Relative contributions from temperature and wind velocity fluctuations to the statistical moments of a sound field in a turbulent atmosphere

Expressions are presented for the vertical profiles of the variances, integral length scales and structure-function parameters of temperature and wind velocity fluctuations for different turbulence regimes in an unstable atmospheric boundary layer. Based on these expressions, two ratios of velocity-to-temperature terms are obtained. The first of these ratios characterizes the relative contributions from wind velocity and temperature fluctuations to the statistical moments of a sound field in a turbulent atmosphere when this field is affected mainly by large-scale inhomogeneities. The second ratio characterizes these contributions in the opposite case when a sound field is affected mainly by relatively small-scale inhomogeneities in the inertial subrange. The vertical profiles of the second ratio, obtained for different meteorological conditions, are used to study the effects of wind velocity fluctuations on the echo signal measured by a monostatic sodar in a stratified, moving atmosphere. The common practice of interpreting returns from monostatic sodars solely in terms of the temperature structure-function parameter is found to be tenuous in many typical atmospheric conditions.