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1.
Spilled oil floats and travels across the water’s surface under the influence of wind, currents, and wave action. Wave-induced Stokes drift is an important physical process that can affect surface water particles but that is currently absent from oil spill analyses. In this study, two methods are applied to determine the velocity of Stokes drift, the first calculates velocity from the wind-related formula based upon a one-dimensional frequency spectrum, while the second determines velocity directly from the wave model that was based on a two-dimensional spectrum. The experimental results of numerous models indicated that: (1) oil simulations that include the influence of Stokes drift are more accurate than that those do not; (2) for medium and long-term simulations longer than two days or more, Stokes drift is a significant factor that should not be ignored, and its magnitude can reach about 2% of the wind speed; (3) the velocity of Stokes drift is related to the wind but is not linear. Therefore, Stokes drift cannot simply be replaced or substituted by simply increasing the wind drift factor, which can cause errors in oil spill projections; (4) the Stokes drift velocity obtained from the two-dimensional wave spectrum makes the oil spill simulation more accurate. 相似文献
2.
Effect of Stokes drift on upper ocean mixing 总被引：1，自引：0，他引：1
Stokes drift is the main source of vertical vorticity in the ocean mixed layer. In the ways of Coriolis - Stokes forcing and Langmuir circulations, Stokes drift can substantially affect the whole mixed layer. A modified Mellor-Yamada 2. 5 level turbulence closure model is used to parameterize its effect on upper ocean mixing conventionally. Results show that comparing surface heating with wave breaking, Stokes drift plays the most important role in the entire ocean mixed layer, especially in the subsurface layer. As expected, Stokes drift elevates both the dissipation rate and the turbulence energy in the upper ocean mixing. Also, ilffluence of the surface heating, wave breaking and wind speed on Stokes drift is investigated respectively. Research shows that it is significant and important to assessing the Stokes drift into ocean mixed layer studying. The laboratory observations are supporting numerical experiments quantitatively. 相似文献
3.
Hidekazu Yasuda 《Journal of Oceanography》2009,65(4):455-476
Time-dependent wind drift currents in a basin with finite depth have been solved analytically in order to understand their
fundamental behavior in coastal waters. The drift currents due to the land/sea breeze, as a typical example of time-dependent
winds, have been examined with attention to the manner of their oscillation in their vertical profiles. The theoretical analysis
indicates that the drift current due to the land/sea breeze might be amplified effectively around the southern part of Japan,
where the oscillating period of the wind is near to the inertial period. The analysis of the physical process of the drift
current reveals the following two important aspects: the Ekman boundary layer in a rotating frame is physically consistent
with the Stokes boundary layer due to oscillating currents in an inertial frame, and so the inertial motion due to the wind
is dispersed to the deeper level by the vertical viscosity in a rotating frame. The harmonic analysis was performed for the
residual data after removal of the four main tidal constituents, M2, S2, K1 and O1, from the raw data observed in Suonada
sound, the Seto Inland Sea. The feature of the analytically solved drift currents corresponded well to the observed picture.
The vertical viscosity in this field has been estimated at 10−3 m2/s by adjusting the harmonically analytical result of the observed data to the vertical profile of the analytically solved
drift current. 相似文献
4.
