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1.
In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity and pure gravity wave energy are discussed by using the WKB approximation method.The conditions for conservation of wave energy,generalized wave action and wave enstrophy are obtained.The necessary condition of instability for internal gravity waves and the equation governing the refraction of wave rays are derived.Two types of critical levels are given.Finally,the wave rays for different distributions of stratification are calculated by using the fourth-order Runge-Kutta method. 相似文献
2.
Walter C. Dragani Paula B. Martin Guadalupe Alonso Jorge O. Codignotto Bárbara E. Prario Guido Bacino 《Climatic change》2013,121(4):649-660
Several works reported wind-wave climate changes at Buenos Aires Province continental shelf. The aim of this work is to investigate the impact of these changes in the coastal processes of the region. This study is carried out by means of visual wave parameters gathered at the surf zone of Pinamar and by a conveniently implemented and validated numerical wave model (SWAN). Numerical results corresponding to a grid point located 30 km off Pinamar show a significant increase of wave heights from the S and SSE directions and in the frequency of occurrence of waves coming from the S, SSE and E. It is shown that these slight offshore appreciated trends would not have significant effects on the breaker heights observed at the surf zone at Pinamar. On the contrary, the slight positive trend observed offshore in the frequency of occurrence could be affecting the incidence of waves onshore, producing an increase in the number of cases of normal incidence at the surf zone and, consequently, a significant decrease in the alongshore wave energy flux assessed at Pinamar. This reduction in the alongshore wave energy flux could be responsible for some coastal changes detected in the region as, for instance, the remarkable shortening of Punta Rasa spit located 70 km northward Pinamar. 相似文献
3.
文中利用ＷＫＢ近似，讨论了非均匀层结对惯性重力内波和纯重力内波能量传播路径的影响，得到了波的能量密度，广义波作用密度，和广义拟能密度守恒的条件，导得了重力内波不稳定的必要条件，给出了在波的传播过程中控制波射线折射的方程，得到了两类不同的临界层，最后还利用四阶Ｒｕｎｇｅ－Ｋｕｔｔａ方法计算了不同层结分布下的波射线。 相似文献
4.
V. V. Novotryasov S. P. Zakharkov D. V. Stepanov 《Russian Meteorology and Hydrology》2016,41(8):564-568
The results are presented of hydrological studies in the coastal zone of the Sea of Japan in autumn in different years. It is revealed that the typical density stratification of water is formed there in autumn. The amplitudes are estimated of regular (with the periodicity of tidal harmonic M2) vertical displacements of isotherms in the intermediate layer and maximum values of flow velocity in the surface and bottom layers. It is demonstrated that temperature perturbations are induced at the shelf edge and propagate to the coastal zone with the velocity that is close to the velocity of the first mode of internal gravity waves with the frequency of the tidal harmonic M2. 相似文献
5.
Heat Flux in the Coastal Zone 总被引：5，自引：4，他引：1
L. Mahrt Dean Vickers Jim Edson Jielun Sun Jørgen Højstrup Jeffrey Hare James M. Wilczak 《Boundary-Layer Meteorology》1998,86(3):421-446
Various difficulties with application of Monin–Obukhov similarity theory are surveyed including the influence of growing waves, advection and internal boundary-layer development. These complications are normally important with offshore flow. The transfer coefficient for heat is computed from eddy correlation data taken at a mast two kilometres off the Danish coast in RASEX. For these coastal zone data, the thermal roughness length shows no well-defined relation to the momentum roughness length or roughness Reynolds number, in contrast to previous theories. The variation of the momentum roughness length is dominated by wave state. In contrast, the thermal roughness length shows significant dependence on wave state only for small values of wave age where the mixing is apparently enhanced by wave breaking. The development of thin internal boundary layers with offshore flow substantially reduces the heat transfer and thermal roughness length but has no obvious influence on momentum roughness length. A new formulation of the thermal roughness length based on the internal boundary-layer depth is calibrated to the RASEX data. For the very stable case, the turbulence is mainly detached from the surface and existing formulations do not apply.As an alternative to adjusting the thermal roughness length, the transfer coefficient is related directly to the stability and the internal boundary-layer depth. This avoids specification of roughness lengths resulting from the usual integration of the non-dimensional temperature function. The resulting stability function is simpler than previous ones and satisfies free convection similarity theory without introduction of the gustiness factor. The internal boundary layer also influences the moisture transfer coefficient. 相似文献
6.
S. A. Myslenkov V. S. Arkhipkin A. V. Pavlova S. A. Dobrolyubov 《Russian Meteorology and Hydrology》2018,43(10):670-678
The results of wind wave hindcast for the Caspian Sea for the period of 1979–2017 are presented. The WAVEWATCHIII wave model and wind forcing from the NCEP/CFSR reanalysis are used. The modeling is performed on the unstructured grid with the spacing to 1 km in the coastal zone. Mean and extreme values of wave height, length, and period are provided. It is shown that the maximum height of waves of 3% probability of exceedance is 11.7 m. The interannual variability of wave parameters is analyzed. No unambiguous trend towards increase or decrease in the storm activity was revealed over the hindcasting period. 相似文献
7.
