On the effect of strong internal waves on surface waves

Propagation of gravity-capillary surface waves (SW) in the presence of a current produced by a large-amplitude internal wave (IW) is considered in the short-wave approximation. The evolution of trajectories of SW packets in the "coordinate-wave vector" domain with the change of an IW amplitude is investigated. In particular, the authors have studied the location of maxima and minima of the surface-wave spectral density, W. It is shown that the minimum of W for an arbitrary wavelength lies above a large-amplitude internal solitary wave (IW soliton) when both IW and SW propagate in the same direction, the maximum of W being located over a forward slope of the IW soliton. It is in agreement with the results of the Coastal Ocean Probing Experiment (COPE), where extremely strong internal solitary waves were observed. Some numerical results with the use of a kinetic equation are also presented.