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Using the limit surface slope as a criterion of wave breaking,a simple model for estimatingthe spatial fraction of breaking surface of sea at an instant,which is regarded as the whitecap coverge inthis paper,is analytically derived from the probability density of surface slope based on Gaussianstatistics.The resulting fraction is found depending on the fourth moment of wave spectum,m_4,as well asthe critical threshold of surface slope.By expressing the fourth moment in terms of the Neumannspectrum,a formula linking the fraction and wind speed for fully developed sea states is obtianed.Anotherformula relating the fraction to both wind speed and fetch(or duration)is achieved by expressing m_4 interms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave pre-dicting technique.A comparison between these results and the field data of whitecap coverage collected byMonahan and O＇Muircheartuigh shows an encouraging agreement.
Using the limit surface slope as a criterion of wave breaking, a simple model for estimating the spatial fraction of breaking surface of sea at an instant, which is regarded as the whitecap coverge inthis paper, is analytically derived from the probability density of surface slope based on Gaussianstatistics. The fraction is found depending on the fourth moment of wave spectum, m_4, as well asthe critical threshold of surface slope. BY expressing the fourth moment in terms of the Neumannspectrum, a formula linking the fraction and wind speed for fully developed sea states is obtianed.Anotherformula relating to fraction to both wind speed and fetch (or duration) is achieved by expressing m_4 interms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave pre-dicting technique. A comparison between these results and the field data of whitecap coverage collected by Monahan and O’Muircheartuigh shows an encouraging agreement.