&lt;title&gt;Recent advances in ocean-surface characterization by a scanning-laser slope gauge&lt;/title&gt;

Lee, Peter H.Y.; Barter, J. D.; Beach, Kory; Hindman, C. L.; Lake, Bruce M.; Rungaldier, H.; Schatzman, James C.; Shelton, John P.; Wagner, Richard N.; Williams, A. B.; Yee, Richard W.; Yuen, Henry C.

doi:10.1117/12.138852

Cited by 14 publications

(6 citation statements)

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“…To overcome these problems, spatial measurements of capillary-gravity waves have been recently attempted. Banner et al [1989] used stereophotogrammetry from an offshore rese.•ch platform to obtain wavenumber spectra for waves between 0.2 and 1.6 m. For shorter waves, a scanning laser slope gauge (SLSG) has been used by Barter et al [1990], Lee et al [1992], and Li et al [1993]. Jiihne and Riemer [1990] have conducted extensive measurements of wavenumber spectra in the capillarygravity range using a digital image processing technique at a large wind-wave flume.…”

Section: Introductionmentioning

confidence: 99%

In situ measurements of capillary‐gravity wave spectra using a scanning laser slope gauge and microwave radars

Hara¹,

Bock²,

Lyzenga³

1994

J. Geophys. Res.

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Capillary-gravity wave spectra are measured using a scanning laser slope gauge (SLSG), and simultaneously by X and K band Doppler radars off the Chemotaxis Dock at the Quissett campus of the Woods Hole Oceanographic Institution at Woods Hole, Massachusetts. Wave spectral densities estimated from the radar measurements using the Bragg theory agree with those measured using the SLSG at the Bragg wavenumber to within a few decibels, suggesting that Bragg scattering theory is valid for the conditions of this experiment. The observed degree of saturation of capillary-gravity waves is in reasonable agreement with measurements by J•ihne and Riemer (1990) obtained from measurements in a large wind-wave flume at intermediate wind speeds, but our data indicate a higher degree of saturation at very low wind speeds. The rate at which the slope-frequency spectrum falls off, however, is much lower in the field than in laboratories, even at moderate winds, suggesting long waves are responsible for a large Doppler shift of capillary-gravity waves. Close examination of combined wavenumber-frequency slope spectra also reveals significant smearing of the spectra in the frequency domain due to long waves. These observations confirm that spatial measurements (wavenumber spectra measurements) are essential for characterizing short capillary-gravity waves, since this strong Doppler shift will dramatically change apparent frequency spectra. in idealized conditions [Hara and Mei, 1994]. The parameterization of the surface roughness in practical conditions still relies heavily on empirical observations [e.g., Charnock, 1955]. Many theoretical, as well as experimental, studies are available on the generation, the nonlinear wave-wave interaction, and the dissipation of the capillary-gravity waves Paper number 94JC00531. 0148-0227/94/94JC-00531 $05.00 separately. In particular, recent numerical [Ruvinsky et al., 1991], theoretical [Longuet-Higgins, 1992], and experimental [Perlin et al., 1993] studies have advanced our understanding of the interaction between steep gravity waves and parasitic capillary waves near their crests. How-ever, studies of the combined effects of the three forcing mechanisms, namely, wind input, wave interaction, and wave dissipation, are still scarce either theoretically [Janssen, 1986[Janssen, , 1987; Hara and Mei, 1994] or experimentally. As a result, theoretical modeling of capillary-gravity waves in a field environment has been limited to the simple approach based on the conservation of wave action with the above three mechanisms added independently. Further progress of theoretical modeling is hindered partly because reliable direct ob'servations of capillary-gravity waves in a field environment are almost nonexistent except for the many radar backscatter measurements that come with their own uncertainties owing to the lack of knowledge regarding the mechanism of microwave reflection at the air-sea interface.Conventional single-point wave-height or wave-slope measurements are not appropriate to characterize capi...

