Internal Wave–Wave Interactions. Part I: The Role of Internal Wave Vertical Divergence

Small-scale internal waves are numerically ray-traced through random 3D Garrett and Munk internal wave backgrounds. Past ray-tracing investigations of the transfer of internal wave energy toward small scales have considered only interactions with background vertical shear Vz = (Uz, Vz). Here, scale analysis and numerical simulations indicate a nonnegligible role for vertical divergence Wz. Background low-frequency vertical shear Vz transfers high-frequency test waves toward small scales while background vertical divergence Wz transfers low-frequency test waves toward small scales. These ray-tracing results resemble those of weak resonant-triad interaction theory, although the interactions considered here are not limited to be weak or resonant.