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Numerical study of baroclinic tides in Luzon Strait 总被引：6，自引：1，他引：5
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. 相似文献
3.
内潮耗散与自吸-负荷潮对南海潮波影响的数值研究 总被引：1，自引：0，他引：1
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。 相似文献
4.
吕宋海峡由于剧烈变化的地形成为内潮产生的源地,内潮是海洋混合的重要原因。为了认知南海的内潮能通量分布,对南海的内潮有更好的理解,本文利用21世纪以来发射的多颗高度计卫星:J2、J1T、GFO以及EN,提取了吕宋海峡附近内潮的能通量。研究使用了调和分析和高通滤波等方法来提取第一模态内潮,主要提取K_1,K_2,M_2,N_2,O_1,P_1,Q_1和S_2八个分潮。同时结合WOA数据对能通量进行计算。结果表明,目标区域潮汐以全日分潮为主,所选区域的全日分潮中K_1所占比例最大;半日分潮中M_2分潮最强,而内潮的能通量则是M_2分潮所占最大,在吕宋海峡区域M_2能通量为6.45GW。内潮主要产生在地形变化剧烈的地方,海域的大部分地区内潮能量很小。在吕宋海峡中部,全日分潮能通量要小于南部地区,而半日分潮则有较大值。 相似文献
5.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(3):449-473
Mode-1 internal tides were observed the western North Atlantic using an ocean acoustic tomography array deployed in 1991–1992 centered on 25°N, 66°W. The pentagonal array, 700-km across, acted as an antenna for mode-1 internal-tides. Coherent internal-tide waves with O(1 m) displacements were observed traveling in several directions. Although the internal tides of the region were relatively quiescent, they were essentially phase locked over the 200–300 day data record lengths. Both semidiurnal and diurnal internal waves were detected, with wavenumbers consistent with those calculated from hydrographic data. The M2 internal-tide energy flux was estimated to be about 70 W m−1, suggesting that mode-1 waves radiate 0.2 GW of energy, with large uncertainty, from the Caribbean island chain at this frequency. A global tidal model (TPXO 5) suggested that 1–2 GW is lost from the M2 barotropic tide over this region, but the precise value was uncertain because the complicated topography makes the calculation problematic. In any case, significant conversion of barotropic to baroclinic tidal energy does not occur in the western North Atlantic basin. It is apparent, however, that mode-1 internal tides have very weak decay and retain their coherence over great distances, so that ocean basins may be filled up with such waves. Observed diurnal amplitudes were an order of magnitude larger than expected. The amplitude and phase variations of the K1 and O1 constituents observed over the tomography array were consistent with the theoretical solutions for standing internal waves near their turning latitude. The energy densities of the resonant diurnal internal waves were roughly twice those of the barotropic tide at those frequencies. 相似文献
6.
利用1992—2002年的温盐深数据与2012—2016年的Argo数据,基于细尺度参数化方法研究了吕宋海峡及周边海域(12°—30°N,115°—129°E)湍流混合的时空分布特征,并分析了地形粗糙度、内潮以及风输入的近惯性能通量对湍流混合的影响。结果表明,吕宋海峡和东海陆坡处具有强混合的特征,扩散率高达4×10~(-3) m~2/s,主要是由内潮产生导致的,其中吕宋海峡主要是M2、K1和O1内潮的贡献,而东海陆坡处主要是M_2内潮的贡献;南海北部也呈现较强的混合,且陆坡处的混合比海盆高1—2个量级;南海中央海盆和离岸的菲律宾海混合较弱,扩散率为O (10-5 m2/s)。此外,在研究区域内,湍流混合的年际变化和季节变化均不明显,且混合扩散率与风输入的近惯性能通量未表现出明显的季节相关。 相似文献
7.
