Action of strong internal solitary waves on surface waves

Abstract

Transformation of gravity capillary surface waves on the current created by a large‐amplitude internal wave (IW) is considered. The trajectories of surface wave packets in a domain of coordinate and wave number are calculated for different IW amplitudes. In particular, the location of maxima and minima of the surface wave (SW) spectral density W with respect to the IW profile is studied. It is shown that for sufficiently large‐amplitude internal solitary waves (solitons) propagating in the same direction as the surface wave the minimum of W for all SW lengths is situated over the crest of the soliton. The corresponding “critical” value of the soliton amplitude is calculated. The noncollinear propagation of internal and surface waves is also considered. Finally, some numerical results obtained using the kinetic equation that describes the transformation of W in a field of large‐amplitude internal wave solitons are presented that are in agreement with the qualitative description and with recent observations of radar scattering from strong internal waves in a coastal area.