浙江近海潮汐潮流的数值模拟

用三维陆架海模式(HAMSOM)对浙江近海的潮汐、潮流进行了数值模拟,并采用网格嵌套和动边界技术对原模式作了改进,以提高计算的精度,改进后的模式在浙江近海的应用中被证明是成功的.沿岸50个潮位站计算与实测值的比较表明,加入动边界以后的小区域细网格计算较之粗网格以及未加动边界以前精度普遍提高,比较的均方差结果为:M₂分潮振幅差4.6cm,相角差7.14°;S₂分潮振幅差5.0cm,相角差5.4°;K₁分潮振幅差2.25cm,相角差5.76°;O₁分潮振幅差1.56cm,相角差5.5°,可见计算与实测符合良好.另外,选取了105个实测潮流点,比较了表层M₂和K₁分潮流调和常数分量Ucosξ,Usinξ,Vcosη,Vsinη的实测值与计算值的偏差,结果表明计算与实测的符合程度较好.在此基础上,给出了各主要分潮的潮位同潮图、潮流同潮图、潮汐性质、潮流性质、潮流椭圆和潮流的运动形式等,发现4个主要分潮M₂,S₂,K₁,O₁在本区内均未出现无潮点;M₂分潮流在29°18'N,122°46'E处有一个圆流点.此外还得到了一些有意义的结论,都与实测情况符合良好,从而对整个浙江沿海区域的潮汐潮流特性有了一个全面认识.     

莫桑比克海峡及其邻近海区正压潮流数值模拟与能量收支分析*

莫桑比克海峡及其邻近海区是全球海洋潮流和潮能耗散最强的海区之一。文章利用高分辨率通用环流模式对该海区的正压潮流进行模拟, 并对该海区潮能通量和潮能耗散特征进行分析。结果表明, 莫桑比克海峡及其邻近海区的潮波主要是半日分潮占主导地位, 全日分潮可忽略不计, M₂分潮形成1个左旋潮波系统和1个右旋潮波系统, S₂分潮形成1个左旋潮波系统。莫桑比克海峡和马达加斯加岛南部等绝大数区域的M₂和S₂半日潮流是逆时针旋转, 在马达加斯加岛顶部等局部区域是顺时针旋转, 而且在海峡通道等复杂地形处潮流流速量级较大。潮能通量矢量主要来自东边界, 大部分潮能通量沿马达加斯岛北部传入莫桑比克海峡区域, 其中经过马达加斯加岛北部和进入莫桑比克海峡的M₂ (S₂)分潮的潮能通量分别为156.86GW (40.53GW)和148.07GW (36.05GW), S₂分潮潮能通量的量级大约为M₂分潮的1/5~1/4。底摩擦耗散主要发生莫桑比克海峡和马达加斯加岛南北部, 其中莫桑比克海峡M₂ (S₂)分潮的底摩擦耗散为1.762GW (0.460GW), 占其底部总耗散的43.74% (39.72%)。     

半日潮流作用下悬移质泥沙的运动特征及其影响因素研究

本文通过建立一维水深平均悬沙模型，对典型潮流控制的水道内悬沙运动特征进行研究。模型以泥沙再悬浮、沉降和平流为主要物理过程，动力因素包含M₂、S₂分潮及余流，采用湄洲湾2007年8月潮位、潮流、悬沙、底质同步观测资料进行分析和验证。通过三角傅里叶分析，将悬沙的时间序列分解为12个主要的谐波分量，其中主要分量包括:M₂分潮作用下产生的具有M₂倍潮角速度的1/4日分潮项，M₂与S₂分潮共同作用下且角速度为两分潮角速度之和的1/4日分潮项，及水平悬沙梯度、余流与M₂分潮共同作用下具有M₂分潮角速度的半日潮项。悬沙在时间上的平均值受到余流、悬沙水平梯度、M₂分潮流及悬沙起动条件等因素控制。余流导致了悬沙序列中相邻周期之间的不对称性。反映泥沙特性的参量对悬沙的曲线特征具有重要影响，泥沙沉降速度影响悬沙的相位，并影响其振幅；再悬浮有关的参量仅影响各谐波分量的振幅，但不影响相位。     

