Computer Simulation of Coastal Acoustic Tomography by a Two-Dimensional Vortex Model

Computer simulation of coastal acoustic tomography with four, five, seven and nine stations was applied to two-dimensional vortex fields of horizontal domain 5 km × 5 km. Travel time data obtained in reciprocal directions between all pairs of acoustic stations were analyzed to reconstruct the vortex fields by the stochastic inverse method, reduced to the damped least squares method. The weighting factor appearing in the inverse analysis was determined by applying the L-curve method, in which a point making both the size of estimated error ‖y - Ex‖ and solution ‖x‖ as small as possible in a balance is specified as an optimum. The performance of this method was examined using two-dimensional vortex models which have different wavenumber spectra and adding the random error of different levels to the travel time difference data y. This study suggests that in the selection of the optimal weighting factor the horizontal section of the simulated tidal vortex fields can be well reconstructed by the coastal acoustic tomography system composed of five to seven acoustic stations located in the periphery of the vortex fields. This revised version was published online in August 2006 with corrections to the Cover Date.     

A coastal acoustic tomography experiment in the Tokyo Bay

Eight sets of coastal acoustic tomography (CAT) systems were deployed during November 29 to December 10, 2002 at the coasts on both sides of Tokyo Bay to measure tidal current structures at 15-rain interval.Sound transmission across the Tokyo Bay (between Yokohama and Chiba)was successfillly traced,even under severe interference from ship generated wakes and bubbles.Tidal current fields changing from northward to southward flow are well reconstructed by the inverse analysis of travel-time difference data for a period with the best sound transmission condition. It is suggested that the CAT is the most powerful tool to continuously map tidal current fields in the coastal seas with heavy shipping traffic and fisheries activity.     

胶州湾流速场的声层析反演研究

采用结合匹配法和经验正交函数法的射线声层析反演方法,针对流场水平分布不均匀特点,使用距离等效分段方法对反演算法进行改进,利用三个断面声层析数据,对胶州湾口潮流场的垂直和水平分布进行反演。与传统方法比较,大大降低与实测流速垂直分布间的偏差,平均偏差小于0.02 m/s,流场垂直分布间的相关系数提高到0.85以上。分析了声传播断面上不同的流场结构,以及涨潮期间在胶州湾团岛附近出现的涡流现象,并计算得到湾口海水流量变化。结果表明,改进的射线声层析反演方法可有效地用于水平分布不均匀流场监测,仅采用少量声学观测站位,即可获得大范围的复杂流场三维信息,有利于近海海洋资源开发、海洋环境保护和船舶航行安全。     

东海东南陆架外缘冬、夏季实测海流FFT分析

使用FFT法首次将东海陆架冬、夏季2次定点ADCP测流资料在频率域内分解成3个部分：不随时间变化的定常海流、周期为6～25h的潮流和剩余流,再将潮流分解为垂向均匀的全流(也称正压潮流)和剩余的斜压潮流。结果表明：夏季测站定常海流、潮流和剩余流能量分别占总能量的5．3％,93．9％和0．9％,而冬季测站分别占10．8％,80．9％和8．4％。夏、冬季测站的斜压潮流与正压潮流能量之比分别为20．7％和4．1％。     

长江口悬沙动力特征与输运模式

本项研究用ADCP在长江河口进行高频、高分辨率三维流速和声学浊度的定点观测,通过对定点站位潮周期内的悬沙浓度、流速和盐度的分析,计算悬沙输运率;悬沙输运机制分析表明平流作用、斯托克斯漂移效应在悬沙输运中占据主导地位.此外,从河口内向河口外,潮周期内的水动力特征与悬沙净输运具有明显的地域性差异,主要表现在悬沙输送的贡献因子、盐度的垂向混合和分布特征、垂向流速等方面.在拦门沙下游和口外地区,悬沙均向西、北方向输送,而拦门沙上游则向东、南方向输送.这种悬沙输运格局,对于长江口拦门沙及附近最大浑浊带的形成有着重要的作用.     

