WMOD00299

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

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Wasatch of southern Utah (Long, 1984) and the mountains near Elko

County, Nevada (Grant and Elliott, 1974).

Of the thirteen previously reported programs, three (Elko, Jemez,

Wolf Creek Pass Experiments) had only a statistical component and will

not be reviewed here. Of the remaining ten, six reported limited

measurements of natural cloud physical structure and four had more

comprehensive measurements. These programs are reviewed below.

(1) Climax I and II

The Climax experiments (Mielke et al., 1981) were primarily

statistical experiments. However, extensive physical observations of

surface ice nuclei (Grant and Mielke,1967) and limited studies of ice

crystal concentrations (Hindman, 1967; Chappell, 1967), precipitation

characteristics (Grant, 1965; Hindman, 1967: Chappell, 1970), and radar

echo characteristics (Furman, 1967) were collected during certain

seasons of the experiment. Additional work was carried out by Chappell

(1970) to establish the conditions where the rate of condensate supply

balanced the rate of diffusional growth in clouds, but physical data to

support the theoretical work was unavailable at the time.

Grant and Mielke (1967) reported the results of extensive nuclei

~easurements during the five years of the Climax I experiment. The data

base consisted of surface ice nuclei measurements over a broad

~emperature range. The measurements were repeated twice a day on most

~ays of the experiment from two sites. With the exception of one

~nomalous year, they found that ice nuclei concentrations seldom
-1 o. -1
exceeded 10 1 at -20 C and were generally less than 1 1 on unseedeq

days. On seeded days, sUbstantially higher concentrations were recordeq.