On the skewness of sea-surface elevation

1986 ◽  
Vol 164 ◽  
pp. 487-497 ◽  
Author(s):  
M. A. Srokosz ◽  
M. S. Longuet-Higgins
Keyword(s):  
Gravity Waves ◽  
Simple Relation ◽  
Statistical Properties ◽  
Sea Surface ◽  
Surface Elevation ◽  
Statistical Measure ◽  
Constant Ratio ◽  
Surface Gravity Waves ◽  
Different Types ◽  
The Waves

Surface skewness is a statistical measure of the vertical asymmetry of the air-sea interface – exemplified by the sharp crests and rounded troughs of surface gravity waves. Some authors have proposed a constant ratio between surface skewness and the ‘significant slope’ of the waves. Here it is shown theoretically that no such simple relation is to be expected.Wave records are of at least two different types; Eulerian (as made with a fixed probe) or Lagrangian (as with a free-floating buoy). The corresponding statistical properties are examined. At first sight it might appear that the degree of skewness in corresponding records would be different. However it is shown that to lowest order the skewness is invariant; only the apparent mean level is different, at second order.

scholarly journals Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin

2009 ◽  
Vol 627 ◽  
pp. 235-257 ◽  
Author(s):  
M. ONORATO ◽  
L. CAVALERI ◽  
S. FOUQUES ◽  
O. GRAMSTAD ◽  
P. A. E. M. JANSSEN ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Order Theory ◽  
Second Order ◽  
Statistical Properties ◽  
Surface Elevation ◽  
Surface Gravity ◽  
Surface Gravity Waves ◽  
Wave Basin ◽  
Dimensional Wave

A wave basin experiment has been performed in the MARINTEK laboratories, in one of the largest existing three-dimensional wave tanks in the world. The aim of the experiment is to investigate the effects of directional energy distribution on the statistical properties of surface gravity waves. Different degrees of directionality have been considered, starting from long-crested waves up to directional distributions with a spread of ±30° at the spectral peak. Particular attention is given to the tails of the distribution function of the surface elevation, wave heights and wave crests. Comparison with a simplified model based on second-order theory is reported. The results show that for long-crested, steep and narrow-banded waves, the second-order theory underestimates the probability of occurrence of large waves. As directional effects are included, the departure from second-order theory becomes less accentuated and the surface elevation is characterized by weak deviations from Gaussian statistics.

Laboratory observations of mean flows under surface gravity waves

2007 ◽  
Vol 573 ◽  
pp. 131-147 ◽  
Author(s):  
S. G. MONISMITH ◽  
E. A. COWEN ◽  
H. M. NEPF ◽  
J. MAGNAUDET ◽  
L. THAIS
Keyword(s):  
Gravity Waves ◽  
Stokes Drift ◽  
Bottom Boundary Layer ◽  
Mean Velocity ◽  
Surface Gravity Waves ◽  
End Conditions ◽  
Different Types ◽  
Stokes Waves ◽  
Rotational Waves ◽  
Gerstner Waves

In this paper we present mean velocity distributions measured in several different wave flumes. The flows shown involve different types of mechanical wavemakers, channels of differing sizes, and two different end conditions. In all cases, when surface waves, nominally deep-water Stokes waves, are generated, counterflowing Eulerian flows appear that act to cancel locally, i.e. not in an integral sense, the mass transport associated with the Stokes drift. No existing theory of wave–current interactions explains this behaviour, although it is symptomatic of Gerstner waves, rotational waves that are exact solutions to the Euler equations. In shallow water (kH ≈ 1), this cancellation of the Stokes drift does not hold, suggesting that interactions between wave motions and the bottom boundary layer may also come into play.

