Infrasound and internal gravity waves generated by atmospheric storms

Abstract

The recordings of infrasound and internal gravity waves (IGWs) obtained during 2015-2016 at infrasound station I43 IMS and a network of microbarographs installed by Obukhov Institute of Atmospheric Physics (OIAP) are presented. The OIAP network of microbarographs is capable of detecting simultaneously an infrasound at frequencies less than 3 Hz and IGWs with periods ranging from 5 min to 3 hr. It is shown that the low-frequency wave processes generated by atmospheric fronts retain high coherence (0.6-0.9) over the areas with horizontal dimensions of a few tens of km. It is found that after the passage of atmospheric front the internal wave trains were observed with the amplitudes considerably exceeding those of IGWs that were detected before the passage of the atmospheric front. The discrete periods of 35 min, 56 min, and 110 min were found in the frequency spectra of the observed wave trains. For these periods, the coherence between atmospheric pressure variations measured at different points reach local maxima, and the sum of the phase differences between selected three points tends to zero. The phase speeds for the observed IGWs are in the range of 10-50 m/c. The wave “precursors” with amplitudes of 10 Pa and periods of 15-20 min were also detected 10 to 15 hr before a passage of the atmospheric front through a network. Along with IGWs, the infrasound associated with atmospheric front was also detected (August 2016) by I43 in the frequency range 0.1-0.4 Hz.