WMOD00310

• Title: Cloud Physics Investigations - University of Wyoming - 1977-1981
• Date: 11/1/1982
• State: WY
• Weather Modification - Doc Type: Report

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al. (1981) found a substantial difference in liquid water contents

from 1979 to 1980, with substantially lower liquid water contents in

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1980.

(Although at Miles City the rainfall in 1978 greatly exceeded

that in 1979 or 1980, most of the difference occurred in May. The

combined June and July rainfall was similar for the three years; see

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Hartzell and Jameson, 1981, Table 6.)

A similar study of cloud base temperatures was made for the 1976

NHRE flights studied in July 1976. In comparison to those clouds, the

med ian of the clouds in Montana was about 20C warmer and about 80 rob

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lower. The NHRE clouds, located an average of 2.5 km above the surface,

were slightly higher above the ground than the Montana clouds.

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In Florida, our brief studies (Hobbs and Cooper, 1982) indicated

that cloud base temperatures were typically near +200C, similar to the

repres~ntative temperature of +220C reported by Hallett et ale (1980).

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The greater cloud depth below the freezing level, the higher

available liquid water content, and the larger droplets in Florida led

to precipitation processes very different from those in Montana. The

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Florida evolution proceeds via coalescence development of large

supercooled drops, soon followed by rapid glaciation (Hallett et aI.,

1978), while supercooled water drops are seldcm found in Montana

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(Hobbs et al., 1980; Cooper, 1978b). ~~s difference in precipitation

character is primarily attributable to the difference in cloud base

te!!lperature, since most other significant characteristics (such as

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droplet concentrations, cloud lifetime, or initial ice concentrations)

appear~si~ifar in the two areas.

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