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1.
N. A. Panteleev 《Physical Oceanography》1999,9(6):405-416
We present an analytic survey of a series of works devoted to the direct methods for the investigation of turbulence in natural
basins originated under the guidance of A. G. Kolesnikov in the 50s. We describe the principal results of the early stage
which formed the basis for future investigations. The main scientific directions of the latest period are also considered
from the viewpoint of the development of Kolesnikov's ideas: investigation of the processes of generation and energy supply
of small-scale turbulence, relationship between turbulence and the fine vertical structure and internal waves, and the mechanisms
of vertical turbulent exchange in the ocean. A model of vertical exchange under the conditions of intermittent “source” turbulence
is distinguished. We also discuss the directions of development and prospects of the investigation of turbulence.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
2.
A. A. Slepyshev 《Izvestiya Atmospheric and Oceanic Physics》2007,43(5):649-654
In the Boussinesq approximation, topographic waves entrained by a sloping bottom are considered with allowance for turbulent viscosity and diffusion. The mean flows induced by a wave through nonlinearity are determined. The turbulent exchange coefficients are expressed in terms of the density of turbulent energy by using the relations of the semiempirical theory of turbulence. The equation for boundary-layer wave solutions and the equation of turbulent energy balance are solved jointly, which makes it possible to determine the vertical distribution of the density of turbulent energy in the area of the given wave. In the diffusion approximation, the vertical distribution of the concentration of wave-suspended sediments is obtained for the case when the tangential bottom stress exceeds the critical values corresponding to the start of sediment motion. 相似文献
3.
The influence of high vertical velocity gradients in the Black Sea Rim Current on the intensity of the vertical turbulent exchange is demonstrated on the basis of numerical modeling based on CTD data. The vertical turbulent exchange is confirmed by the anomalous distribution of the hydrochemical parameters in the redox layer. A system of equations for the kinetic energy of the turbulence and dissipation rate (k-? model) is used for the calculation of the coefficient of the vertical turbulent viscosity (diffusivity). 相似文献
4.
Takashige Sugimoto 《Journal of Oceanography》1974,30(6):260-270
The treatment of diffusion due to the tidal current in the near-shore ocean, and the similitude in the hydraulic model experiment are studied.In broad and shallow tidal bays and in the coastal seawaters near irregular boundaries, horizontal eddy-currents induced geometrically and turbulence caused by their cascading have predominant effect on dispersion of river and waste waters. These turbulent diffusion processes are similarly reproduced in the Froude models of turbulent resume, by adding the similitude for the self-similar structure of the spectral density of turbulence, or the eddy diffusivity. The similitude means to take the scale ratios of the time and the vertical length as the two-thirds power of the scale ratio of the horizontal length.Similitudes are also derived for the system of the gravitational circulation, the stratification and the salt-mass transport in partially and well-mixed estuaries. Generally, the vertical eddy diffusivity must be exaggerated by a half power of the model distortion externally by some methods of agitation. When the tidal bay is broad and very shallow, the Rayleigh number and the Hansen number are small, and the effect of density current and stratification on the flushing is small. Instead the effect of local eddies, geometrically induced tidal residual circulations become predominant. In this special case, there is no need to satisfy the similitude for density difference and vertical shear effects on dispersion. 相似文献
5.
海浪破碎对海洋上混合层中湍能量收支的影响 总被引：2，自引：1，他引：2
海浪破碎产生一向下输入的湍动能通量,在近海表处形成一湍流生成明显增加的次层,加强了海洋上混合层中的湍流垂向混合。为了研究海浪破碎对混合层中湍能量收支的影响,文中分析了海浪破碎对海洋上混合层中湍流生成的影响机制,采用垂向一维湍封闭混合模式,通过改变湍动能方程的上边界条件,引入了海浪破碎产生的湍动能通量,并分别对不同风速下海浪破碎的影响进行了数值研究,分析了混合层中湍能量收支的变化。当考虑海浪破碎影响时,近海表次层中的垂直扩散项和耗散项都有显著的增加,该次层中被耗散的湍动能占整个混合层中耗散的总的湍能量的92.0%,比无海浪破碎影响的结果增加了近1倍;由于平均流场切变减小,混合层中的湍流剪切生成减小了3.5%,形成一种存在于湍动能的耗散和垂直扩散之间的局部平衡关系。在该次层以下,局部平衡关系与壁层定律的结论一致,即湍动能的剪切生成与耗散相平衡。研究结果表明,海浪破碎在海表产生的湍动能通量影响了海洋上混合层中的各项湍能量收支间的局部平衡关系。 相似文献
6.
