The effect of weak shear and rotation on internal waves

Abstract

The effect of constant shear on internal waves is studied in a simplified oceanic model with constant Brunt-Väisälä frequency and high dynamical stability. As observed in the non-rotating case (Phillips, 1966), the wave number is rotated, the energy transferred to the mean flow and the frequency decreased. A lower bound at inertial frequency is found as expected, but a shear instability will probably occur before the frequency reaches this limit.

Equilibrium frequency spectra are derived and compared to relevant observations. A good agreement is observed with the horizontal kinetic energy spectrum obtained at Site D, below the thermocline, whereas no inconsistency is found in comparison with other (less relevant) oceanic data. It is concluded that the interaction between shear and internal waves could play an important role in some region of the ocean.