Showing papers on "Internal wave published in 1979"
519 citations
01 Jan 1979
TL;DR: In this article, the authors introduce linear internal waves and herar flows in a stratified fluid and double-diffusive convection in stably stratified fluids, and show that the shear flows can produce turbulence.
Abstract: Preface 1. Introduction and preliminaries 2. Linear internal waves 3. Finite amplitude motions in stably stratified fluids 4. Instability and the production of turbulence 5. Turbulent shear flows in a stratified fluid 6. Buoyant convection from isolated sources 7. Convection from heated surfaces 8. Double-diffusive convection 9. Mixing across density interfaces 10. Internal mixing processes Bibliography and author index Recent publications Subject index.
311 citations
TL;DR: The transient evolution of internal waves which are forced by the flow of stably stratified fluid over two-dimensional topography exhibits several pronounced nonlinear effects for geophysically relevant values of the governing parameters as mentioned in this paper.
Abstract: The transient evolution of internal waves which are forced by the flow of stably stratified fluid over two-dimensional topography exhibits several pronounced nonlinear effects for geophysically relevant values of the governing parameters. For homogeneous flows in which the internal Froude number is constant, the importance of nonlinearity is determined by the aspect ratio of the topography and the flow in the steady-state regime is as predicted by Long's model. When the background flow is inhomogeneous, Long's model no longer applies and new nonlinear effects may occur. One example of such an effect is the marked increase in the efficiency with which resonant lee waves are excited beyond the linear efficiency. A second example concerns the possibility of the trapping and subsequent amplification of the internal wave beneath its own level of supercritical steepening. The latter process appears to be important in understanding the strong downslope windstorm which occurred at Boulder, Colorado, on 1...
247 citations
TL;DR: In this paper, a 200-kHz acoustic backscattering system was used to detect the evolution of internal wave packets in Massachusetts Bay during ebb tide, and large overturning events were observed acoustically and in density profiles.
Abstract: Observations in Massachusetts Bay of high-frequency internal wave packets indicate that they are caused by lee waves generated outside a submarine bank at the Bay's seaward margin during ebb tide. The lee waves propagate into the Bay as the tide turns to flood, steepen nonlinearly, and develop into the packet. A 200-kHz acoustic back-scattering system detected the evolution of the packets. Large overturning events were observed acoustically and in density profiles. Plankton distributions undergo strong vertical displacements and mixing associated with the wave packet passage.
228 citations
TL;DR: In this article, in situ observations made at three locations on the mid-Atlantic continental shelf during 1975--1976 clearly show intermitten movement of bottom sediment caused by currents, waves, and other forcing mechanisms.
Abstract: Long-term in situ observations made at three locations on the mid-Atlantic continental shelf during 1975--1976 clearly show intermitten movement of bottom sediment caused by currents, waves, and other forcing mechanisms. In winter, storm-associated bottom currents greater than 30 cms/sup -1/ resuspended and transported sediments. Net water particle excursions during storms were about 20--30 km longshelf and 5--10 km cross-shelf. Wave-induced bottom currents also resuspended sediments during periods of low mean flow. Sediment motion was observed in summer, although bottom conditions were generally tranquil. Significant changes in suspended matter concentration were observed that were only partially related to bottom currents. These changes may have been caused by biological activity or advection. Bottom currents on the mid-Atlantic region of the continental shelf were characterized by a coherent, primarily cross-shelf tidal flow of 5--10 cm s/sup -1/ and a low-frequency longshelf component of 5--20 cm s/sup -1/. The longshelf current was coherent over length scales of 100 km at tidal frequencies and for motions with periods greater than 50 hours. For these longer periods the longshelf flow was coherent with wind stress, which implies that winds were a mojor driving force of the longshelf current. The cross-shelf current was not coherent at stationsmore » separated by 100 km except at tidal frequencies. Packets of high-frequency internal waves were observed during stratified conditions in summer with bottom currents as large as 20 cm s/sup -1/.« less
138 citations
132 citations
01 Dec 1979
TL;DR: In this paper, seven transects of the East Greenland portion of the Polar Front were made by HM nuclear submarine Sovereign in October 1976, where the sound velocity profiles include steep thermal fronts, highfrequency structure, possibly due to internal waves and found mainly in the Front; and warm water patches within the zone of Polar Water, probably due to eddies.