Assessment of turbulence closure models for resonant inertial response in the oceanic mixed layer using a large eddy simulation model 总被引：1，自引：0，他引：1
Large eddy simulation (LES) of the resonant inertial response of the upper ocean to strong wind forcing is carried out; the
results are used to evaluate the performance of each of the two second-order turbulence closure models presented by Mellor
and Yamada (Rev Geophys Space Phys 20:851–875, 1982) (MY) and by Nakanishi and Niino (J Meteorol Soc Jpn 87:895–912, 2009) (NN). The major difference between MY and NN is in the formulation of the stability functions and the turbulent length scale,
both strongly linked with turbulent fluxes; in particular, the turbulent length scale in NN, unlike that in MY, is allowed
to decrease with increasing density stratification. We find that MY underestimates and NN overestimates the development of
mixed layer features, for example, the strong entrainment at the base of the oceanic mixed layer and the accompanying decrease
of sea surface temperature. Considering that the stability functions in NN perform better than those in MY in reproducing
the vertical structure of turbulent heat flux, we slightly modify NN to find that the discrepancy between LES and NN can be
reduced by more strongly restricting the turbulent length scale with increasing density stratification. 相似文献
7.
Effects of Stokes production on summer ocean shelf dynamics 总被引：1，自引：0，他引：1
A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman transport in an idealized shelf region in summer.The energy input from SP is parameterized and included into the Mellor-Yamada turbulence closure submodel.Results reveal that the intensity of wind-driven upwelling fronts near the sea surface is weakened by the SP-associated turbulent kinetic energy input.The vertical eddy viscosity coefficient in the surface boundary layer is enhanced greatly owing to the impact of SP,which decreases the alongshore velocity and changes the distribution of upwelling.In addition,the SP-induced mixing easily suppresses the strong stratification and significantly increases the depth of the upper mixed layer（ML） under strong winds. 相似文献
8.
A finite-difference system of motion equations for a baroclinic ocean with an irregular bottom is developed on the basis of the box method and the method of indefinite coefficients. The numerical model is shown to possess the property of conserving momentum, mass, and energy. In the case of barotropic motion, the finite-difference scheme retains potential enstrophy. A numerical experiment on the adaptation of hydrophysical fields in the Equatorial Atlantic in summer was carried out within the framework of the model developed. We managed to obtain a series of features of the equatorial circulation when the coefficients of turbulent exchange and diffusion were small enough.Translated by Mikhail M. Trufanov. 相似文献
9.
S. N. Moshonkin V. B. Zalesny A. V. Gusev R. Tamsalu 《Izvestiya Atmospheric and Oceanic Physics》2014,50(1):49-60
A physical formulation of the problem is considered. A mathematical model and a numerical algorithm of the turbulence model as part of the ocean circulation model for simulations for decades are formulated. The model is based on the evolution equations for turbulent kinetic energy (TKE) and the frequency of its viscous dissipation. A numerical solution algorithm for both the circulation model and the turbulence model is based on implicit schemes of splitting with respect to physical processes and geometric coordinates. For the turbulence model, this provided analytical solutions at a splitting step related to TKE generation and dissipation. Numerical experiments have been performed with a model of the joint circulation of the North Atlantic, the Arctic Ocean, and the Bering Sea to reproduce the annual cycle and synoptic disturbances of ocean characteristics. The model has a resolution of 0.25° in latitude and longitude and 40 levels in the vertical, which are compressed toward the surface to reproduce the process of developed turbulence better. The results are compared with observations and with the results of simulations using traditional parameterizations of the upper ocean mixing. It is shown that the model reproduces ocean characteristics correctly, only slightly increasing the computation time in comparison with simple parameterizations. Spatial and temporal characteristics of turbulence are analyzed. 相似文献
10.
M. Mohandesi Namin A. A. Bidokhti A. Karami Khaniki I. Hasan Zadeh M. Torabi Azad 《Marine Geodesy》2016,39(2):141-164
Complex process of turbulent mixing in Persian Gulf that is a semi-closed sea makes it a good media to test the performance of different turbulence schemes. In this research, we used the 3D ocean model COHERENS (COupled Hydrodynamical Ecological model for REgioNal Shelf seas) for the Persian Gulf with the open boundary in the Hormuz Strait. Of the turbulence schemes for the vertical diffusion available in the COHERENS, we tested four models to investigate the hydrodynamic characteristics of the Persian Gulf. The results show that all of the schemes presented the sea surface salinity (SSS) distribution rather accurately but the k-l and flow-dependent models results have better agreements with observations. The most noticeable difference between the results of four schemes is the differences found in the simulation of turbulent parameters. The turbulent closure schemes generally provide better results, but the algebraic schemes show turbulent parameters far from reality and they do not show substantial changes with time. Generally, the vertical structures of turbulence in the water basins and parameterization of turbulence in water column is very sensitive to the selection of the type of the turbulence scheme. However, large-scale structures that take place within the inflow and outflow area are approximately quasi-horizontal, and the vertical small-scale turbulence does not affect them as much. As a result, they show less sensitivity to the performance of various turbulence schemes. 相似文献
11.