Discussed are the results of long-term hydrophysical studies carried out on the northeastern shelf of Sakhalin Island in the area of summer-autumn fattening of the Okhotsk-Korea population of grey whales. It is demonstrated that the inflow of water desalinated by the Amur River runoff and the coastal upwelling caused by the summer monsoon are of great importance for the hydrological regime in the given area. These phenomena are interrelated and depend on interannual variations of atmoispheric circulation. Presented are the results of studying the parameters of internal waves obtained using the anchored autonomous vertical system of measurement. Measured are the velocities of the orbital movement of water particles in the propagating nonlinear internal waves and the respective vertical displacements of water layers. Demonstrated are the peculiarities of the thermohaline structure of water under the slick formed on the sea surface by the internal wave. 相似文献
8.
In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity andpure gravity wave energy are discussed by using the WKB approximation method.The conditions for conservation ofwave energy,generalized wave action and wave enstrophy are obtained.The necessary condition of instability for inter-nal gravity waves and the equation governing the refraction of wave rays are derived.Two types of critical levels are giv-en.Finally,the wave rays for different distributions of stratification are calculated by using the fourth-orderRunge-Kutta method. 相似文献
9.
The mechanism of flattening of surface wind waves in the centimetre wavelength range under the action of internal waves and in the presence of surfactants is considered. It is shown that internal waves give rise to perturbations of surfactant concentration proportional to the orbital velocities of wave particles. Accordingly, the damping coefficient of centimetre wavelength ripples is also modulated. Evolution of the wind wave spectrum is described by the energy balance equation. In the right-hand side of the equation the Phillips excitation mechanism, the Miles mechanism with a nonlinear spectrum limitation, and the dissipation caused by a surface-active film are taken into account. Assuming that the energy source and sink balance of the wind wave spectrum over the centimetre wavelength range is local, relative spectra (contrasts) for the case of gentle breeze are calculated. It is shown that the spectral components of ripples in the slicks can be order less than the uperturbed spectrum values. 相似文献
10.
R. H. J. Grimshaw 《Dynamics of Atmospheres and Oceans》1985,9(2):85-120
We consider the three-dimensional reflection and diffraction properties of internal waves in a continuously stratified rotating fluid which are incident on the junction of a vertical slit and a half-space. This geometry is a model for submarine canyons on continental slopes in the ocean, where various physical phenomena embodying reflection and diffraction effects have been observed. Three types of incident wave are considered: (1) Kelvin waves in the slit (canyon); (2) Kelvin waves on the slope; and (3) plane internal waves incident from the half-space (ocean). These are scattered into Kelvin and Poincaré waves in the slit, a Kelvin wave on the slope and Poincaré waves in the half-space. Most of the discussion is centered around case (1). Various properties of the wave field are calculated for ranges of the parameters c/cot θ, γα and ƒ/ω where cot θ is the topographic slope, c is the internal wave ray slope, α is the canyon half-width, γ is the down-slope wave-number, ƒ is the Coriolis parameter and ω is the wave frequency. Analytical results are obtained for small γα and some approximate results for larger values of γα. The results show that significant wave trapping may occur in oceanic situations, and that submarine canyons may act as source regions for internal Kelvin waves on the continental slope. 相似文献
11.
12.
The dispersion relation is derived for long coastal trapped waves of sub‐inertial frequency that propagate along a single‐step continental shelf in a two‐layer fluid. When the internal (Rossby) deformation radius is smaller than the shelf width, we show that the dispersion relation can be factored exactly, giving two possible modes: i. an internal Kelvin wave modified by topography; ii. a continental shelf wave modified by the stratification. A detailed discussion of the eigen‐functions associated with each of these modes is presented. Then the shelf wave dispersion relation is plotted for parameters applicable to the Oregon‐Washington coast. Theoretical values for the periods and wavelengths predicted from these plots are shown to agree favorably with observed values for this region. 相似文献
13.
