WMOD00277

• Contract/Permit #: 14-06-D-6467
• Title: An Operational Adaptation Program for the Colorado River Basin
• Prepared By: Lewis O. Grant, Chappell, Crow, Mielke Jr., Rasmussen, Shobe, Stockwell, Wykstra
• Date: 10/1/1969
• State: CO
• Country: United States
• Weather Modification - Doc Type: Report

TABLE VIII. --Estimate of scale changes during seeded periods with respect to
non-seeded periods as computed by three statistical methods. Scale chan~es
are shown as a function of the 500 mb wind direction.
With Controls Without Controls
Total Sample Scale Scale
Stratification Sample Size Change Change
(Degrees) Size Utilized Method (%) P- Value (%) P- Value
Climax I
210 thru 230 S 15 S 15 NPl +68 .248 >+200 .0344
NS 17 NS 17 NP2 +33 .397 +144 .166
(S 12, NS9) PAR +12 .405
240 thru 270 S 47 S 47 NPl 0 .496 +5 .409
NS 38 NS 38 NP2 +29 .138 +16 .316
(S33, NS28) PAR +13 .255
280 thru 300 S 34 S 34 NPl -12 .221 -33 .075
NS33 NS 33 NP2 -8 .302 -32 .059
(S2 7, NS28) PAR -20 .117
310 thru 360 S 24 S 24 NP1 +58 .093 -7 .448
NS 43 NS 43 NP2 +9 .359 +2 .394
(S18, NS37) PAR +42 .102
Climax II
210 thru 230 S 7 S 7 NPl -9 .386
NS 8 NS 8 NP2 +53 .330
(S5, NS5) PAR +49 .337
240 thi'u 270 S 22 S 22 NPl +27 .075 +174 .0268
NS 18 NS 18 NP2 +56 .072 +98 .049
(S19, NSI2) PAR +14 .251
280 thru 300 S 19 S 19 NPl -18 .176 -34 .0274
NS 13 NS 13 NP2 -31 .142 -12 . 115
(S16;NSI2) PAR -32 .111
310 thru 360 S 13 S 13 NPl +48 .166 -20 .352
NS 27 NS 27 NP2 -23 .421 -11 .452
(S9, NS24) PAR +56 .136

Wolf Creek Summit
220 thru 240 S 41 S 36 NPl +23 .152 +16 .245
NS 50 NS 47 NP2 +13 .212 +17 .212
(S:29, NS42) PAR +60
250 thru 280 S 61 S 55 NPl +46 .056 +60 .043
NS 69 NS 60 NP2 +69 .0146 +66 .0202
(s:n, NS45) PAR +77 .0046
290 thru 360 and S 62 S 56 NPl +10 .386 +27 .221
o thru 210 NS 79 NS 74 NP2 +13 .323 +5 .421
(S:~8, NS34) PAR +18 .255

drents having 700 mb wind sp~eds from 11 mps
tlirough 16 mps~ All tests indicate these snowfall
increases to be significant at the 30/0 level, with
rrtost tests indicating significance near the 1 % level. The
distribution of seeding effects with the 700 mb wind
sp~ed for the Climax samples suggest a double mode
with snowfall increases observed when seeding events
h~ving speeds from 6 mps to 7 mps and again fr0m
12 mps to 15 mps. This double mode is even more
apparent when seeding effects are distributed with the
500 mb wind speed (Table X). Snowfall increases are
observed for events having 500 mb wind speeds from
12 mps through 16 mps and again from 22 mps through

27 mps. For the Climax I sample all tests indicate
the snowfall increases of near 100% to over 200% are
significant at ab out the 2% level. when seeding events
having 500 mb wind speeds from 22 mps through
27 mp s. Some of the tests also indicate that the
snowfall increases observed \'.h en seeding events
having 500 mb wind speeds from 12 mps through
16 mps are significant at tae 1 % level. Thus,
significance is indicated by at least some tests for
both wind speed modes. The existence of this double
mode at Climax has been discussed previously by ,
Chappell (1967) and is thought to relate to generator-
t~rget spacings embodied in the experimental design.

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