WMOD00412

• Title: Final Report on Utah Cloud Seeding Experimentation Using Propane During the 2003/04 Winter
• Date: 3/1/2005
• State: UT
• Weather Modification - Doc Type: Report

I

I

I

TAR. It also provided ratings of targeting success for 60 experiments, based on the peak ice nuclei
concentrations observed with the acoustical counter. A rating system was described which dividl~d cases
into "good," "fair" or "bad." "Poor" will be substituted for "bad" in this report because some AgI reached
the TAR in all rated cases. Transit times were also listed, based on the clock time between start of AgI
release and the ice nuclei detection peak at the TAR. In some cases this time had to be estimated by
relationships established with wind speeds at the two locations.

I

I

The transit times were used to match the appropriate 60 min or 30 min averaging periods at the HAS.
For example, if the transit time was 20 min for a particular experiment, averaging of the HAS wind
direction data would begin about 20 min prior to AgI arrival at the TAR. HAS data were available as 6
min averages so the best fit period was chosen in each case. TAR data were available as 1 min averages
and 30 min or 60 min averaging began with AgI plume arrival, whether a continuous plume or the first
AgI "tag."

I

I

Figure 6 shows the frequency distribution of HAS wind directions for 59 experiments. One additional
outlier with a poor rating and average wind direction of 324 deg, due to a wind shift, is not plotted. It can
be seen that all good targeting cases had HAS winds in the 195 to 255 deg sector with 14 of 23 cases
(61%) between 210 to 225 deg. The actual lowest and highest values were 195 and 244 deg. Fair
targeting cases were within the same 195 to 255 deg sector with the exceptions of the lowest and highest
values of 171 and 266 deg. The poor targeting cases had a somewhat wider range, including the 324 deg
outlier not plotted. Limiting allowable wind directions to 190 to 250 deg would exclude 9 of the 17 poor
targeting cases (53%), but also 2 of the 20 fair targeting cases. A range of 170 to 270 deg would include

I

I

I

...,
20 Frequency of Targeting --j
Ratings by HAS Wind Dlr. """'t
Sectors for 1994/95 and
1995/96 Winters, ~
1Il I
Cl 23 Good = Black -I
c
.. 16 20 Fair = Gray
tll
0:: 16 Poor = White
Cl -I
c
..
CD ---j
~
~ -i
C') 12 ~
.e
JIJ -I
c
G) --j
E
"C -i
CD
Q.
~ 8
-
0 -I
"-
CD
s:l -
E
::J -t
z
4 ---<

I

I

I

I

I

-t

I

o

150 165 180 195 210 225 240 255 270 285
Mean HAS Wind Direction (deg true)

I
I
I

Fig. 6. Frequency distribution of HAS wind directions for 59 experiments with good, fair or poor TAR targeting
conducted during the winters of 1994/95 and 1995/96.

14