A physical model of the short wind wave spectrum in

the wavelength range from a few millimeters to few meters is

proposed. The spectrum shape results from the solution of

the energy spectral density balance equation.

Special attention is paid to the description of the capillary

range of the short wave spectrum.

It is assumed that in this range the spectrum shape is

determined mainly by the mechanism of generation of parasitic

capillaries. This is described as the cascade energy transfer

from the gravity to the capillary waves. Thus the capillary

wave spectrum results through the balance between generation

of capillaries and their viscous dissipation.

The short gravity wave spectrum results through the balance

between wind input and dissipation due to wave breaking.

A parameterization of wind input is obtained in part 1 of the

present paper. To describe the dissipation due to wave

breaking, the approach developed by Phillips (1985) is used.

The spectral rate of energy dissipation is presented in the

form of a power dependence of the ratio of the saturation

spectrum to some threshold level. It is further shown that

the threshold level depends on the drift current shift in

the water viscous sublayer, which affects the energy losses by

wave breaking.

To obtain a short wave spectrum which is valid in the whole

wavenumber domain, the capillary and the short gravity wave

spectra are patched in the vicinity of the wavenumber

corresponding to the minimum phase velocity.

This short wave spectrum is incorporated into the wind over

waves coupled model developed in part 1 of the present paper.

The measured statistical properties of the sea surface related

to the short waves, such as the spectral shape of

omnidirectional and up-wind spectra, their wind speed

dependence and angular spreading, and the wind speed

dependence of integral mean square slope and skewness

parameters, are well reproduced by the model. Also the model

well reproduces the measured wind speed dependence of the

drag coefficient and of the coupling parameter.

VN Kudryavtsev, VK Makin, B Chapron. Coupled sea surface-atmospheric model 2. Spectrum of short wind waves

published, J. Geophys. Res., 1999, 104

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