WMOD00306 ‎(2)‎

• Title: Discusison of "Weather Modification in Arizona in 1971" by Herbert A. Osborn
• Date: 6/1/1972
• State: AZ
• Weather Modification - Doc Type: Report

chilled by evaporation; hence it was the negatively buoyant, descend-
ing air into which the latent heat of fusion was released, thus
detracting from the total circulation and dumping most of the silver
iodide into downdraft or detritus regions. Only much later would
some portion of the silver iodide find its way by further mixing
into the central updraft, by which time the cloud would have passed
its phase of active growth and be dissipating. Thus the model pro-
vides a framework for reasoning that the ARIDROP treatment contrib-
uted to growth of the treated cloud and the Catalina treatment to
its dissipation.

This reasoning is in general agreement with the outcome not only of
the Flagstaff versus the Catalina experiments but also of a consid-
erable number of others where, on the one hand silver iodide was
released directly into the updrafts of clouds selected for their
suitability (e.g., Bethwaite, et aI, 1966; Henderson, et aI, 1968)
and on the other hand the treatment was simi lar to that of Catalina
(e.g., Godson, et aI, 1966; Decker & Schickedanz, 1967; Decker. et
ai, 1971; Smith, 1967). If one extends the comparison further by
assuming that silver iodide seeding from ground-based generators,
by dispersing the nucleant from the source level of cloud-building
heat and moisture, results in selective uptake of nucleant into the
strongest cloud-building updrafts (Howell, 1966), and hence that
this procedure more nearly resembles the Flagstaff than the Catalina
treatment as it affects cloud dynamics, then the area of general
agreement between the prediction and experience is widened and a

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