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

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TABLE IV. -'--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 equivalent potential temperature.
With Controls Without Controls
Total Sample Scale Scale
Stratification Sample Size Change Change
(0 K) Size Utilized Method ("/0) P- Value (0/0) P- Value
Climax I
281. 0 to < 294.7 S 23 S 23 NPl -31 .074 -27 .079
NS 22 NS 22 NP2 -7 .345 -22 .074
(S20, NS2l) PAR -29 . 123
294.7 to < 305.7 S 61 S 61 NPl -3 .413 -18 .156
NS 64 NS 64 NP2 -24 . 123 -12 .227
(S46, N850) PAR -1 .476
305.7 to < 325.7 S 36 S 36 NPl +95 .040 +108 .054
NS 45 NS 45 NP2 +78 .089 +120 .047
(S26, N831) PAR +64 .0166
Climax II
281. 0 to < 294.7 S 14 S 14 NPl -32 .134 -17 .164
NS 12 NS 12 NP2 -16 .264 -18 .081
(Sl1, N811) PAR -40 .142
294. 7 to < 305. 7 S 28 S 28 NPl +7 .371 -5 .401
NS 34 NS 34 NP2 -50 .169 -1 .484
(S23, NS27) PAR -3 .440
305.7 to < 325.7 S 19 S 19 NPl +130 .089 +95 .203
NS 20 NS 20 NP2 +6'6 .174 +112 .102 I
(S15,NS15) PAR +59 .106 ,I
Wolf Creek Pass
285.0 to < 297.6 S 30 S 30 NPl -28 .100 -30 .145
NS 42 NS 41 NP2 -39 .042 -32 .099
(819, NS32) PAR -22 .164
29.7. 6 to < 304. 6 S 36 S 33 NPl +23 .206 +6 .409'
NS 53 NS 53 NP2 +11 .305 +7 .386
(S21, NS34) PAR +37 .085
304.6 to < 309.6 S 47 S 40 NPl +24 .166 +34 .154
NS 51 NS 49 NP2 +36 ;136 +28 .212
(S23, NS26) PAR +33 . 134
309.6 to < 325.6 S 51 S 44 NPl +139 .0329 >+200 .0019
NS 52 NS 38 NP2 >+200 .0146 >+200 .0048
(S31, NS29) PAR

Snowfall decreases appear in all
three samples when seeding tlE strong bar-oclinic
conditions. This is thought to result from extremely
high wind speeds that exist during many of these
events and this possibility will be discusSF'cl further
when orographic influences are considered. Vilhen
near barotropic conditions are seeded at Climax,
little effect or slight decreases are observed. Only
small snowfall increases are noted at Wolf Creek
"Summit for the same conditions.

d. Orographic effects
The orientation of the mountain
barrier with respect to the air flow will have impor-
tant bearing on the upward speed imparted to the air
:~rossing the mountain barrier. This in turn, is

vital to determining the rate at which cloud water is
supplied in the cloud system. It would be expected
that the larger supply rates would exist in flows
nearly normal to the mountain massif. Since the
Continental Divide runs east to wt:st 1n thE: Climax
area and southeast to northwest in the Wolf Creek
Pass area, one would expect that seeding effects
might be distributed differently with wind direction at
the two sites.

Table VII and Table VIII show seeding
effects distributed with the 700 mb wind direction and
the 500 mb wind direction respectively. At Climax
it is noted that snowfall increases result mainly from
seeding the north-northwest and south-southwest wind

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