WMOD00299

• Title: Physical Structure of Northern Colorado River Basin Cloud Systems
• Date: 9/1/1985
• State: CO
• Weather Modification - Doc Type: Report

14

I
I
I
I
I
I
I
I
I-
I
I
I
I
I
1
I
I
I
I

Additional work emphasizing the transport and dispersion of silver
iodide in the Climax region was conducted by Reid (1976) and Orgill
(1971). Re~d studied the dispersion of silver iodide with aircraft and
surface measurements. Orgill (1971) simulated the transport of seeding
material using a physical model of the Climax region in a wind tunnel.
(2) Park RanRe AtmosDheric Water Resources Proaram (PRP)
The PRP was the first major wintertime weather modification field
effort to conduct an extensive physical evaluation of the effects of
cloud seeding to augment precipitation (Rhea et al., 1969). Analysis of
the physical data was supported by the use of a steady-state numerical
model of orographic precipitation developed at EGG Inc. (Willis, 1970).
A significant number of transport and dispersion studies were also
conducted. The majority of the physical results of the experiment were
based on data collected during the 1968-69 field season. The analysis
of the 1968-69 data set incorporated both the case study approach as
well as statistical analyses of the precipitation data. Unfortunately,
only limited data were presented concerning natural cloud system
structure. The majori ty of the data were associated with identification
of seeding signatures. This was primarily through analysis of ice
crystal replicas, measurements of ice nuclei and silver in snow during
pulsed seeding events.
The major results of the PRP based on five winter seasons ,of
operation are summarized by Rhea et ale (1969). During the program,
significant amounts of seeding material were found in target area
precipitation, in timing and location with calculated occurrence of
seeding effects. In several case studies, a positive seeding effect was
clearly evident, During the seeding period, small hexagonal plates were