2001年秋季风对坦帕湾盐度平衡的影响

利用三维高分辨率有限体积的近海海域模型FVCOM来分析2001年秋季期间风作用对坦帕湾区域盐度平衡的影响。为了区分风的影响,分别设计了两个实验：一个由潮汐和河流作为驱动,另一个由潮汐、河流以及风场共同驱动。结论如下：首先,风作用会使盐度产生变化,能够明显地使坦帕湾内的盐度增加,并导致水平和垂直方向上盐度梯度的减少;随后,本文分析了坦帕湾区域内的盐度平衡,主要的盐度平衡来自于全部（水平和垂直方向上）平流的盐度流量分歧以及除去海峡底部的垂直方向上盐度流量分歧;最后,对由风引起的盐度变化进一步进行分析,结果表明风作用不能改变盐度平衡地位的相对重要性,由风引起的盐度平衡改变高度依靠于特殊的地形,除此之外,全部平流盐度流量分歧和垂直散布盐度通量分歧能够抵消,并且两者都远大于水平散步盐度流量分歧。     

热带东印度洋表层环流季节变化特征研究

利用近20年的卫星遥感海面绝对动力高度(Absolute Dynamic Topography,ADT)数据、表层流数据及Argos表面漂流浮标数据等研究了热带东印度洋表层环流的季节变化特征。分析结果显示,热带东印度洋表层环流的变化与季风演替基本同步,赤道以北海域环流季节变化特征甚为显著。与此大尺度环流年循环同步,孟加拉湾湾口环流也相应变化:湾口东部在5~9月为南向流,一直延伸至苏门答腊岛外海,其他月份,从湾口东部至整个苏门答腊岛外海(4°S以北)为北向流;湾口西部经向流的变化大体与东部相反。Argos漂流浮标轨迹进一步揭示了湾内外各季节水交换路径:西南季风期,源自阿拉伯海及印度半岛南部海域的漂流浮标主要通过西南季风漂流由湾口西侧进入湾内,湾内的漂流浮标通过湾口东侧沿着苏门答腊岛进入赤道印度洋;东北季风期,漂流浮标进出湾口的途径大体与西南季风期相反。本研究还表明,季风海流及赤道急流的纬向流速季节变化最大,而经向流速的季节方差最大的则为东印度沿岸流及拉克沙群岛高压(拉克沙群岛低压)。     

广西主要港湾余流特征及其对物质输运的影响

广西5个主要海湾各有自己的环流特征：铁山湾存在一个反气旋涡，廉州湾存在一个海湾尺度的气旋环流，钦州湾青菜头南端存在一个气旋式环流，防城湾口有一个气旋环流。珍珠湾余流，在深水航道内自湾内指向湾外。冬季，受北风影响，各湾从湾内流向湾外的余流分量加强。由于反气旋或气旋环流存在，形成和环流相应的泥沙输运。     

潮汐驱动下的辽东湾水动力及入海污染物输移特征

通过建立水动力学模型、物质输运模型和年龄模型,对渤海辽东湾潮汐驱动下的水动力状况和污染物输移扩散过程进行了数值模拟研究。结果表明,辽东湾海域入海径流对辽东湾整体流场和水交换过程影响不大,其主要影响集中在河口附近海域。在潮汐的驱动下,辽东湾内形成了复杂的环流结构,辽东湾南北海域分别存在顺时针、逆时针的环流,而辽东湾湾口又存在逆时针环流,使得水交换能力较弱,对辽东湾向外海的物质输运产生不利影响,湾顶附近海域的物质主要通过扩散过程与外海进行交换。年龄模型的计算结果表明,辽东湾河流入海污染物在河口附近停留时间较长,向远区的输运需要较长时间。入海污染物的影响具有局地性,对局部海域水质尤其是辽东湾湾顶的水质会产生不利影响。     

大亚湾及其邻近海域冬季温度、盐度的分布及日变化特征

根据2018年1月冬季航次的水文实测资料,详细分析了大亚湾海水温度(T)、盐度(S)的分布特征。整体而言,观测海区海表相对于海底具有高温低盐的特征;同时,无论是表层还是近底层,大亚湾湾内的海水相对于湾外都呈现高温低盐的特征。观测期间,应是受到大亚湾核电站温排水的影响,湾内西侧存在一个高温中心。盐度的差异在近底层更加明显,低盐中心位于大亚湾的湾顶和大亚湾的中部海域,而高盐中心则主要分布于湾口西侧及惠东以东附近海域。太阳辐射和潮流变化是影响大亚湾温度、盐度变化的两大重要因素。其中,太阳辐射的影响主要局限于表层3~4 m,对近底层海水的影响较小;其加热效应使湾内和湾口附近的表层海水都表现出明显的昼夜变化。由潮汐和温度、盐度的对应关系可知,潮流对湾内温度、盐度的影响较大,而对湾外温度、盐度的影响较小。     

