap tide but above it on a spring tide within the middle and lower reaches of the Channel. This suggests that tidal variation of mixing may be able to generate the tidal straining circulation during the periodic stratified spring tide. The interaction between significant river shear flow and longitudinal density gradient, a process termed "river effect" in this study, is revealed as the major reason for seasonal variation of stratification. The competition between tidal stirring, gravitational circulation and river effect could produce an increase in tidal mean value of the potential energy anomaly (phi) from neap to spring tides. Tidal mean value of the Simpson number (Si) over a neap tide surpasses the critical value (8.4 x 10(-1)) within the middle reach of the Channel, suggesting the occurrence of persistent stratification there. Tidal mean Si over a spring tide is in the order of 8.4 x 10(-1)-8.8 x 10(-2) within the middle reach, suggesting the occurrence of strain induced periodic stratification (SIPS). Shear prevails within the pycnocline in the middle and lower reaches of the Channel on a neap tide, with the value of squared shear (S-2) exceeding 10(-3) S-2. Calculated gradient Richardson number (Ri) is small at the salt-fresh water interface, indicating the occurrence of Kelvin-Helmholtz instability there. (C) 2015 Elsevier B.V. All rights reserved.
机译：在2月17日至24日（旱季）和2012年8月12日至18日（长江口北通道）沿长江北口的10个水文计量站，对水位，流速，盐度和悬浮泥沙浓度的时间序列进行了现场同步观测（雨季）。试图对这些数据进行定量分析，以了解该河口沿深水航行通道的环流和混合。陆上潮汐流仅在潮汐期间出现。在干燥季节，最大底部陆运速度分别为0.05-0.1 m.s（-1），在潮湿季节为0.15-02 m.s（-1）。在干旱和潮湿季节，计算出的混合参数（M）（潮汐时标与垂直混合时标之比）在小潮时均低于临界值（1.0），而在中间潮汐时高于临界值（1.0）。和海峡下游。这表明，在周期性的分层春季潮汐期间，混合潮汐变化可能会产生潮汐应变循环。显着的河流剪切流量与纵向密度梯度之间的相互作用（本研究中称为“河效应”的过程）被揭示为分层季节性变化的主要原因。潮汐搅动，引力环流和河流效应之间的竞争可能会使从潮汐到春季的势能异常（phi）的潮汐平均值增加。潮汐中辛普森数（Si）的潮汐平均值超过通道中游范围内的临界值（8.4 x 10（-1）），表明该处存在持续分层。春季潮汐的平均Si在中游范围内为8.4 x 10（-1）-8.8 x 10（-2），表明发生了应变诱发的周期性分层（SIPS）。在潮汐潮汐中，剪切作用主要发生在河道中部和下游，比方切应力（S-2）的值超过10（-3）S-2。盐-淡水界面的计算出的梯度理查森数（Ri）很小，表明在那里发生了Kelvin-Helmholtz不稳定性。 （C）2015 Elsevier B.V.保留所有权利。

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