WMOD00426

• Title: Desert Research Institute Fields Operations - 1994 NOAA/UTAH Field Program - Final Report
• Date: 11/1/1994
• Weather Modification - Doc Type: Report

In situations where clouds are relatively ice free, the radar can potentially detect
the formation of ice within seeding plumes. The close range to the seeding plumes
improves this possibility. All of the 1994 seeding experiments will be assessed to
determine if radar seeding effects were detectable. In addition, the tracking of specific
radar echo features will provide additional information on the wind field in the cloud layer
over the Plateau.
Radar chaff are mylar fibers cut to the half wavelength of the radar to maximize
their backscattered return. These light weight fibers generally move with, and are
dispersed by, the wind. On several occasions chaff was released from ground generator
sites (HAS and AHS in Fig. 1) to simulate the release of seeding material. This was done
when wind conditions were similar to real storm situations, but when. clouds and
precipitation were generally absent and would not interfere with the signals returned from
the chaff filaments.
Table 5 summarizes the operational periods of the K.-Band radar. The analyses
of the data will be prioritized as follows. Each significant storm period will be described
in terms of general radar echo development. Echo heights will be converted to
temperatures using sounding data, and the temporal evolution of radar echo
heights/temperatures will be plotted for each storm period. The data also analyzed for
the detection of seeding effects. Only those cases which display a minimum, or no radar
echo between generators and the target will be initially considered. Ground-based and
aircraft documentation of seeding plume locations will be used to evaluate radar echo
inside and outside seeding plumes. Additional cases with higher backgrounds of natural
echo may be adged. For these cases a more objective analysis technique will be used
to average radar returns inside and outside documented plume locations, to determine

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if seeded regions have substantially different radar returns compared to unseeded
regions.

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