Stability Analysis of Inertio—Gravity Wave Structure in the Middle Atmosphere

Abstract

We present a stability analysis of the environment due to a large-amplitude inertio—gravity wave. Our purpose is to examine the conditions under which the Kelvin-Helmholtz (KH) instability may be an effective wave saturation process in the middle atmosphere. The concurrence, range of wavenumber, and growth rate of the KH instability are shown to depend on the IGW frequency and the KH orientation within the wave field because of the influence of wave frequency on the shear and local stratification. Results of the analysis indicate that the KH instability is likely a preferred mode of instability for sufficiently low gravity wave frequencies, but that it cannot occur for high-frequency wave motions in the absence of a mean shear. Inertio—gravity waves are also most unstable to KH instabilities aligned transverse to the direction of large-scale wave propagation.