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 stable stage was characterized by blooked flOW. During the
stable stage, precipitation developed primarily by diffusional growth
and liquid water was rarely observed. The neutral stage typically was
characterized by deep cloud systems. Liquid water was observed
primarily over the barrier during this stage. During the late storm
stage, convection was frequently observed. Liquid water was found in
three regions: (1) slightly upwind of the barrier; (2) 15-20 km upwind
of the barrier associated with the release of convective instability;
and (3) 60-70 km upwind of the range associated with an initial rise in
the topography. Cooper and Marwitz (1980) stressed the importance of
the zone of convergence 15-20 km upwind as a mechanism to transport
seeding material to cold cloud levels.
During storm events, ice crystal concentrations far exceeded
natural ice nuclei concentrations. According to Cooper and Saunders
(1980), no known ice multiplication mechanism oould be attributed to
these high ice crystal concentrations. Hobbs et ale (1975a) also found
high ice crystal concentrations but attributed them to ioe
multiplication. No mechanism was proposed.
Cooper and Saunders discussed microphysioal aspeots of the liquid
water and ice crystal distributions during San Juan storms. These
observations will be discussed more fully later.
(6) Elk Mountain EXDeriments
Elk Mountain, an isolated peak in south-central Wyoming, has been
the site of a cloud phYSiCS observatory operated by the University of
Wyoming for over 15 years. Numerous reports and publications have
resulted from studies of orographic clouds which occur over this peak.
Two summary papers concerning Elk Mountain cap clouds have been