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Section: Introductionmentioning

confidence: 99%

In situ measurements of capillary‐gravity wave spectra using a scanning laser slope gauge and microwave radars

Hara¹,

Bock²,

Lyzenga³

1994

J. Geophys. Res.

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“…The long wave breaking significantly increases the probability of very large slopes beyond six times of the standard deviation. This has been observed by Lee et al (1995Lee et al ( , 1996 from the grazing-angle-dependent signals and their Doppler spectra. The long wave breaking and cresting give strongly reflecting facets at angles well beyond those predicated in simple specular-point theory, including out to grazing angles.…”

Section: F Non-gaussian Pdf Of Slopesmentioning

confidence: 72%

“…The long wave breaking and cresting give strongly reflecting facets at angles well beyond those predicated in simple specular-point theory, including out to grazing angles. Lee et al (1995) found strong evidence that in low grazing angles, lifetimedominated, non-Bragg scattering contributes noticeably to returns for both polarizations, but is dominant in providing return for the horizontal polarization. Without consideration of long wave breaking, our model on the PDF of slopes cannot accurately predict the returns of both polarizations at low grazing angles, especially for the horizontal polarization.…”

Section: F Non-gaussian Pdf Of Slopesmentioning

confidence: 97%

“…Until now, only few spatial measurements of gravitycapillary waves in the field have been performed (Lee et al 1992;Hara et al 1994;Hwang et al 1996;Klinke and Jähne 1995). The discrepancy between the curvature spectra from the above field measurements is about 10 times greater than the order of the lower one.…”

Section: (U * /C) 2 Dependence and U * /C Dependencementioning

confidence: 98%

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The Mean-Square Slope of Ocean Surface Waves and Its Effects on Radar Backscatter

Liu

Yan

et al. 2000

J. Atmos. Oceanic Technol.

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The mean-square slope (MSS) of the sea surface for upwind and crosswind is derived, based on Phillips' equilibrium spectrum and the model herein on gravity-capillary wave spectrum. The MSS integrated from the above two spectra over high-frequency dissipation length (1 mm) fits the optical observations very well. The radar backscatter cross section (RBCS), calculated from specular reflection theory using the Ku-band filtered MSS, is in keeping with the empirically based Ku-band models by Brown for the GEOS-3 13.9-GHz altimeter, and by Witter and Chelton for the Geosat 13.5-GHz altimeter. Also, the RBCS, calculated using the C-band filtered MSS, is in keeping with the ERS-1/-2 scatterometer empirically based algorithms CMOD3 and CMOD4. The physics included in this model on gravity-capillary wave spectrum is also illustrated. The shortwave dissipation due to wave-drift interactions has the effect of suppressing the spectral density at high wind condition, which further influences the directional spreading rate. This effect can be denoted by c 2 / orc 2 / dependence 2 2 U c 10 p of shortwave spectrum. It is suggested that the k p /k dependence observed in the range of gravity waves should not be extended to the region of short waves. The parasitic capillary wave dissipation due to molecular viscosity can be balanced by the energy supply from the underlying waves, hence it is removed from the model. The eddy viscosity is due to turbulence at the wind-drift layer, which suppresses the spectrum of high-frequency waves with wavelengths on the order of millimeters.

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“…(2) Field data obtained by Valenzuela (1978) using a four-frequency radar show that the spectrum between wavelengths of 72 cm and 2 cm under U10 = 2.5 ms -1 has a slope steeper than co 5 More spectra with steeper slopes than m 5 in the ocean were also observed by Palm et al (1976), Tang and Shemdin (1983) and Lee et al (1992) by using a laser-optical sensor.…”

Section: Introductionmentioning

confidence: 81%

Directional spectrum of wind waves: Part I—model and derivation

Liu

Yan

2003

J Ocean Univ. China

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A new model on the directional spectrum of wind waves for deep water is proposed based on the statistics of wind waves. This model contains three parameters: the wave age, the inverse spectral bandwidth and the local spectral-peak angular frequency. The inverse spectral bandwidth is a robust parameter for describing the spectral steepness of wind waves. Using the inverse spectral bandwidth parameter, the proposed model can well describe various observations obtained from the open ocean and laboratory tank.

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<title>Recent advances in ocean-surface characterization by a scanning-laser slope gauge</title>

Cited by 14 publications

References 0 publications

In situ measurements of capillary‐gravity wave spectra using a scanning laser slope gauge and microwave radars

In situ measurements of capillary‐gravity wave spectra using a scanning laser slope gauge and microwave radars

The Mean-Square Slope of Ocean Surface Waves and Its Effects on Radar Backscatter

Directional spectrum of wind waves: Part I—model and derivation

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