Traveltimes for infrasonic waves propagating in a stratified atmosphere

Abstract

The tau-p method of Buland and Chapman (1983) is reformulated for sound waves propagating in a stratified atmosphere under the influence of a height-dependent wind velocity profile. For a given launch angle along a specified azimuth, the ray parameter is redefined to include the influence of the horizontal wind component along the direction of wave propagation. Under the assumption of negligible horizontal wind shear, the horizontal wind component transverse to the ray propagation does not affect the direction of the wave normal, but displaces the reference frame of the moving wavefront, thus altering the observed incidence azimuth. Expressions are derived for the time, horizontal range, and transvers range of the arriving waves as a function of ray parameter. Algorithms for the location of infrasonic wave sources using the modified tau-pM formulation in conjucntion with regional atmospheric wind and temperature data are discussed.