370
MACHTA
preciate the consequences of a proposed or accidental release of radioactivity. The second category involves the forecast of fallout on a current basis, either just before or soon after an event.
Planning
Climatological winds and past fallout experience form the basis for
estimating the distribution of fallout from tropospheric injections of
particulate radioactivity.
Global-scale air motions are mainly zonal in nature. Superimposed
on the zonal basic current are waves producing north to south motions.
This general airflow should result in a global fallout pattern with highest deposition or air concentrations at about the latitude of the test site,
generally decreasing with distance from the source. The middle part of
Fig. 1 shows this expected pattern, It has been obtained by averaging
the global gross deposition on gummed paper during the Operation
Upshot-Knothole tests in Nevada in 1953 around eachcircle of latitude.!
8
SOT.
TT TTT T_T TTT
“
Iw AIR CONCENTRATION (80°W MERIDIAN)
8
JUNE AND JULY 1958
a
2
z
=
~
2
APACIFIC SURFACE BURSTS
2 IT
<
GLOBAL GUMMED-FILM DEPOSITION
a
MARCH THROUGH JUNE 1963
>
_
¢
w
.
=
NEVADA
TOWER
BURSTS
0
Ms,
= 100 |
=
WU
NOVEMBER AND DECEMBER 1961_| ,..
2
YW
8
=5
=
3
&
Oo
,
‘Se!
o
U.S.S.R. AIR BURSTS
}
S0PN 60°N
|
{|
30°N
|
£z
AIR CONCENTRATION
(80°W MERIDIAN)
"
‘
0°
|
30°S
i
{|
=
>
{ tHo
a
60°S 90°S
LATITUDE
Fig. 1—Latitudinal variation of surface observations of tropospheric
radioactivity as a function of injection point.