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

SYNOPSIS

Presentod in this preliminary report is an analysis of the
climatological data for the period March 1, 1951 to June 1, 1951,
during the cloud-seeding operations over north central Colorado.

'fhe results of the various methods of am,lysis are as follows:
the rIarch, April, and May, 1951, mean depth of precipitation on
the target area was 4.36 inches as compared to a forty-year
nor;~al of 5.40 inches and the probability study revealed that
the 4.36 inches which fell during the three month period on the
target area has been equaled or exceeded 69 percent of the time
or approximately every two years out of three. Secular series
stud.i.es for the period of March, April, and Nay indicate a
significant upward trent in precipitation and the pres8nce of a
possible wet cycle.

The moan depth of prec~pitation on the control area for the
month of ;.1arch, 1951, was found to be 62 percent of the normal
mean depth of precipitation on the control area for the month of
March, whereas the mean depth of precipitation on the target
area for the month of Harch, 1951, was found to be 52 percent of
the normal mean depth of procipitation on the target area for the
month of :larch.

The moan depth of snow-water content increase on the target
area for the period of March and April, 1951, was 4.9 inches as
compared to a thirteen-yeaI' normal of 3.1 inches. However, the
above normal water content increllse for the period of liarch and
April, 1951,was a~parently the result of the below normal monthly
temperatures, which reduced tho snow molt, for the sane period,

The moan depth of snow-water content increase on the control
aroa for the period of March and April, 1951, was 147 porcent of
the thirteen-yoar non~al; whereas, the mean depth of water con-
tent increase on the target area for the sarne period was 158
percont of the thirteon-year normal.

",

A study of the procipitation in the western United States for
the period of March, April, and l1ay, 1951, showed that in general
the Pac~fic coastal states, the eastern Rocky 110untain states,
and tho southwostern states were below normal in precipitation;
whereas, the western Rocky rIountain states, tho plains states,
and the mid-\'lostern s tn tes ]lore above normal in precipitation.

I..

Tho analysis of climatological data to detormine any change
in ralnfllll patterns resulting from cloud seeding has not beon
completed to dato; the study will be ~resented in the final roport.

The results indicate that there was no apparent increase in
precipitatlon resulting from cloud seeding during the period
March 1, 1951, to Juno 1, 1951, over north contral Colorado.

Thoro is also no proof that possibly good results cannot be
brought about by artificial cloud seeding, Extensive field

140/l

Hi