WMOD00296 ‎(2)‎

• Contract/Permit #: 14-06-D-5640
• Title: Park Range Atmospheric Water Resources Program Final Report
• Date: 9/30/1969
• Weather Modification - Doc Type: Report

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SECTION 1. 0

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SU MMARY OF PURPOSE, DESIGN, AND CONCLUSIONS

1. 1

Objectives of the Project

The main purpose of the project was to obtain definitive evidence as to whether
it is physically and economically possible to augment precipitation in the head-
waters of drainage basins by engineering-scale application of weather modifi-
cation techniques. Specifically, the study was planned to test the applicability
of ground and airborne silver iodide seeding in orographic precipitation sys-
tems.

In order to accomplish the primary objective, a satisfactory experimental
design had to be established. This design then had to be supported by a spec-
ialized data collection network with sufficient time and space resolution to
supply adequate measurement for analysis. Accordingly, secondary objectives
of the program were the development and testing of experimental techniques
for weather modification studies, and evaluation of the usefulness of various
seeding, observing, and analysis methods.

1. 2 Experimental Design

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The experiments were carried out in the Park Range near Steamboat Springs,
Colorado. Figure 1 shows the experimental area and the seeding and obser-
ving stations as they existed during the ~ year of the stlldy:.
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1. 2. 1

Pulsed Seeding Design

A rather novel experimental design W8.8 originally established. The design
applied power spectral analysis procedures to precipitation-rate time histories,
in order to determine the effect of one cycle per hour (1 cph) pulsed silver io-
dide seeding. This design was employed during the seasons of 1965-613, 1966-
67, and part of 1967-68. During the first year of operation (1964-65), no
seeding was done, but the collected precipitation rate data was used to estab-
lish natural background power spectrum features.

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In the latter two-thirds of the 1967 -68 season the frequency of pulsed seeding
was decreased to i cph or i cph and the seeding site was moved further upwind
of the target. Airborne seeding events were introduced in January and Feb-
ruary 1968, and continued during the 1968- 69 season. The short-period vari-
ability of wind and stability was found to smear the seeding period into the
short unseeded period, and thus, conclusive results concerning seeding effect
were not obtained by this method.

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