共查询到20条相似文献，搜索用时 31 毫秒
1.
Propagation of Rossby Waves over Ridges Excited by Interannual Wind Forcing in a Western North Pacific Model 总被引：1，自引：4，他引：1
Numerical experiments with a multi-level general circulation model have been performed to investigate basic processes of westward
propagation of Rossby waves excited by interannual wind stress forcing in an idealized western North Pacific model with ocean
ridges. When the wind forcing with an oscillation period of 3 years is imposed around 180°E and 30°N, far from Japan, barotropic
waves excited by the wind can hardly cross the ridges, such as the Izu-Ogasawara Ridge. On the other hand, a large part of
the first-mode baroclinic waves are transmitted across the ridges, having net mass transport. The propagation speed of the
first-mode baroclinic wave is accelerated (decelerated) when an anticyclonic (cyclonic) circulation is formed at the sea surface,
due to a deeper (shallower) upper layer, and to southward (slightly northward) drift of the circulation. Thus, when the anticyclonic
circulation is formed on the northern side of the cyclonic one, they propagate almost together. The second-mode baroclinic
waves converted from the first-mode ones on the ridges arrive south of Japan, although their effects are small. The resulting
volume transport variation of the western boundary current (the Kuroshio) reaches about 60% of the Sverdrup transport variability
estimated from the wind stress. These characteristics are common for the interannual forcing case with a longer oscillation
period. In the intraseasonal and seasonal forcing cases, on the other hand, the transport variation is much smaller than those
in the interannual forcing cases.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
S. F. Dotsenko 《Physical Oceanography》2006,16(2):77-88
Within the framework of a linear model of long waves in a two-layer ocean, we obtain the analytic solution of the problem
of evolution of an axially symmetric initial displacement of the jump of density. In the process of adaptation of the fields,
internal waves in the form of a decaying (in time) wave packet are emitted from the zone of initial perturbation. These waves
are quasiinertial and their dispersion is conditioned by Earth’s rotation. We study the time evolution of the wave packet
and the dependence of its characteristics on the width of the zone of initial perturbation and the depth of the jump of density.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 12–23, March–April, 2006. 相似文献
3.
完全非线性孤立波的直墙反射 总被引：2，自引：2，他引：0
报道了应用边界积分方法模拟完全非线性孤立波的传播与直墙反射,给出了波形演变过程。结果表明,本模型对计算孤立波的传播与直墙反射是有效的。三阶Boussinesq方程的孤立波解比低阶方程的孤立波解更接近完全非线性的数值解.当来波波高增大时,孤立波直墙反射的相位滞后变小。若考虑大波高孤立波的直墙反射或波——波相互作用,一阶理论预报的相位滞后往往低估实际情况。 相似文献
4.
Within the framework of the linear model of long waves, we study the transformations of the ocean surface under the conditions
of uniform motion of a zone of disturbances of atmospheric pressure. The analysis is based on the evaluation of a two-dimensional
integral appearing in the exact expression for the shape of the free surface of the ocean. It is shown that Earth’s rotation,
the increase in the horizontal scale of the atmospheric anomaly, and the decrease in the depth of the basin make the displacements
of the sea level smaller than those predicted by the law of inverted barometer. The motion of the baric anomalies leads to
the opposite effect. In the open ocean, the displacements of its surface under a moving front are more pronounced than in
the case of a moving circular anomaly of atmospheric pressure.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 3–14, March–April, 2007. 相似文献
5.
基于布放在南海东北部陆坡海域的5套潜标观测到的内孤立波波列数据和孤立波扰动KdV(PKdV)理论,研究内孤立波在趋浅陆架上的传播特征。得出如下结果:1)观测到的内孤立波属于C型内孤立波,即平均重现周期为(23.41±0.31)h。2)内孤立波在西传爬坡过程中,其振幅表现为先增大后减小再增大,与该海域温跃层深度的变化趋势一致;由观测数据和理论计算得到的孤立波振幅增长率(SAGR)数值接近,表明该海域的内孤立波的振幅变化可以采用由孤立波PKdV方程导出的趋浅温跃层理论来描述。3)随着水深变浅,内孤立波传播方向向北偏移,传播速度减小,即在A,B和D站位,传播方向分别为279°,296°和301°,偏转角度达22°;传播速度分别为2.36,2.23和1.47 m/s,减小38%。 相似文献
6.
