Numerical ray tracing in the atmospheric surface layer

Abstract

A numerical ray-tracing model, including calculation of the sound pressure, was developed. It is valid for propagation from a point source in a moving, stratified atmosphere. Numerical integration of the ray equations was performed, and all rays reaching a specific point were found. Several expressions for the height dependency of the wind speed and the temperature were used, e.g., Monin–Obukhov similarity theory functions, the parameters of which were determined by use of a least-squares method. Measurements of sound propagation from a point source over finite impedance ground were made. Meteorological parameters were monitored simultaneously, wind direction and relative humidity at a single height, wind speed and temperature at five elevations. Comparison with the model was made out to a distance of 150 m. The agreement between the model values and those measured was good. The influence of the directional characteristics of the source was studied, and found to be very important.