Acoustic-gravity nonlinear structures

Abstract

Abstract.A catalogue of nonlinear vortex structures associated with acoustic-gravity perturbations in the Earth's atmosphere is presented. Besides the previously known KelvinStewart cat's eyes, dipolar and tripolar structures, new solutions having the form of a row of counter-rotating vortices, and several weakly two-dimensional vortex chains are given. The existence conditions for these nonlinear structures are discussed with respect to the presence of inhomogeneities of the shear flows. The mode-coupling mechanism for the nonlinear generation of shear flows in the presence of linearly unstable acoustic-gravity waves, possibly also leading to intermittency and chaos, is presented.

Nonlinear acoustic–gravity waves

“…the Earth's atmosphere where γ ≈ 1.4) we note that the resonance conditions for three-wave interactions can be approximately satisfied (e.g. Yeh and Liu 1970;Juren and Stenflo 1973) and that three-wave interactions thus can play a major role in the amplitude development of atmospheric waves. Due to algebraic difficulties the coupling coefficients appeared first as rather complex expressions (Dysthe et al 1974;Ostrovskii and Petrukin 1981), which limited the interest in applying them.…”

“…Further studies (Jovanovic et al 2002) have resulted in a catalogue of nonlinear vortex structures associated with acoustic-gravity perturbations in the Earth's atmosphere. This includes Kelvin-Stewarts cats eyes, tripolar (Jovanovic et al 2001) structures as well as new solutions having the form of a row of counter-rotating vortices. Generalizations to three-dimensional solitary vortex structures (Pokhotelov et al 2001) show that monopole vortices of finite height can also be found.…”

Spectral properties of acoustic gravity wave turbulence

“…Stationary nonlinear solutions of (3) and (4) in the form of a double vortex and a vortex chain have been presented by many authors [Stenflo, 1987Jovanovic et al, 2002;van Heijst and Kloosterziel, 1989;Aburdzhaniya, 1996;Pokhotelov et al, 2001;Yeh and Liu, 1972].…”

“…The AGWs are lowfrequency disturbances associated with the density and velocity perturbations of the atmospheric fluid in the presence of the equilibrium pressure gradient that is maintained by the gravity force. The frequency w of the AGWs is given by the dispersion relation [Stenflo, 1987Jovanovic et al, 2002] …”

“…[2] Studies of acoustic gravity waves (AGWs) [Yeh and Liu, 1974;Fritts and Alexander, 2003;McKenzie and Axford, 2000;Stenflo, 1987;Jovanovic et al, 2002] in the Earth's middle atmosphere, in the solar atmosphere, as well as in planetary magnetospheres have been motivated by the need to obtain accurate predictions of the dynamics of the atmosphere under various meteorological conditions, and include the profiles of the density, pressure, and the presence of shear flows in the winds. The AGWs are lowfrequency disturbances associated with the density and velocity perturbations of the atmospheric fluid in the presence of the equilibrium pressure gradient that is maintained by the gravity force.…”