辐射沙脊群潮滩地形遥感遥测构建

潮滩地形是合理开发利用潮间带滩涂最重要的指标之一。滩涂水边线测量法是目前公认的具有可操作性的滩涂地形遥感测量方法。本文以水边线测量方法为基础,提出一种基于水位测站基线的潮滩地形遥感遥测构建方法。以江苏沿海大面积潮滩为研究区,将该区域自建的4座水位测站的连线作为水位测站基线,结合不同潮情下采集的遥感影像提取的滩涂水边线数据,通过水位测站基线计算滩涂水边线高程,从而构建出辐射沙脊群潮滩地形。采用实测地形数据进行检验,结果表明:构建的DEM能够反应当前潮滩的基本形态,平面精度达30 m,垂直精度达20 cm。     

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。     

渤海、黄海和东海的潮余流特征及其与近岸环流输送的关系

渤海、黄海和东海是西北太平洋陆缘海,有宽广的大陆架,太平洋潮波长驱直入,在大陆架海域形成显著的潮汐运动,由此而产生的潮余流输送在许多地区显示出重要作用。已有很多学者(方国洪等,1985;黄祖柯,1992)用数值方法计算过渤海的潮波运动,并给出了那里的潮余流分布。渤海的潮余流计算大体上有两种方法:(1)用二维或三维潮波运动方程组计算潮汐和潮流,然后再计算欧拉潮余流(方国洪、杨景飞,1985;于克俊、张法高,1987;黄祖柯,1992);(2)以弱非线性三维拉格朗日平均流理论为基础,计算拉格朗日潮余流,它不仅包括最基本的欧拉余流,而且还包括在浅水比较显著(与欧拉余流同量级)的斯托克斯漂移速度和高阶的拉格朗日漂移速度订正值(郑连远,1992;王辉等，1993)。上述两种方法理应给出大体相近的潮余流分布,但从现有的计算结果来看,这两种方法在渤海给出了几乎完全相反的潮余流输送。 汤毓祥(1990)曾计算过南黄海和东海大陆架区的M2分潮余流,并考虑了斯托克斯速度漂移对它的影响,所得结果和已知的南黄海环流概况颇有相似之处,但由于计算边界取在东海大陆架外缘,那里的潮余流可能失真较大。Chio (1980) 也曾给出过渤海、黄海和东海大陆架区的欧拉潮余流分布,但由于他的开边界也取在东海大陆架外缘,面且他给出的潮汐、潮流数值在靠近中国大陆一侧,误差较大,因此所得潮余流也不能令人满意。 最近,我们完成了包括渤海、黄海和东海全海区的潮汐、潮流二维数值计算工作(Zhao et al,1993),与实测资料相比,其结果达到的准确程度,无论在潮位还是在潮流方面都比较好。本文以这一数值计算结果为基础,给出了渤海、黄海和东海全海区的潮余流分布，同时还讨论了潮余流与近岸环流的关系。     

埕岛油田及附近地区的水位

在渤海内,M2分潮有两个无潮点,一个在秦皇岛东面,另一个位于渤海湾至莱州湾之间。此外,渤海海峡附近还有一个K1分潮的无潮点。埕岛油田位于M2分潮无潮点和K1分潮波的腹部附近。整个石油开发区半日潮差均较小,其中以东南部最小,西北部有明显增加。全日潮差由东北向西南增加,变化幅度较小。在一般天气条件下,海面高度主要决定于潮汐,潮差不大,但在台风影响下,可能引起异常的增水,寒潮可以引起大的减水或增水。国内不少单位在黄河口做过潮汐观测,但资料甚少。埕岛油田位于黄河口的西北部,海上水位资料十分缺乏。我们利用12井位和20井位进行了4个月的水位观测,使用Aanderaa水位计,取样间隔为15min。岸边站(3站)是在岸边打桩,使用滚筒式水位计,获得了一年的水位观测资料,这些资料十分宝贵。本文详细地分析了该区域的水位特征,并给出施工设计需要的各个参数。     

Three-dimensional tidal current numerical model of the Oujiang Estuary

The characteristics of three-dimensional (3-D) tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, a 3-D numerical model on an unstructured triangular grid has been developed. The σ coordinate transformation, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simu...     

广东红海湾海流季节性特征分析

基于2017年春季和冬季的海流资料分析了红海湾海区海流特征、潮流状况、涨落潮流特性、余流特征及表层漂流特征。研究海域共布设3个临时潮位观测站和11个全潮水文观测站。根据流速、流向过程曲线和潮位过程曲线的关系，得出涨(落)潮流速最大的时刻和最小流速发生时刻与潮位关系并非固定在高(低)潮时或半潮面左右，由此看出，研究海域的潮波介于驻波与前进波之间，属于不规则半日潮流主导的海域。研究海域中大部分站位潮流属于往复流，少数站位潮流运动具有一定的旋转性，平均涨潮流速最大为7 cm/s，平均退潮流速最大为14 cm/s。春季大潮期和中潮期各站余流流向整体为偏东向，小潮期，除少数测站余流流向偏向南东向，其余测站余流流向偏西向；冬季大潮期和中潮期各站余流流向整体为偏西向，小潮期，湾西侧余流流向偏西向，湾东侧余流流向偏南东向。垂向上各层余流流速由表至底逐渐减小，流向基本一致。     

