Booms and Busts in the Deep

Abstract Deep sea (5 km) pressure and velocity at the Hawaii-2 Observatory (H2O), midway between Hawaii and California, exhibit a number of remarkable features that are interpreted using the Longuet–Higgins theory of acoustic radiation from oppositely directed surface waves. A change in the slope of the bottom spectra near 5 Hz can be associated with a transition near 2.5 Hz (25-cm wavelength) of the surface wave spectrum from the classical κ−4 saturated (wind independent) Phillips spectrum to a distinct band of ultragravity waves. Bottom spectra are remarkably stable. Occasional 15-dB busts in the gravities and booms in the ultragravities are prominent features in the bottom records and can be associated with calms and storms at the sea surface. For strong winds, two broad lobes in the directional spectrum of the gravity waves are nearly perpendicular to the wind; as the wind drops, the lobes become narrower and more nearly aligned with the wind, leading to busts.

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Estimates of Surface Waves Using Subsurface EM-APEX Floats under Typhoon Fanapi 2010

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-17-0121.1 ◽

2018 ◽

Vol 35 (5) ◽

pp. 1053-1075 ◽

Cited By ~ 2

Author(s):

Je-Yuan Hsu ◽

Ren-Chieh Lien ◽

Eric A. D’Asaro ◽

Thomas B. Sanford

Keyword(s):

Surface Wave ◽

Surface Waves ◽

Wave Spectrum ◽

Nonlinear Least Squares ◽

Peak Frequency ◽

Wave Propagation Direction ◽

Model Studies ◽

Surface Wave Propagation ◽

Left Quadrant ◽

Field Inclination

AbstractSeven subsurface Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats measured the voltage induced by the motional induction of seawater under Typhoon Fanapi in 2010. Measurements were processed to estimate high-frequency oceanic velocity variance associated with surface waves. Surface wave peak frequency fp and significant wave height Hs are estimated by a nonlinear least squares fitting to , assuming a broadband JONSWAP surface wave spectrum. The Hs is further corrected for the effects of float rotation, Earth’s geomagnetic field inclination, and surface wave propagation direction. The fp is 0.08–0.10 Hz, with the maximum fp of 0.10 Hz in the rear-left quadrant of Fanapi, which is ~0.02 Hz higher than in the rear-right quadrant. The Hs is 6–12 m, with the maximum in the rear sector of Fanapi. Comparing the estimated fp and Hs with those assuming a single dominant surface wave yields differences of more than 0.02 Hz and 4 m, respectively. The surface waves under Fanapi simulated in the WAVEWATCH III (ww3) model are used to assess and compare to float estimates. Differences in the surface wave spectra of JONSWAP and ww3 yield uncertainties of <5% outside Fanapi’s eyewall and >10% within the eyewall. The estimated fp is 10% less than the simulated before the passage of Fanapi’s eye and 20% less after eye passage. Most differences between Hs and simulated are <2 m except those in the rear-left quadrant of Fanapi, which are ~5 m. Surface wave estimates are important for guiding future model studies of tropical cyclone wave–ocean interactions.

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Surface waves on water of non-uniform depth

Journal of Fluid Mechanics ◽

10.1017/s0022112058000690 ◽

1958 ◽

Vol 4 (6) ◽

pp. 607-614 ◽

Cited By ~ 109

Author(s):

Joseph B. Keller

Keyword(s):

Wave Propagation ◽

Surface Wave ◽

Surface Waves ◽

Linear Theory ◽

Gravity Waves ◽

Geometrical Optics ◽

Surface Wave Propagation ◽

Special Cases

Gravity waves occur on the surface of a liquid such as water, and the manner in which they propagate depends upon its depth. Although this dependence is described in principle by the equations of the ‘exact linear theory’ of surface waves, these equations have not been solved except in some special cases. Therefore, oceanographers have been unable to use the theory to describe surface wave propagation in water whose depth varies in a general way. Instead they have employed a simplified geometrical optics theory for this purpose (see, for example, Sverdrup & Munk (1944)). It has been used very successfully, and consequently various attempts, only partially successful, have been made to deduce it from the exact linear theory. It is the purpose of this article to present a derivation which appears to be satisfactory and which also yields corrections to the geometrical optics theory.

