Sea-tower measurements of wind-wave spectra in the Caspian sea

Abstract High frequency spectra of wind generated waves corresponding to mean wind speeds from 3.5 to 13.5 m s−1 were measured at the research tower in the Caspian Sea. The techniques used made it possible to evaluate spectra S(ω) in the frequency range extending to 10 Hz. The data obtained clearly show that there is no equilibrium range in the high frequency part of the wind wave spectrum. The measured spectra within the frequency range from 2.4 to 7.2 Hz fit a power law, S(ω) = α·ω−n, with the values of n changing from 3.2 to 4.8, and the values of the spectral density at the fixed frequency Sωl within this range were shown to increase with wind speed. The dependence of the shapes of the measured spectra on wind speed and the parameters of the long wave components is discussed. A new expression for the wind-wave frequency spectrum S(ω) within the range ω>ωm (ωm is the frequency of the spectral peak) is proposed based on the experimental data: it is expressed in terms of the difference between a particul...