By compiling all the tidal data gathered from island-wide results of simple harmonic analysis, anomalous amplifications of semidiurnal tides along the western coast of Taiwan are illustrated. The mechanisms are investigated both theoretically and numerically by applying the linear shallow-water wave equations. Waves trapped by a continental shelf and resonance of tidal co-oscillation are identified theoretically. Numerically, a two-dimensional finite element model is applied to real topography for tidal computations. The co-range and equi-phase charts of three main semidiurnal constituents (M2, S2, and N2) and one diurnal constituent K1 are calculated. Anomalous amplifications of semidiurnal tides that appear as partially standing waves are demonstrated. 相似文献
8.
We adopt a parameterized internal tide dissipation term to the two-dimensional (2-D) shallow water equations, and develop the corresponding adjoint model to investigate tidal dynamics in the South China Sea (SCS). The harmonic constants derived from 63 tidal gauge stations and 24 TOPEX/Poseidon (T/P) satellite altimeter crossover points are assimilated into the adjoint model to minimize the deviations of the simulated results and observations by optimizing the bottom friction coefficient and the internal tide dissipation coefficient. Tidal constituents M2, S2, K1 and O1 are simulated simultaneously. The numerical results (assimilating only tidal gauge data) agree well with T/P data showing that the model results are reliable. The co-tidal charts of M2, S2, K1 and O1 are obtained, which reflect the characteristics of tides in the SCS. The tidal energy flux is analyzed based on numerical results. The strongest tidal energy flux appears in the Luzon Strait (LS) for both semi-diurnal and diurnal tidal constituents. The analysis of tidal energy dissipation indicates that the bottom friction dissipation occurs mainly in shallow water area, meanwhile the internal tide dissipation is mainly concentrated in the LS and the deep basin of the SCS. The tidal energetics in the LS is examined showing that the tidal energy input closely balances the tidal energy dissipation. 相似文献
9.
The phase of semi-diurnal tides (M2 and S2) propagates clockwise in the central part of the Gulf of Thailand, although that of the diurnal tides (K1, O1 and P1) is counterclock-wise. The mechanism of clockwise phase propagation of semi-diurnal tides at the Gulf of Thailand in the
northern hemisphere is examined using a simple numerical model. The natural oscillation period of the whole Gulf of Thailand
is near the semi-diurnal period and the direction of its phase propagation is clockwise, mainly due to the propagation direction
of the large amplitude part of the incoming semi-diurnal tidal wave from the South China Sea. A simplified basin model with
bottom slope and Coriolis force well reproduces the co-tidal and co-range charts of M2 tide in the Gulf of Thailand. 相似文献
10.
南海北部陆架区内孤立波向岸传播过程研究 总被引：1，自引：0，他引：1
南海北部是全球海洋中内孤立波最强和最为活跃的海域。然而,内孤立波在传入陆架区后,其形态发生显著变化,其传播演变过程表现出高度的复杂性。本研究综合卫星图像和数值模式手段研究了内孤立波在向岸传播过程中的空间变化特征。可见光卫星图像研究结果显示,南海北部陆架区存在三种形态的内孤立波,分别为第一模态下凹型内孤立波、第一模态上凸型内孤立波和第二模态内孤立波。受水深和层结变化的控制,它们的分布区域显著不同。基于MITgcm的数值模拟研究表明,上凸型内孤立波由第一模态下凹内孤立波经过极性转换过程发展而来,而第二模态内孤立波由第一模态下凹内孤立波与急剧变浅地形相互作用而产生。 相似文献
11.
The evolution of energy, energy flux and modal structure of the internal tides(ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a～14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m~2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs.From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1. 相似文献
12.
Shenn-Yu Chao Dong-Shan Ko Ren-Chieh Lien Ping-Tung Shaw 《Journal of Oceanography》2007,63(6):897-911
The Luzon Strait is blocked by two meridional ridges at depths, with the east ridge somewhat higher than the west ridge in
the middle reaches of the Strait. Previous numerical models identified the Luzon Strait as the primary generation site of
internal M2 tides entering the northern South China Sea (Niwa and Hibiya, 2004), but the role of the west-versus-east ridge was uncertain.