Jin-Bao Song 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(5):659-671
The response of near-surface current profiles to wind and random surface waves are studied based on the approach of Jenkins [1989. The use of a wave prediction model for driving a near surface current model. Dtsch. Hydrogr. Z. 42, 134–149] and Tang et al. [2007. Observation and modeling of surface currents on the Grand Banks: a study of the wave effects on surface currents. J. Geophys. Res. 112, C10025, doi:10.1029/2006JC004028]. Analytic steady solutions are presented for wave-modified Ekman equations resulting from Stokes drift, wind input and wave dissipation for a depth-independent constant eddy viscosity coefficient and one that varies linearly with depth. The parameters involved in the solutions can be determined by the two-dimensional wavenumber spectrum of ocean waves, wind speed, the Coriolis parameter and the densities of air and water, and the solutions reduce to those of Lewis and Belcher [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans. 37, 313–351] when only the effects of Stokes drift are included. As illustrative examples, for a fully developed wind-generated sea with different wind speeds, wave-modified current profiles are calculated and compared with the classical Ekman theory and Lewis and Belcher's [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans 37, 313–351] modification by using the Donelan and Pierson [1987. Radar scattering and equilibrium ranges in wind-generated waves with application to scatterometry. J. Geophys. Res. 92, 4971–5029] wavenumber spectrum, the WAM wave model formulation for wind input energy to waves, and wave energy dissipation converted to currents. Illustrative examples for a fully developed sea and the comparisons between observations and the theoretical predictions demonstrate that the effects of the random surface waves on the classical Ekman current are important, as they change qualitatively the nature of the Ekman layer. But the effects of the wind input and wave dissipation on surface current are small, relative to the impact of the Stokes drift. 相似文献
5.
Global estimates of wind energy input to subinertial motions in the Ekman-Stokes layer 总被引：1，自引：0，他引：1
By incorporating the wave-induced Coriolis-Stokes forcing into the classical Ekman model, the wind energy input to the Ekman-Stokes
layer is investigated, with an emphasis on the surface wave effects when the direction of Stokes drift deviates from that
of wind stress. Theoretical analysis of the kinetic energy balance of the Ekman-Stokes layer shows that the total wind energy
input consists of the direct wind energy input and the wave-induced energy input. Details of the direct wind and wave-induced
energy input are discussed. Based on the ECMWF ERA-40 Re-Analysis wind stress and surface wave data, the global total wind
energy input to subinertial motions in the Ekman-Stokes layer is estimated at 2.19 TW, including 0.26 TW (12%) wave-induced
energy input and 1.93 TW (88%) direct wind energy input. The effect of sea-ice coverage on the energy input to the Ekman-Stokes
layer is also considered. It is shown that the global total energy input could be overestimated by 0.08 TW (about 4%) without
taking the sea-ice coverage into account. 相似文献
6.
Joseph M. Bishop 《Ocean Engineering》1979,6(3):273-284
A simple operationally oriented model of surface wind-driven currents is presented in which Lagrangian surface drift is assumed to be composed of a linear combination of a wave-induced Stokes drift plus a wind-driven Ekman drift. Using this approach, Stokes drift accounts for as much as half the total surface current magnitude. The Lagrangian current is predicted to be about 3.5% of the 10 m wind magnitude directed in the sense of an Ekman spiral about a 20° deviation angle. For comparison to this model, a second model is proposed that accounts for the interaction of Stokes current and Coriolis force. An inference drawn from this model is that there is only weak coupling between Coriolis force and Stokes drift. Such a conclusion, if correct, leads one to focus attention on the Lagrangian model for operationally oriented current estimates. Results of the Lagrangian model agree with observations of investigators for currents at the air-sea interface and may have application in the movement f oil slicks or surface drifters at sea under fetch or duration limited sea states. 相似文献
7.
基于Jenkins(1989)建立的包含Stokes漂流、风输入和波耗散影响的修正Ekman模型,采用Paskyabi等(2012)使用的推广的Donelan等(1987)中的谱和波耗散函数,并利用Paskyabi等(2012)中修正方法给出的包含高频波的风输入函数,在粘性不依赖于水深及粘性随深度线性变化的条件下,研究了包含高频毛细重力波的随机表面波对Stokes漂流和Song(2009)导出的波浪修正定常Ekman流解的影响。结果表明高频表面波使Stokes漂流在海表面剪切加强,对定常Ekamn流解的影响通常不能忽略,但对Ekman流场的角度偏转影响很小。最后,将考虑高频表面波尾谱影响所估算的定常Ekman流解与已有观测结果以及经典Ekman解进行了比对分析。 相似文献
8.