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。     

垂直分辨率对长江口海域M2分潮模拟的影响

基于EFDC(Environmental Fluid Dynamics Code)模式建立了长江口及其邻近海域的三维水动力学模型, 研究模型的垂直分辨率对该海域M₂分潮模拟的影响。结果表明:垂直分辨率的变化对M₂分潮传播方向的模拟结果影响较小, 但其可通过底摩擦和湍流耗散两个计算过程来影响潮能通量的模拟结果, 最终对长江口和杭州湾内的M₂分潮振幅产生显著的影响。最底层厚度较大时, 上层自由水体的高流速特征在最底层过于明显, 进而导致计算的底摩擦应力偏高, 此时提高底层的垂直分辨率会降低底摩擦对能量的耗散。另一方面, 垂直湍流混合作用会随垂直分辨率的增加而增强, 所以垂直分辨率增加到一定程度后, 上层自由水体的高流速会经由增强的湍流混合而更多的传入底层, 使计算的底摩擦应力随垂直分辨率的提高而有重新增加的趋势, 进而又增强底摩擦对潮能的耗散。     

杭州湾和钱塘江潮波的联合数值模型

本文应用有限差分法,对杭州湾采用二维模型,对钱塘江采用一维模型进行了潮波联合数值计算,得到了全日((O₁+K₁)/2)、半日(M₂)和浅水(M₄)分潮的调和常数,计算结果比单纯的二维模型结果更符合杭州湾潮汐潮流的实际情况,并得出了关于余水位和余流的更可信的结果。     

渤海潮汐及大风作用下水位的数值模拟

本文以M₂,S₂,K₁及O₁ 4个主要分潮之和为开边界条件,用“ADI”法对渤海的潮位和潮流进行了数值模拟。潮位和潮流的计算值与潮汐表的预报值(或无风情况下的实测值)比较吻合。在潮汐模拟的基础上,还进行了大风影响下水位场和流场的数值模拟,亦获得了比较满意的结果。     

北部湾潮汐潮流的三维数值模拟

基于二阶湍流闭合模型计算涡动粘性系数的POM三维水动力模式,采用细网格,考虑6个岛屿、海底摩擦系数进行划片取值,模拟北部湾潮汐潮流.所得潮汐调和常数与81个实测站比较,绝对平均误差:K₁分潮振幅为46cm,迟角为9°;O₁分潮振幅为56cm,迟角为7°;M₂分潮振幅为62cm,迟角为15°.由模拟结果分析出该海区潮汐、潮流、余水位和潮余流,以及水平速度垂直分布等特征.     

渤海、黄海、东海M2潮汐潮流的三维数值模拟

利用建立的一种新的半隐半显三维数值格式,将渤海、黄海、东海作为一个整体,采用球面坐标系下的三维潮波方程组,考虑了引潮力的作用,数值模拟了渤海、黄海、东海的M₂分潮的潮汐与潮流,结果较好地体现了渤海、黄海、东海M₂分潮的特征.通过比较65个验潮站的实测值与计算值,所得计算结果的振幅差平均为6.4cm,相角差为6.1°,计算与实测符合良好.本文给出的问潮图与Fang于1986年给出的实测占数值综合结果基本一致.对选取的47个测流站,比较了各层潮流调和常数Ucosζ、Usinζ、Vcosη、Vsinη的计算值与实测值的偏差,偏差绝对值的平均在2.6～4.9cm/s之间.并比较分析了潮流的垂直结构,所得结果与实测符合较好.首次揭示出回流点的水平位置不随深度变化这一特性.最后给出了M₂分潮的潮能消耗.     

