WMOD00313

• Title: Cloud Physics Studies in Utah During 1978
• Date: 9/1/1978
• State: UT
• Weather Modification - Doc Type: Report

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and changed directions slightly, moving from the west northwest. On the
east side of the Uintas it recurved cyclonically to a west southwest flow.
From Figure 4. 1.6c at 3.0 km pressure altitude the flow is seen to be
from a westerly direction with speeds from 10 to 15 m s-l and the stream-
lines are parallel to the 8 lines.
e
Figure 4.1.7 contains analog traces of the reverse flow temperature
2D-P concentrations, 2D-C concentrations, the liquid water content from the
FSSP and the liquid water content from the Johnson-Williams 1 iquid water
meter. The period of time when these observations were taken was from
1415 to 1421, which occurred during the north to south pass across the
center of the Uinta Mountains at a flight altitude of about 4.8 km (See
Figure 4.1.5 and 4.1.6a). From this figure it may be seen that the
temperature varied between -18 and -190C, the 2D-P concentrations were 10
to 20 t-1 and the 2D-C concentrations were 50 to 100 t-1. The FSSP
indicated no substantial 1 iquid water with small concentrations of less than
0.1 g m-3 throughout the cloud. A slightly larger amount of liquid water
was observed on the northern side of the mountain near 1419. The Johnson-
Williams 1 iquid water meter indicated no liquid water except near 1419
when 0.1 9 m-3 was observed.
The 2D-images observed from 1418 to 1419 did not show marked changes
from regions of high 2D-concentrations to regions of low 2D-concentrations.
A typical example of the 2D-images recorded is shown in Figure 4.1.8.
Plate-like and stellar-like irregular crystals were the dominant type, and
many of these were as large as mm in diameter. There were also a few
columns. These were typically < 500 ~m in length and most of them appeared
to be unrimed.
From the data it is clear that the crystal concentrations were more
than adequate to naturally deplete the available liquid water in the cloud.
Seeding of the Uinta Range was not attempted nor does it appear that any
potential for snow augmentation existed.

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