Velocity and pressure acoustic-gravity wave perturbations in the nonisothermal atmosphere have been considered. Shaping of a narrow domain with elevated pressure in the resonance region where the horizontal phase wave velocity is equal to the sound velocity is examined theoretically within the framework of linearized set of equations. According to the obtained model solution, the wave pressure perturbation has singularity near the resonance altitude where the horizontal phase velocity is equal to the sound velocity. The perturbation vertical velocity turns to zero at the resonance altitude . The wave perturbations do not penetrate higher than resonance layer. In the atmosphere, the considered singularity operates as a filter. At altitudes where the sound velocity increases with increasing altitude, the perturbations with comparatively low horizontal phase velocities are filtered out first. If the horizontal perturbation scale on the Earthâ€™s surface is determined by the source size, then the frequency of the waves, which do not propagate into the upper atmosphere, is increased with increasing altitude. Numerical simulations for the model profiles of atmospheric temperature and viscosity confirm analytical result for the special feature of wave fields. The formation of the narrow domain with plasma density irregularities in the D and low E ionospheric layers caused by the acoustic gravity wave singularity is discussed. The obtained results are important both for understanding of the three-dimensional structures of wave perturbations in the windless atmosphere and for explaining the properties of ionospheric features in D and E ionospheric layers.

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**Reference.**

O.N Savina, P.A. Bespalov. Acta Geophysica. 2014. DOI: 10.2478/s11600-014-0246-1.