Similarity laws of the wind wave and the coupling process of the air and water turbulent boundary layers

Self-contained upward-looking ADCP data obtained at station (20.21'N, 1560.11'E) during the TOGA/COARE TOP were carefully analyzed to extract the echo amplitude (AGC) returning from the sea surface. The AGC values at the surface were found to have a good correlation with the wind speed data obtained from the ATLAS buoy at the same site and ranging from 0 to 13ms-1. This study opened the possibility of predicting the wind speed from the surface AGC although the reason why backscatter from the sea surface increased with the wind speed was not sufficiently elucidated.

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“…(Toba, 1988;Gill, 1982). This is our first report on the sea surface data obtained by the upward-looking ADCP.…”

Section: Summary and Discussionmentioning

confidence: 99%

Sea Surface Measurement by a Self-Contained Upward-Looking ADCP

Nakajima

Kaneko

Gohda

et al. 1995

Journal of the Meteorological Society of Japan

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“…This result can be explained in view of the existence of the 3/2-power law of wind-waves. A more detailed argument on this point is given by Toba (1988) with respect to the physical interpretation of the similarity lows of wind waves.…”

Section: Statistical Features Of the Large-scale Structurementioning

confidence: 99%

“…As will be reported elsewhere (Toba, 1988), this relationship is interpreted as another aspect of the local equilibrium between the wind and the wind wave, where tlle similarity laws of wind waves as represented by tile 3/2-power law exist.…”

Section: Introductionmentioning

confidence: 98%

Turbulent structure in water under laboratory wind waves

Yoshikawa¹,

Kawamura

Okuda

et al. 1988

Journal of the Oceanographical Society of Japan

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Abstract:The structure of the turbulent boundary layer underneath laboratory wind waves was studied by using a combination of a high-sensitivity thermometer array with a two-component sonic flowmeter. The temperature fluctuations are used to detect movements of water parcels, with temperature as a passive quantity. The turbulence energy was dominant in the frequency range (0.01 ~ 0.1Hz), which was much smaller than the wind-wave frequency (2 ~ 5Hz), and in which the turbulence was anisotropic.There was a frequency range (0.2 ~ 2Hz for velocity, 0.2 ~ 5Hz for temperature fluctuation) where the turbulence was isotropic and had a -5/3 slope in the energy spectrum. These points are the same as those in previous works. However, by analyses of the time series by using a variable-interval time-averaging technique (VITA), it has been found that conspicuous events in this main turbulence energy band are the downward bursting from the vicinity of the water surface.Thus the structure of the water layer underneath the wind waves has characters which are similar to the familiar turbulent boundary layer over a rough solid wall, as already conceived. It has been found that, at the same time, the turbulence energy can be related to quantities of the wind waves (the root mean squared water level fluctuation and the wave peak frequency), for different wind and wave conditions. That is, the turbulence underneath the wind waves develops under a close coupling with the wind waves.

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“…When pure wind waves are growing under a steady wind, the wind-driven breaking adjustment, as discussed by Toba (1988), is performed in order for the 3/2-power law (Toba, 1972) to be satisfied, and the momentum of the air flow is transferred to the water more effectively than over solid surfaces. Since the Reynolds number is sufficiently large, turbulence in the surface layer of the sea plays a large role in such a situation, the conditions being independent of the molecular viscosity u.…”

Section: Introductionmentioning

confidence: 99%

Sea-surface roughness length fluctuating in concert with wind and waves

Toba

Ebuchi

1991

Journal of the Oceanographical Society of Japan

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When the nondimensional aerodynamic roughness parameter for the sea surface (gzo/u, 2, g being the acceleration of gravity, u, the air friction velocity) is plotted as a function of the wave age, the data points in the diagram are distributed mostly in a triangle area between the Charnock formula and the Toba-Koga formula; the nondimensional roughness perameter is not expressed as a unique function of the wave age, but rather there seem to be multiple regimes. In order to investigate the cause of the data point scattering, a reanalysis was made of the 4.5-hour time series of the wind profile and wind-wave statistics which were obtained at an oceanographic tower station under the conditions of a winter monsoon wind having slightly fluctuating speed and steadily growing wind waves.It is concluded that the averaged variation of z0 is given by the Toba-Koga formula with a constant of value 0.015. However, as a result of the wind fluctuation on the time scales ranging from several minutes to an hour, data points show a conspicuous fluctuation on the nondimensional roughness parameter-wave age diagram in the direction transverse to the averaged variation. The variation in z0 directly reflects the degree of over-or under-saturation in the high-frequency range of the wind-wave spectra. Physical interpretation of these variations is also presented.

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Similarity laws of the wind wave and the coupling process of the air and water turbulent boundary layers

Cited by 25 publications

References 49 publications

Sea Surface Measurement by a Self-Contained Upward-Looking ADCP

Sea Surface Measurement by a Self-Contained Upward-Looking ADCP

Turbulent structure in water under laboratory wind waves

Sea-surface roughness length fluctuating in concert with wind and waves

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