WMOD00313

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

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water contents as deduced by the FSSP were substantial. The mean droplet
diameter as measured by the FSSP was about 15 ~m throughout most of this
segment. The vertical velocities fluctuated between -2 ms-1 to +8 ms-1.
6e typically increased in association with observed increases in liquid
water. Note that there were four large negative ~pikes on the altitude
trace. These noisy records occurred throughout all of the Utah fl ights
and in a number of cases much more so than on this day. This negative
spike also occurs in the JW liquid water, the FSSP liquid water, FSSP
data, the vertical velocity data, and of course, the 6e data. We were
aware of this problem throughout the project, but it was only after the
project was over that our engineers were able to isolate it and correct
the system.
The FSSP spectra obtained from 164840 to 164912 is shown in Figure
4.1. IS. This time corresponded to the penetration of a region of high
liquid water content. The plot, which was fairly typi.cal of results
obtained during the project, shows a peak at about 20 ~m and a rapid
fall-off at larger sizes.
The 20 images recorded from 1650 to 1651 are shown in Figure 4.1.16.
Needles were the most common type of particle, and there were also some
graupel particles. Most of the needles were < 500 ~m in length, although
a few were as long as 800 ~m. The needles were either unrimed or lightly
rimed. Some of the graupel particles were up to 2-3 mm In diameter.
The many streaks which are visible near 1650 may be Indicative of water
drops or lee/water particles present wrthin the strong updrafts occurring
at this time.
Figure 4.1.14 is interesting in that it was taken essentially down-
wind and at a higher altitude from the region in the Figure 4.1.13 where
the convective clouds were forming and moving over the barrier. This
segment of data encompasses a penetration of a well-defined convective
cloud turret penetrated between 1735 and 1737. The 2D-P concentrations
were as high as 25 to 30 ~-l and the 2D-P concentrations reached peak
values of about 250 t-1. The JW liquid water meter did not register any
significant liquid water, but the FSSP showed peak values of liquid
water on the order of 0.5 g m-3. The FSSP cloud droplet concentrations
were on the order of 50 to 75 cm-3. The mean droplet diameter at this
altitude Increased to approximately 18 ~m. The magnitudes of the