WMOD00403

• Title: Special Regional Weather Modification Conference Augmentation of Winter Orographic Precipitation in the Western US
• Date: 11/11/1975
• Weather Modification - Doc Type: Report

in operation each season during the five years of the Pilot Project. Monitor and
meteorological data were automatically interrogated from the remote sites on a 3-hourly
basis on all non-experimental and no-seed days. The interrogation frequency was in-
creased to an hourly basis during seeding plariods for closer monitoring of the perfor-
mance of the remote generators. During four of the five operating seasons when pre-
cise data was recorded on the operation of the telemetry system, 116,512 automatic
interrogations of the remote stations were lnade and 111,082 station responses were
received for an overall operational efficiency of 95.3 percent. The remote transceiver
system was calibrated before and after each season to insure the drift of the electro-
nics equipment was less than 1.5 percent.

During the 71 declared seed days, 669 remotl! and 514 manual generators were requested
to operate for a total of 15,864 hours. A total of 575 remote and 452 manual gener-
ators operated for 13,348 hours for an operiational seeding efficiency of 84.1 percent.
During the 13,348 hours the generators operated, 319,476 grams of silver iodide was
burned. The manual generators operated only 384 hours at the 140 gm burn rate. The
generators mainly operated at a burn rate of 20 gm AgI per hour per site. The solution
that was burned was a 4.0 percent silver iodide and 1.2~ percent sodium iodied solu-
tion in acetone.

Prior to the start of the first operating sleason, a calibration of the outputs of the
two types of nuclei generators was per-formed at Colorado State University's Cloud
Simulation Laboratory. Following each operating season a recheck by Colorado State
University of the generator outputs WB.S again conducted. No appreciable changes were
observed in the effective nuclei output fr01l11 the generators or the effectiveness of
the silver iodide solution with time.

Two acoustical and two expansion type ice nuclei counters were operated during each
of the five operating seasons of the Pilot Project by EG&G, Inc. The counters operated
on 420 of the 588 required periods for nuclei observations for an operational effi-
ciency of 71.4 percent. Ice nuclei CCiunts 'were taken both in and upwind of the Target
area to determine both background ice nuclei counts and the presence and concentration
of additional artificial ice nuclei on seed days.

Rawinsonde observations were taken dai.1y using an RD-65 unit at 0500 MST on non-
experimental days and on a 3-hour1y basis on all experimental days during the five
operating seasons. Rawinsonde observations were also taken during suspended storm
periods that would have met the operational criteria and during periods of some days
that nearly met the operational criteria. The flights were normally conducted up
through the 300 mb level. A total of 2021 rawinsonde flights were completed during
the five operational seasons. The ra~rinsonde data is of exceptionally good quality
and was extremely helpful in identifytng experimental periods and in evaluating the
seeding effects of the Pilot Project. \

REVIEW OF PROJECT FINDINGS

Several studies were undertaken and completed throughout the duration of the Pilot
Project to identify special meteorological conditions and consequently improve the
ability of the meteorologists to identify and conduct more effective seeding operations
on experimental days. The identification of the factors leading to a sharp backing
of the southwesterly winds near 700 mb over the target area to the southeast was one
such study. Another study verified the general reliability of the instantaneous
telemetered wind observations obtained from the remote meteorological sites.

The direct transfer of the stable topped or-ographic cloud concept from the Ct~max
Project to the Pilot Project has turnE!d out to be an incorrect assumption. A large

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