Some Results of Simulation of Long-Range Infrasonic Propagation in the Atmosphere

• Published in: Izvestiya. Atmospheric and oceanic physics 2004-03, Vol.40 (2), p.202-215
• Main Authors: Kulichkov, S N, Avilov, K V, Popov, O E, Otrezov, AI, Bush, G A, Baryshnikov, A K
• Format: Article
• Language: English
• ISSN: 0001-4338

Results of simulating long-range infrasonic propagation in the atmosphere with the use of both the method of normal waves (MNW) and the parabolic equation method are presented. The effect of the atmospheric fine structure on the amplitude and phase characteristics of infrasonic signals from surface explosions is studied. The MNW is used for a model of the medium in the form of a piecewise-linear profile of the acoustic refractive index squared. This profile was obtained from a regular rocket sounding of the atmosphere to heights of about 80 km. The high-frequency approximation of the MNW is considered. An expression is obtained for the phase of the coefficient of sound reflection from a half-space with a piecewise-linear profile of the square of the acoustic refractive index with an arbitrary number of layers. It is shown that, if the atmosphere has a fine layered structure, the phase of the reflection coefficient psi differs from the phase of a monochromatic wave psi calculated for a layered medium in the geometric-acoustics approximation in the appearance of an additional term eta depending on the parameters of the atmospheric fine structure along the path of sound propagation. It is also shown that the effect of the fine-layered structure of the atmosphere on acoustic signals recorded in the region of refractive audibility is mainly responsible for the occurrence of additional extrema in the form of these signals. For the case of the MNW high-frequency approximation, which is considered in this work, this effect is equivalent to the violated condition of the constructive interference of normal waves. The profiles of acoustic signals recorded in both the acoustic audibility and geometric-shadow regions at large distances from explosions are obtained with both the MNW and the pseudodifferential parabolic equation method. There is a satisfactory agreement between the calculation results and experimental data on infrasonic signals recorded in the audibility and shadow regions at a distance of about 300 km from surface explosions equivalent to 20-70 t of TNT.