南麂岛附近海域潮汐和潮流的特征

以2008年冬季在浙江近海南麂岛附近投放的4个底锚系观测的水位和流速资料为依据,分析了潮汐和潮流特征。水位谱分析结果显示半日分潮最显著,全日分潮其次;近岸的浅水分潮比离岸大。水位调和分析结果表明:潮汐类型均为正规半日潮,近岸处的平均潮差大于3m,最大可能潮差大于6m,潮汐呈现出显著的低潮日不等和回归潮特征。流速谱分析结果显示半日分潮流最强,全日分潮流其次,且比半日分潮流小得多;近岸浅水分潮流比远离岸显著。流速调和分析结果表明:潮流类型均为正规半日潮流,靠近岸的两个站浅水分潮流较显著;最显著的半日分潮流是M2分潮流,其最大流速介于0.32～0.48m/s之间,全日分潮流均很弱,最大流速小于0.06m/s。M2分潮流均为逆时针旋转,椭圆率越靠近海底越大;最大分潮流流速分布为中上层最大、表层略小、底层最小;最大分潮流流速方向的垂向变化很小,底层比表层略为偏左;最大分潮流流速到达时间随深度的加深而提前,底层比中上层约提前30min。潮流椭圆的垂向分布显示这里的半日分潮流以正压潮流为主;日分潮流则表现出很强的斜压性。     

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.     

北部湾潮波数值研究

利用普林斯顿海洋模式(POM08)建立了北部湾及其临近海区潮汐潮流数值模式,模拟了K1,O1,M2和S2这4个主要分潮,分析了模拟的潮汐和潮流分布特征,从潮波能量的角度讨论了琼州海峡对北部湾潮波系统的影响,并给出北部湾潮能的耗散情况。研究表明,北部湾是典型的全日潮海区,K1和O1分潮在南部湾口形成半个旋转潮波系统,无潮点位于越南顺安附近岸边。琼州海峡中的欧拉潮汐余流为西向流,潮余流造成的水通量约为0.034×106m3/s;余流出海峡西口后,先折向北,然后转向南流出湾外。研究海区中两个强潮流区分别位于琼州海峡和海南岛的西侧,同时这也是两个潮能的高耗散区。北部湾的潮能自南部湾口由外海传入,通过西口涌入琼州海峡,到达海峡东口时日潮波的能量已基本耗散殆尽,在海峡内耗散的4个分潮的潮能约为3.33 GW,相当于北部湾潮能耗散量的35%左右。数值试验表明,琼州海峡作为潮能耗散的重要海区,其存在对于北部湾潮波系统的形成具有较大影响。计算了底边界潮能耗散,结果表明在北部湾和琼州海峡,底边界耗散的潮能分别占该海区总耗散的83%和80%。     

内潮耗散与自吸-负荷潮对南海潮波影响的数值研究

利用非结构三角形网格的FVCOM海洋数值模式,在其传统二维潮波方程中加入参数化的内潮耗散项和自吸-负荷潮项,计算了南海及其周边海域的M_2、S_2、K_1和O_1分潮的分布。与实测值的比较表明,引入这两项对模拟准确度的提高有明显效果。根据模式结果本文计算分析了研究海域的潮能输入和耗散。能量输入计算表明,能通量是潮能输入的最主要构成部分,通过吕宋海峡断面进入南海的M_2和K_1分潮能通量分别为38和29GW;半日周期的自吸-负荷潮能量输入以负值居多,而全日周期的自吸-负荷潮能量输入以正值居多,因而自吸-负荷潮减弱了南海的半日潮,并加强了南海的全日潮。引潮力的作用也减弱了半日潮而加强了全日潮,但其作用要小于自吸-负荷潮。潮能耗散的分析显示底摩擦耗散在沿岸浅水区域起主导作用,内潮耗散则主要发生在深水区域。内潮耗散的最大值出现在吕宋海峡,且位于南海之外的海峡东部的耗散量大于位于南海之内的海峡西部的耗散量。对M_2和K_1分潮吕宋海峡的内潮耗散总值分别达到16和23GW。     

