WMOD00313

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

16

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

the generators were being shut down and all but one of the generators
were turned off by noon.
The flight times for the King Air are also indicated in Figure 4.1.3.
The KIA was flown over the Uinta Range for 3 hrs during the afternoon
of 12 March and was also flown over the Wasatch Range for about 1.5 hrs
late in the day on 12 March.

4.Z.Z Uinta Flight
The flight track for the first flight on 12 March is shown in
Figure 4.1.4. The research mission began on the downwind or north side
of the Uinta Range at about 1230 and was flown over the Range for approx-
imately 2 hrs. The mission then proceeded to Salt Lake City to land.
During the descent into Salt Lake City, the indicated airspeed on the
data system malfunctioned. The indications were that it had frozen due
to water collected in the pitot tube plumbing system. This was confirmed
upon landing.
Figure 4.1.5 is a sounding taken during descent over the My ton VOR
~outh of the Uinta Range. The sounding shows some convective instability
ae
(~< 0) below 750 mb with neutral stability present above that level.
az
Cloud base was observed at 670 mb (3.4 km*). From the hodograph of the
winds shown also in Figure 4.1.5, the surface winds are seen to be <
2 m s-l from the northwest with the subcloud winds all westerly between
10 and 15 m s-l. The cloud layer winds were from the west-northwest at
approximately 10 m s-l. Clearly, the convective instability would not be
released over the Uinta Range with these winds.
Figures 4.1.6a, b, c, contain aircraft data observed at pressure
altitudes at 4.8, 4.0 and 3.0 km, respectively. From Figure 4.1 6a it may
be seen that the winds above the Uintas at 4.8 km were from the west
northwest with speeds of 8 to 10 m s-l. Equivalent potential temperature
(0 ) is shown as dashed lines at 0.5 K intervals. Since 0 increases
e e
in the downwind direction, the air was descending over the Uinta Mountains
at this altitude.
From Figure 4.1.Gb it may again be seen that the flow was from the
west as the air approached the western part of the Uintas then began des-
cending as indicated by the increasing e along the stream lines and
e

*
All aircraft altitudes are pressure altitude.