Kern E. Kenyon 《Journal of Oceanography》2007,63(2):327-331
A rigid open-ended pipe is submerged in the ocean below the troughs of the surface waves and held fixed in the vertical position,
the lower end being at or below the depth of wave influence. When surface gravity waves propagate past the pipe, water flows
up as long as waves are present. The steady upward vertical velocity in the center of the pipe is calculated to be proportional
to the square of both the average wave steepness and the pipe’s radius. An application is to bring nutrient rich waters up
into the sunlit surface layers of the open oceans. 相似文献
7.
为获取南海北部陆坡海区第一模态内孤立波的动力结构及时间变化特征,本文利用该海区1套内孤立波浮标观测数据,对陆坡海区的内孤立波现场观测数据分析,识别判定了2021年5月5日至6月3日共30 d的179次第1模态内孤立波过程,并进行了内孤立波的特征分析。南海北部陆坡海区第1模态内孤立波剖面流场为双层结构,上层主要为西偏北向流动,下层流向与之相背,流速转向发生在100～150 m深度处。内孤立波期间,最大流速多发生于上层,流速为60～120 cm/s,底层流增强,上层流与下层流流向相反。受内潮影响,研究区域内孤立波存在半日和全日2个周期,主要以20～30 min间隔的波列形式向西偏北方向传播。本文关于南海北部陆坡海区第一模态内孤立波的分析研究有助于提升对该海区内孤立波时空变化特征的认识,为工程水下施工提供参考和依据。 相似文献
8.
Masahisa Kubota 《Journal of Oceanography》1985,41(2):105-112
Numerical experiments are performed on shelf waves forced by wind stress with a spectral peak around a period of 100 hr. Water depth in the numerical model is a function of offshore distance only and resembles a bathymetric profile off the Fukushima coast. A pair of vortices alined in the offshore direction and a large vortex are reproduced and they propagate southward outside the forced region. Judging from the propagation speed, the former corresponds to the second-mode and the latter to the first-mode shelf waves. In the forced region, the propagation speed of a trough and a ridge is slow, 3–5km hr–1. These propagation characteristics reproduce those observed along the Fukushima coast and this propagation speed corresponds to that of second-and third-mode shelf waves. Thus, it is concluded that the periodical current fluctuations observed in the inshore region along the Fukushima coast are due to motions associated with the second-and third-mode shelf waves. 相似文献
9.
Oceanic pycnocline depth retrieval from SAR imagery in the existence of solitary internal waves 总被引：2，自引：1，他引：1
Oceanic pycnocline depth is usually inferred from in situ measurements. It is attempted to estimate the depth remotely. As solitary internal waves occur on oceanic pycnocline and propagate along it, it is possible to retrieve the depth indirectly in virtue of the solitary internal waves. A numerical model is presented for retrieving the pycnocline depth from synthetic aperture radar （SAR） images where the solitary internal waves are visible and when ocean waters are fully stratified. This numerical model is constructed by combining the solitary internal wave model and a two-layer ocean model. It is also assumed that the observed groups of solitary internal wave packets on the SAR imagery are generated by local semidiurnal tides. A case study in the East China Sea shows a good agreement with in situ CTD （conductivity-temperature-depth） data. 相似文献
10.