基于FVCOM的廉州湾及周边海域三维潮汐潮流数值模拟

基于采用不规则三角网格和有限体积方法的FVCOM模式,建立廉州湾三维潮流数值模型来重现廉州湾及周边海域的潮位和潮流变化状况。根据模拟结果计算得到了较以往更为精细的廉州湾及周边海域K₁、O₁和M₂分潮的同潮图,并计算了由此3个分潮引起的潮汐不对称的变化情况。K₁和O₁分潮在廉州湾外主要以驻波的形式存在,进入廉州湾后转化为前进波;M₂分潮在廉州湾外主要以前进波的形式存在,进入廉州湾后前进波特征更为明显。K₁和O₁分潮流在廉州湾外以旋转流为主,在廉州湾内以往复流为主;M₂分潮流在整个研究海域以往复流为主。由潮余流场的分布特点可以看出自南向北由外海进入廉州湾的潮余流,在冠头岭处分为两支,一支逆时针转向西,另一支被冠头岭阻挡在其南侧形成顺时针封闭环流。在廉州湾内部同时存在2个环流系统,湾顶的气旋式环流和口门处的反气旋式环流。     

Three-dimensional numerical model study of the residual current in the South China Sea

A three-dimensional baroclinic shelf sea model is employed to simulate the tidal and non-tidal residual current in the South China Sea. The four most significant constituents, M₂, S₂, K₁ and O₁, are included in the experiments with tidal effect. At most stations, the computed harmonic constants agree well with the observed ones. The circulations of the South China Sea in summer (August) and winter (December) are mainly discussed. It is shown that the barotropic tidal residual current is too weak to affect the South China Sea circulation, whilst the contribution of the baroclinic tidal residual current to the South China Sea circulation would be important in the continental shelf sea areas, especially in the Gulf of Thailand and Gulf of Tonkin. In the deep-sea areas, the upper barotropic or baroclinic tidal residual current is relatively very weak, however, the speed order of the deep baroclinic tidal residual current can be the same as that of the mean current without tidal effect. Moreover, the baroclinic tidal residual current seems to be related to the different seasonal stratification of ocean.     

Nonlinear tidal waves in a kind of estuary with gradually varying cross-section

-Nonlinear tidal waves in a kind of estuary are studied in the paper using one-dimensional nonlinear hydrody-namic equations with friction. The estuary has exponentially varying width B=B0 e-bx and uniform depth h. The one-dimensional hydrodynamic equations are solved by perturbation method. It was found that our solution included two special cases, Pelisenpeki's solution and Airy's solution. The former can be got by letting b=0 in our solutions, and the latter by setting 6 = 0 and f= 0 (f is linear frictional coefficient). In terms of the second-order solution, the physical mechanism of nonlinear tidal waves in estuaries with gradually varying cross-section is explored. It is shown that, under the assumption of linear friction coefficient, shallow water constituent waves consist of two parts, one is produced by shallow water nonlinear effect outside the estuary, the other is generated by shallow water nonlinear effect inside estuary. In addition, the physical mechanism of the residual tidal current and     

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。     

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。     

楚科奇海夏季潮流和余流观测研究

根据2008年8月5日至9月7日在楚科奇海布放的一套锚碇潜标观测系统(71°40.024′N,167°58.910′W)获得的海流剖面资料研究了该海区的海流分布特征,重点探讨了潮流的垂向结构、余流剖面特征及海流的斜压性.结果表明:(1)该海域主要分潮为半日潮M1,S2和N2,近日分潮O1,天文分潮MM和MSF,其中以M...     

