AffiliationInstitute of Atmospheric Physics, The University of Arizona
KeywordsRain-making -- Arizona -- Santa Catalina Mountains.
Clouds -- Mountains -- Weather control.
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DescriptionThis report is one of a series dealing with a research program carried out jointly by the University of Chicago and the University of Arizona.
AbstractDuring July and August 1957, orographic cumuli over the Santa Catalina Mountains of southeastern Arizona were seeded from an airplane with silver iodide. The experimental design of the program involved the randomized seeding by pairs of days; one of two days with suitable clouds was seeded on a random basis. On seven pairs of days, observations were made of the cumuli with a pair of K-17 cameras on a 1.3 mi baseleg. At the same time, radar observations were made with a 3-cm vertically-scanning radar set. On the basis of the analysis of the camera and radar observations an investigation has been made of the occurrence of precipitation as a function of cloud size and temperature. It was found that there is a large variability in cloud behavior from year to year. Natural clouds in the arid southwest do not produce precipitation until their vertical thicknesses are of the order of at least 8 to 10,000 feet. From a comparison of seeded and non-seeded clouds it appears that the silver iodide particles may have produced changes in the precipitation formation mechanisms in orographic cumuli.
Series/Report no.University of Arizona, Institute of Atmospheric Physics, Scientific Report No. 9
SponsorsThe research reported in this report was sponsored by various agencies: The National Science Foundation under Grant No. NSF-G4175 to the University of Chicago; University of Arizona; Geophysics Research Directorate, Air Force Cambridge Research Center under Contract No. AF 19(604 )-1388.
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