本文通过理想化的外部强迫以及海洋站点实测数据驱动普林斯顿海洋模式来研究海洋热力学效应和斯托克斯漂流对上混合层数值模拟的影响。在Mellor-Yamada湍流闭合方案中，经常出现夏季海表面温度偏暖和混合层深度偏浅的模拟误差。实验表明，斯托克斯漂流在冬季和夏季均能增强湍流动能，加深混合层深度。这种效应可以改善夏季的模拟结果，但与观测数据相比，将增大冬季混合层深度的模拟误差。斯托克斯漂流可以通过增强湍动能来加深混合层深度。结果表明，将斯托克斯漂流与冷皮层和暖层对上部混合层的热效应相结合，可以正确地模拟混合层深度。在夏季，海洋冷皮层和暖层通过“阻挡结构”和双温跃层结构模拟出更真实的上混合层变化。在冬季，海洋热力学效应通过增强上层海洋层结平衡了斯托克斯漂流的影响，并且由斯托克斯漂流引起的过度混合被校正。 相似文献
9.
Bohai Sea oil spill model: a numerical case study 总被引：2，自引：0，他引：2
Zengan Deng Ting Yu Xiaoyi Jiang Suixiang Shi Jiye Jin Linchong Kang Feng Zhang 《Marine Geophysical Researches》2013,34(2):115-125
An operational Bohai Sea oil spill serving module (BSOSSM) that can provide users with trajectory and movement information of the released oil is developed for the purpose of informing mitigation of oil spill incidents in the Bohai Sea, China. BSOSSM is one of the serving modules that had been integrated in China digital ocean prototype system, a marine information platform for managing, displaying and disseminating all the data investigated by China 908 Program. The oil spill trajectory is calculated by an oil spill model (OSM), which serves as a component in BSOSSM. The impacts of wind, current, as well as Stokes drift on oil spill trajectory are studied by sensitivity experiments conducted using OSM. Simulation results indicate that wind forcing is the most important factor in controlling the oil trajectory at the sea surface in Bohai Sea, whereas current and Stokes drift play relatively less important roles. However, because the direction of waves generally follows that of the wind, Stokes drift does lead to an increase in oil drift and spreading velocity. Case studies of the Penglai 19-3 oil spill incident (June 2011) and Xingang oil spill (April 2005) demonstrate that OSM can generally reproduce the oil spreading, and is therefore capable of supporting the emergency response of future oil spills in the Bohai Sea through BSOSSM. 相似文献
10.
M.A.C. Teixeira 《Ocean Modelling》2011,36(1-2):149-162
The structure of turbulence in the ocean surface layer is investigated using a simplified semi-analytical model based on rapid-distortion theory. In this model, which is linear with respect to the turbulence, the flow comprises a mean Eulerian shear current, the Stokes drift of an irrotational surface wave, which accounts for the irreversible effect of the waves on the turbulence, and the turbulence itself, whose time evolution is calculated. By analysing the equations of motion used in the model, which are linearised versions of the Craik–Leibovich equations containing a ‘vortex force’, it is found that a flow including mean shear and a Stokes drift is formally equivalent to a flow including mean shear and rotation. In particular, Craik and Leibovich’s condition for the linear instability of the first kind of flow is equivalent to Bradshaw’s condition for the linear instability of the second. However, the present study goes beyond linear stability analyses by considering flow disturbances of finite amplitude, which allows calculating turbulence statistics and addressing cases where the linear stability is neutral. Results from the model show that the turbulence displays a structure with a continuous variation of the anisotropy and elongation, ranging from streaky structures, for distortion by shear only, to streamwise vortices resembling Langmuir circulations, for distortion by Stokes drift only. The TKE grows faster for distortion by a shear and a Stokes drift gradient with the same sign (a situation relevant to wind waves), but the turbulence is more isotropic in that case (which is linearly unstable to Langmuir circulations). 相似文献
11.