Yeli Yuan Lei Han Fangli Qiao Yongzeng Yang Ming Lu 《Dynamics of Atmospheres and Oceans》2011,51(1-2):55-74
A linearized instability analysis model with five unknowns was proposed to describe disturbance motions under general oceanic background conditions, including large-scale current shear, density stratification, frontal zone, and arbitrary topography. A unified linear theory of wavelike perturbations for surface gravity waves, internal gravity waves and inertial gravity waves was derived for the adiabatic case, and the solution was then found using Fourier integrals. In this theory, we discarded the assumptions widely accepted in the literature concerning derivations of wave motions such as the irrotationality assumption for surface gravity waves, the rigid-lid approximation for internal gravity waves, and the long-wave approximation for inertial gravity waves. Analytical solutions based on this theory indicate that the complex dispersion relationships between frequency and wave-number describing the propagation and development of the three types of wavelike perturbation motions include three components: complex dispersion relationships at the sea surface; vertical invariance of the complex frequency; and expressions of the vertical wave-number (phase). Classical results of both surface waves and internal waves were reproduced from the unified theory under idealized conditions. The unified wave theory can be applied in the dynamical explanation of the generation and propagation properties of internal waves that are visible in the satellite SAR images in the southern part of the China Seas. It can also serve as the theoretical basis for both a numerical internal-wave model and analytical estimation of the ocean fluxes transported by wavelike perturbations. 相似文献
14.
15.
A.V. Ivanov L.A. Ostrovsky I.A. Soustova L.Sh. Tsimring 《Dynamics of Atmospheres and Oceans》1983,7(4):221-232
Within the framework of the semiempirical theory of turbulence for stratified fluids some aspects of the problem of internal wave-turbulence interaction in the upper layer of the ocean are discussed. The conditions of amplification and sustaining of turbulence by internal waves are investigated. Stationary distributions of turbulent energy are found for a stratified fluid with a shear flow produced, for example, by a low-frequency internal wave. The internal wave damping due to both turbulent viscosity and turbulent diffusion in the thermocline is studied. For a two-layer model damping constant is determined as a function of the wave number. The variation of surface turbulence by internal waves is estimated and the role of this process in slick formation is considered. 相似文献
16.
The present and future role of coastal wetland vegetation in protecting shorelines: answering recent challenges to the paradigm 总被引：2，自引：0，他引：2
Keryn B. Gedan Matthew L. Kirwan Eric Wolanski Edward B. Barbier Brian R. Silliman 《Climatic change》2011,106(1):7-29
For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal
communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we
conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support
of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from
erosion, storm surge, and potentially small tsunami waves. In biophysical models, field tests, and natural experiments, the
presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated
and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland
vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale
regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation.
However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial
protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal
protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore
critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase
shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines
against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm
still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection. 相似文献
17.
Hideshi Hanazaki 《Dynamics of Atmospheres and Oceans》1996,23(1-4)
Three-dimensional flow of a linearly stratified Boussinesq fluid is studied numerically. The flow is assumed to be confined in a rectangular channel and internal waves are excited by bottom topography. Near resonance of the first vertical internal wave mode, it was found that the reflection of the internal wave at the sidewall is ‘abnormal’ in the sense that the reflection angle is larger than the incident angle and a third wave perpendicular to the sidewall is generated. The waves become straight crested (two-dimensional) as this third wave becomes longer. The whole mechanism is similar to the ‘Mach reflection’ observed in the general stratified fluid in which the usual solitary waves are generated. In the case of the linearly stratified Boussinesq fluid, the abnormal reflection occurs even though the wave near the sidewall has a sinusoidal profile and not a sech2 profile. This suggests that the abnormal reflections similar to Mach reflection always occur when the wave amplitude is large enough, irrespective of the wave profile. 相似文献
18.
This paper reports on experimental observation of internal waves that are focused due to a sloping topography. A remarkable mixing of the density field was observed. This result is of importance for the deep ocean, where internal waves are believed to play a role in mixing. The experiments were performed on the rotating platform at the Coriolis Laboratory, Grenoble. The rotation, its modulation and density stratification were set to be in the internal wave regime. After applying various data processing techniques we observe internal wave rays, which converge to a limiting state: the wave attractor. At longer time scales we observe a remarkably efficient mixing of the density field, possibly responsible for driving observed sheared mean flows and topographic Rossby waves. We offer the hypothesis that focusing of internal waves to the wave attractor leads to the mixing. 相似文献
19.
During internal wave investigations in summer on the Pacific shelf of Kamchatka, internal wave depressions were recorded as having either a steepened forward face or a steepened back face. It was established that these changes in profile are correlated with tidal phase. Waves with a steepened leading face were most common during flood tide and those with a steepened back face dominated during ebb tide. Significant properties of the observed internal waves were revealed: the higher the amplitude of the waves, the less the steepening of the face, and the waves spreading during ebb tide have higher amplitude than those in flood tide. 相似文献
20.
The far-field amplitude of the waves generated by a steadily propagating radially symmetric disturbance on the beta-plane is calculated using Lighthill's method. From this can be obtained the fluxes of quantities such as wave energy which are radiated away from the disturbance. The radiated wave power is computed for a variety of forms of the disturbance. The rate of change of pseudomomentum in the system is also calculated: the component parallel to the motion of the disturbance is the radiated wave power divided by velocity. Results are compared to previous work and some physical issues are discussed. 相似文献