Modified ray-mode (phase) theory: Understanding counter-wind propagation effects from atmospheric explosions

We have incorporated horizontal winds into ray-mode theory including the full spectrum of acoustic–gravity waves for a perfectly stratified, range-independent, steady-state model atmosphere for frequencies from 10−4 to ∼10 Hz. This approach has also been applied to a specific atmospheric propagation problem that has long defied a solution, namely counter-wind propagation arrivals at a location ∼300 km up-wind of the source. Our modified ray-mode theory predicts reliable up-wind solutions, but only if small-scale sound speed fluctuations were added to the mean seasonal sound speed profiles. Since full-waveguide theory and modified ray-mode mode theory incorporate diffraction and scattering propagation effects, we have performed additional analyses to determine the mechanism through which these fluctuations produce the up-wind signals. We have concluded that the dominant mechanism is through diffraction due to the presence of semi-permanent turbulence and internal gravity waves located near the stratopause.