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9
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Sr89 IN RAINFALL, MC/SQ MILE /MONTH
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5
A,
Fig. 5— Regression of Sr® in gummed film on Sr™ in rain water from 20 stations in May 1956.
Table 6——COMPARISON OF Sr*’ IN GUMMED FILM TO Sr®* IN RAIN WATER
Sampling
Average Sr®?
Average Sr”?
in rain water
in gummed film
month
(me/sq mile/month)
March
1.2
1.1
0.57
May
1.6
0.14
April
June
July
(me /sq mile/month)
0,44
1.0
1.5
0.022
0.063
Ratio
2.7
1.9
11
45
24
Correlation
coefficient
0.24
0,20
0.49
0.02
0.01
Since there is more Sr’in the northern region, the activity levels in the troposphere are
not uniform over the United States. However, when areas are chosen that are small enough to
have nearly the same tropospheric activity levels, the Sr®° in rain water is proportional to the
amount of precipitation.
There is some justification for accepting the theory that a selective entrance zone for
stratospheric fallout exists. This is demonstrated in the initial separation of data, wherein
northern sites show little correlation although they have a higher mean level per inch of rain.
Rainout for the southern stations is definitely proportional to the amount of rainfall, suggesting
a more uniform activity level in the atmosphere. It should be noted that no correlation for
southern stations existed in July, when there was fresh fallout.
9
SUGGESTIONS
The validity of the assumptions made from these data suffer from several sources of error.
In the event a more comprehensive study is undertaken in the future, there are several changes
that should be made.
1. The scope of the experiment should be extended to operate over a larger area anda
longer period of time.
393