We used a hydrostatic model for the northern South China Sea and a nonhydrostatic, process-oriented model to evaluate how
the west ridge of Luzon Strait modifies westward propagation of internal tides, internal bores and internal solitary waves.
The dynamic role of the west ridge depends strongly on the characteristics of internal waves and is spatially inhomogeneous.
For M2 tides, both models identify the west ridge in the middle reaches of Luzon Strait as a dampener of incoming internal waves
from the east ridge. In the northern Luzon Strait, the west ridge is quite imposing in height and becomes a secondary generation
site for M2 internal tides. If the incoming wave is an internal tide, previous models suggested that wave attenuation depends crucially
on how supercritical the west ridge slope is. If the incoming wave is an internal bore or internal solitary wave, our investigation
suggests a loss of sensitivity to the supercritical slope for internal tides, leaving ridge height as the dominant factor
regulating the wave attenuation. Mechanisms responsible for the ridge-induced attenuation are discussed. 相似文献
13.
B. A. Kagan A. A. Timofeev E. V. Sofina 《Izvestiya Atmospheric and Oceanic Physics》2010,46(5):652-662
The modeling results of surface and internal M2 tides for summer and winter periods in the Arctic Ocean (AO) are presented. We employed a modified version of the three-dimensional
finite-element hydrothermodynamic model QUODDY-4 differing from the original model by using a rotated (instead of spherical)
coordinate system and by considering the equilibrium-tide effects. It has been shown that the modeling results for the surface
tide differs little from the results obtained earlier by other authors. According to these results, the amplitudes of internal
tidal waves (ITWs) in the AO are significantly lower than in other oceans and the ITWs proper have the character of trapped
waves. Their source of generation is located at the continental slope northwest of the New Siberian Islands. Our results are
consistent with the fields of average (over a tidal cycle) and integral (by depth) densities of baroclinic tidal energy, the
maximum baroclinic tidal velocity, and the coefficient of diapycnic mixing. The local rate of baroclinic tidal energy dissipation
at the AO ridges increases as it approaches the bottom, as was observed on Mid-Atlantic and Hawaii ridges (but merely within
the bottom boundary layer) and is two to three orders of magnitude lower than in other oceans. The ITW degeneration scale
in the AO is several hundreds of kilometers in summer and winter, remaining within the range of its values between 100 and
1000 km in mid- and low-latitude oceans. In both seasons, the integral (over the AO area) rate of baroclinic tidal energy
dissipation is two orders of magnitude lower than the global estimate (2.5 × 1012 W). 相似文献
14.
A vertically integrated 2D numerical model was developed for the simulation of major tidal constituents (M2, S2, N2, K1 and O1) in the Bay of Bengal. The bathymetry for the model domain was derived from an improved ETOPO5 dataset prepared in our earlier work. The simulated tidal elevations showed good agreement with the hourly tide gauge observations at Paradip, Visakhapatnam, and Chennai. The amplitudes and phases of M2, S2, K1, and O1 at the coastal stations, obtained from harmonic analysis of simulated tides, were found to agree well with those obtained from Admiralty Tide Tables with the RMS misfit 9.2, 5.6, 2.9 and 3.1 cm, respectively. In the Bay of Bengal, semi-diurnal tides (M2, S2, and N2) attain highest amplitudes (180, 80, 30 cm, respectively) in the Gulf of Martaban while amplitudes of diurnal tides (K1, O1) reaches maximum (20, 12 cm, respectively) in the Malacca Strait. The continental shelf in the head bay and along the southern coast of Myanmar is about 200 km wide and the amplitudes of semi-diurnal tides are doubled in these regions while the diurnal tides amplify only marginally, which is consistent with Clarke and Battisti theory. In the north eastern end of the head bay and the Gulf of Martaban, the geometrical configuration of the coastline, in addition to the wide continental shelf, could contribute to the amplification of both semi-diurnal and diurnal constituents. In the Malacca Strait, the amplitudes of both semi-diurnal and diurnal tides are found to increase gradually from the northern end to the 2.5°N and decreases towards southern boundary. The co-tidal and co-range charts of M2 and S2 tidal constituents also show the presence of two degenerate amphidromic points in the head bay. A virtual amphidromic point for M2 is identified in the Malacca Strait. 相似文献
15.
