The effects of the wind velocity fluctuations on the sound backscattering cross section in the stratified moving atmosphere

Abstract

Recent studies have shown that, in the case of strong diffraction, the relative contributions from wind velocity and temperature fluctuations to many statistical moments of a sound field propagating in a turbulent atmosphere are determined by the ratio of the normalized variances of wind velocity and temperature fluctuations, multiplied by factor 4. On the other hand, for weak diffraction, these relative contributions are determined by the ratio of the normalized structure–function parameters of wind velocity and temperature fluctuations, multiplied by factor 22/3. In this paper, we calculate the vertical profiles of both ratios for different turbulent regimes in unstable atmospheric boundary layers. Furthermore, vertical profiles of the ratio for weak diffraction are used to study the effects of the wind velocity fluctuations on the sound backscattering cross section in a stratified moving atmosphere. This study is important for acoustic remote sensing of the atmosphere by monostatic sodars which measure a signal proportional to the backscattering cross section. [Work supported in part by the U.S. Army Research Office under Contract No. DAAG55-98-1-0463, and an NRC-ETL Research Associateship.]