WMOD00313

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

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Figure 4.1. 12a is a vertical cross section along the 1800 radial
from Salt Lake City. This vertical cross section is a composite of two
flight times: from 1635 to 1650, and from 1738 to 1748. The cloud
bases were close to the ground, and the cloud tops were observed to be
just above 4 km and at a temperature' of about -150C. The wind barbs on
this diagram again Indicate that the winds at all levels varied between
west and northwest at approximately 5. to 10 m s-l.
Figure 4.1. 12b is a vertical cross section along the 2000 radial
from Salt Lake City. The figure contains data taken during the south-
bound pass and after 1715 on the return flight along the crest line of
the Wasatch Range. The southern track was designed to proceed along the
western edge of the Wasatch Range flying at MOCA throughout that track
unless we were able to fly VFR. When VFR was possible, we would occa-
sionally descend much closer to the ground. Throughout this flight, of
course, we were in cloud except intermittedly between convective elements
where the ground was visible. A number of convective elements were pene-
trated during this pass, both along the lower altitude southbound track
and along the northbound crestline track. Individual turrets were easily
seen and penetrated on the northbound leg. The winds continued to be
from 2700 ~ 300. Wind speeds were rather light at < 5 m s-l. The tops
of the convective elements varied from -20oC to -25QC.
Figures 4.1.13 and 4. 1.14 contain a series of analog traces taken
during the southbound and northbound legs, respectively. The data in
Figure 4.1.13 were taken at the lower altitude, while that in Figure 4.1.14
were taken at the higher altitude. It may be seen from the time intervals
of these figures that the data were taken between 70 and 100 km along the
2000 radial of Salt. Lake City. This radial was through the northernmost
convective element shown in Figure 4.1.12b. From Figure 4.1.13 it may
be seen that the aircraft descended from. about 4 km to just under 3 km
and was then flown at a constant altitude during the last three minutes.
No ice nuclei were detected during this Interval. The concentration of
particles observed by the 2D-P were very few at < 3 r1. The con'"
centration of particles recorded by the 2D-C probe were 10 to 20 ~-l.
The liquid water concentration as measured by the JW was 0.2 to 0.3 g m-3
within the cloud. The FSSP indicated that the 1 iquid water contents had
occasional peaks as high as 1.8 g m-3. The fluctuations in the liquid