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No attempt Is mode In the following notes fo arrive af quantitative results. However, enough dota exist, espectally in the form of photographs of the clouds that form as
a result of nuclear explosions, fo enable a qualitative hypothesis to be constructed. The
hypothesis will be concerned with the manner In which the fireball ts fronsformed Into the
fomiliar mushroom cloud of past atomic tests. This topic has not Been the subject of
recent extended .reseorches, ond the principles upon which it Is usually discussed seem fo
be Inadequate to explain the mefeorological concomitonts of the initiation and growth of
the cloud, It oppecrs thot the fireball hos been treated as if It were a bubble of heated
gas, which it indeed Is, and thet the events subsequent to its formotion can be accounted
for by the rise of the ball, much cooled, but still as o bubble, moving upward under
buoyancy forces with little chonge in shape. Changes in shope actually observed have been
attributed to atmospheric turbulence resulting in’*entrainment"’of outside alr, in the form of
a wake stream.
The speculctions odvonced here arise from the observation that the formas
tion and movement of the cloud and the circulation within “It ore much too regular, especially
under conditions of little wind sheor, for the phenomena to be entirely accounted for by turBulence theory. With the larger bombs, the Integrity of the otmospheric circulations over
time Intervals of many minutes suggests that there are present regular streamline motions
dynamically Independent of ond only slightly distorted by small scole atmospheric turbulence.
The conditions with which these speculations begin are those following a detonation
af some distonce above ground and after the resulting fireball has reached its maximum exe
pansion. Within the region Imited by the wovefront of the shock wave, the Isobaric surfoces may be considered, except in the immedicte vicinity of the mass of heated gas, to
hove returned to approximately thelr normal catmospherle orientation, that ts, quasi-horizontal,
In standard meteorological texts on expression may be found which gives the acceleration
of the circulation around ony atmospheric path due to the so-called solenoidal field,
Con-
sider the vertical paths through the fireball residual and the surrounding atmosphere, shown
in Figure 1.
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Figure 1;
“Hourwitz, -B.
Acceleration of circulation
Dynamic .Meteardogy.
McGraw-Hill, New -York, 1941.
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