Internal gravity wave perturbations and their impacts on infrasound propagation in the atmosphere

Abstract

The model of shaping of the 3-D and 1-D wavenumber spectra for the wind velocity and temperature fluctuations induced by atmospheric gravity waves is described here. Using the 3-D spectrum of gravity wave perturbations, the variances of the fluctuations of sound travel time along refracting ray paths and the azimuth of arrival of acoustic signals are estimated. These variances define the errors in localization of infrasound sources caused by gravity wave perturbations. The results of theory and numerical modeling of infrasound scattering from gravity wave perturbations are presented. With a recently developed infrasound probing method the vertical profiles of the horizontal wind velocity fluctuations in the upper stratosphere (height range is 30-52 km) and lower thermosphere (90-140 km) are retrieved. The method is based on analytic relation between scattered infrasound field in the shadow zone and the vertical profile of the layered inhomogeneities of the effective sound speed. The obtained results show a capability of the probing method in the retrieval of the detailed wind-layered structure in the stratosphere, mesosphere and lower thermosphere. The vertical wavenumber spectra of the retrieved vertical profiles of the wind velocity fluctuations in the upper stratosphere and their coherence functions are analyzed.