Incorporation of a large‐scale wind‐driven turbulence model into a range‐dependent parabolic equation

Abstract

Atmospheric turbulence contains numerous scales ranging from a few centimeters to a few kilometers. As shown by Daigle et al. [J. Acoust. Soc. Am. 64, 622–630 (1978)], the effects of small scale turbulence (L<10 m) can be handled fairly well from a statistical standpoint. This approach works because for most of the time, small‐scale turbulence can be treated as isotropic over short ranges. However, large‐scale turbulence is anisotropic in nature. This results in variations in temperature and wind speed with range. In order to account for the effects of wind‐driven large‐scale turbulence on acoustic propagation, a large‐scale turbulence model was developed. This large‐scale turbulence model assumes elongated longitudinal vortex pairs roughly aligned with the mean wind speed with height and range due to the passage of an eddy pair. The wind speed variations are used to calculate range‐dependent sound‐speed profiles. The sound‐speed profiles are used by a range‐dependent parabolic equation to calculate variations in the received amplitude and phase of an acoustic wave as the eddy pair passes through the field of propagation.