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Investigations Of Internal Sea Waves Effect On The Energy-carrying Part Of The Sea Surface Wave Spectrum From Remote Sensing Data

[Proceedings] IGARSS'91 Remote Sensing: Global Monitoring for Earth Management ◽

10.1109/igarss.1991.575515 ◽

2005 ◽

Author(s):

V.Y. Raizer ◽

A.V. Smirnov ◽

V.S. Etkin

Keyword(s):

Remote Sensing ◽

Surface Wave ◽

Wave Spectrum ◽

Remote Sensing Data ◽

Sea Surface ◽

Sea Waves ◽

Sensing Data ◽

Sea Surface Wave

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Ocean surface wave dynamics, energy and momentum air-sea transfer under a variety of wind and waves conditions

10.5194/egusphere-egu2020-12912 ◽

2020 ◽

Author(s):

Francisco J. Ocampo-Torres ◽

Pedro Osuna ◽

Nicolas Rascle ◽

Hector Garcia-Nava ◽

Carlos F. Herrera-Vazquez ◽

...

Keyword(s):

Surface Wave ◽

Momentum Transfer ◽

Wave Spectrum ◽

Sonic Anemometer ◽

Correlation Method ◽

Ocean Surface ◽

Eddy Correlation ◽

Wave Number ◽

Directional Spectrum ◽

Ocean Surface Wave

<p>Direct measurements have been conducted from a spar buoys deployed in the Gulf of Mexico, and in the vicinity of Todos Santos Island, offshore Ensenada BC, Mexico, in order to better understand ocean surface wave modulated processes under a variety of oceanographic and meteorological conditions. Full ocean surface wave directional spectrum is estimated from sea surface elevation data acquired with an array of capacitance wires, to represent directional spectrum as a function of frequency and direction, as well as a function of the wave number components Kx and Ky. Momentum transfer between ocean and the atmosphere is calculated directly through the eddy correlation method applied to wind velocity components acquired with a sonic anemometer. Momentum transfer variability is analysed to study its dependance on the surface wave conditions, with special emphasis on mixed sea states. Comparison between single peak spectra results with those cases where bi-modal spectra were present are performed in order to detect wind stress variability effects. Ocean-atmosphere transfer of momentum is studied and explained in terms of the shape and evolution of the surface wave spectrum. This research is funded by SENER-CONACYT 249795 and 201441 projects.</p>

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The directional spectrum of ocean waves, and processes of wave generation

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1962.0010 ◽

1962 ◽

Vol 265 (1322) ◽

pp. 286-315 ◽

Cited By ~ 15

Keyword(s):

Pressure Fluctuations ◽

Wave Spectrum ◽

Ocean Waves ◽

Wave Generation ◽

Air Pressure ◽

Sea Surface ◽

Shear Instability ◽

Main Stage ◽

Sea Waves ◽

Directional Spectrum

This paper describes some recent observations of the directional spectrum of sea waves and of air pressure fluctuations at the sea surface, and discusses their implications for theories of wave generation. The angular spread of the wave energy in the generating area is found to be comparable with the ‘resonance angle’ sec -1 ( σU/g ) ( σ = wave frequency, U = wind speed) but lies slightly below it in the middle range of frequencies. The best fit to the directional spectrum F ( σ, ɸ ) is shown to be a cosine-power law: F ( σ, ɸ ) ∝ cos 2s (1/2 ɸ ), where s decreases as σ in creases. At the higher frequencies the total spectrum satisfies the equilibrium law: F ( σ ) ∝ σ -5 . The initial stages of wave generation are attributed to turbulence in the air stream, and the main stage of growth to the shear instability mechanism described by Miles. At the highest frequencies the form of the spectrum suggests that wave breaking plays a predominant part, as proposed by Phillips. The broadening of the angular distribution at the highest frequencies may also be due partly to third-order ‘resonant’ interactions among components of the wave spectrum . The air-pressure fluctuations are nearly in phase with the vertical displacement of the sea surface (over most of the frequency range) and are consistent with the shear-flow model proposed by Miles. The turbulent component of the air pressure is much smaller than was previously supposed.