基于数值模式的南海北部深层内潮季节变化特征分析

本文基于MITgcm非静力数值模式,采用实际地形、层结和潮流强迫,开展南海北部内潮数值模拟敏感性试验,分析夏冬两个季节南海北部深层内潮的差异。结果显示在南海北部深层,冬季K₁和M₂内潮流速振幅比夏季强10.1%和44.7%。垂向模态分析结果进一步表明,尽管南海北部深层冬季第一模态内潮动能密度比夏季低15.5%,但第二和第三模态内潮则是冬季比夏季高约25.1%和33.2%,导致冬季深层流速的垂向剪切大于夏季,表明冬季较强的高模态内潮可能是冬季南海深层强混合的一个原因。     

A study of non-linear tidal propagation in shallow inlet/estuarine systems Part I: Observations

The offshore tide becomes strongly distorted as it propagates into shallow estuarine systems. Observations of sea surface elevation and horizontal currents over periods ranging from three days to one year, at nine stations within Nauset inlet/estuary, document the non-linear interaction of the off-shore equilibrium tidal constituents. Despite strong frictional attenuation within the estuary, the overtides and compound tides of M₂, S₂ and N₂, in particular, reach significant amplitude, resulting in strong tidal distortion. High frequency forced constituents in sea surface are phase-locked, consistently leading the forcing tides by 60–70°, resulting in a persistent distortion where falling tide is longer than rising tide. Forced constituents in currents are more nearly in phase with equilibrium constituents, producing flood currents which are shorter but more intense than ebb currents. A compound fortnightly tide, MS_f, modulates the mean water level such that lowest tides occur during neap phase instead of spring phase. This fortnightly tide can be contaminated by storm surge, changing the phase characteristics of this constituent. Implications of the overtides, compound tides, and lower frequency tides on near-bed, suspended and dissolved material transport are profound.     

泰国湾及邻近海域潮汐潮流的数值模拟

本文基于FVCOM(Finite-Volume Coastal Ocean Model)模式,模拟了泰国湾及其周边海域K1、O1、M2和S2四个主要分潮。采用47个验潮站实测调和常数与模拟结果进行比较,所得4个分潮的均方差分别为4.06cm、3.76cm、8.22cm和4.71cm,符合良好。根据计算结果分析了泰国湾及其周边海域的潮汐、潮流的分布特征和潮波的传播特征。数值试验表明,现有的数字水深资料(ETOPO1,ETOPO5,DBDB-V)的准确度不足以合理地模拟泰国湾潮波。     

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.     

Strong Tidal Mixing and Ventilation of Cold Intermediate Water at Kashevarov Bank, Sea of Okhotsk

Tidal mixing at the Kashevarov Bank, Sea of Okhotsk, has been investigated using observations of bottom pressure and currents. The tides are dominated by the diurnal constituents. The water motion over the Bank is predominantly controlled by strong diurnal tidal currents, which bring cold water on the bank from its source, a cold intermediate layer. The temperature fluctuations are about 1.2°C at the southern edge of the bank. The maximum observed velocity is about 164 cm/s at the top of the bank. A superposition of the original diurnal constituents K₁ and O₁ reveals a strong fortnightly (M_f) variability of the current speed. Tidal-induced mixing is responsible for ventilation of the cold intermediate layer of the Sea of Okhotsk. Strong tidal mixing creates a well-defined tidally mixed front around the bank. This front acts like a barrier separating well-mixed water on the bank from stratified water on its flanks. There is a residual current of the order of 10 cm/s.     

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.     

象山港内湾潮汐应变对横向流及其余环流垂向空间结构的调控研究

横向流 (垂直于海湾主轴方向的流动) 对横向动量以及物质分布具有重要影响。已往研究表明,潮汐应变对横向流的垂向空间结构具有重要的调控作用。但这种认识仅局限于强层化海区,弱层化条件下潮汐应变对于横向流空间结构的影响仍未可知。为此,本文以象山港为例,基于实测数据阐释了弱层化条件下潮汐应变对横向流及其余环流垂向空间结构的调控作用。结果显示,象山港内湾横向流的垂向空间结构随大小潮呈现出明显的变化规律。大潮时,潮汐应变现象明显,涨潮时较强的垂向混合使得横向流在高潮阶段呈现出一层结构;落潮时垂向混合较弱,横向流在低潮时呈现两层结构。小潮时,潮汐应变受到抑制,垂向混合在涨落潮时均较弱,因此横向流在高低潮阶段均呈现出两层结构。经过潮时均进一步得到的横向余环流呈现出上层向南、下层向北的两层结构。由于潮汐应变的大小潮变化,横向余环流的反转深度反转点自大潮到小潮呈现出上升的趋势。     