12.
深层叶绿素最大值(Deep Chlorophyll Maximum, DCM)现象的数值模拟是研究海洋表层生态系统和全球碳循环的重要组成部分之一。但是由于自身的复杂性和观测的局限性,数值模式中物理参数的不确定性给模拟结果带来了一定程度的误差。其中,垂向湍流扩散系数(vertical turbulence diffusion)是模式所包含的物理参数中很难直接通过观测来确定的参数,它在模式中的来源和取值往往具有很大的不确定性。本文通过条件非线性最优(参数)扰动(Conditional nonlinear optimal perturbation related toparameter, CNOP-P)方法,研究了垂向湍流扩散系数的不确定性对模式模拟结果的影响。我们发现,垂向湍流扩散系数对 DCM 模拟产生最大影响的 CNOP 型扰动位于生产力层的上半部分。并且,去掉生产力层内湍流扩散系数的误差,模式模拟的改进程度最高达到了 80%。可见,垂向湍流扩散对生态系统的发展和保持起着极其重要的作用,改进垂向湍流扩散系数的不确定性,对 DCM 的数值模拟有着重要意义。 相似文献
13.
14.
利用2019年7月在长江口科学考察实验研究夏季航段(NORC2019-03-02)中获得的MSS90L湍流剖面仪的直接观测数据,本文计算并分析了该断面的湍动能耗散率ε和垂向湍扩散系数KZ的分布情况。湍动能耗散率的大小为1.72×10?10～2.95×10?5 W/kg;垂向湍扩散系数的大小为3.24×10?7～4.55×10?2 m2/s。湍动能耗散率和垂向湍扩散系数的分布相似,均为上层最强,底层次之,中层最弱。上层由于风应力的作用,使得湍动能耗散率和垂向湍扩散系数较大;温跃层处层化较强,抑制了湍动能的耗散和垂向上的湍混合。盐度锋面的次级环流会促使低盐水团脱离,锋面引起的垂向环流会加强海洋的湍混合。低盐水团与外界的能量交换较少,湍动能耗散率较弱。长江口海区存在明显的上升流和下降流,它们是由锋面的次级环流产生的;上升流和下降流的存在促进湍动能的耗散与湍混合。 相似文献
15.
The upper ocean response to a moving typhoon 总被引：1，自引：0，他引：1
The upper ocean response to the translation speed of typhoons is studied using a three-dimensional primitive equation model.
Similar models studied previously have applied stability criteria rather than the diffusion term to simulate the vertical
mixing process. This study retains the diffusion term and uses the level-2 turbulence closure scheme to estimate the vertical
eddy viscosity. The model results indicate that in the forced period, the mixed-layer temperature decrease is greater for
a slow-moving storm due to stronger upwelling caused by the longer residence time. A fast-moving storm can attain a similar
cooling intensity in the wake period if its residence time allows the wind to resonate with the current. The significant downward
momentum diffusion and advection in the first few inertial periods of these events leads to strong, persistent inertial pumping
throughout the upper ocean in the wake period. The mixed layer is further cooled by turbulent mixing supported by vertical
current shears. Meanwhile, the upper thermocline exhibits a compensating temperature increase. The vertical transfer magnitude
and penetration scale are smaller in the slow-moving case, when the inertial motion decays rapidly. The model results also
indicate that the dominant cooling process can be inferred from the non-dimensional storm speed. However, this value may be
misleading for rapidly moving storms in which the current response is so distant from the storm that little wind work is performed
on the ocean. 相似文献
16.
To assess each of the two possible mechanisms responsible for the fortnightly modulation of semi-enclosed basin–ocean water
exchange (‘density tides’), a set of numerical experiments is carried out using a vertically two-dimensional numerical model
with realistic situations in Puget Sound in mind. It is found that, although the localized vertical viscosity (or the localized
vertical diffusivity) enhanced in the entrance sill region primarily controls the bottom-water transport (or the bottom-water
density) during spring tides, it does not lead to any appreciable variations of bottom-water density (or bottom-water transport).