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Acoustic radiation by ocean surface waves

Journal of Fluid Mechanics ◽

10.1017/s0022112000008636 ◽

2000 ◽

Vol 415 ◽

pp. 1-21 ◽

Cited By ~ 32

Author(s):

STEVE ARENDT ◽

DAVID C. FRITTS

Keyword(s):

Surface Waves ◽

Gravity Waves ◽

Acoustic Waves ◽

Acoustic Radiation ◽

Three Dimensional ◽

Phase Speed ◽

Ocean Surface ◽

Surface Gravity ◽

Ocean Surface Waves ◽

Surface Gravity Waves

We calculate the radiation of acoustic waves into the atmosphere by surface gravity waves on the ocean surface. We show that because of the phase speed mismatch between surface gravity waves and acoustic waves, a single surface wave radiates only evanescent acoustic waves. However, owing to nonlinear terms in the acoustic source, pairs of ocean surface waves can radiate propagating acoustic waves if the two surface waves propagate in almost equal and opposite directions. We derive an analytic expression for the acoustic radiation by a pair of ocean surface waves, and then extend the result to the case of an arbitrary spectrum of ocean surface waves. We present some examples for both the two-dimensional and three-dimensional regimes. Of particular note are the findings that the efficiency of acoustic radiation increases at higher wavenumbers, and the fact that the directionality of the acoustic radiation is often independent of the shape of the spectrum.

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Coupling of surface and internal gravity waves: a mode coupling model

Journal of Fluid Mechanics ◽

10.1017/s0022112076001195 ◽

1976 ◽

Vol 77 (1) ◽

pp. 185-208 ◽

Cited By ~ 48

Author(s):

Kenneth M. Watson ◽

Bruce J. West ◽

Bruce I. Cohen

Keyword(s):

Energy Transfer ◽

Surface Wave ◽

Internal Wave ◽

Surface Waves ◽

Wave Field ◽

Internal Waves ◽

Wave Spectrum ◽

Coupled Model ◽

Internal Gravity Waves ◽

Growth Time

A surface-wave/internal-wave mode coupled model is constructed to describe the energy transfer from a linear surface wave field on the ocean to a linear internal wave field. Expressed in terms of action-angle variables the dynamic equations have a particularly useful form and are solved both numerically and in some analytic approximations. The growth time for internal waves generated by the resonant interaction of surface waves is calculated for an equilibrium spectrum of surface waves and for both the Garrett-Munk and two-layer models of the undersea environment. We find energy transfer rates as a function of undersea parameters which are much faster than those based on the constant Brunt-ViiisSila model used by Kenyon (1968) and which are consistent with the experiments of Joyce (1974). The modulation of the surface-wave spectrum by internal waves is also calculated, yielding a ‘mottled’ appearance of the ocean surface similar to that observed in photographs taken from an ERTS1 satellite (Ape1 et al. 1975b).

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On narrow V-like ship wakes

Journal of Fluid Mechanics ◽

10.1017/s0022112094002375 ◽

1994 ◽

Vol 275 ◽

pp. 301-321 ◽

Cited By ~ 11

Author(s):

Daifang Gu ◽

O. M. Phillips

Keyword(s):

Boundary Layer ◽

Surface Wave ◽

Turbulent Boundary Layer ◽

Gravity Waves ◽

Wave Spectrum ◽

Outer Edge ◽

Sar Images ◽

Ship Wakes ◽

Oscillating Motion ◽

Ship Speed

This paper is concerned with the generation of short gravity waves and their radiation from the outer edge of the turbulent boundary layer and wake of a ship. They arise primarily near the ship's stern. The wave spectrum in the direction of wavenumber vector at an angle (90° – δ) to the ship's track is: \[\Phi_{\delta}(\omega) = \Psi\left(\frac{UT_d}{2l},\frac{U\sin\delta}{c_g},\frac{R}{UT_d}\right)\frac{1}{k_0R}\frac{2l\omega^2}{g^2}\gamma\left(0,\frac{\pi}{l};0,\omega \right),\] where Ψ is dimensionless and a function of three dimensionless parameters. γ is the spectrum of the oscillating motion at the boundary, U the ship speed, Td the decay timescale of the oscillating motion, 2l the lengthscale of the eddies, and R the distance away from the boundary along the wavenumber vector. Generally, Φδ has large values near δ = 0 and small values at large δ; it behaves as 1/R at distances not far from the ship, then may vary slower than 1/R at intermediate distances, and finally behaves as 1/R again at distances far from the ship. These are consistent with the pattern found in SAR images of narrow V-like ship wakes. The method developed here is also applicable to various problems of surface wave generation by turbulence in water.

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