Measuring Sea Surface Gravity Waves Using Smartphones

Ports 2019 ◽  
2019 ◽  
Author(s):  
Matheus de Paula Vieira ◽  
Pedro Veras Guimarães
Keyword(s):  
Gravity Waves ◽  
Sea Surface ◽  
Surface Gravity ◽  
Surface Gravity Waves

Sea Surface Gravity Waves Excited by Dynamic Ground Motions from Large Regional Earthquakes

2020 ◽  
Vol 91 (4) ◽  
pp. 2268-2277 ◽  
Author(s):  
Yoshihiro Ito ◽  
Spahr C. Webb ◽  
Yoshihiro Kaneko ◽  
Laura M. Wallace ◽  
Ryota Hino
Keyword(s):  
Gravity Waves ◽  
Seismic Waves ◽  
Ground Motions ◽  
Maximum Amplitude ◽  
Sea Surface ◽  
Surface Gravity ◽  
Accretionary Wedge ◽  
Low Velocity ◽  
Infragravity Waves ◽  
Surface Gravity Waves

Abstract Infragravity waves on the sea surface near coastlines are occasionally excited by static displacement caused by large local earthquakes and recorded as tsunamis. However, tsunamis induced by ground motions from seismic waves are rarely observed, especially far from earthquake focal areas. We investigated seafloor pressure variations in the infragravity band at the Hikurangi subduction zone following the M 7.8 Kaikōura and M 7.1 Te Araroa earthquakes. Anomalous infragravity waves were observed at 0.2–20 mHz at sites overlying a low-velocity accretionary wedge offshore of the east coast of New Zealand’s North Island accompanying the Rayleigh-wave arrivals. The maximum amplitude of these ultra-low-frequency waves was similar to the tsunami that propagated from the earthquake focal area hours later. The amplitude of the pressure signal from these waves observed offshore varied inversely with water depth, suggesting that sea surface gravity waves were excited by Rayleigh or Love waves amplified within the accretionary wedge.

Phase velocity and dispersion relations of surface gravity waves in shallow sea

1994 ◽  
Vol 45 (6) ◽  
pp. 993
Author(s):  
VA Kalmykov
Keyword(s):  
Phase Velocity ◽  
Gravity Waves ◽  
Experimental Studies ◽  
Finite Depth ◽  
Dispersion Relations ◽  
Sea Surface ◽  
Surface Gravity ◽  
Linear Wave ◽  
Shallow Sea ◽  
Surface Gravity Waves

Phase velocity and dispersion relations of surface gravity waves on the sea have been modelled by two numerical methods and the results compared with previous experimental studies. Wave nonlinearities cause deviations from linear wave relations and these deviations are seen on the sea surface in the form of sharply crested waves. The effects are amplified if wave steepness increases or wave spectra become narrower. When the effects of finite depth of water are included in the calculations, the deviations from linearity are found to increase significantly.

scholarly journals Freely Decaying Weak Turbulence for Sea Surface Gravity Waves

2002 ◽  
Vol 89 (14) ◽  
Author(s):  
M. Onorato ◽  
A. R. Osborne ◽  
M. Serio ◽  
D. Resio ◽  
A. Pushkarev ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Sea Surface ◽  
Surface Gravity ◽  
Weak Turbulence ◽  
Surface Gravity Waves

scholarly journals Coral Reef Drag Coefficients—Surface Gravity Wave Enhancement

2018 ◽  
Vol 48 (7) ◽  
pp. 1555-1566 ◽  
Author(s):  
S. J. Lentz ◽  
J. H. Churchill ◽  
K. A. Davis
Keyword(s):  
Coral Reefs ◽  
Pressure Gradient ◽  
Gravity Waves ◽  
Relative Size ◽  
Pressure Sensors ◽  
Surface Gravity ◽  
Bottom Stress ◽  
Surface Gravity Waves ◽  
Average Current ◽  
The Waves

AbstractA primary challenge in modeling flow over shallow coral reefs is accurately characterizing the bottom drag. Previous studies over continental shelves and sandy beaches suggest surface gravity waves should enhance the drag on the circulation over coral reefs. The influence of surface gravity waves on drag over four platform reefs in the Red Sea is examined using observations from 6-month deployments of current and pressure sensors burst sampling at 1 Hz for 4–5 min. Depth-average current fluctuations U′ within each burst are dominated by wave orbital velocities uw that account for 80%–90% of the burst variance and have a magnitude of order 10 cm s−1, similar to the lower-frequency depth-average current Uavg. Previous studies have shown that the cross-reef bottom stress balances the pressure gradient over these reefs. A bottom stress estimate that neglects the waves (ρCdaUavg|Uavg|, where ρ is water density and Cda is a drag coefficient) balances the observed pressure gradient when uw is smaller than Uavg but underestimates the pressure gradient when uw is larger than Uavg (by a factor of 3–5 when uw = 2Uavg), indicating the neglected waves enhance the bottom stress. In contrast, a bottom stress estimate that includes the waves [ρCda(Uavg + U′)|Uavg + U′|)] balances the observed pressure gradient independent of the relative size of uw and Uavg, indicating that this estimate accounts for the wave enhancement of the bottom stress. A parameterization proposed by Wright and Thompson provides a reasonable estimate of the total bottom stress (including the waves) given the burst-averaged current and the wave orbital velocity.

