Knowledge on intermittency of wave breaking is so far limited to a few summary statistics,while the probability distribution of time interval between breaking events can provide a full view of intermittency.Based on a series of experiments on wind wave breaking,such probability distributions are investigated.Breaking waves within a wave group were taken as a single breaking event according to recent studies.Interval between successive wave groups with breaker is the focus of this paper.For intervals in our experiments with different fetch and wind conditions,their distributions are all skewed and weighted on small intervals.Results of Kolmogorov–Smirnov tests on time series of these intervals indicate that they all follow gamma distribution,and some are even exponential type.Average breaking-group-interval decreases with friction velocity and significant steepness until the wind is strong enough;most of them are more than 10times the dominant wave period.Group breaking probability proposed by Babanin recently and the average number of breaking waves in wave groups are also discussed,and they are seemingly more reasonable and sensitive than traditional breaking probability defined in terms of single wave.
A sea spray generation function(SSGF)for bubble-derived droplets that takes into account the impact of wave state on whitecap coverage was presented in this study.By combining the new SSGF with a previous wave-state-dependent SSGF for spume droplets,an SSGF applicable to both bubble-derived and spume droplets that includes the impacts of wave state was obtained.The produced SSGF varies with surface wind as well as with wave development.As sea surface wind increases,more sea spray droplets are produced,resulting in larger SSGFs and volume fluxes.Meanwhile,under the same wind conditions,the SSGF is mediated by wave state,with larger SSGFs corresponding to older waves and larger windsea Reynolds numbers.The impact of wave state on sea spray heat flux was then estimated by applying this SSGF while considering the thermodynamic feedback process.Under given atmospheric and oceanic conditions,the estimated sea spray heat flux increases with wind speed,wave age,and windsea Reynolds number.
A laboratory experiment was conducted inside a wind wave tank to investigate the wave induced turbulence. In this experiment, the wave surface elevation and velocity beneath the water surface were measured simultaneously to investigate the relation between the wave status and wave induced turbulence. The profile of the turbulent dissipation rate and Reynolds stress were calculated using experimental data. The effect of the wave status on turbulence is investigated with regard to the wind wave, swell, and mixed wave conditions. It was depicted that the turbulence decreased with increasing depth from the water surface and that the turbulence that was induced by a wave with larger wavelength and wave height is much stronger for the same wave status. Finally, we observed that the wind wave is more effective in activating the wave induced turbulence.