深圳湾海域环境容量及污染总量控制研究——I.潮汐、潮流数值模拟

基于美国普林斯顿大学的POM(Princeton Ocean Model)模型,将干湿网格技术引入到模型中,利用模型的外模式(二维)对深圳湾海域的潮汐、潮流和余流进行了数值模拟研究。模拟结果与实测值吻合较好。计算结果表明:深圳湾海域属不正规半日潮,水平潮流具有明显的往复流性质,主要呈西南—东北走向;落潮流速略大于涨潮流速;受地形及陆地河流径流的影响,湾中到湾口及航道附近流速较大,湾顶和靠近香港的滩涂部分流速较小;深圳湾余流场较弱,余流流向指向湾外;整个深圳湾水交换较弱,海域自净能力较差。     

深圳湾海域环境容量及污染总量控制研究——Ⅰ.潮汐、潮流数值模拟

基于美国普林斯顿大学的POM(Princeton Ocean Model)模型,将干湿网格技术引入到模型中,利用模型的外模式(二维)对深圳湾海域的潮汐、潮流和余流进行了数值模拟研究。模拟结果与实测值吻合较好。计算结果表明:深圳湾海域属不正规半日潮,水平潮流具有明显的往复流性质,主要呈西南—东北走向;落潮流速略大于涨潮流速;受地形及陆地河流径流的影响,湾中到湾口及航道附近流速较大,湾顶和靠近香港的滩涂部分流速较小;深圳湾余流场较弱,余流流向指向湾外;整个深圳湾水交换较弱,海域自净能力较差。     

胶州湾水交换及湾口潮余流特征的数值研究

利用基于普林斯顿海洋模式建立的胶州湾及临近海域潮汐潮流数值模型,结合胶州湾口走航式声学多普勒海流剖面仪(ADCP)测流资料,研究了胶州湾口的潮(余)流特征,并在潮流模型的基础上耦合建立了水质模块,模拟了胶州湾的水交换过程。考虑M2,S2,K1,O1,M4和MS4六个主要分潮,胶州湾口潮流场的模拟与ADCP观测数据吻合较好。外湾口水道上的潮流非常强,大潮期间观测到201 cm/s的峰值流速。团岛岬角的两侧分别存在一个流向相反的余流涡旋,两涡旋在团岛附近辐合,形成了57 cm/s的离岸强余流。整个胶州湾平均水体存留时间为71 d,平均半交换时间为25 d。胶州湾水体交换能力在空间分布上有很大差异:湾口海域最强,向湾顶逐渐减弱。湾内存在两个弱交换区,分别位于湾的西-西南部和东北端,水体存留时间多超过80 d,湾西局部水域最长达120 d,而半交换时间也大多超过40 d。潮流场的结构、强度,以及与湾口距离的远近是造成湾内水交换能力空间差异的主要原因。     

罗源湾海水交换三维数值模拟

利用ECOMSED模式中的示踪粒子三维追踪模块分析罗源湾的水交换情况。结果表明,水交换能力的强弱与纳潮量的大小成正比。这里分析湾内水逗留期的空间分布,然后根据湾水存留期的不同将湾内划分为4个地区。进一步的研究表明不同海区湾水逗留期的差异主要是由欧拉余流场的结构差异造成的。由于风场可以影响当地的海流,因此不同的风场也会影响水交换能力。本文结果表明西南方向的风有利于水交换;而作为罗源湾全年主导风向的东北风,在平均风速的情况下,却阻碍了湾内水体的交换。本文还发现在不同投放时刻水交换能力的不同。初始投放时刻的不同对质点总数的减少速度有较明显的影响,高潮时和落潮中间时投放的质点数要比涨潮中间时和低潮时投放的质点数减少得快。罗源湾水交换能力的垂直分布不是均匀的:表层交换率较快,底层较慢,整个海域的交换能力与中层的相当。     

湾口建闸海湾水体交换及景观水位数值模拟

大幅度的潮位变动对近岸景观和亲水性有较大影响,为此往往在湾口建闸控制湾内潮位变动,通过设置景观水位改善以上问题,但这将带来湾内的水动力及水体交换条件下降。本研究以马銮湾为例通过潮流数学模型模拟,研究湾口开闸孔数、开闸位置及不同景观水位与湾内水动力和水体交换的关系。利用湾口闸门调度,在湾内形成大尺度环流提高水体交换效率,对马銮湾景观水位和闸门调度方式提出了建议,有效地解决了湾内潮差减小引起水体交换效率减低的问题。     