scholarly journals Skewness and Kurtosis of the Surface Wave in the Coastal Zone of the Black Sea

2021 ◽  
Vol 37 (4) ◽  
Author(s):  
A. S. Zapevalov ◽  
A. V. Garmashov ◽  
◽  
Keyword(s):  
Black Sea ◽  
Wind Waves ◽  
Correlation Coefficients ◽  
Sea Surface ◽  
Statistical Moments ◽  
Surface Elevation ◽  
The Black Sea ◽  
Sea Waves ◽  
Wide Range ◽  
The Waves

Purpose. The aim of the study is to analyze variability of the statistical moments characterizing deviations of the sea surface elevation distributions from the Gaussian one. Methods and Results. Field studies of the sea waves’ characteristics were carried out from the stationary oceanographic platform located in the Black Sea near the Southern coast of Crimea. The data obtained both in summer and winter, were used. The statistical moments were calculated separately for wind waves and swell. The measurements were performed in a wide range of meteorological conditions and wave parameters (wind speed varied from 0 to 26 m/s, wave age – from 0 to 5.2 and steepness – from 0.005 to 0.095). For wind waves, the coefficients of skewness correlation with the waves’ steepness and age were equal to 0.46 and 0.38. The kurtosis correlation coefficients with these parameters were small (0.09 and 0.07), but with the confidence level 99.8% – significant. For swell, the correlation coefficients were 1.5 – 2.0 times lower. Conclusions. The statistical moments of the sea surface elevations of the third and higher orders are the indicators of the wave field nonlinearity, which should be taken into account when solving a wide range of the applied and fundamental problems. The deviations of the surface elevation distributions from the Gaussian one are not described unambiguously by the waves’ steepness and age. At the fixed values of these parameters, a large scatter in the values of the surface elevations’ asymmetry and kurtosis is observed. This imposes significant limitations on the possibility of applying the nonlinear wave models based on the wave profile expansion by small parameter (steepness) degrees, in engineering calculations.

scholarly journals Dynamics and Transformation of Sea Surface Gravity Waves at the Shelf of Decreasing Depth

2021 ◽  
Vol 9 (8) ◽  
pp. 861
Author(s):  
Grigory I. Dolgikh ◽  
Olga S. Gromasheva ◽  
Stanislav G. Dolgikh ◽  
Alexander A. Plotnikov
Keyword(s):  
Sea Of Japan ◽  
Gravity Waves ◽  
Surf Zone ◽  
Sea Surface ◽  
The Sea Of Japan ◽  
Surface Gravity Waves ◽  
Half Wavelength ◽  
Progressive Waves ◽  
Crust Deformation ◽  
Laser Strainmeters

This paper reviews the results of the processing of synchronized data on hydrosphere pressure variations and the Earth’s crust deformation in the microseismic range (5–15 s), obtained over the course of numerous experiments, using a coastal laser strainmeter and laser meters of hydrosphere pressure variations installed in various points of the Sea of Japan shelf. Interpreting the results, we have discovered new regularities in the dynamics of surface progressive gravity waves, and their transformation into primary microseisms, when waves move at the shelf of decreasing depth. For example, we found non-isochronous behavior of progressive waves, which manifests itself in a decrease in the periods of gravity waves due to the transformation of a part of their energy into the energy of primary microseisms. Furthermore, when processing the synchronous fragments of the records, made by laser strainmeters and laser meters of hydrosphere pressure variations, we identified approximate zones of the most effective transformation of the energy of gravity progressive waves into the energy of primary microseisms, which start from the depth of less than a half-wavelength and stretch to the surf zone.

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