Estimation of the “whitecap” lifetime of breaking wave

Abstract

The paper presents the results of a study of the lifetime of wind-wave breaking (“whitecaps”) and the spatial distribution of the moments of wave-breaking initiation along the profile of a long surface wave. The results obtained during the specialized experiments from an oceanographic platform in the Black Sea are given. The registration of the whitecaps was carried out based on the video recordings of the sea surface. The surface waves’ characteristics were measured and the meteorological information was recorded simultaneously with the video recordings. It is shown that the distribution of the whitecaps’ lifetime is well described by an exponential law. It was found that the ratio of the lifetime of an individual whitecap to the period of the breaking wave is 0.3. The distributions of the above-mentioned ratio are similar for different wind and wave conditions. It is indicated that the generation of whitecaps occurs mainly in the region of the crest of a long wave with a shift to its front slope on average by 9.6 of the phase of the long wave. The whitecap having arisen at the leading edge shifts to the trailing edge of the long wave during its lifetime, so that the phase difference between the breaking initiation and the maximum of the surface fraction covered by the whitecaps equals 21.6.