Winds and buoyancy-driven circulation in the Tampa Bay

INTROOCCrIOWWiththeimplementationoftimeseriesobservationsspanningseveralsynopticweathersystempassages,theimPOrtanceoftheattnosphericallyforcedpartofestuarinecirculationbecameclearinthe1970s.WeisbetgandSturges(1976)examinedthewindeffectindrivingthenetcirculationintheWestPassageoftheNarragansettBay.Usingvelocitymeasurementsofapproximatelyonemonthduration,theyconcludedthatthelocalwindscoulddominatethegravitationalconvectionindeterminingthenetestuarinecirculationprofileofapartiallymixedestu…     

Influence of Wind on Dynamics and Flushing of Shallow Estuaries

Observations of two small estuaries in Cape Cod, U.S.A. indicate large variations in salinity structure that are forced by variations in along-estuary wind stress. During onshore winds, the estuarine circulation is reduced, and the along-estuary salinity gradient increases as freshwater accumulates. During offshore winds, the surface outflow is enhanced, freshwater is flushed out of the estuary, and the along-estuary salinity gradient becomes weak. Constrictions block the wind-induced flushing, resulting in strong salinity fronts across the constrictions. The residence time of one of the estuaries varies by more than a factor of three in response to variations in wind-induced flushing. The other estuary has little variation of flushing associated with winds, due to a constriction at the mouth that inhibits the wind-induced exchange. The strong influence of winds on the flushing of these estuaries is due in part to their shallow depths, which accentuates the influence of wind stress relative to the effects of the horizontal density gradient. In addition, the residence times of the estuaries are comparable to the time scale of wind forcing, allowing large changes in water properties during wind events.     

Biogeochemical factors influencing the residence time of microconstituents in a large tidal estuary, Delaware Bay

Generally the large tidal estuaries of the eastern United States, such as Delaware Bay, are characterized by rather high suspended particle concentrations at the landward end and high biological activity at the seaward end. As such, these estuaries can be conceptualized as geochemical and biochemical “reactors” for those processes controlling the transmission of trace elements from fresh to the coastal shelf waters. The efficiency of these reaction processes relative to estuarine flushing will control the residence times of microconstituents in such estuaries.Evidence is drawn from the Delaware estuary to illustrate biogeochemical estuarine reaction processes using salinity distribution data and mass balance calculations. The Delaware retains some of its estuarine trace elements as sedimented estuarine particles, while others are more conservative and largely exported. Those retained by sedimenting processes include trace elements in primarily geochemical (particle reactive) chemistries, while those exported appear recycled by biochemical (nutrient reactive) chemistries. Often, the behavior of trace elements (e.g., Fe, Cd) and nutrients (e.g., PO₄) appear biogeochemically linked. Other examples are drawn from mixing studies to illustrate particle interaction, and benthic flux measurements to illustrate limited diagenetic reflux.The residence time of estuarine microconstituents should depend seasonally on the relative turbidity, flushing rate, and primary production of tidally dominated estuaries such as the Delaware. Thus, residence times of the more biogeochemically reactive microconstituents must be substantially shorter (days to weeks) than the average flushing times of these larger estuaries, while the residence times of the less reactive ones should approach such flushing times (weeks to months). True estuarine residence times of microconstituents can only be modeled after using large data sets averaged over time (season, tides) and space (salinity).     

Modelling and observations of tidal wave propagation, circulation and residence times in Puttalam Lagoon, Sri Lanka

Tidal measurements and a depth-averaged 2D model are used to examine wave progression and circulation in a long, shallow, micro-tidal lagoon in Sri Lanka. Ranges and phase lags for different tidal constituents are used to calibrate the model. A single drag coefficient, C_d = 0.0032, gives almost perfect agreement with data. Current measurements are used for validation of the model. The lagoon tide consists of a combination of progressive and standing waves, where progressive waves dominate in the outer part and standing waves in the inner. A Lagrangian based particle-tracking method is developed to study tidally and wind induced residence times. If tides were the only factor affecting the residual circulation, the residence time inside the narrowest section would be approximately 100 days. Steady winds (of typical monsoon average) decrease the residence times to 60–90 days. Estuarine forcing due to net freshwater supply is not modelled (due to lack of reliable runoff data), but independent, long-term salinity observations and calculations based on volume and salt conservation during periods of negligible freshwater supply (the lagoon is seasonally hypersaline) indicate residence times ranging from 40 to 80 days. Model derived residence times based on tides alone represent a minimum exchange. Even weak forcing, through winds, excess evaporation or freshwater supply efficiently reduces residence times.     

