A two-dimensional effective sound speed parabolic equation model for infrasound propagation with ground topography.

A terrain capable parabolic equation (PE) propagation algorithm for long range infrasound propagation modeling has been implemented using Padé approximations for the various operator valued functions that arise in PE algorithms. In this work, the influence of the winds are captured by the effective sound speed approximation and propagation is restricted to the range-altitude plane. The ground topography is included by the addition of an impenetrable fluid below the ground surface. The impedance condition at the ground is handled explicitly, including both vertical and radial components. It is found that including terrain can have a large influence on long range propagation. In particular, reflections from a sufficiently steep slope can change the inclination angle enough to move the propagation path from one atmospheric duct to another.