Harmonic analysis of tides and tidal currents in South San Francisco Bay,California

Water level observations from tide stations and current observations from current-meter moorings in South San Francisco Bay (South Bay), California have been harmonically analysed. At each tide station, 13 harmonic constituents have been computed by a least-squares regression without inference. Tides in South Bay are typically mixed; there is a phase lag of approximately 1 h and an amplification of 1·5 from north to south for a mean semi-diurnal tide. Because most of the current-meter records are between 14 and 29 days, only the five most important harmonics have been solved for east-west and north-south velocity components. The eccentricity of tidal-current ellipse is generally very small, which indicates that the tidal current in South Bay is strongly bidirectional. The analyses further show that the principal direction and the magnitude of tidal current are well correlated with the basin bathymetry. Patterns of Eulerian residual circulation deduced from the current-meter data show an anticlockwise gyre to the west and a clockwise gyre to the east of the main channel in the summer months due to the prevailing westerly wind. Opposite trends have been observed during winter when the wind was variable.     

基于FVCOM 的辽东湾水动力特性数值模拟

辽东湾属于半封闭性海湾, 水动力过程具有一定的代表性。本文基于无结构化三角形网格的有限体积海岸海洋模型FVCOM（Finite-Volume Coastal Ocean Model）, 构建了辽东湾及其邻近海域的三维水动力数值模型, 并利用实测数据对6 个潮位验潮站、4 个潮流验潮站的大小潮时刻的潮位、流速、流向进行了对比验证, 该模型能够准确地模拟辽东湾的潮汐、潮流等水动力场情况, 可进一步为研究辽东湾温盐、泥沙、水质、污染物扩散等提供研究基础。     

莱州湾潮余流及粒子运移特征

为掌握莱州湾潮余流特征和粒子运移特征,文章采取平面二维数值模拟的方法,计算得到莱州湾的潮流场,并分析潮流结构;在潮流场的基础上,计算和分析欧拉余流场;通过在不同位置释放自由运动的粒子,得到潮流作用下自由运动粒子的运移轨迹。研究结果表明：莱州湾涨潮时的最大流速约为2.19 m/s,落潮时的最大流速约为2.66 m/s,且均在湾口处出现最大流速;莱州湾欧拉余流速度较小,且湾口附近较大而湾内较小;莱州湾分布均匀的粒子在自由运移时出现不同程度的聚集,且整体运移趋势是向岸聚集。     

A BFG model for calculation of tidal current and diffusion of pollutants in nearshore areas

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基于遥感反演的莱州湾悬沙分布及其沉积动力分析

选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。     

ADCP measurements of suspended sediment flux at the entrance to Jiaozhou Bay, western Yellow Sea

The purpose of the present contribution is to explore the technique to use Acoustic Doppler Current Pro- filers （ADCPs） for suspended sediment flux measurements, which may be applied to coastal embayment environments such as estuaries and tidal inlets for sediment exchange and budget studies. Based on tidal cycle measurements from the entrance of ]iaozhou Bay, Shandong Peninsula, eastern China, statistical rela- tionships between the suspended sediment concentration （SSC） and ADCP echo intensity output are estab- lished. Echo intensity data obtained during an ADCP survey along two cross-sections during a spring tidal phase were transformed into SSC data. The ADCP current velocity and SSC data were then used to calculate the flux of fine-grained sediment. The results show that net sediment transport at the entrance is directed towards the open sea, with an order of magnitude of 103 t per spring tidal cycle; hence, although Jiaozhou Bay is a low SSC environment, the tidally induced suspended sediment transport can be intense.     

A finite differences formulation for the linear and nonlinear dynamics of 2D catenary risers

A finite differences (FD) solution method is proposed for the numerical treatment of the dynamic equilibrium problem of 2D catenary risers. The method is based on the so-called Box approximation, which in the scope of the present contribution is applied to the complete nonlinear model as well as to the reduced linearized formulation. The application of the Box method transforms the original governing systems into convenient sets of algebraic equations, which in turn are solved efficiently by the relaxation method. Extensive numerical calculations are presented that describe the dynamic behaviour of the structure and evaluate the amplification in loading due to the dynamic components. The effect of the geometric nonlinearities is assessed through comparative calculations that concern both mathematical formulations examined in the present, i.e. the complete nonlinear, and the reduced linearized model. Special attention is paid to the heave excitations as they amplify significantly the magnitudes of the loading components.     