Abstract: Seven transects of the East Greenland portion of the Polar Front were made by HM nuclear submarine Sovereign in October 1976. The transects, between 71 and 81°N, comprise continuous horizontal sound velocity profiles at depths of between 67 and 125 m, accompanied by inverted sonar profiles of the ice canopy overhead. Features of the sound velocity profiles include steep thermal fronts ; high-frequency structure, possibly due to internal waves and found mainly in the Front; and warm water patches within the zone of Polar Water, probably due to eddies. Once the submarine passed through the Front twice by diving, which enables an estimate of its slope to be made. The nature of the features that suggest internal waves and eddies is considered, and an analysis is made of the extent to which a warm surface eddy can cause the ice cover to melt if assisted by wave action. A laboratory experiment is also described in which the East Greenland Current was modelled by releasing a cylinder of salt water placed in the centre of a rotating circular tank of freshwater, with a radial barrier simulating Greenland. A current was obtained along the eastern side of the barrier, reproducing many of the qualitive features of the East Greenland Current.
97 citations
TL;DR: In this article, the search for regions of the deep ocean where the canonical Garrett-Munk spectrum does not apply is continued, in an effort to obtain a zero-order wave climatology and some insight into wave dynamics.
Abstract: The search for regions of the deep ocean where the canonical Garrett-Munk spectrum does not apply is continued here in an effort to obtain a zero-order wave climatology and some insight into wave dynamics. A number of such regions have been found 1) within canyons, 2) in immediate proximity to topographic features, 3) in regions of high mean shear and 4) on the equator. Near topographic features energy levels are higher (especially within a canyon), and there is a pronounced anisotropy, but the shape of the frequency spectrum changes little. The absence of the inertial peak on the equator seems to make little difference to the frequency spectrum there. Elsewhere the level and shape of the internal wave frequency spectrum are remarkably constant. Apparent deviations in the wavenumber spectrum do occur in proximity to the equator and in the Florida Current. Horizontal polarization changes are associated with topography and large mean shears.
83 citations
TL;DR: In this article, a nonlinear internal wave equation that describes stratified fluids with finite depth was studied, and the $N$-soliton solutions obtained tend to either the Korteweg-de Vries equation or the Benjamin-Ono equation in the shallow or deep-fluid limit.
Abstract: A nonlinear internal wave equation that describes stratified fluids with finite depth has been studied. $N$-soliton solutions were found through Hirota's method. Although the equation tends to either the Korteweg-de Vries equation or the Benjamin-Ono equation in the shallow- or deep-fluid limit, respectively, the $N$-soliton solutions obtained tend to the Korteweg-de Vries solitons in the shallow-fluid limit but do not tend to the Benjamin-Ono solitons in the deep-fluid limit. Therefore, there is no smooth transition from one kind of soliton to another with varying depth of the fluid.
82 citations
TL;DR: In this paper, the phase velocities and coherences of random waves in the first half of a wind-wave flume were measured with a linear array of wave gauges, and the measured results were compared with the nonlinear theory of two-dimensional random waves, which has been presented in part 1.
Abstract: Random waves are generated by wind in the first half of a wind-wave flume. The latter half of the flume is kept free from wind to measure the waves unaffected by the wind and wind-generated current. The random waves in the latter area are measured with a linear array of wave gauges, and their phase velocities and coherences are determined by a usual technique of the cross-spectral analysis. The measured results are compared with the nonlinear theory of two-dimensional random waves, which has been presented in part 1 of this paper (Masuda, Kuo & Mitsuyasu 1979). Agreement between the theory and the experiment is satisfactory, and observed characteristics of the phase velocity and coherence of the spectral components can be attributed to the effects of the nonlinearity and angular dispersion of the random waves.