内波破碎引起的能量耗散和混合是海洋内部的重要物理过程。通过在二维内波水槽进行实验室实验,分析内波与地形的作用,探究内孤立波与平顶海山地形作用时波要素、能量以及湍耗散率的时空变化。本实验利用重力塌陷法在两层流体中制造第一模态内孤立波,通过粒子图像测速技术(particle image velocimetry, PIV)获得内孤立波与地形作用时的流场结构,定量分析整个作用过程。结果表明,地形会改变波形甚至引起破碎,内波与地形作用时,振幅和能量密度会在内孤立波爬坡时迅速增大,在地形前缘产生强烈能量耗散。入射波的能量与塌陷高度呈二次函数关系,透射波能量随地形升高减小,反射波能量随地形升高增大。地形前缘局地湍耗散率极值时间序列在部分实验中呈双峰结构,对应内孤立波界面处剪切加强引起湍流耗散和波后缘翻转破碎。破碎引起的地形前缘区域平均湍耗散率量级在10~(-5)m~2/s~3,局地湍耗散率极值与入射波振幅呈指数关系,所有实验中局地湍耗散率的最大值接近10~(-3) m~2/s~3量级。 相似文献
11.
Temporal variations of area of the North Pacific Intermediate Water (NPIW), in the repeat hydrographic section along 137°E
meridian conducted by the Japan Meteorological Agency, are investigated using the de-trended variables from 1972 to 2008.
Variations of NPIW area show a clear quasi-decadal (about 10 years) modulation and it is caused by the vertical displacement
of isopycnal surfaces in the lower portion of NPIW around the northern boundary of its distribution (30–32°N): The downward
(upward) movement of isopycnal surfaces in the lower portion of NPIW as a result of the first-mode baroclinic ocean response
stretches (shrinks) the density layer equivalent of NPIW and causes strengthening (weakening) of westward flows associated
with the Kuroshio Counter Current, and then it can induce an increase (decrease) of volume transport of NPIW from the east.
Consequently, the NPIW northern boundary shifts northward (southward) and an increase (decrease) of the NPIW area is induced.
Large-scale atmospheric forcing controlling the vertical displacements of isopycnal surfaces is explored using a wind-driven
hindcast ocean model. The vertical displacements stem from the first-mode baroclinic ocean response to the two types of Aleutian
Low (AL) activities: in particular, the meridional movement of the AL imparts more potential influence on them than the AL
intensity variation does. 相似文献
12.
基于遥感与现场观测数据的南海北部内波传播速度 总被引：2，自引：0，他引：2
南海北部是全球海洋中内波最为活跃、生成和演变机制较为复杂的海域,本文利用多源卫星遥感数据(MODIS、GF-1、ENVISAT ASAR、RADARSAT-2)和现场观测数据开展了南海北部内波传播速度的研究。通过匹配捕获同一条内波的相邻两幅遥感图像,由内波的空间位移和时间间隔反演传播速度,并以0.5°×0.5°网格给出了南海北部内波传播速度的分布图。研究结果表明,内波传播速度受背景流场、水体层结和底地形变化等多因素影响,特别是水深。在南海北部由东至西、由南至北方向,内波传播速度逐渐递减。深海区内波传播速度最大,可达3m/s以上;内波在向西大陆架传播过程中,随着水深变浅速度逐渐减慢,传播速度为1—2m/s;大陆架浅海的内波传播速度较小,仅为零点几米每秒。同时,利用Kd V方程反演了内波传播速度理论值,对遥感数据提取的内波传播速度进行了精度验证,结果较为一致。 相似文献
13.
The run-up and back-wash processes of single and double solitary waves on a slope were studied experimentally. Experiments were conducted in three different wave flumes with four different slopes. For single solitary wave, new experimental data were acquired and, based on the theoretical breaking criterion, a new surf parameter specifically for breaking solitary waves was proposed. An equation to estimate maximum fractional run-up height on a given slope was also proposed. For double solitary waves, new experiments were performed by using two successive solitary waves with equal wave heights; these waves were separated by various durations. The run-up heights of the second wave were found to vary with respect to the separation time. Particle image velocimetry measurements revealed that the intensity of the back-wash flow generated by the first wave strongly affected the run-up height of the second wave. Showing trends similar to that of the second wave run-up heights, both the back-wash breaking process of the first wave and the reflected waves were strongly affected by the wave–wave interaction. Empirical run-up formula for the second solitary wave was also introduced. 相似文献
14.
