474
MAHLMAN
a
S12
=
.
y~ 10 F>
> gL
<
x
< oF
aah
—
_
4
oo
a
9
0 21
poet
10
_
|
i
tf
i
py
40
70
100
130
160
tof
190
220
fj
ft
fy
250
280
310
te
340
370
400
2
460
DEC. JAN. FEB. MAR. APR. MAY JUN. JUL. AUG. SEP. OCT. NOV. DEC. JAN. FEB. MAR.
1962
1963
1964
Fig. 3—Natural decay curve for a mixed debris sample computed
from Table 2. Source intensity at time 100 days (mid-March 1963) is
assumed to be 10 pc per cubic meter of air. Abscissa is in monthly
increments along with the approximate time in days. Time 100 days is
marked on the curve with a vertical line. The circles represent mea-
sured decay relative to the original source for a particular time.
Extrapolated values are denoted by an x.
established between the magnitude of this parameter and the relative
amount of fallout subsequently observed. This is very probably due to
a number of complicating factors not taken into account in the simplified model presented here.
SUMMARY AND FUTURE OUTLOOK
An index designed to measure the relative amount of cyclonic
activity in the atmosphere was developed to compare its variations
with changes in seasonal-fallout intensity. A definite relation between
the index and seasonal-fallout variations was not substantiated. On the
other hand, the analysis indicated that an apparent correlation existed
between large decreases of the cyclone index and subsequent shorter
period increases in surface fallout over that of the mean seasonal
curve,
It thus appears that tropopause-level cyclogenesis is the predominate mechanism leading to the intrusion of stratospheric air into
the troposphere, as hypothesized earlier,'’:'!?" However, it cannot be
stated that these cyclogenetic processes are the primary causes of
the spring fallout peaks, It appears that the spring fallout maximum
is
probably
understood,
due
to
a
combination
of factors that are still poorly