62 citations
Abstract: To gain insight into the orbital motion in waves on the point of breaking, we first study the trajectories of particles in some ideal irrotational flows, including Stokes’ 120° corner-flow, the motion in an almost-highest wave, in periodic deep-water waves of maximum height, and in steep, solitary waves.In Stokes’ corner-flow the particles move as though under the action of a constant force directed away from the crest. The orbits are expressible in terms of an elliptic integral. The trajectory has a loop or not according as q [sqcup ] c where q is the particle speed at the summit of each trajectory, in a reference frame moving with speed c. When q = c, the trajectory has a cusp. For particles near the free surface there is a sharp vertical gradient of the horizontal displacement.The trajectories of particles in almost-highest waves are generally similar to those in the Stokes corner-flow, except that the sharp drift gradient at the free surface is now absent.In deep-water irrotational waves of maximum steepness, it is shown that the surface particles advance at a mean speed U equal to 0·274c, where c is the phase-speed. In solitary waves of maximum amplitude, a particle at the surface advances a total distance 4·23 times the depth h during the passage of each wave. The initial angle α which the trajectory makes with the horizontal is close to 60°.The orbits of subsurface particles are calculated using the ‘hexagon’ approximation for deep-water waves. Near the free surface the drift has the appearance of a thin forwards jet, arising mainly from the flow near the wave crest. The vertical gradient is so sharp, however, that at a mean depth of only 0.01L below the surface (where L is the wavelength) the forwards drift is reduced to less than half its surface value. Under the action of viscosity and turbulence, this sharp gradient will be modified. Nevertheless the orbital motion may contribute appreciably to the observed ‘winddrift current’.Implications for the drift motions of buoys and other floating bodies are also discussed.
TL;DR: Partial reflection drift observations were made at Saskatoon, Canada (52°N) for four 10-day intervals in January, April, August and October, 1976 as discussed by the authors, and the data analysed to give the amplitudes of planetary, tidal (24, 12 h) and internal gravity (I.G.) waves (1.5 ≲ τ ≲ 6 h).
TL;DR: In this paper, the authors compare the performance of the traditional ƒ-plane and β-plane solutions to illustrate the effect of wind stress on the inertial oscillations.
Abstract: If a wind stress is suddenly imposed on an ocean at rest, inertial oscillations are produced according to the traditional ƒ-plane solution. However, if the inertial period varies with latitude, this is true only for a short time, and the solution is strongly modified after only five periods or so because of ‘β dispersion.’ Some comparisons between ƒ-plane and β-plane solutions are made to illustrate the effect. In particular, the way in which energy can move latitudinally, in the latter case, away from the region in which it is produced by the wind is illustrated. The main features of the β-plane results can be explained using WKB ray-tracing techniques. Although the model is very simple, it is not inconsistent with the internal wave experiment spectrum, which shows low-frequency energy propagating toward the southeast. It is suggested that this directionality in the spectrum at low frequencies may be associated with β dispersion.
TL;DR: In this article, Stigebrandt et al. showed that the vertical diffusion coefficient of tracer dye below the sill depth in the same fjord was an order of magnitude less than the overall coefficient for vertical diffusion of density during the same period.
Abstract: In an earlier paper (Stigebrandt, 1976), a model was proposed for internal wave-induced vertical mixing in a sill fjord. The observational evidence for the theory at that time was rather sparse, but the void is materially filled by observations presented in this note. Current measurements show, in accordance with the theory, that progressive internal waves radiate out from the Drobak sill in the Oslofjord. An experiment with tracer dye below the sill depth in the same fjord showed that the coefficient of vertical diffusion of the tracer was an order of magnitude less than the overall coefficient for vertical diffusion of density during the same period. This finding, indicating large horizontal inhomogeneities in the mixing field, gives strong support to the mixing model proposed in the earlier paper referred to above.