One-Dimensional Unsteady Analytical Solution of Salinity Intrusion in Estuaries

Based on the one-dimensional salinity transport equation with constant diffusion coefficient, and separated water flow velocity into runoff and tidal current with the single-frequency in an idealized estuary, the simplest unsteady analytical so- lution of salinity intrusion is deduced and the estimation formula of diffusion coefficient is obtained in this paper. The unsteady solution indicates that salinity process in estuaries results from the interaction of runoff and tidal current, and its amplitude is in direct proportion to the product of the velocity of runoff water and the amplitude of tidal flow velocity and in inverse proportion to the diffusion coefficient and the tidal angular frequency, and its phase lag tidal flow with 7/2 which reveals the basic features of the maximum salinity appearing after flood slack and the minimum salinity appearing before ebb slack under the effect of runoff （the advance or lag time is relative to the magnitude of runoff and tidal flow）. According to the measured flow velocity and salinity data, the salinity diffusion coefficient could be estimated. Finally, with the field data of observing sites on the deepwater navigation channel of the Yangtze Estuary, the diffusion coefficient is calculated and a comparative analysis of simulated and measured of salinity process is made. The results show that the solution can comprehensively reflects the basic characteristics and processes of salinity intrusion under the interaction of runoff and tidal flow in estuaries. The solution is not only suitable for theoretical research, but also convenient for estimating reasonable physical parameters and giving the initial condition in the salinity intrusion numerical simulation.     

杭州湾枯季水沙若干特征分析

根据2014年1月及2017年2月杭州湾大、小潮水沙资料,计算了流速、含沙量、单宽潮量、单宽输沙量,进而分析了潮周期断面净潮量、净输沙量和区域冲淤分布。研究发现杭州湾涨、落潮平均流速比值整体较20世纪八九十年代增大,绝大部分区域大于1.0,涨潮流相对增强,澉浦南岸和金山北岸尤为显著。含沙量平面上分布澉浦、杭州湾南岸两个高值区(大潮大于3 kg/m³,小潮大于1.3 kg/m³)以及北岸湾口至乍浦之间的低值区(大潮小于2 kg/m³,小潮小于0.9 kg/m³),随潮汛变化显著,最大含沙量浓度通常滞后于急流时刻。各测站涨、落潮量和输沙量呈现“大涨大落”和“大进大出”的特征,造成杭州湾短时间尺度内的“大冲大淤”。大潮两涨两落金山与乍浦、乍浦与澉浦之间区域净输沙量可达几千万吨,净冲淤则在几百万吨。     

Numerical Simulation of Tidal Current in a Bay

—Based on the multilevel model,numerical calculations of tidal current affected by the M_2 tidein the Tokyo Bay have been carried out.The results of calculation are compared with the data observed inthe Tokyo Bay and the result calculated by an approximate formula as the Tokyo Bay is regarded as a rec-tangular bay,and good agreement is found.It is proved that the mathematical model and the calculationmethod are correct and useable.     

基于FVCOM的泉州湾海域三维潮汐与潮流数值模拟

基于FVCOM海洋数值模式,采用非结构的三角形网格和有限体积法,建立了泉州湾海域高分辨率(26 m)的三维潮汐、潮流数值模型。模拟结果同2个验潮站和3个连续测流站的观测资料符合良好,较好地反映了泉州湾内潮汐、潮流运动的变化状况和分布特征,给出了M₂、S₂、K₁、O₁ 4个主要分潮的同潮图、表层潮流椭圆分布,以及模拟区域内最大可能潮差、表层最大可能潮流流速和潮余流分布。分析表明,4个分潮的最大潮汐振幅和迟角差分别为219 cm和19°,85 cm和25°,26 cm和12°,26 cm和9°;石湖港以东海域的潮波为逆时针旋转的驻波,以西海域为前进波;最大可能潮差由湾口的8.0m向湾内增加至8.8 m。湾内潮流类型为规则半日潮流,落潮最大流速大于涨潮最大流速,北乌礁水道为强流区,表层最大可能潮流流速为2.4 m/s;湾口潮流运动以逆时针方向的旋转流形式为主,湾内的潮流运动以往复流形式为主,长轴走向主要沿着水道方向,与等深线和海岸线平行;四个分潮流表层最大流速分别为1.4 m/s,0.58 m/s,0.12 m/s,0.10 m/s。余流流速大小与潮流强弱有密切的联系,表、中、底层最大余流流速分别为26 cm/s,20 cm/s,16 cm/s,三者在水平方向基本呈北进南出的分布形态。     