J. UOTILA 《地球，A辑:动力气象学与海洋学》2001,53(1):112-128
The wind dependence of sea‐ice motion was studied on the basis of ice velocity and wind observations, and weather model output. The study area was a transition zone between open water and the ice‐covered ocean in the northern Baltic Sea. In the centre of the basin the sea‐ice motion was highly wind‐dependent and the linear relationship between the wind and the drift velocities explained 80% of the drift's variance. On the contrary, the wind‐drift dependence was low near the coast. The wind‐drift coherence was significant over a broader frequency range in the central part of the basin than for the coastal drift. The ice motion was simulated by a numerical model forced with five types of wind stress and with two types of current data, and the outcome was compared with the observed buoy drift. The wind and the wind‐induced surface current were the main factors driving the ice in the basin's centre, while internal ice stresses were of importance in the shear zone near the fast ice edge. The best wind forcing was achieved by applying a method dependent on atmospheric stability and ice conditions. The average air–ice drag coefficient was 1.4×10−3 with the standard deviation of 0.2×10−3 . The improvement brought about by using an accurate wind stress was comparable with that achieved by raising the model grid resolution from 18 km to 5 km. 相似文献
12.
The continuous research and improvement of ocean modelling helps to provide a more sustainable development of coastal and offshore regions. This paper focuses on ocean modelling at the NW Mediterranean using the POLCOMS–WAM model with new developments. The Stokes’ drift effect on currents has been included and the distribution of surface stress between waves and currents has also been considered. The system is evaluated in the NW Mediterranean and an evaluation of different forcing terms is performed. The temperature and salinity distributions control the main patterns of the Mediterranean circulation. Currents are typically small and therefore the modification of waves due to the effect of currents is minimal. However, the wave induced currents, mainly caused by a modified wind drag due to waves, produce changes that become an important source of mass transport. POLCOMS was able to reproduce the main Mediterranean features, its coupling with WAM can be a very useful tool for ocean and wave modelling in the Mediterranean and other shelf seas. 相似文献
13.
漂浮于自由水面的污染物的的迁移、扩散会受到天然随机海浪的影响。之前的研究（以Herterich和Hasselmann（1982）为代表）普遍认为，随机波浪作用下的斯托克司漂移速度会引起水面污染物的离散，这个离散甚至有可能跟风和海流引起的离散同一量级。本研究就随机波浪作用下的斯托克司漂移速度是否会引起水面漂移物的离散进行理论和试验探讨。从理论推导可知，随机波浪下的质量输移速度是个定常分量，因此它不会随时间变化而引起水面漂移物的离散。随后我们在实验室水槽中进行了漂移物在随机波浪（P-M谱）作用下的漂移过程的测量。试验结果也印证了随机波浪作用下的斯托克司漂移速度不会引起水面漂移物离散的结论。 相似文献
14.
将波浪辐射应力,特别是地转意义下的波浪辐射应力引入海流数值模式POM(princeton ocean model),在渤海海域进行了初步的数值研究。在目前的数值分析中仅考虑了波浪辐射应力的横向分量(也是最重要的分量)。在POM模式中引入非地转和地转意义下的波浪辐射应力两种方案,并与原模式直接运行(即不考虑波浪辐射应力)的结果进行比较。比较显示,波浪辐射应力,特别是地转意义下的波浪辐射应力对海流模式结果的影响不容忽略。在海浪场存在的条件下,由风应力和地转意义下浪致作用力共同作用产生的海流强度应比理论上Ekman漂流的强度大,尤其是在浪致作用力显著的表层,表层流将明显增强,且不会完全符合Ekman漂流理论的转向规律。 相似文献
15.
Improving the estimate of wind energy input into the Ekman layer within the Antarctic Circumpolar Current 总被引：2，自引：2，他引：0
ZHANG Yuming WU Kejian ZHANG Xiaoshuang BI Fan SONG Zhaoyang LIU Shouhua 《海洋学报(英文版)》2013,32(3):19-27
Based on the data and method offered by Liu et al. (2009), the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current (ACC) area are reestimated since the results of the former have been proved to be underestimated. And the result shows that the total rate of energy input into the Ekman-Stokes layer within the ACC area is 852.41 GW, including 649.75 GW of direct wind energy input (76%) and 202.66 GW of Stoke drift-induced energy input (24%). Total increased energy input, due to wave-induced Coriolis-Stokes forcing added to the classical Ekman model, is 52.05 GW, accounting for 6.5% of the wind energy input into the classical Ekman layer. The long-term variability of direct wind and Stokes drift-induced energy inputs into the Ekman layer within the ACC is also investigated, and the result shows that the Stokes drift hinders the decadal increasing trend of direct wind energy input. Meanwhile, there is a period of 4-5 a in the energy spectrums, as same as the Antarctic circumpolar wave. 相似文献
16.
