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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the clouds. Ground observations of Humphries and Moore (1981) indicate
that irregular crystals account for half of the precipitation,
indicating that crystal fracturing (Vardiman. 1978) also occurs. Warm
rain processes have also been identified (Stewart, 1979).
Evidence presented by Humphries and Moore (1979) confirm the
earlier work of Reinking (1975) at CENSARE t~a~a~~~etion is ~ d~nan~
growth process in the Sierras and that the liquid water in the cloud is
";'::"'-,~-.-_.~---- .

generally in the low cloud levels. Summaries of the SCPP aircraft

observations of liquid water and ice crystal distributions by Heggli et

ale (1983) for the seven cloud types identified by Huggins (1981) have

indicated that, at aircraft altitudes, convective clouds have the

highest concentration of supercooled water, particularly 40-90 km upwind

of the crest and at temperatures warmer than -10oC. The liquid

water/ice crystal concentration ratio was largest 7-10 hours after 700

mb trough passage. Largest liquid water contents were generally between

OoC and -SoC. Wide-area and banded cloud systems were found to contain

high ice crystal concentrations and low liquid water contents.

B. Inland mountain ra~es

During the last 30 years, wintertime cloud physics and weather

modification research programs have been conducted in nine regions of

the intermountain west. These inolude the Park Range area of Northern

Colorado (Rhea et al., 1969 and present study), the Climax region of

central Colorado (Mielke et al., 1971, 1981), the San Juan mountains of

southern Colorado (Grant and Elliott, 1974; Elliott et al., 1978), tpe

Bridger Range of Montana (Super and Heimbach, 1983), Elk Mountain of

Wyoming (Politovich and Vali, 1983), the Jemez mountains of New Mexico

(Keyeset ale, 1973), the Wasatch of northern Utah (Hill, 1979), the