Hydrodynamic and water column properties at six stations associated with mussel farming in Pelorus sound, 1984–85

Mussel farming places a benthic organism in a pelagic environment; it is therefore important to understand the driving force that transports the food to the mussels. The hydrodynamic regimes in the sidearms and embayments in Pelorus Sound are dominated by the lunar tide, and a net estuarine circulation in the main channel flowing inwards along the bottom and outwards along the top. Salinity gradients extend throughout the sound from the river inflows, with strongest density stratification in the sidearms and embayments: nearest the head of the sound. There, the water column is separated at the pycnocline into upper and lower layers which tend to move in different directions or at different velocities. Local circulation patterns modify tidal flushing patterns, producing extended residence times in some embayments, whereas other embayments off the side of the main channel tend to be flushed more rapidly by through‐flow water and have shorter residence times than would otherwise be expected. The changing inflow of fresh water modifies the local hydraulic regimes in the inner sounds, especially during flood conditions.     

潮汐和风对马六甲海峡海流的影响

基于非结构有限体积法海洋模型FVCOM(Finite-Volume Community Ocean Model), 建立了马六甲海峡及其毗邻海域高分辨率水动力数值模型, 研究了风和潮流作用下的余环流结构以及水体输运特征。结果表明, 马六甲海峡航道中央潮流运动以往复流为主, 边缘存在旋转流; 主要研究区域内落潮流速略大于涨潮流速, 东南窄道处流速最大; 因峡道束窄变浅, 在涨落潮过程中潮流发生汇聚与分离; 主要研究区域东南段存在3个显著的潮致余环流; 东北季风驱动时模型响应为海峡海流整体向西北方向流动, 西南季风时反之; 季风期间潮致表层余环流结构被破坏, 但底层余流仍存在水平环流结构, 且随着风速增加, 底层余环流的数目、大小、形状、位置均会产生变化; 季风过渡期余环流结构也会发生部分改变, 尤其是小潮期间风场影响效果显著。     

基于波-流耦合模型的珠江口悬浮泥沙数值模拟

为研究珠江口悬浮泥沙输运动力机制，本文发展了一套三维波、流、泥沙耦合数值模型。模型结果与观测数据吻合较好，统计显示模型获得良好的评分分值。利用数值模拟研究了不同强迫（径流，波浪和风）对珠江口中悬浮泥沙的影响。模型结果表明，河口重力环流对珠江口最大浑浊带的发展起着重要作用，特别是在小潮期间。另外，径流的增加可导致泥沙向海输运。底部的悬浮泥沙浓度随着波浪底部轨迹速度和波高的增大而增加。由于西滩水深较浅，波浪对西滩悬浮泥沙的影响大于东槽。西南风引起的波浪对悬沙的影响大于东北风引起的波浪的影响，而东北风致流对悬沙的影响略大于对西南风致流的影响。在其他条件相同情况下，稳定的西南风比稳定的东北风更有利于伶仃洋悬浮泥沙浓度的增加；在稳定的西南风下，伶仃洋平均悬浮泥沙浓度约为稳定东北风下的1.1倍。     

Effect of channel bifurcation on residual estuarine circulation: Winyah Bay, South Carolina

The residual circulation pattern of Winyah Bay, the fourth largest estuary on the eastern coast of the US, is examined using stationary and shipborne current measurements during periods of low freshwater discharge. The estuary has a complex morphology with a single channel and narrow banks at the river entrance and the bay mouth, and a bifurcated channel system (main and western channels, respectively) in the middle part that appears to affect the residual circulation.Overall, the upper (single channel morphology) and middle (dual-channel morphology) parts of the estuary exhibit a baroclinic residual circulation. The presence of bifurcated channels in the middle part of the estuary modifies the typical gravitational circulation. The near-bed landward-directed residual flow is stronger in the deeper main channel than the shallower western channel. This is the result of the fact that the magnitude of residual flow scales with the water depth of the channel and it is also influenced by the opposing patterns of channel alignment in the northern and southern junctions. Analytical modeling confirms that the observed residual currents in the upper and middle estuary are density-induced. In the lower estuary, residual flow is directed seaward throughout the water column of the channel while in the adjacent shoals the residual flow is directed landward, suggesting that in contrast to the upper and middle estuary, the residual flow near the mouth is barotropic, controlled by the tides and the channel-bank morphology.     

A numerical model investigation of the residual circulation in Hauraki Gulf,New Zealand

The homogeneous residual circulation in Hauraki Gulf arising from the tides, steady winds, and oceanic inflows is considered by use of a depth‐averaged 2‐dimensional numerical model. Vertical current structure of the wind‐driven circulation is derived by using the computed wind‐induced sea surface slopes, the wind stress, and a prescribed vertical eddy viscosity. Tidal residual circulation is weak, less than 0.01 ms^‐1 over most of the Gulf. The response of the Gulf to wind‐forcing indicates a preference for north‐west/south‐east directed winds, the flow through the Gulf being more than 3 times as strong as for winds from other directions. Surface currents are mainly in the wind direction, but subsurface currents reveal closed circulation cells in near‐coastal areas. Simple oceanic inflows give rise to water movements which penetrate to the inner part of the Gulf.