The dispersion of a pressure pulse in the atmosphere

Abstract

The object is to find what pressure oscillations would be observed on the ground at a great distance from an explosion. The explosion is represented mathematically by a Fourier integral, corresponding to the introduction of a large Volume into the atmosphere at a point on the ground. The resulting pulse is calculated for various distances for a model atmosphere consisting of a troposphere with a constant lapse-rate of temperature and cm isothermal stratosphere. It is composed of those oscillations that can be propagated horizontally as gravity waves in this model atmosphere, namely, those of period exceeding a cut-off period of 111 sec. The pulse consists of a series of waves of decreasing amplitude and period, terminating with a period of 12.7 sec. The results are compared with the oscillations observed on the occasion of the fall of the Great Siberian Meteorite and the energy which it is estimated to have communicated to the atmosphere is about 4 x 1024 ergs only a fraction of which resided in the gravity wave. Neglect of the warmer layers in the higher levels in the stratosphere means that the calculated pulse terminated too soon, and a second series of waves of considerable amplitude and of greater frequency is completely absent. The form of these has not been calculated because of the prohibitive amount of computing involved.