Absorption of infrasound and acoustic-gravity waves in the atmosphere

Abstract

Long-range propagation of infrasound and acoustic-gravity wave fields in the middle and upper atmosphere are strongly affected by air viscosity and thermal conductivity. To characterize the wave dissipation, it is typical to consider idealized environments, which admit plane-wave solutions. This paper presents an asymptotic approach that relies instead on the assumption that spatial variations of environmental parameters are gradual. Unlike the traditional approach, the asymptotic theory allows one to derive AGW dispersion equations in a consistent manner for a wide range of scenarios and to describe the wave attenuation more realistically. Realistic assumptions about the atmosphere are found to lead to rather different predictions for absorption of atmospheric waves than the plane-wave solutions. Wind speed and wave frequency appear only through the intrinsic wave frequency in the dispersion equation, including the terms that describe the effects of viscosity and thermal conductivity. It is found that th...