WSP07322

• File Number: 8040.980
• Description: Section D General Studies-Weather Modification
• Date: 7/1/1951
• Author: Sol D Resnick
• Title: Preliminary Report-Analysis of Climatological Data for the Spring Cloud Seeding Period Over North Central Colorado
• Water Supply Pro - Doc Type: Report/Study

CHAPTER IV
CONCLUSIONS

,

The results of the analysis of the climatological data
led to the conclusion that there was no apparent increase
in precipitation as a res lIt of cloud seeding over north
central Colorado for the period of i1arch 1, 1951, to
June 1, 1951.

The above conclusion is supnorted by the following
results of the analysis:

1. The mean depth of precipitation on the target area
during the seeding perlod was less than normal and has been
equaled or exceeded naturally every two years out of three for
the past forty years.

2. The precipitation on the areas to the east and west
of the seeded area was above normal durinG the cloud-seeding
period. A conclusion that the natural precipitation on the
target area would have been significantly less than that
which actually fell is held to be unlikely.

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3. The mean depth of precipitation, as a percent of
normal, on the control area for E.?:rch, 1951, was approximately
equal to the mean depth of precipitation, as a percent of
normal, on the target area for Harch, 1951. This does not
indicate any increase in precipitation on the target area
due to cloud seeding. The a.)proximation of equality was
used, although the control area was ten percent higher than
the target area, because a difference of this magnitude
observed for only one period is not considered significant,
either as to the degree or the cause.

4. The mean depth of snow-water content increase, as a
percent of normal, on the control area for the period of
March and April, 1951,was approximately equal to the mean
depth of snow.water content increase, as a percent of normal,
on the target area for the same period. This does not
ind:l.cate any significant increase in snow pacle in the target
area due to cloud seeding. Again, the approximation of
equality was used, although the target area was eleven percent
higher than the control area, because such a small difference
was not considered significant in view of the short period
considered. If such a difference were maintained consistently
over a long period of years under similar teMperature con-
ditions, then the question would arise as to the cause. The
mean depths of snow-water content increase on both the
control and target area were above normal for the period of
March and April, 1951, but the greater than normal increase
for both areas was due, in part at least, to the below normal
monthly temperatures and resulting decreased snow melt for
the sarne period.

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