WMOD00378

• Title: Physical Investigations of Winter Orographic Clouds in Utah
• Date: 3/1/1984
• State: UT
• Weather Modification - Doc Type: Report

to rather than toward the Tushar Mtns. If material does follow a trajec-

tory into clouds over the Tushar Mtns then delivery is limited by the

narrow plume. Even with a narrow plume only 36% of the soundings con-

sidered showed seeding material was delivered to the clouds. In one case

seeding material was delivered to the clouds only from a high-altitude

generator above the "dead" air.

Che~ical analysis of the snowpack showed little silver above back-

ground levels, and indium concentrations above background were less than

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expected naturally.

These results probably were due in part to the

limited delivery of seeding material likely accomplished in 1983.

Additional factors restricting the number of samples with silver or indium

concentrations above back ground were the compaction of the snowpack and

the 4 cm resolution of the snow sampling technique.

f.

Climatological representativeness of 1983 weather.

Weather

during the 1983 research period was abnormal in several respects. Zonal

rather than meridional flow was dominant. At 700 mb and 500 mb winds were

more southerly than normal and temperatures were warmer than normal.

Rawinsonde-derived cloud tops were lower and warmer than usual, and STORM

duration was shorter than usual. At Beaver minimum surface temperatures

were above normal and precipitation was above average.

-- -......--.-

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1983 field investigations and physical

Principal conclusions of the

analysis are that substantial amounts of supercooled liquid water are pre-

sent in the study clouds, primarily in their lower levels and over the

Tushar. Mtns, but that delivery of seeding material to the clouds from low-

altitude ground generators is frequently limited by meteorologica~ .c:...o~~/

._~,..,.. -.;.-,.-,--;:.,.,.--,...~-...,.-.--

ditions.

....--. .:::>:"'"

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