印度尼西亚海域潮波的数值研究

基于ROMS模式构建了模拟区域为(15.52°S-7.13°N,110.39°~134.15°E)水平分辨率为2′的潮波数值模式,分别模拟了印尼海域M2、S2、K1、O1四个主要分潮。模拟结果与29个卫星高度计交叠点上的调和常数进行比较,符合较好。M2分潮的振幅均方根差为3.4cm,迟角均方根差为5.9°;S2分潮的振幅均方根差为1.7cm,迟角均方根差为6.3°;K1分潮振幅均方根差为1.1cm,迟角均方根差为5.8°;O1分潮振幅均方根差为1.2cm,迟角均方根差为4.4°。M2、S2、K1、O1分潮向量均方根差分别为3.8cm、2.4cm、1.9cm和1.3cm,模拟结果的相对偏差在10%左右。根据计算结果分析了印尼海域的潮汐特征及潮能传播规律,结果显示:爪哇海以外的印尼海域主要为不规则半日潮区;全日潮潮能主要由太平洋传入印尼海域,而半日潮潮能则是从印度洋传入印尼海域。     

Modelling the tides and their impacts on the vertical stratification over the Sofala Bank,Mozambique

The Sofala Bank, a wide shelf located along the central coast of Mozambique, hosts tides with high amplitudes. The Regional Ocean Modelling System (ROMS) was used to analyse the tidal currents on the bank and to investigate their effects on the stratification and generation of tidal fronts. During spring tides, barotropic tidal currents with maximum values ranging from 40 cm s^–1 to 70 cm s^–1 are found on the central bank. The major axis of the tidal ellipses for M₂ and S₂ follow a cross-shelf direction with mainly anticlockwise rotation. Similar to observations, three distinct regimes occur: (i) a warm well-mixed region on the inner shelf where the depths are <30 m; (ii) a wellmixed colder region above the shelf edge; and (iii) a stratified region offshore. The model shows that the tides lead to cooling where two criteria are satisfied: the Simpson and Hunter parameter log₁₀(h/U³) <3.2 and the depth h >30 m. The shelf edge of the bank is important for internal tide generation. Two frontal structures result, one offshore between cooler mixed waters and warmer stratified waters and the other in shallow inshore waters, between cooler mixed waters and solar heated mixed waters.     

渤海开边界潮汐的伴随法反演

潮汐潮流数值模拟中的一个主要难点在于开边界条件的确定。本文采用伴随法 ,由渤海沿岸 1 9个验潮站的潮汐调和常数来反演渤海海域的开边界条件 ,以实现渤海潮波的数值模拟。计算所得调和常数与实测值之差的绝对平均值 :m1 潮波振幅差为 1 4cm ,迟角差为5 0°;M2 潮波振幅差为 2 4cm ,迟角差为 5 0°。数值模拟结果正确地反映了渤海m1 和M2 潮波的基本特征     

Observed and modelled tidal currents in the New Zealand region

Tidal currents derived from current meter measurements are compared with the output from a barotropic tidal model of the New Zealand region. For the semi‐diurnal constituents there was very good agreement for the M₂ tide and good agreement for the S₂ tide. For the diurnal constituents (K_l, O_l) it was found that as the amplitude of the constituents decreased so did both the model/observation agreement and the accuracy of the observed tidal ellipse parameters. Consequently it was not possible to decide whether differences arose through shortcomings in the model or in the data. However, the overall performance of the model as a prognostic tool for ocean tidal current simulation appears to be good.     

渤海潮波系统的数值模拟

利用二维非线性潮波方程组,讨论了渤黄海主要分潮(全日潮、半日潮及浅水分潮) 数值模拟中的有关问题。数值模拟中同时考虑了4个主要分潮(M2,S2,K1,O1)和两个浅水分潮(M4,MS4)。分析表明,在渤黄海潮波系统数值模拟中,稳定后选取14 d的数值模拟结果进行调和分析能够取得最佳(最合理)的调和分析结果。计算出调和常数的模拟值与实测值之差的绝对平均值:M2分潮的振幅差为4cm,迟角差为3.3°,S2分潮的振幅差为2cm,迟角差为4.2°,K1 分潮的振幅差为1cm,迟角差为3.7°,O1分潮的振幅差为2 cm,迟角差为5.5°。实验结果较好地体现了渤黄海潮波系统的特征。     

