WMOD00378

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

further up the Tushar Mtns slopes. Thus even greater liquid water depths

than the 0.31 mm, 0.245 mm, and 0.32 mm measured for A, C, and NP PETs in

the eastern quadrant over the mountains should be present higher up the

slopes.

The Ku-band radar and Iidar shed light on the vertical distribution of

liquid water.

From the radar it is concluded that liquid water respon-

sible for particle growth at subzero temperatures lies at temperatures of

about -5C or colder. The lidar confirms this by showing an average maxi-

mum temperature of liquid water of about -GC. Median height of maximum

radar reflectivities varies from about 1.2 to 1.7 km AGL, and the mean

height of the base of the water in the Iidar data is 1.4 km AGL. Uquid

water is thus located near ground level. It is often below the cre!st of

the Tushar Mtns which is 1.7 km above the remote sensing site.

d. Temporal distribution of supercooled liquid water. Superc:ooled

liquid water was present in the clouds overhead about two-thirds of the

time' according to the lidar. Radiometric liquid water depth was greater

----~..._._-~'~~.,..

than 0.13 mm one-half of the time or for about 4.5 hr in an average STORM.

During a STORM liquid water develops first over the mountains, alnd it

remains there toward the end of a STORM after it has disappeared from

other directions. There is a quasi-periodic variation in the liquid water

in at least half the STORMS possibly due to mesoscale disturbances.

e.

Delivery of seeding materials.

Deliv_~.I'"'t. of seeding material to

clouds over the Tushar Mtns from ground generators is limited, .a.~~~~r..(;:tiQg

.~..<r-,','!","'I,,,,,,,,.,,";,,,:,:~

to model studies, by downslope flow from the east, entrapment of the
_.~~' .-'It'........Klliiit..~...~~
-~.""..,'.,."

seeding material in "dead" air, and northerly or southerly flow parallel

xxv