Mark Sprague Richard Raspet
Phys. Acoust. Res. Group, Univ. of Mississippi, University, MS 38677
V. E. Ostashev
Inst. of Atmospheric Phys., Russian Academy of Sci., Pyzhevskii 3, Moscow 109017, Russia
Ray theory says that a ray moving in a crosswind will drift out of the plane of propagation, and that this effect can be significant with high windspeeds and over long propagation distances. White and Li [Michael J. White and Y. L. Li, J. Acoust. Soc. Am. 92, 2405 (A) (1992)] and Wilson [D. Keith Wilson, J. Acoust. Soc. Am. 92, 2405 (A) (1992)] developed two-dimensional fast-field programs (2DFFPs) to calculate the sound pressure levels of windy atmospheres. They reported that crosswind effects were negligible for the cases they considered and that a one-dimensional stationary phase solution yields accurate results. Ray analysis of the two-dimensional phase space used in the 2DFFP indicates that there is a small region that contributes significantly to the sound level. In the presence of a crosswind, the one-dimensional stationary phase approximation does not include all of this region. 2DFFP calculations for realistic windspeeds that show crosswind drift are presented, and the 2DFFP calculations are compared to the calculations of a one-dimensional stationary phase approximation.