Measurements of a saturated range in ocean wave spectra

Abstract

Wavestaff measurements made in the Gulf of Mexico and Waverider measurements from the Baltimore Canyon area have been used to study the form of ocean wave spectra at high frequencies. The observations are statistically consistent with the idea that the tail of the spectrum is in equilibrium with the local wind. Analysis showed that the spectral range between the mean wave frequency and about two and one half times that frequency is consistently proportional to the inverse of the fourth power of the frequency. At higher frequencies, the classical inverse fifth power law seems to hold. In the inverse fourth power range, the amplitude of the spectrum is also proportional to the wind friction velocity. These relationships should permit a reliable specification of this saturated range when only local wind observations are available. If the significant wave height and mean period are known, the amplitude of the tail of the spectrum can be predicted with somewhat greater accuracy. However, this relationship should be used with caution when the height and period statistics are influenced by swell.