Wave propagation inside an inertia wave. Part II: Wave breaking

By launching monochromatic gravity wave packets of different frequencies, wavenumbers, and amplitudes below a localized inertia "background" wave, several assumptions and issues related to gravity wave dissipation and parameterizations are investigated: the influence of the time dependence of the background wave on wave breaking: the dependence of wave breaking on the initial wave packet frequency, vertical wavenumber, and amplitude; and the existence of a high-vertical-wavenumber cutoff beyond which all wave packets are dissipated into turbulence. An intermediate model is used that is two-dimensional, linear, and that models wave breaking with a mixed shear and convective adjustment scheme. Wave breaking is found to be reduced by the time dependence of the background wave, which has negative phase velocity, when the gravity waves are initially convectively stable. Large-scale dissipation, that is, dissipation associated with layers deeper than 400 m. occurs for gravity waves of initial vertical wavenumbers close to or smaller than 2 π/5 rad km ¹. Large-scale dissipation is not enhanced by the time dependence of the background wave. However, large-scale dissipation might be enhanced by the time dependence of the background wave if the initial amplitudes of the gravity waves are larger, for example, if the gravity waves are initially convectively unstable.