Excitation of long internal waves by groups of short surface waves incident on a barrier

Abstract

The effects of diffraction by a long barrier on second-order long waves forced by sinusoidally modulated short incident waves are examined for a two-layered model ocean. When the group velocity of the short waves lies between the phase velocities of the longest baroclinic and barotropic modes, long internal waves of the frequency equal to twice the modulational frequency of the short waves are found to radiate away from the edge ray which divides the geometrical shadow and the illuminated region. In particular the baroclinic wave can penetrate the shadow. This penetration occurs when the internal long wave is not resonated by short surface waves.