The paper is concerned with the evaluation of the drift current parameters derived through the use of an analytical model.
In this model, effective when stratification is stable and indifferent, the vertical turbulence coefficient profile is prescribed
by the power function, and hydrodynamic quantities are prescribed using the external parameters of the problem (wind stress,
the Coriolis parameter, and the dimensionless stratification parameter). Model data are compared with the observations of
the upper mixed layer in the vicinity of the oceanic Station C, conducted during one year. It is shown that, under the spring-summer-time
warming conditions, the model at issue is capable of adequately simulating the upper ocean layer dynamics.
Translated by Vladimir A. Puchkin. 相似文献
17.
破波带内外都有质量输移流存在，其对破波带内污染物输移有怎样的影响，需要进一步深入研究。本文基于实验以及考虑质量输移流的对流扩散数学模型研究了平直斜坡上破波带内质量输移流对污染物输移影响。数学模型包括波浪模型、近岸流模型以及对流扩散模型。首先建立了破波带内污染物输移数学模型，其中波浪场基于波能守恒方程来计算，波导流场基于Longuet-Higgins提出的辐射应力模拟，污染物对流扩散方程中考虑了质量输移流的影响，并利用算例验证该数学模型。其次简要介绍了平直斜坡上破波带内污染物输移实验，并分析了污染物输移特性。连续投放污染物会形成污染带，本文分析了两种波况下不同时刻污染带与岸线夹角的变化，以及污染物在垂直岸线和沿岸线方向的输移速度，结果表明对两种波况来说在初始10-40s污染团向岸线方向输移速度分别约为0.05m/s、0.017m/s，之后速度分别减小为0.001m/s、0.011m/s。数值模拟结果与实验结果比较表明：考虑质量输移流的模拟结果与实验更为吻合。因而，通过实验以及数模研究表明破波带内质量输移流对破波带内污染物在垂直岸线方向的输移有重要影响，而对沿岸方向的输移则影响较小。 相似文献
18.
19.
The paper provides a simple analytical tool which can be used to give estimates of the mean value and the standard deviation of the Stokes drift for sea states. This is achieved by providing bivariate distributions of significant wave height with surface Stokes drift as well as with volume Stokes transport. These Stokes drift parameters are defined in terms of significant wave height and characteristic wave periods. Also bivariate distributions of spectral peak period and these two Stokes drift parameters are provided. The paper presents statistical aspects of the Stokes drift parameters, such as the conditional expected values and the conditional variances for given significant wave height, as well as examples of results corresponding to typical field conditions. The present analytical results can be used to make assessment of Stokes drift based on e.g. global wave statistics. 相似文献
20.
In this article, the authors study the influence of a constant wind on the displacement of a vortex. The well known Ekman current develops in the surface layer and is responsible for a transport perpendicular to the wind: the Ekman drift.An additional process is, however, evidenced, whose importance is as strong as the Ekman drift. There indeed exists a curl of the wind-driven acceleration along isopycnic surfaces when they are spatially variable (they enter and leave the depth where the wind stress acts), which generates potential vorticity anomalies. This diabatic effect is shown to generate potential vorticity anomalies which acts on the propagation of vortical waves and non linear vortices.It is shown that this effect drastically reduces the effect of the Ekman drift for linear waves and surface intensified vortices, while extending its effect to subsurface vortices. It also generates along wind propagation, whose sign depends on the vortex characteristics. 相似文献