The Excitation of Radiating Waves and Kelvin-Helmholtz Instabilities by the Gravity Wave-Critical Level Interaction

Abstract

The gravity wave-critical level interaction is found to excite both radiating waves and Kelvin-Helmholtz instabilities through nonlinear interactions near the critical level. Radiating waves are forced directly by perturbations in the harmonies of the incident gravity wave and Kelvin-Helmholtz instabilities, once excited through nonlinear interactions, grow on the unstable velocity shears created by the incident wave. Results are presented which demonstrate that radiating waves can significantly increase the wave-action and momentum flux which is found above a critical level and that Kelvin-Helmholtz instabilities are responsible for stabilizing the induced unstable velocity shears. Finally, the implications of these results for the atmosphere and the oceans are discussed.