WMOD00552

• Title: Seedability of Winter Orographic Storms in Utah
• Date: 12/1/1977
• State: UT
• Country: United States
• Weather Modification - Doc Type: Report

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able batteries. Six disposable batteries will last at
least one year.

2.2 Supporting Observation System

2.2.1 Rawinaonde and Radar. A Bureau of
Reclamation RD-65 unit was used throughout the
experimental- periods to obtain observations of
temperature. humidity, pressure-height and wind
velocity. Two primary locations were used. During
most of the aircraft seeding experiment the unit was
located at Cache Peak (elevation about 1740 m); for
the ground seeding experiment the unit was located at .
Mendon (elevation 1372 m). For the aircraft seeding
experiment one or two rawinsondes were released, "
and Salt Lake City data were used to supplement this '
information. For the ground seeding experiment a
rawinsonde was released every two hours for a total of
five per storm.

A mOdified, three centimeter, T-9 tracking. radar
was operate4 ,<luring the aircraft seeding experiment
on Cache Peak near the western border of the target
area. This equipment was . used to ,provide flight
controlinformatioD to the pilot, determin~regions of
cell genesis, and provide information and photography
of cell intensity and movement. The radarwaS.also'
employed in. a vertical, pointing m.ode in order to obtain
cloud depth and cloud. top pOpulations for the area. A '
meth6d was devised'forphotographing continuously a
vertical cross-section of the ,cloud system.

2.2.2 Facsimile Data Collection. An Alden
weather facsimile machine was placed in operation at
UWRL during thewinterseason:The output from this
equipment was used to control operational activities
and subsequent analyses of the experiments. A
service A teletype machine was also installed in order
to obtain hourly surface data and other special
reports.

2.2.3 Ice Nucleus Counts. A Summit Hut was
designed and built on the Wasatch Ridge east of
Logan. This hut is a 6 m x 8.5 m A-frame type
structure with a loft for storage and sleeping quarters.
The hut is at an elevation of 2650 m and lies within the
primary target area. This structure served as a base
for monitoring ice nuclei, cloud condensation nuclei
and ice crystal characteristics during seeded and
non-seeded periods.

Ice nuclei data were collected at the ground
during winter seasons using a borrowed NCAR
counter and from the air using a cold box furnished by
Atmospherics, Inc. Counts were taken at a tempera-
ture of -200C. The NCAR counter was mounted in a
stationwagon and counts were obtained at several
locations during operational events. The aircraft cold
box was used for plume tracking the Mt. Pisgah-based
seeding generator.

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2.2.4 Silver Concentration of Snow. As part of
the observing system, a network of silver sampling
sites was established. Snow-chemistry sampling sites
for the three-year aircraft seeding experiment are
shown in Figure 5.

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Figure 5. Snnw chemistry 8ampling Bite8 (FY 70-71).

Snow samples were generally taken whenever
the snow depth on the route exceeded 8 cm (3 inches)
during a storm. Each sample was taken by a
technician who placed a fresh conventional polyethy-
lene bag over his hand and scooped new snow into a
wide mouthed 41/z liter polypropylene bottle previous-
ly stabilized with 5 ml of glacial acetic acid. The tightly
closed containers were taken to the laboratory .
Analysis of these data will be discussed in Section
6;1.3.

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