TL;DR: In this article, the spectral energy transfer for deep-water surface waves and a simple three-layer model of the stability frequency were discussed, and the transfer to the internal wave field in the oceanic main thermocline was found to be negligible compared with the effect of other processes.
Abstract: The generation of internal waves by resonantly interacting surface waves is examined in the framework of spectral scattering theory in the random-phase approximation. Coupling coefficients are derived from Euler's equation of motion for arbitrary stratification. The spectral energy transfer is discussed for deep-water surface waves and a simple three-layer model of the stability frequency. Analytical and numerical evaluation of the transfer integral leads to a parametrization in terms of the basic model parameters. These are the depth, thickness and stability frequency of the thermocline and the scale parameters and bandwidth of the surface wave spectrum. Strong dependence on some of these parameters, in particular the surface wave energy and the ratio of surface and internal wave frequencies, indicates a large spatial and temporal variability of the transfer rate. The transfer to the internal wave field in the oceanic main thermocline is found to be negligible compared with the effect of other processes. High frequency waves in the seasonal thermocline may be generated very efficiently.
TL;DR: In this article, the rectified flow induced by wind-driven internal seiches in a rotating lake is studied, where friction and nonlinearity combine to generate a secondary mean flow which is calculated analytically for a uniform depth lake and numerically for variable depth.
Abstract: The rectified flow induced by wind-driven internal seiches in a rotating lake is studied. Friction and nonlinearity combine to generate a secondary mean flow which is calculated analytically for the case of a uniform depth lake and numerically for variable depth. The theory is applied to Lake Kinneret, the former Sea of Galilee, where the diurnal wind forcing produces a large internal Kelvin wave and which has a strong cyclonic mean flow. The uniform depth model reproduces the diurnal response adequately, but variable depth is required to reproduce the mean flow.
TL;DR: In this article, a higher-order perturbation theory for the modulation of short gravity waves by longer-scale periodic flows is developed, starting with Boltzmann's transport equation and including the input from the wind, energy transfer by nonlinear resonant interactions, and dissipation.
Abstract: A higher-order perturbation theory for the modulation of short gravity waves by longer-scale periodic flows is developed, starting with Boltzmann's transport equation and including the input from the wind, energy transfer by nonlinear resonant interactions, and dissipation. Specific results are given for a model dealing with the straining of short gravity waves coupled to ‘parasitic’ capillary waves by second-order resonant interactions. The initial value problem yields a relaxation rate for the short gravity waves equal to their growth rate. The predicted phase of the short gravity waves in relation to the crest of the longer gravity waves with this relaxation rate is in better agreement with measurements. Explicit expressions are obtained for the second-order results in terms of Uo/C (ratio of orbital to phase speed of the modulating wave). Numerical results are obtained for the reduction of the short gravity waves amplitude and for the modulation and phase of the backscattered power of microwave sensors probing this system of water waves. The second-order results predict the reduction of the linear modulations, but the reduction is not large enough to match the measurements for Uo/C ratios larger than 0.1. Accordingly, perturbation solutions do not converge fast enough for the larger Uo/C ratios.
01 Jul 1979
TL;DR: In this article, a finite difference model for predicting the nearshore circulation due to wind and waves is presented which attempts to solve the same problem as an earlier model created by Birkemeier and Dalrymple (1975).
Abstract: : A finite difference model for predicting the nearshore circulation due to wind and waves is presented which attempts to solve the same problem as an earlier model created by Birkemeier and Dalrymple (1975). Their model iteratively solved the linear set of conservation equations of both mass and momentum, which were time averaged (over one wave period) and depth integrated, for mean velocities and free surface displacements. The wave characteristics used in the momentum equations were found using the wave refraction and shoaling routines, including wave-current interaction, developed by Noda, et al. (1974). The model also included a linear bottom friction formulation as well as a surface wind stress capability. The present model discussed herein includes the addition of convective accelerations, horizontal mixing and a quadratic bottom friction term in the conservation of momentum equations. This bottom friction term is 'exact' in the sense that it includes the velocity vectors due to both mean and wave-induced currents. The model is applied to the cases of a single wave train impinging on a plane beach, a barred profile, and a bottom with a periodically spaced rip channel.