2-D Current Field Numerical Simulation Integrating Yangtze Estuary with Hangzhou Bay

—In this paper,integrating the Yangtze Estuary with the Hangzhou Bay,a 2-D velocity fieldmodel is established.In the model,fine self-adaptive grids are employed to adapt to the complicated coast-al shape.The hydrodynamic equations satisfied by two contravariant components of velocity vector andsurface elevation in non-orthogonal curvilinear coordinates are used.In each momentum equation thecoefficients before the two partial derivatives of surface elevation with respect to variables of alternative di-rection coordinates have different orders of magnitude,i.e.,the derivative with the larger coefficient mayplay a more important role than that with the smaller one.With this advantage,the ADI scheme can beeasily employed.The hydrodynamic factors include tidal current,river runoff and wind-induced current.In terms of tidal current,seven main constituents in the area are considered in the open boundaries.Theverifications of surface elevation process and current velocity process in the spring tide and in the n     

钦州湾水交换能力数值模拟研究

基于普林斯顿海洋模式（Princeton Ocean Model,POM）,以M₂、S₂、K₁、O₁、M₄和MS₄ 6个分潮为驱动,建立了包含漫滩处理的高分辨率钦州湾水动力模式。与现场观测的数据对比表明,该模式能较好地刻画钦州湾的水动力特征。在此基础上建立了水质模型,模拟钦州湾的水交换过程。模拟结果表明:钦州湾水交换能力整体上较强,整个湾平均的水体半交换时间约为18 d,水体平均存留时间为45 d。空间分布上,钦州保税港区以南海域水交换能力最强,半交换时间小于1 d;沿着水道向北,水交换能力逐渐减弱;茅尾海中部半交换时间为26~28 d;茅尾海的东、西、北3个部分存在水交换滞缓区,半交换时间超过50 d。数值实验表明,采用漫滩技术对准确模拟钦州湾潮流速度和水交换能力非常重要,不考虑漫滩过程会低估钦州湾的潮流速度和水体交换能力。水平扩散系数对流速及交换时间都有影响,但影响有限。     

Tide and surge dynamics along the Iberian Atlantic coast

The eastern Atlantic barotropic dynamics (in a region spanning from 20° N to 48° N and 34° W to 0°) are studied through numerical modelling and in situ measurements. The main source of data is the tidal gauge network REDMAR, managed by Clima Marítimo (Puertos del Estado). The numerical model employed is the HAMSOM, developed both by the Institut für Meereskunde (Hamburg University) and Clima Marítimo.In this paper, tidal and storm surge dynamics are studied for the region, focusing particularly on the nonlinear transfer of energy between the different forcings.The results of tidal simulations show good agreement between semidiurnal harmonic components and the values obtained from the tidal gauges (both coastal and pelagic) and current metres. The nonlinear transfers of energy from semidiurnal to higher order harmonics, such as M4 and M6, were mapped. Those transfers were found to be important in only two areas: The French continental shelf in the Bay of Biscay and the widest part of the African shelf, south of Cabo Bojador. The modelled diurnal constituents show larger relative differences with measurements than semidiurnal harmonics, especially in data concerning the phase.A method to isolate the nonlinear transfers of energy between tidal and atmospheric forcing during a storm surge was developed. These transfers were found to be significant in the same areas where tidal nonlinear activity was present. The effect of short period wind generated waves on sea surface elevation was also investigated. The magnitude of the spatial derivatives of radiation stress was compared with wind-induced stress. As a result of this comparison, we found the inclusion of a forcing term that depends on radiation stress in ocean model simulations at this scale and resolution to be not essential. The effect of computing wind-induced stresses, with a formulation that explicitly depends on sea state, was also explored by means of a coupled run of the HAMSOM and the spectral wave model WAM for a storm surge event in the Spanish coast. This formulation was not found to be an improvement over a classical parameterisation which only depends on wind fields.     

Tidal residual flow in Kasado Bay

A current measurement was carried out in Kasado Bay to understand the vertical structure of tidal residual flow and its dependence upon the tidal range. The tidal residual flows have almost the same flow direction in the upper and the lower layer and its magnitude in the upper layer is larger than that in the lower layer. The tidal residual flow at spring tides is stronger than that at neap tides.     

