--—@F -.
~
an
Fe
<"
Fe
2d
Pu
(d)
Thrucut the whole cloud, all radioactive particles are of
(e)
In each layer, the central partiele falls, without diffusion,
the same size, ami fall at 50,000 ft per hour.
as directed by the winds, while other particles diffuse horizontally away
from the center equally in all directions so that, when the layer arrives
on the surface, the distribution about the center is sivon by
e¢ (r) = Co em (gq)?
o*
(p)?
where p = 4S, q = r/a,, 3 = total horizontal distance travelled by the
So
central particle, So > 5,2 ae (The last quantity may be pictured as the
horizontal distence back to a fictitious point source of the cloud layer).
(f£)
The dose rate at any point is proportional to the sum of the
concentrations from all of the layers as estimated from the prececing
forma.
:
&. «apart from the assumption of a sinrle particle size this formlatia
nas a mumber of other obvicus defects, e.:5.
a.
The sum of the quantities Coa? should be made proportional
to the total rediocective yield of the"bomb."
In practice, the final
cstimates were adjustod samewhat on account of expected yield.
in effect, allowed for the influence on Cy, but not on aoe
This,
bse The estimation of S as total horizontal distance is rather
unsatisfactory in local foreeasting where tho atoll dimensions are not
much greater than the heicht of the cloud.
«lso, there wes no timo to find out whether better results could be
obtained by choice of some other values for parameters such as rate of
fall for the particles.
From the test of the method asainst the Bikini
Patterns, it wos clear that it was good emough for the purpose at hand.
It appeared that differences between forecast and actual winds would be
likely to rroduce much larger errors than those inherent in the assumptions.
5.
In ap-lication, the method is not as tedicus as micht aprear.,
The
standard hodogreph plot, giving the loeation of central perticles falling
&t 5,000 ft per hour, is prepared for the Command Briefing as a matter of
Course, It can be superimposed on a ten times magnified atoll map,
allowing for the 50,000 ft per hour fall rate assumed in the methrd. With
® ruler of corresponding scale, the distances S, alonz the ziz-zagz path
to each of the height points on the hodograph ean be quickly moasured or
a
UNCLASSIFIED
oN
D219