TL;DR: In this article, a direct integration of gravity wave propagation through a two-component thermosphere with vertically-varying inter-species collision frequencies is performed using a direct integrated method.
Abstract: Numerical calculations of gravity wave propagation through a two-component thermosphere with vertically-varying inter-species collision frequencies are performed using a direct integration method. Reflection of upgoing gravity wave energy into downgoing gravity waves appears to be small though nonnegligible at typical thermospheric periods and wavelengths. Coupling into diffusion waves is completely insignificant in most cases and may be determined in part by the relative abundance of the minor species. Temperature perturbation differences between species can be greater than 10% above 300 km altitude even though coupling into diffusion waves is small. Diffusive dissipation of gravity wave energy can be significant in the lower thermosphere and may be comparable to dissipation by viscosity and heat conduction below about 225 km altitude. Heating by diffusive dissipation may also be comparable to direct heating by solar radiation in the lower thermosphere. As a result of dissipative filtering of long-period and short-wavelength waves and the sensitivity of He-N2 density perturbation phase differences to diffusion, the AE-C satellite wave observations can only be fit by internal gravity waves with periods no greater than about 25 min and horizontal wavelengths no less than about 200 km.
TL;DR: In this paper, the authors used the constant depth and isopycnal-following tows to estimate the, towed vertical coherence of the internal wave field, at vertical separations of 8.5, 18, 28 and 70 m.
Abstract: Constant depth and isopycnal‐following tows are used to estimate the, towed vertical coherence of the internal wave field, at vertical separations of 8.5, 18, 28 and 70 m. The depths of the tows are ∼750 m at the maximum of the buoyancy frequency in the main thermocline of the Sargasso Sea, and near 350 m in the buoyancy frequency minimum between the main and seasonal thermoclines. The towed spectra and towed vertical coherence are compared with three model spectra (GM75, GM76 and IWEX): at 750 m the agreement between data and models is very good, with IWEX being slightly better. At 350 m several of the measured towed vertical coherence spectra are more complex than the spectra from the deeper tows, there are anomalously high coherences in a band from 0.7 to 2 cycles per kilometer that are not predictable by the models. We suggest this coherence bump may be evidence of Eckart resonance, i.e., modes tunneling between the two thermoclines into the region of low buoyancy frequency.
TL;DR: In this paper, the authors extended the classification of the normal modes of parallel flow of an inviscid stratified fluid presented by Banks, Drazin & Zaturska (1976) to encompass modes which propagate at infinity.
Abstract: The linear perturbations of the flow of a non-diffusive fluid are considered. The classification of the normal modes of parallel flow of an inviscid stratified fluid presented by Banks, Drazin & Zaturska (1976) is here extended to encompass modes which propagate at infinity. When the basic flow is unbounded and the buoyancy frequency is non-zero at infinity the five classes presented earlier are augmented by three further classes: for a given flow and wavenumber they are ( a ) a continuous class of non-singular stable modes which are modifications of internal gravity waves by shear; ( b ) a continuous class of stable modes which are singular at each critical layer but otherwise similar to those of class ( a ); and ( c ) a finite number of marginally stable singular modes with over-reflexion. This classification is illustrated by many new results. Some asymptotic properties of the stable and unstable modes are found for large values of the Richardson number and for long waves. Two prototype problems, in which the basic flows are a piecewise-linear shear layer and a triangular jet, are solved analytically. The modified internal gravity waves for a Bickley jet with uniform buoyancy frequency are treated to illustrate the complementary nature of the propagating and evanescent modes. This treatment is both analytical and numerical. The general ideas are further illustrated by a numerical study of the stability characteristics of a hyperbolic-tangent shear layer. Finally the modes for a basic flow of boundary-layer type are found in exact terms of a hypergeometric function.
