Gravity wave-fine structure interactions: A reservoir of small-scale and large-scale turbulence energy

A direct numerical simulation of gravity wave – fine structure interactions is performed to evaluate the effects of such a superposition on instability and turbulence for fine structure shears and a gravity wave (GW) amplitude that are individually stable. The superposition leads to deformations of the fine structure and GW fields that exhibit Kelvin‐Helmholtz (KH) shear instabilities and turbulence extending over more than 20 buoyancy periods. KH instabilities occur on multiple scales, deplete the kinetic energy of the initial fine structure, and yield a layering of the potential temperature field resembling “sheet and layer” structures observed in the oceans and the atmosphere. The interactions have a much smaller effect on the GW amplitude. Such interactions among GWs and fine structure are likely ubiquitous throughout the atmosphere and oceans and may account for sporadic bursts of turbulence and its persistence in regions of apparent static and dynamic stability (Ri > 1/4).