Atmospheric waves caused by large explosions

Abstract

This paper considers the harmonic oscillations of several simple model atmospheres. The oscillations are of two types. In the first, the kinetic energy per unit volume tends to zero at great heights; in the second, the kinetic energy per unit volume remains finite. A large explosion at ground level excites a spectrum of both types of oscillation. The pulse ultimately separates into two parts—a train of travelling waves which can be observed at ground level at great distances, and a train of travelling waves which disappear into the upper atmosphere. The complete range of experimental observations on the pressure oscillations caused by explosions of energies varying between 10 20 and 10 24 ergs can only be interpreted with model atmospheres having one or more sound channels, i.e. having at least one minimum in the temperature-height relationship of the atmosphere. In spite of the complexity of the phenomena, the theory throws light on some of the characteristic features of the observations. The average period of the largest waves is roughly proportional to the cube root of the energy released by the explosion. The amplitudes of the waves from large explosions can be calculated. Conversely, good records enable the size of the explosion to be estimated. The energy of the Siberian meteorite of 1908 was about 10 16 cal, or 10 MT (T signifying a ton of t.n.t.).