TL;DR: In this article, a model of frontal-scale dynamics applicable to established, persistent upper ocean density fronts was developed and analyzed, where the effects of interfacial friction and mass entrainment arising from turbulent dissipative processes were incorporated as well as the effects from earth rotation and wind stress.
Abstract: The paper develops and analyzes a model of frontal-scale dynamics applicable to established, persistent upper ocean density fronts. The effects of interfacial friction and mass entrainment arising from turbulent dissipative processes are incorporated as well as the effects of earth rotation and wind stress. The model is of hydrodynamic character in that the circulation is not permitted to do its own mixing. The equations of motion are solved after their integration over the vertical from the pycnocline bottom to the sea surface. Two independent frontal length scales are found. one is Lt, the dissipative length scale, defined as the ratio of the asymptotic pycnocline depth to the magnitude of the interfacial entrainment coefficient; the other is the baroclinic Rossby radius, the internal wave phase speed divided by the Coriolis parameter. The ratio of these length scales forms the fundamental parameter of the model dynamics, Pr, called the rotation parameter. For large values of Pr the frontal len...
TL;DR: Fluctuating magnetic gradients over oceans come from electric currents flowing in seawater arising from its motions across the earth's magnetic field.
Abstract: Fluctuating magnetic gradients over oceans come from electric currents flowing in seawater arising from its motions across the earth's magnetic field. Gradients of 0.3 to 0.6 picoteslas per meter for each meter of internal wave displacement have been measured at frequencies of 2 to 5 millihertz with a superconductive magnetic gradiometer supported 7 meters above the surface of water 18 meters deep about 1.5 kilometers offshore from San Diego, California.
TL;DR: In this article, the effects of wave-induced diffusion on the characteristics of plane acoustic gravity waves in the earth's thermosphere are investigated by means of a two fluid model atmosphere in diffusive equilibrium.
Abstract: The effects of wave-induced diffusion on the characteristics of plane acoustic gravity waves in the earth's thermosphere are investigated by means of a two fluid model atmosphere in diffusive equilibrium. At wave periods greater than the shortest characteristic diffusion time for the minor gas, diffusion induced by the wave is considered to act to eliminate amplitude and phase differences between the wave-induced density fluctuations of individual gases and restore the perturbed fluid to diffusive equilibrium. Vertical diffusion is most important at large scale sizes, but horizontal diffusion dominates for horizontal wavelengths of less than several hundred kilometers. As a result of wave-induced diffusion, AE-C satellite measurements of neutral density fluctuations of thermospheric constituents are only compatible with relatively small scale internal gravity waves. Velocity and temperature differences for acoustic-gravity waves are greatest at periods near the mean collision time and diffusion time and lead to the dissipation of wave energy. The predictions of the theory are consistent with a high latitude, low altitude source for the medium scale waves and a more localized random source for the waves observed by AE-C.
TL;DR: In this paper, the role of internal waves in the vertical diffusion of large scale momentum is investigated, using the IWEX data set, and the time variability of the vertical flux of horizontal internal wave momentum (estimated from temperature and current data) is compared to that of the mean vertical shear.
Abstract: The relation between internal wave variability and larger and smaller scales of motion is investigated, using the IWEX data set. To investigate the role of internal waves in the vertical diffusion of large scale momentum, the time variability of the vertical flux of horizontal internal wave momentum (estimated from temperature and current data) is compared to that of the mean vertical shear. It is found that internal waves cannot cause a vertical viscosity as large as proposed by Muller (1976), but that the data are too noisy to detect a possible wave-induced viscosity in absolute value of the order of 10−2 m2 s−1 or less. Similarities in the time behavior of the total internal wave energy and that of the square mean vertical shear suggest that some kind of dynamical coupling exists between internal waves and larger scale flows. There is some evidence that the level of temperature finestructure activity also varies in a related way. An analysis of CTD station data taken during Mode demonstrates the mappability of the finestructure activity, and again suggests a relation with the geostrophic eddy flow.
