Effects of internal gravity waves on acoustic pulse propagation in the atmospheric wave guides

Abstract

Recently developed theoretical model of a random internal wave field in the atmosphere is used for calculating the statistical characteristics of the parameters of acoustic pulses propagating in the atmospheric wave guides. The variances, frequency spectra and spatial structure functions of the internal wave-associated fluctuations of the acoustic pulse travel times and grazing angles are calculated and compared to those obtained in the experiments on pulse sounding of the atmosphere. The effects analyzed here include: a scattering of acoustic waves from highly anisotropic wind speed and temperature inhomogeneities into the so-called acoustic shadow zones; a discrete character of the observed frequency spectra of the fluctuations of acoustic pulse parameters in the range 1min-1h; an error caused by internal waves in determining of the angle of arrival of the acoustic signal in the waveguide.