The effect of stratification on the propagation and decay of near-inertial waves on a β-plane
• Vamsi Krishna Chalamalla
Wind-excited near-inertial waves (NIWs) rapidly propagate towards the equator on a β-plane. In this letter, we model the evolution of NIWs under the β-effect by imposing initial zonal velocity in the mixed layer. We varied the background stratification strength and observed the changes in wave characteristics and also quantified the decay rate of the mixed layer kinetic energy. Varying the interior stratification strength leads to higher vertical modes and faster decay of mixed layer kinetic energy. We observed a strong double-inertial frequency signal in the FFT spectrum, which could result from the nonlinear interactions between near-inertial waves. The faster decay of mixed layer kinetic energy at higher stratifications is due to the increasing vertical wave flux at the base of the mixed layer. We also observed strong shear at the base of the mixed layer with $Ri_g$ values dropping below 0.25 in this region.