Energy Balance of Evanescent Acoustic-Gravity Waves

Abstract

The features of the energy balance of evanescent acoustic-gravity waves in the atmosphere are investigated. In the case of freely propagating AGWs in an ideal isothermal atmosphere without dissipation, the period-average densities of kinetic and potential energy are equal to each other. This is true for the acoustic and gravity regions of the AGW spectrum. It is shown that the period-average kinetic and potential AGW energy densities are not equal to each other in the general case in the evanescent spectral region. The exceptions are the Lamb wave and the Brunt–Väisälä oscillations, in which the particles oscillate only along one coordinate (horizontally or vertically). Also, the densities of kinetic and potential energy are equal for the evanescent f- and γ-modes at the points where they touch the regions of freely propagating waves. An assumption is made that the evanescent modes for which the average values of kinetic and potential energies are equal are implemented first.