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 VII. --Estimate of scale changes during seeded periods with: respect to
non-seeded periods as computed by three statistical methods. Scale changes
are shown as a function of the 700 mb wind direction.

I

With Controls Without Controls
Total Sample Scale Scale
8tra tification Sample Size Change Change
(Degrees) Size Utilized Method (0/0) P- Value (0/0 ) P- Value
Climax I
210 thru 240 S 14 S 14 NPl >+200 .062 > +200 .071
NS 16 NS 16 NP2 +37 .239 +159 .109
(S9, NS9) PAR +100 .079
250 thru 300 S 63 8 63 NP1 -6 .367 -29 .090
NS 73 NS 73 NP2 +2 .429 -23 .142
(S43, NS59) PAR +4 .397
310 thru 350 S 25 S 25 NP1 +64 .099 +24 .251
NS 26 NS 26 NP2 +20 .323 +22 .215
(S?':l, NS?2) PAR +23 . 212
o thru 200 S 18 S 18 NPl -46 .087 -3 .352
NS 16 NS 16 NP2 -31 .108 0 .496
(815, N812) PAR -25 .176
Climax II
210 thru 240 S 6 S 6 NP1 +30 .258
NS 6 NS 6 NP2 +6 .488
(84, NS4) PAR +151 .097
250 thru 300 S 32 S 32 NP1 +5 .390 -15 .261
NS 35 NS 35 NP2 +2 .436 -4 .352
(S24, NS29) PAR +5 .429
310 thru 350 S 13 S 13 NP1 +45 .195 +15 .309
NS 16 NS 16 NP2 -29 .330 +6 .334
(Sll, NS14) PAR +27 .236
o thru 200 S 10 S 10 NP1 -4 .421
NS 9 NS 9 NP2 -1 .448
(S10, NS6) PAR +1 .492
Wolf Creek Summit
220 thru 270 S 74 S 63 NP1 +60 .0129 +79 .0099
NS 91 NS 81 NP2 +79 .0027 +84 ; 0035
(S45, NS59) PAR +60 .0019
230 thru 250 S 44 S 39 NP1 +109 .0071 +146 .UU:)6
NS 45 NS 38 NP2 t-141 .0024 +164 ' .0006
(S28, NS28) PAR +129 .0001
260 thru 360 and S 120 S 108 NP1 +10 .295 +15 .274
o thru 220 NS 153 NS 143 NP2 +8 .337 -4 .460
(S67, NS92) PAR +13 .212
wind speeds, since the boundary condition may be have low supply rates of cloud water due to the small
reached where crystals start escaping over the orographic effect and usually there would be suffi-
mountain barrier that would have naturally fallen on cient natural ice nuclei to convert the cloud water to
the E10untain summit. ice form.

Table IX and Table X show the
distribution of seeding effects with respect to the
700 mb and 500 mb wind speeds, respecti vely.
Table IX indicates decreases in snowfall for all
three samples when seeding the highest 700 mb wind
speed categories. The snowfall decreases are
significant at the 50/0 level for most tests at Wolf
Creek Summit. The seeding effect is near zero or
slightly negative when seeding events in the lowest
700 mb wind speed category. These events would

There is an irregular increase in
~ositive seeding effects as the 700 mb wind speed
mcreases toward the highest category. Snowfall
increases of about 1000/0 are observed in the Climax I
sample when events having 700 mb wind speeds from
12 mps through 15 mps are seeded. Some of the
tests indicate these increases to be significant at the
'3'/0 level. In the Wolf Creek I sample snowfall in
increases of over 100% are indicated when seeding

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