The effect of the stratopause on the structure of the infrasound signal from the August 4, 2020, Beirut explosion.

The influence of wind velocity and temperature stratification in the upper stratosphere on the waveform of the infrasound signal received at a distance of 2398 km from the epicenter of the powerful explosion in Beirut that occurred on August 4, 2020 is studied using ray trace and pseudo-differential parabolic equation (PDPE) methods. Given a high temporal variability of the wind velocity in the stratopause predicted by the European Centre for Medium-Range Weather Forecasts model, it is assumed that within the stratopause layer, the increase in effective sound speed with increasing height is very small, on the order of 1 m/s. When modeling propagation of the signal from the explosion, the presence of a fine-scale layered structure of wind velocity and temperature in the real atmosphere was also taken into account.

Modeling propagation of infrasound signals observed by a dense seismic network.

The long-range propagation of infrasound from a surface explosion with an explosive yield of about 17.6 t TNT that occurred on June 16, 2008 at the Utah Test and Training Range (UTTR) in the western United States is simulated using an atmospheric model that includes fine-scale layered structure of the wind velocity and temperature fields. Synthetic signal parameters (waveforms, amplitudes, and travel times) are calculated using parabolic equation and ray-tracing methods for a number of ranges between 100 and 800 km from the source.

Mesoscale variations in acoustic signals induced by atmospheric gravity waves.

The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal wave-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated.

Acoustic pulse propagation through a fluctuating stably stratified atmospheric boundary layer.

Mesoscale wind speed and temperature fluctuations with periods from 1 min to a few hours significantly affect temporal variability and turbulent regime of the stable atmospheric boundary layer (ABL). Their statistical characteristics are still poorly understood, although the knowledge of such statistics is required when modeling sound propagation through the stable ABL. Several field experiments have been conducted to study the influence of mesoscale wind speed fluctuations on acoustic pulse propagation through the stable ABL.