基于船载ADCP观测对罗源湾湾口断面潮流及余流的分析

基于对罗源湾可门水道的25 h连续走航ADCP观测,成功构建了沿走航断面共12个站位的连续海流时间序列,并对这些站位的潮流、余流以及潮通量等进行了分析。结果表明可门水道内的潮流为正规半日潮流,驻波性质明显,涨潮首先出现在水道中下层而退潮则首先发生在水道上层。水道内的潮流为往复流,水道南部M₂分潮流流速较大,并且其倾角自北向南逐渐增加。此外,水道两端的浅水区域内浅水分潮M₄振幅较显著。可门水道内余流呈现出两层结构,20 m以浅余流沿东北向流出海湾,并且出流的核心位置偏南,而20 m以深的余流沿西南向流入湾内,入流的流核位于偏北的近底层区域。对潮通量的积分计算表明通过可门水道进入罗源湾的潮通量约为4.81×108 m3。     

Tidal energy balance in the Seto Inland Sea

The tidal volume transport in the Seto Inland Sea is calculated. The cross-section where the volume transport of the M₂ tide is zero, is located around the western part of Bisan Strait. The tidal energy dissipation of the M₂ tide by friction is 6.30×10¹⁶ ergs s^–1 in the Seto Inland Sea. The quality factorQ for the M₂ tide is 20.2. The total energy dissipation of the M₂, S₂, K₁ and O₁ tides is 7.99×10¹⁶ ergs s^–1.     

江苏海岸中部近岸冬季潮汐和潮流特征

南黄海西侧的江苏海岸近岸区域,素以地形复杂、潮流强劲、悬沙输运剧烈著称,但是较长期的同步潮位和潮流观测数据仍然缺乏,尤其是在近岸(20 km)浅水(20 m)区域。2014年1月在大丰港附近开展了连续潮位和潮流观测,获得的数据揭示了一系列特征。此地潮汐潮流为正规半日潮,浅水分潮显著。平均潮差为3.05 m,最显著的两个分潮为M2和S2分潮,振幅分别为1.45 m和0.52 m。潮流最显著的半日分潮M2分潮和最显著的浅水分潮M4分潮在沿岸方向上振幅分别为0.84m/s和0.12m/s,在跨岸方向上振幅分别为0.24 m/s和0.01 m/s,沿岸方向占绝对优势。潮波的沿岸传播介于前进波和驻波之间,驻波的特征稍强。M2分潮潮流椭圆最大流(长轴)方向为南偏东7.4°。存在冬季沿岸向北的余流,垂向平均值的大小为2.2 cm/s。以上潮汐潮流特征为该区域海洋物质输运研究提供了基础资料。     

Ocean Tide Models Developed by Assimilating TOPEX/POSEIDON Altimeter Data into Hydrodynamical Model: A Global Model and a Regional Model around Japan

A global ocean tide model (NAO.99b model) representing major 16 constituents with a spatial resolution of 0.5° has been estimated by assimilating about 5 years of TOPEX/POSEIDON altimeter data into barotropic hydrodynamical model. The new solution is characterized by reduced errors in shallow waters compared to the other two models recently developed; CSR4.0 model (improved version of Eanes and Bettadpur, 1994) and GOT99.2b model (Ray, 1999), which are demonstrated in comparison with tide gauge data and collinear residual reduction test. This property mainly benefits from fine-scale along-track tidal analysis of TOPEX/POSEIDON data. A high-resolution (1/12°) regional ocean tide model around Japan (NAO.99Jb model) by assimilating both TOPEX/POSEIDON data and 219 coastal tide gauge data is also developed. A comparison with 80 independent coastal tide gauge data shows the better performance of NAO.99Jb model in the coastal region compared with the other global models. Tidal dissipation around Japan has been investigated for M₂ and K₁ constituents by using NAO.99Jb model. The result suggests that the tidal energy is mainly dissipated by bottom friction in localized area in shallow seas; the M₂ ocean tidal energy is mainly dissipated in the Yellow Sea and the East China Sea at the mean rate of 155 GW, while the K₁ energy is mainly dissipated in the Sea of Okhotsk at the mean rate of 89 GW. TOPEX/POSEIDON data, however, detects broadly distributed surface manifestation of M₂ internal tide, which observationally suggests that the tidal energy is also dissipated by the energy conversion into baroclinic tide.