Some recent NOAA theoretical work on echo sounding in the atmosphere

Abstract

This paper reviews some recent theoretical work on the effects of a nonzero mean wind on the propagation and scattering of sound by turbulent refractivity fluctuations. The paper includes a study of the deformation of the scattering cross section due to advection of the scatterers and analyses of the broadening of the frequency spectra of the acoustic pressure and pressure amplitude for forwardscatter and backscatter modes. The results have immediate applications both for determining the accuracy of echosonde measurements and for providing sensitive parameters for remote sensing of atmospheric structure. As early as 1874 Tyndall observed, as was rephrased byRayleigh [1945],.. 'that the very limited distances to which sounds are sometimes audible are due to an actual stopping of the sound by a flocculent condition of the atmosphere arising from unequal heating or moisture.' In addition, Tyndall [1874]