Vertical structure of the M<Subscript>2</Subscript> tidal current in the Yellow Sea

The vertical structure of the M₂ tidal current in the Yellow Sea is analyzed from data acquired using an acoustic Doppler current profiler. The observed vertical profiles of the M₂ tidal current are decomposed into two rotating components of counter-clockwise and clockwise, and restructured using a simple one-point model with a constant vertical eddy viscosity. The analyzed results show that the internal fictional effect dominates the vertical structure of the tidal current in the bottom boundary layer. In the Yellow Sea, the effect of the bottom friction reduces the current speed by about 20–40% and induces the bottom phase advance by about 15–50 minutes. In the shallower coastal regions, the effects of bottom topography are more prominent on the vertical structure of tidal currents. The vertical profile of the tidal current in summer, when the water column is strongly stratified, is disturbed near the pycnocline layer. The stratification significantly influences the vertical shear and distinct seasonal variation of the tidal current.     

飞雁滩油田岸滩防护方案探索

为了降低成本,维持滩海油田的开敞式开发,针对飞雁滩油田的岸滩侵蚀情况提出了几种岸滩防护设想,并进行了对比分析,最后确定了飞雁滩油田岸滩防护初步方案。该方案充分利用自然力,通过人为干扰促使防护区外泥沙起动,借助海上潮流使高含沙海水流经防护区,实现岸滩蚀退的快速防护,对滩海油田的防护具有指导意义。     

Coastal currents adjacent to the Caeté Estuary,Pará Region,North Brazil

We examined and compared tidal currents and water column structure between a near-shore station (12 km from the coast) and an offshore station (32 km from the coast) adjacent to the Caeté River, Pará Region, Brazil. Although the coastal system of Pará is largely influenced by local tides and wind, we found substantial differences in the dominant forcing agents between stations. Water column dynamics at the near-shore station were largely affected by local tidal processes, while differences between surface and bottom layer flows also indicated the importance of gravitational circulation at this station and a substantial influence of the adjacent Caeté River discharge. In comparison, at the offshore station, water column structure was largely influenced by a semi-diurnal tidal flow, an along-coastal current flow (mainly associated with the North Brazil Current) and the dynamics of local wind flow. The near-shore station at low tide showed a high level of stratification; at high tide such stratification was reduced. In comparison, stratification was only apparent within the upper 6 m at the offshore station, the rest of the water column was relatively well-mixed. The stratification within Station 1 at low tide was a result of the bi-directional movement of water discharged from the Caeté River, with lower salinity surface water and high salinity bottom water resulting in an estuarine-like circulation environment. The spatial variability and lack of correlation in current flow and water column structure between the near-shore and offshore stations suggest that a flow field resulting from differences in local circulation, tidal variability and wind persistence separate areas. We argue that this separation may indicate that the offshore station is located in a transition region between the Caeté River waters and the local coastal area.     

Numerical modelling of Lagrangian residual current in the Bohai Strait

The Bohai Strait is the only passage-way of the semienclosed Bohai Sea into the outer ocean. The various dynamical processes have great effects on both sides of the strait, especially on the Bohai Sea. Tidal current dominates in the strait, and among the tida! components the M, component tide is prevailing.The seawater in the strait is homogeneous vertically almost the whole year because of strong tidal mixing. The M, component tide was simulated numerically using two dimensional barotropical model, and the Eulerian tide-induced residual currents were also deduced. The results showed that the tidal currents were dominated by the coastal line and topography. There exist many eddies in the tide-induced residual current fields, particularly near the northern coast.On the basis of the simulation of the tidal currents, the movements of the water particles in the strait were tracked by means of Lagrangian techniques. Consequently the Lagrangian residual currents were obtained. Somewhat similar to the Eulerian     

Morphodynamic responses to the deep water harbor development in the Caofeidian sea area,China's Bohai Bay