Using all of the atmospheric patterns classified by Polyakova A.M., we accomplished calculations of the surface wind fields
over the North Pacific for wind waves observable 6, 12, 18, and 24 hours after a storm and the swell waves observable 24,
48, and 72 hours after a storm. The considerable extension of the ocean creates quasi-unlimited speeding up of the wind waves
during continuous strong winds (over 20 meters per second). This determines the presence of wide areas of highly developed
wind waves with a 5% probability that the wave heights will exceed the 10–12 meter estimates. The swell waves decay faster:
their height reduces by half in 24 h, while, in 72 h, they achieve the background level of the ocean’s swell waves. 相似文献
15.
LIAO Guanghong YANG Chenghao XU Xiaohu SHI Xingang YUAN Yaochu HUANG Weigen 《海洋学报(英文版)》2012,31(5):26-40
The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f-plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation. 相似文献
16.
Using large eddy simulation (LES) incorporating the effect of the horizontal component of the earth’s rotation vector, we
studied the seafloor turbulent boundary layer to investigate the dependence of the boundary layer thickness on the overlying
geostrophic flow orientation. The thickest boundary layer appears for the westward geostrophic flow: it is almost twice that
of the eastward flow. The turbulent disturbances in the boundary layer are elongated slightly leftward relative to the geostrophic
flow. Linear stability analysis for the Ekman’s spiral flow showed that the growth rate is maximum for the westward geostrophic
flow and the unstable roll-like mode appears, which points slightly leftward relative to the geostrophic flow. These properties
correspond to the feature near the bottom of the developed turbulent layer. 相似文献
17.
Understanding the hydrodynamic interactions between ocean waves and the oscillating water column (OWC) wave energy converter is crucial for improving the device performance. Most previous relevant studies have focused on testing onshore and offshore OWCs using 2D models and wave flumes. Conversely, this paper provides experimental results for a 3D offshore stationary OWC device subjected to regular waves of different heights and periods under a constant power take–off (PTO) damping simulated by an orifice plate of fixed diameter. In addition, a 3D computational fluid dynamics (CFD) model based on the RANS equations and volume of fluid (VOF) surface capturing scheme was developed and validated against the experimental data. Following the validation stage, an extensive campaign of computational tests was performed to (1) discover the impact of testing such an offshore OWC in a 2D domain or a wave flume on device efficiency and (2) investigate the correlation between the incoming wave height and the OWC front wall draught for a maximum efficiency via testing several front lip draughts for two different rear lip draughts under two wave heights and a constant PTO damping. It is found that the 2D and wave flume modelling of an offshore OWC significantly overestimate the overall power extraction efficiency, especially for wave frequencies higher than the chamber resonant frequency. Furthermore, a front lip submergence equal to the wave amplitude affords maximum efficiency whilst preventing air leakage, hence it is recommended that the front lip draught is minimized. 相似文献
18.
A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅰ. Simulation of internal tide transformation 总被引：1，自引：0，他引：1
For settlement of the well-known problem of contemporary radar imaging models, i. e. , the problem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal waters at high radar frequency bands （ X-band and C-band）, the impact of the ocean surface mixed layer turbulence and the significance of strat- ified oceanic model on SAR remote sensing of internal solitary waves are proposed. In the north of the South China Sea by utilizing some observed data of background field the nonlinearity coefficient, the dispersion coefficient, the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately. Through simulations of internal tide transfor- mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of internal wave field are obtained. The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m, but the maximum current speeds take place at depth 20 m in this area of the sea （about 20°30＇N, 114°E） in August. It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation. The obtained results provide the possibility for the simulation of SAR signatures of internal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper. 相似文献
19.
20.
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