胶州湾海面溢油轨迹的数值模拟

对胶州湾湾口两侧——团岛和薛家岛 1个月的潮位观测资料进行调和分析 ,得出湾口两侧 M2 ,S2 ,O1,K1分潮的调和常数 ,进而建立了胶州湾内的预报潮流场。考虑风场对海面溢油的影响 ,给出了预测胶州湾溢油飘移轨迹的数值模型 ,对 1 983年 1 1月 2 5日“东方大使”号油轮在中砂礁触礁后的溢油的油膜漂移轨迹进行了数值模拟 ,结果与事故后观测到的结果相符 ,说明了数值模拟的正确性     

杭州湾南部主水道内温度、盐度、潮流的变化特征

本文基于船载及锚定ADCP、CTD观测,获得了大、小潮时的温度、盐度、浊度、潮位、流速等观测数据,研究杭州湾南部的一个主要弯曲航道——螺头水道内的潮流动力学特性。螺头水道水深超过100 m、最大潮差大于2.5 m。涨潮时,强潮流速出现在水道北岸,落潮时,强潮流速出现在水道南岸,最大流速值分别为约2 m/s和1.8 m/s。受压强梯度、密度梯度、科氏力和离心力影响,涨落潮过渡时在水道的横断面产生较为明显的环流。夏季存在较弱的层化现象,深水处受环流的影响,盐度、温度的混合较强。锚定观测数据表明,温度、盐度的变化频率与潮流的变化频率相似,但存在高于M2分潮频率的谱峰值。因此,笔者认为潮流与横向环流的相互作用,可能导致更高频率的盐度和温度变化。     

The decomposition and simulation of the longitudinal circulation in a coastal lagoon

Current measurements during a 32-day study period in late spring, 1977, are used to quantify the magnitude and relative importance of tidal and wind-driven motion in the interior of the Indian River lagoon, on the Atlantic coast of Florida. Harmonic analysis of the total longitudinal flow along the axis of the lagoon isolates the tidal component of the current; non-tidal flow is revealed by subtracting the tidal current from the total current, and making corrections for non-linear relationships between the current and both surface wind stress and bottom friction. A one-layer, one-dimensional model is developed to simulate wind drift. A quadratic bottom friction term with a drag coefficient of 15 × 10^?3 gives results which compare most favourably with observations. Results indicate that tidal forcing explains approximately 45% of the total variance at the study site, 25 km from the nearest inlet. Local wind forcing accounts for 44% of the non-tidal flow. The remainder of the variance is attributed to freshwater outflow through the lagoon and non-local forcing.     

辽东湾西部海域潮流特征

根据2009年9月在辽东湾获取的3个站位的25 h连续定点海流观测资料进行准调和分析,计算了3个站位6个主要分潮O1、K1、M2、S2、M4、MS4的北、东分量潮流调和常数,并给出了各测站在各层的潮流椭圆要素。计算结果表明:该海区潮流属于正规半日潮流性质,主要呈NE-SW向往复式运动,最大可能流速介于70~120 cm/s之间,流速总体上由表至底逐渐减小。对于O1、K1、M2、S2这4个主要分潮流,北分量基本上大于东分量,底层普遍较表层先转流,最大流速发生时间亦是底层较表层提前,浅水分潮在总海流中占的份额都很小。     

A numerical study of a tide with four harmonic constituents at the open boundary

The tidal current in Kagoshima Bay is simulated by the two-dimensional subdomain finite-element method. At the open boundary, the sea level is forced to be oscillatory with a linear combination of the four harmonic constituents (M2, S2, K1, O1) of the tide. A calculation having only M2 sea level at the open boundary is also performed and the harmonic constants of M2 are compared with those calculated by the four components.In the calculated velocity vector, a large difference between the two maxima or the two minima in one day appears when the vector is directed to the open sea. On the other hand, when it is directed into the bay, the two extreme velocities are almost equal. In tide-killer residual flow, the flow pattern is almost independent of the tidal age; however, the absolute value of the current velocity depends on the tidal age. The pattern is nearly the same as that calculated by giving only M2 sea level at the open boundary.In relation to the nonlinear interaction, the kinetic energy ratio KER is defined by the ratio of kinetic energy of the induced harmonic components to that of harmonic constituents given at the open boundary. KER is large where the tidal current is disturbed by obstacles,e.g. along the west coast at the mouth of the bay and in the southern sea of Mt. Sakurajima. The distribution of KER seems to be independent of the number of harmonic constituents (one or four) given at the open boundary. The difference of kinetic energy of the M2 tidal constituent between the two calculations.i.e. with the open boundary conditions of four components (M2, S2, K1, O1) and of a single component (M2), is found to be large where the current velocity is large.