WMOD00308 ‎(2)‎

• Title: Operation and Evaluation Report of the Santa Barbara County Cloud Seeding Program, 1977-78 Winter Season
• Date: 8/1/1978
• State: CA
• Weather Modification - Doc Type: Report

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is consistent with the results obtained from the research project and
strongly suggests a significant seeding effect in the primary target
area and into the extra (downwind) areas to the east and northeast.

To further test the significance of these results a linear regression
equation was developed for the historical non-seeded period for the
average 48 hour precipitation at eight control stations (Nos. 1-8) and
the eight primary target stations (Nos. 9-16). The developed equation
proved to be a good predictor with a correlation coefficient of .909
(1. 0 would be perfect).

Figure 5 contains a plot of the target versus control precipitation
averages for the 3S historical stOI1nS and for the 9 seeded stonns of
1978. The appa.rent seeding effect on the eight target stations is 41%
(an est~ted increase in the January-February 10 precipitation of 2.61
inches). These results were tested by the students t test ,...hich indicated
the 41% increase was significant at the .09 level (single tailed). This
can be interpretted as indicating the apparent seeding effect should only
be expected to occur by chance nine times in 100. The average control
precipitation and the average target precipitation values used in the
regression are swmnarized in Table 4.

It is well-known that the amount of precipitation that falls in the
target area is considerably different from the southwestern portion of
the target to the northeastern portion of the target due to topography
and exposure to stann systems. Inspection of the 1978 precipitation
totals indicated, that in the January-February 10 period, the stations
in the southern part of the target (Nos. 9-lZ) received over twice as
I1Ulch precipitation as did the other four target stations. Consequently,
another linear regression (Figure 6) was developed for the four stations
(Nos. 9-12) in that portion of the target that produced runoff to Santa
Barbara County. This regression had a very high correlation with the

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