Wave Breaking in the Presence of Wind Drift and Opposed Swell

Results of two our recent studies are combined to show interesting phenomena in the ocean surface where the wind waves are co-existing with a swell propagating against the wind. It is shown that the growth of the wind waves is much intensified by swell propagating against the wind, when the swell steepness increases. This phenomenon shows clear contrast to the attenuation of the wind waves by swell propagating in the direction of the wind. Another interesting phenomenon is that the drift current is much intensified by swell propagating against the wind when the swell steepness increases. The increase of the drift current velocity is much larger than the theoretical prediction of the mechanism proposed by Phillips and Banner (1974).