The effect of stratification on the propagation and decay of
near-inertial waves on a β-plane
Abstract
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.