This indicates that the fortnightly modulation of vertical viscosity and that of vertical diffusivity both play important
roles in creating density tides. In the real ocean, the vertical viscosity and diffusivity are enhanced simultaneously during
spring tides, so that it is difficult to discriminate between both effects on density tides. This causes the widespread misunderstanding
that density tides are mainly caused by the decreased advection of dense bottom-water from outside due to the enhanced vertical
viscosity during spring tides. 相似文献
17.
S. G. Demyshev 《Physical Oceanography》1990,1(6):487-494
A numerical model for ocean thermohydrodynamics is considered whose difference scheme permits a number of linear and quadratic invariants to be retained. The model is used as the basis for adaptive computations in the Equatorial Atlantic ocean. Model equations were integrated using different values of the coefficients of diffusion and momentum turbulent exchange. It has been shown that variations of these coefficients strongly influence the intensity of jet streams and the structure of the thermocline.Translated by Vladimir A. Puchkin. 相似文献
18.
研究建立渤海海域三维斜压场的湍流能量模型。对计算网格无法分辩的湍流运动，引入湍流能量求得垂向动量、质量及能量交换系统，从而形成封闭的湍流运动方程组。定量地计算了湍流能量、湍流速度及有风、无风状况下湍流能量的垂直分布等，探讨了湍流运动对潮波运动的影响。 相似文献
19.
湍流扩散过程导致的硝酸盐垂向输运对海水表层的浮游植物生长和初级生产力的大小有着重要影响。本文基于2018年夏季黄、东海水文环境、硝酸盐浓度和湍动能耗散率的同步、原位数据,分析了海域温度、盐度和硝酸盐的空间分布特征,结果表明营养盐含量丰富的黄海冷水团、长江冲淡水、东海北部底层混合水与黑潮次表层水是影响研究海域硝酸盐分布的主要水团。利用垂向湍扩散硝酸盐通量公式,计算了三个选定断面上的硝酸盐垂向扩散通量,其高值区与湍流扩散系数的高值区的位置基本一致。针对存在明显硝酸盐跃层的站位,计算得到跨硝酸盐跃层的垂向通量FND的范围在-9.78—36.60mmol/（m2·d）之间,在黄海冷水团区,夏季温跃层限制了该区营养盐向近表层的湍流垂向扩散;东海北部底层混合水区,湍流垂向扩散向上层补充了大量硝酸盐,促进了跃层之上浮游植物的生长;黑潮次表层水影响海区,夏季中层水体混合较弱,跨跃层的垂向通量也普遍偏低。开展硝酸盐垂向扩散通量的计算与分析,对进一步明确营养盐的输运机制有着重要研究意义。 相似文献
20.
Shelf seas such as the North Sea and the Baltic Sea are characterised by spatially and temporally varying stratification that is highly relevant for their physical dynamics and the evolution of their ecosystems. Stratification may vary from unstably stratified (e.g., due to convective surface cooling) to strongly stratified with density jumps of up to 10 kg/m3 per m (e.g., in overflows into the Baltic Sea). Stratification has a direct impact on vertical turbulent transports (e.g., of nutrients) and influences the entrainment rate of ambient water into dense bottom currents which in turn determine the stratification of and oxygen supply to, e.g., the central Baltic Sea. Moreover, the suppression of the vertical diffusivity at the summer thermocline is one of the limiting factors for the vertical exchange of nutrients in the North Sea. Due to limitations of computational resources and since the locations of such density jumps (either by salinity or temperature) are predicted by the model simulation itself, predefined vertical coordinates cannot always reliably resolve these features. Thus, all shelf sea models with a predefined vertical coordinate distribution are inherently subject to under-resolution of the density structure.To solve this problem, Burchard and Beckers (2004) and Hofmeister et al. (2010) developed the concept of vertically adaptive coordinates for ocean models, where zooming of vertical coordinates at locations of strong stratification (and shear) is imposed. This is achieved by solving a diffusion equation for the position of the coordinates (with the diffusivity being proportional to the stratification or shear frequencies). We will show for a coupled model system of the North Sea and the Baltic Sea (resolution ∼ 1.8 km) how numerical mixing is substantially reduced and model results become significantly more realistic when vertically adaptive coordinates are applied. We additionally demonstrate that vertically adaptive coordinates perform well in simulating the two dynamically different regions North Sea and Baltic Sea with a single parameter set.An analysis of the computational overhead of the adaptive coordinates indicates an increase of 5–8% in runtime. This is still less expensive than adding more sigma-layers to reduce spurious numerical mixing. 相似文献