23 Oct 1979-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this article, a generalized Lagrangian mean formulation was derived to describe the manner in which the basic flow affects the waves, and two kinds of applications were discussed: (i) steady mean flows, due to waves encountering an inhomogeneity in their environment, such as a varying channel depth; (ii) mean flows induced by modulations in the wave amplitude.
Abstract: An inviscid, incompressible, stably stratified fluid occupies a horizontal channel, along which an internal gravity wave packet is propagating in the presence of a basic shear flow. By using a generalized Lagrangian mean formulation, the equation for wave action conservation is derived to describe the manner in which the basic flow affects the waves. Equations describing the second-order (in amplitude) wave-induced Lagrangian mean flows are obtained. Two kinds of applications are discussed: (i) steady mean flows, due to waves encountering an inhomogeneity in their environment, such as a varying channel depth; (ii) mean flows induced by modulations in the wave amplitude.
TL;DR: In this article, the authors review the development of the theory and experiment for deep and shallow water since 1963, and show that the transmission in deep water can be very good, especially for low frequencies in the SOFAR channel, where what little attenuation there is has been demonstrated to arise from a boron relaxation process.
Abstract: Reviews the development of the theory and experiment for deep and shallow water since 1963. Theoretical approaches use rays, modes and a wide variety of other concepts. The classic case has a constant depth profile of sound velocity, but for long ranges one must allow for profiles varying both with range and with the transverse direction. Experimentally the transmission in deep water can be very good, especially for low frequencies in the SOFAR channel, where what little attenuation there is has been demonstrated to arise from a boron relaxation process. For shallow water the largest uncertainties at low frequencies can come from the unknown nature of the bottom structure. The study of variability has been helped by the existence of fixed sites, showing the occurrence of fluctuations with a great variety of mechanisms and time scales. For most of these the key is multipath interference, e.g. this comes into the acoustic effects of internal waves in the deep sea, and also into the spatial variability in deep channels.
01 Feb 1979
TL;DR: In this article, the energy transfer by the wind to near-inertial internal waves is discussed using a theoretical model developed by Kase and Tang, where the model transfer at the inertial frequency is View the MathML source, where F is the wind stress spectrum and Lj is an integral length scale defined by equation (6).
Abstract: The energy transfer by the wind to near-inertial internal waves is discussed using a theoretical model developed by Kase and TangJournal of the Fisheries Research Board of Canada, 33, 2323–2328, (1976). The model transfer at the inertial frequency is View the MathML source, where F is the wind stress spectrum and Lj is an integral length scale defined by equation (6). It is shown that significant transfer rates of order 1 erg cm−2s−1 as observed for example by LeamanJournal of Physical Oceanography, 6, 894–908 (1976) could be generated by moderate winds in case of small vertical scales Lj, which are the consequence of a mixed layer above a sharp thermocline.
01 Feb 1979
TL;DR: In this paper, an array of current meters and temperature sensors 400 m deep over the continental shelf, strong motions were observed at frequencies in the semidiurnal tidal band and its first overtide, probably due to the bottom slope, which is slightly less steep than the characteristic slope of internal waves at the overtide frequency.
Abstract: At an array of current meters and temperature sensors 400 m deep over the continental shelf, strong motions were observed at frequencies in the semidiurnal tidal band and it its first overtide. These motions are probably due to the bottom slope, which is slightly less steep than the characteristic slope of internal waves at the overtide frequency. The tidal currents are strongest in the longshore direction while the overtide currents are strongest in the up-down slope direction. Analysis shows the motions to be parts of large coherent structures within the water column; the tidal structure is composed of baroclinic and barotropic components while the overtide structure is baroclinic. The observations are consistent with the idea of generation of the baroclinic motions in both frequency bands by the action of the barotropic tide over the sloping bottom, but the mechanism of interaction is poorly understood.