Vast bay-type tidal inlets can be found along the coastal zones of China. They are generally suitable for deep water channels and large harbors because of the presence of large water depth and good mooring conditions. The deep channel, in front of the head of Caofeidian Island in Bohai Bay, China, is a typical bay-type tidal inlet system. The tidal current, a type of reverse flow, makes the key contribution to maintain the deep water depth. The co-action of waves and tidal currents is the main dynamic force for sediment motion. Waves have significant influence on the sediment concentration. Based on the characteristics of waves, tidal currents, sediment and seabed evolution in Caofeidian sea area, a 2D mathematical model for sediment transport under influence of waves and tidal currents is developed to study the development schemes of the Caofeidian Harbor. The model has been verified for spring and neap tides, in winter as well as in summer of 2006. The calculated tidal stages, flow velocities, flow directions and sediment concentrations at 15 stations are in good agreement with the observations. Furthermore, the calculated data on pattern and magnitude of sedimentation and erosion in the related area agree well with the observations. This model has been used to study the effects of the reclamation scheme for Caofeidian Harbor on the hydrodynamic environment, sediment transport and morphological changes. Attentions are paid to the project inducing changes of flow velocities and morphology in the deep channel at the south side of Caofeidian foreland, in the Laolonggou channel and in various harbor basins. The conclusions can provide the important foundation for the protection and use of bay-type tidal inlets and the development of harbor industry.     

Sub-inertial oscillations in the Black Sea generated by the semidiurnal tidal potential

The Black Sea shelf is a region of intense manifestation of various dynamical processes. Under the influence of different natural forces, eddy-wave phenomena develop here, which influence the general circulation of sea waters, biological productivity, and the condition of the engineering structures. Modern numerical models allow us to simulate and analyze the processes of the joint dynamics of marine circulation and large-scale waves. In this work, we study the spatiotemporal spectral characteristics of the sea level and velocity fluctuations formed due to atmospheric forcing and tidal potential. The hydrophysical fields are calculated using the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), σ model based on primitive equations. We use the CORE data as atmospheric forcing at the sea surface; the tidal potential is described by the semidiurnal lunar constituent M₂. Analyzing the simulation results makes it possible to emphasize that accounting for the semidiurnal tidal potential not only improves the accuracy of the sea-level calculation at coastal stations, but also generates subinertial baroclinic oscillations previously found in the Black Sea from the data of in situ observations.     

Subsatellite polygon for studying hydrophysical processes in the Black Sea shelf-slope zone

The first data on the creation of the subsatellite polygon on the Black Sea shelf and continental slope in the Gelendzhik area (designed in order to permanently monitor the state of the aquatic environment and biota) and the plans for maintaining and developing this polygon are presented. The autonomous measuring systems of the polygon in the composition of bottom stations with acoustic Doppler current profilers (ADCP), Aqualog robotic profilers, and thermo-chains on moored buoy stations should make it possible to regularly obtain hydrophysical, hydrochemical, and bio-optical data with a high spatial-time resolution and transmit these data to the coastal center on a real-time basis. These field data should be used to study the characteristics and formation mechanisms of the marine environment and biota variability, as well as the water-exchange processes in the shelf-deep basin system, ocean-atmosphere coupling, and many other processes. These data are used to calibrate the satellite measurements and verify the water circulation numerical simulation. It is assumed to use these data in order to warn about the hazardous natural phenomena and control the marine environment state and its variation under the action of anthropogenic and natural factors, including climatic trends. It is planned to use the polygon subsatellite monitoring methods and equipment in other coastal areas, including other Black Sea sectors, in order to create a unified system for monitoring the Black Sea shelf-slope zone.     

胶州湾潮汐潮流动边界数值模拟

基于普林斯顿海洋模式,通过干湿网格判别法引入潮汐潮流的漫滩过程,考虑M₂,S₂,K₁,O₁,M₄和MS₄六个主要分潮,建立了胶州湾潮汐潮流数值模拟和预报模型,研究了该海域潮汐潮流特征,并讨论了漫滩对潮流模拟的影响。与实测资料的对比验证表明,该模式能够对胶州湾的潮汐和潮流做出较为合理的预测。给出了胶州湾潮汐、潮流、余流等分布特征,模拟的潮流场以及余流场涡旋等现象与观测符合良好;计算了潮波能通量,从能量角度探讨了潮波的传播特性;对潮位与潮流场演变规律,以及潮能通量的分析表明,胶州湾内的潮波以驻波为主。通过数值试验发现,漫滩过程的引入对胶州湾潮流速度的模拟至关重要,不考虑漫滩过程的模式会夸大或者低估潮流流速。对于滩涂面积广阔的海域来说,潮流数值模式中考虑漫滩的影响是必要的。