Estimation of baroclinic tide energy available for deep ocean mixing based on three-dimensional global numerical simulations

The global distributions of the major semidiurnal (M₂ and S₂) and diurnal (K₁ and O₁) baroclinic tide energy are investigated using a hydrostatic sigma-coordinate numerical model. A series of numerical simulations using various horizontal grid spacings of 1/15–1/5° shows that generation of energetic baroclinic tides is restricted over representative prominent topographic features. For example, nearly half of the diurnal (K₁ and O₁) baroclinic tide energy is excited along the western boundary of the North Pacific from the Aleutian Islands down to the Indonesian Archipelago. It is also found that the rate of energy conversion from the barotropic to baroclinic tides is very sensitive to the horizontal grid spacing as well as the resolution of the model bottom topography; the conversion rate integrated over the global ocean increases exponentially as the model grid spacing is reduced. Extrapolating the calculated results in the limit of zero grid spacing yields the estimate of the global conversion rate to be 1105 GW (821, 145, 102, 53 GW for M₂, S₂, K₁, and O₁ tidal constituents, respectively). The amount of baroclinic tide energy dissipated in the open ocean below a depth of 1000 m, in particular, is estimated to be 500–600 GW, which is comparable to the mixing energy estimated by Webb and Suginohara (Nature 409:37, 2001) as needed to sustain the global overturning circulation.     

Three-dimensional structure of tidal current in the East China Sea and the Yellow Sea

A three-dimensional tidal current model is developed and applied to the East China Sea (ECS), the Yellow Sea and the Bohai Sea. The model well reproduces the major four tides, namely M₂, S₂, K₁ and O₁ tides, and their currents. The horizontal distributions of the major four tidal currents are the same as those calculated by the horizontal two-dimensional models. With its high resolutions in the horizontal (12.5 km) and the vertical (20 layers), the model is used to investigate the vertical distributions of tidal current. Four vertical eddy viscosity models are used in the numerical experiments. As the tidal current becomes strong, its vertical shear becomes large and its vertical profile becomes sensitive to the vertical eddy viscosity. As a conclusion, the HU (a) model (Davieset al., 1997), which relates the vertical eddy viscosity to the water depth and depth mean velocity, gives the closest results to the observed data. The reproduction of the amphidromic point of M₂ tide in Liaodong Bay is discussed and it is concluded that it depends on the bottom friction stress. The model reproduces a unique vertical profile of tidal current in the Yellow Sea, which is also found in the observed data. The reason for the reproduction of such a unique profile in the model is investigated.     

The tidal regime of Shark Bay, Western Australia

A non-linear hydrodynamic model is used to describe the tidal dynamics of Shark Bay, Western Australia. The model is forced by tidal elevations generated by M₂, S₂, K₁ and O₁ constituent data at the open boundaries. The absence of suitable boundary data required a ‘calibration’ of the boundary condition against the known constituent data from within the model domain. The model provides a good match to the available field data, and allows the surface-level and current response to be resolved over the entire domain. Due to a near quarter-wave resonance of the semi-diurnal tide along the eastern Hopeless Reach, which increases the semi-diurnal tide by a factor of 2, the tidal characteristics on each of the Reaches are different: on the eastern Hopeless Reach the tides are mainly semi-diurnal while on the western Freycinet Reach the tides are mainly diurnal. The tidal range is also higher along Hopeless Reach. Tidal harmonics, generated by non-linearity, are important in the shallow regions. The tidal wave is shown to propagate as a progressive wave into the Bay. Substantial phase-lag, attenuation and dissipation occur over the Faure Sill, a major shallow region of the eastern reach of the Bay. Non-linear generation of the M₄ and MS₄ tides is also significant in this region. Depth-averaged residual currents are presented, which show a tidally generated circulation that is enhanced in regions of complex topography. Estimates of tidal dissipation indicate that although the total dissipation is small on a global scale, the areal average is comparable with the Gulf of Carpentaria and approximately one-quarter of the value estimated for the Patagonian Shelf.     

Numerical study of baroclinic tides in Luzon Strait

The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional tide model driven by four principal constituents, O₁, K₁, M₂ and S₂, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19 GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%). The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal (O₁ and K₁) and semidiurnal (M₂) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m⁻¹ emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally, which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS. The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is O(10⁻⁷) W kg^{− 1} and the turbulence diffusivity is O(10⁻³) m²s⁻¹, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the SCS waters.