WMOD00376

• Contract/Permit #: 14-06-D-5640
• Project Name: Park Range Atmospheric Water Resources Program
• Title: Park Range Atmospheric Water Resources Program - Phase II - Parts A and B
• Date: 10/6/1967
• Weather Modification - Doc Type: Report

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DIFFUSION

AIRBORNE DIFFUSION TESTS. (P, T. Willis)

The diffusion characteristics of an aerosol released from the
surface in mountainous terrain are complicated and variable, but they
are a pivotal problem in evaluating the results of a ground-based cloud
nucleation program. The continuing se ries of airborne diffusion te sts
is designed to find out what happens to ground-released artificial nuclei
in the Park Range area,

Both zinc sulfide fluore scent trace l' material and silver iodide

are released from 8300 foot Emerald Mountain, and tracked with a

real-time sampling device on an aircraft. Wind information from a

one hundred foot tower at the release site, radar-tracked piba.l data,

and, usually, radiosonde data, are available for analysis work. A

ground- based continuous ice nucleus counter, similar to the one in

the aircraft, is generally operated at either Rabbit Ears Pass or Buffalo

Pass, and a truck-mounted temperature sensor takes tempera.ture

soundings up the Rabbit Ears Pass road.

During the FY67 winter season, there were sixteen diffusion
experiments, Daisy XXXII through Daisy XLVII.

PLUME DIREOTcl0N AND WIDTH CHARACTERISTICS

Most of the work in atmospheric diffusion problems consists
of I) describing wind fluctuations,. and 2) expressing their action in
redistributing the air and thereby dispersing the material carried with
it. For each diffusion te st, a subjective estimate of the plume width
(defined as the envelope containing the detectable tracer material) a.nd
an estimate of the direction of the plume axis, (the direction in which
the particles moved from the release site) was made. Figure 3 shows
the plume mean- direction as a function of the 11,000 ft. MSL wind

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