Tidal observations on the West Coast,South Island,New Zealand 总被引：1，自引：1，他引：0
R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(2):251-261
Harmonic tidal constants, calculated from sea surface elevation observations at Jackson Bay on the West Coast of the South Island, are consistent with available semi‐diurnal and diurnal tidal phase distributions. Current observations taken over a 111 day period at mid‐depth in 1505 m of water on the southern flank of the Challenger Plateau and over a 240 day period in 1430 m of water on the South Island western coast continental slope, are subject to tidal analysis. At both sites there is a component of energy flux directed across the isobaths and only at the northern site for the M2 tide is the phase consistent with a dominant progressive barotropic tide. The successive 30 day harmonic constants at the southern continental slope site exhibit a trend in the M2 tidal ellipse speed and ellipticity suggesting the presence of a regular internal tide. Superposition of ‘internal tidal’ and barotropic tidal flows, as prescribed from progressive‐ and standing‐wave elevations, to fit the observations indicates that the ‘internal tide’ is probably associated with the first baroclinic mode. At the current‐meter depths the speeds of the ‘internal tide’ for the M2 tide are about the same as the barotropic speeds, whereas, the S2 ‘internal tide’ speeds are larger than those of the barotropic tide. The consistency of the trend in ellipse parameters lends support to the theoretical progressive trapped barotropic tidal flows being a good approximation to the actual barotropic tide. Some support for the hypothesis that the S2 tide on the West Coast of New Zealand has a substantial standing wave contribution is given by the northern observations, where the ratio of the S2: M2 internal tidal ellipse current amplitudes are substantially larger than the ratio of the elevations, the internal tide being generated by across‐isobath flows. 相似文献
16.
南海北部陆架海域内潮特征的观测研究 总被引：1，自引：0，他引：1
利用2014年南海东沙岛西北部海域70余天的流速剖面高频观测资料,研究分析了该海区正压潮、内潮的时空分布特征。结果表明,观测海区正压潮流以O_1,K_1,M_2,S_2为主;斜压潮流中,除四大分潮之外,MU_2与2Q_1分潮能量也较强;内潮的主轴方向基本沿东南-西北方向,近似与局地等深线垂直。全日内潮的锁相部分占全日内潮能量的17.5%,而半日内潮的锁相部分占半日内潮能量的30%;进一步研究发现半日内潮主要由第一模态主导,而全日内潮第二模态占比50%,约为其第一模态能量的两倍;内潮模态能量占比显示出显著的大小潮调制的半月周期。对比不同垂向模态计算方法发现,当流速观测深度有限时,利用全水深温盐资料计算观测范围内流速垂向模态是更为准确的方式。 相似文献
17.
一个典型南海北部第二模态内孤立波的观测分析 总被引：1，自引：0，他引：1
第二模态内孤立波在海洋中极少被观测到。本文基于潜标高时空分辨率观测数据,对南海北部陆架区的一个典型第二模态内孤立波进行了分析。结果表明,该第二模态内孤立波的流核出现在135 m深度处,其最大水平流速为0.66 m/s,传播方向为西偏北58°。沿传播方向的内孤立波流速分布在80～170 m的深度范围内,而与传播方向相反的逆流出现在海表和海底附近。垂向模态分析表明,该第二模态内孤立波水平流速的垂向结构与理论结果吻合良好。能量计算结果显示其动能密度的垂向积分可达14 kJ/m2,而波峰线方向单位长度上的动能估算值为5.98 MJ/m。尽管该第二模态内孤立波的动能比陆架区第一模态内孤立波小1个量级,但其高达0.045 s-1的流速垂向剪切约为典型第一模态内孤立波的2倍,表明其导致的混合可能更强。 相似文献
18.
