in cloud models and deposition mechanisms that are introduced by a
change in yield.
Nevertheless, the method is useful and fairly accu-
rate if applied over a limited yield range, not to exceed about two
orders of magnitude.
Wind velocity scaling is even more subject to error than is yield
scaling.
Based upon limited high explosive experimental data, using
dye tracers, it has been postulated that total areas of effect of fallout for a particular detonation are essentially wind-independent, although the specific regions which these areas cover are of course
determined in detail by the wind pattern.
The experimental data ex-
tends only to winds up to 25 knots; however, in the absence of other
information, extrapolation to higher wind velocities is not unreason-
able.
On this basis, then, contour dimensions in a downwind direction
would be scaled in direct proportion to the cube root of the ratio of
the winds involved, while crosswind dimensions would be scaled inversely by the same factor, leaving the area of effect essentially constant.
The effect of winds upon the direction of the fall-out and the
area involved can be shown graphically by setting forth certain assumed
meteorological conditions.
in Figure 9.
One example of such assumptions is presented
Superimposed upon the wind vector plot is a family of
idealized isodose contour lines for a 20 KT ground burst.
It will be
noted that the shaded area, which is due to diffusion, and the A", B”
eeeee F" due to 50 micron particles, do not contribute apprecisbly to
the radiation intensity within the area.
The highest radiation read-
ings in the contour areas are close in to the burst point and the
radioactivity deposited there is carried by the larger particles.
For
purposes of the illustration, the size assumed for the large particles
was 150 microns and the greatest effect by the wind is indicated on
the line A', B’ ..... F'.
The area covered by superweapon detonations
would be much larger and wind shears at high altitude would have a
greater effect upon the true pattern, but the method of illustration
is the same.
Such a superposition is useful in indicating where the
KL