南海北部陆架陆坡区海流观测研究 总被引：3，自引：0，他引：3
针对2006-2009年期间,南海北部陆架陆坡区3个站ADCP海流连续观测资料,采用功率谱分析、潮流调和分析方法,重点分析了陆架陆坡区100 m,200 m和1 200 m水深海域海流的垂向结构,探讨了环流的季节变化和空间分布特征,特别讨论了南海暖流和北陆坡流的时空变化特征。结果表明,陆架陆坡区潮流类型属于不规则日潮,深水站点中层表现为正规全日潮类型,垂向为"三层结构",甚至更加复杂。O1,K1,M2,S2等分潮总体上为顺时针旋转,在深水站点,基本表现为西北－东南走向的往复流形态。从能量角度看,表层和底层海流中,潮流所占份额较大,分别占30%~40%和40%~50%,中层较小,约为20%。对东沙群岛西南陆架陆坡区环流,观测计算结果证实了西向强流的存在,且垂向结构具有显著的季节变化,在200 m水深处没有明显的南海暖流,只是10~30 m以上层次存在逆风海流。海南岛以东海域连续15个月表层环流的结果表明,冬季明显受到南海暖流的影响,存在东北向的逆风海流,夏秋季的环流表现为西南向,流速较强,夏季也存在逆风情况,造成上述情形的原因可能是该地南海暖流的流轴具有季节性变化——冬季偏南,夏季偏北。 相似文献
19.
An array of three bottom-mounted ADCP moorings was deployed on the prevailing propagation path of strong internal tides for nearly 1 year across the continental slope in the northern South China Sea. These velocity measurements are used to study the intra-annual variability of diurnal and semidiurnal internal tidal energy in the region. A numerical model, the Luzon Strait Ocean Nowcast/Forecast System developed at the U.S. Naval Research Laboratory that covers the northern South China Sea and the Kuroshio, is used to interpret the observed variation of internal tidal energy on the Dongsha slope. Internal tides are generated primarily at the two submarine ridges in the Luzon Strait. At the western ridge generation site, the westward energy flux of the diurnal internal tide is sensitive to the stratification and isopycnal slope associated with the Kuroshio. The horizontal shear at the Kuroshio front does not modify the propagation path of either diurnal or semidiurnal tides because the relative vorticity of the Kuroshio in Luzon Strait is not strong enough to increase the effective inertial frequency to the intrinsic frequency of the internal tides. The variation of internal tidal energy on the continental slope and Dongsha plateau can be attributed to the variation in tidal beam propagation in the northern South China Sea. 相似文献
20.
南海是西太平洋最大的边缘海, 由于受季风影响显著以及北部海域的黑潮入侵, 其动力环境复杂多变, 次中尺度过程丰富, 且在空间上和时间上存在多变性。文章基于高分辨率数值模式的结果, 通过对次中尺度动力参数的分析, 对比讨论了南海北部、中部、西部和南部海域4个典型子区域上层海洋次中尺度过程的空间差异、季节变化、影响深度、影响因素等问题。研究发现各区域季节性变化特征和机制有所不同: 北部海域受冬季风和黑潮入侵影响, 冬季次中尺度的混合层不稳定较强; 中部海域同样表现为“冬强夏弱”; 西部海域受夏季风影响显著, 夏季次中尺度过程更为活跃; 而南部海域主要受岛屿地形影响较大, 容易产生地形尾涡, 季节性特征不明显。统计分析表明, 次中尺度过程往往表现出强正相对涡度与高应变特征, 在表层更容易出现负位涡, 流体稳定性较差。此外, 文章从能量学角度对次中尺度过程的主要能量来源、控制因素等进行了讨论。 相似文献