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 III. --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 a computed vertical gradient of potential condensate
in the 700-500 mb layer.

(

With Controls Without Controls
Total Sample Scale Scale
Stra tifica tion Sample Size Change Change
GM/O:<GM)(100 mb) Size Utilized Method (0/0) P- Value (0/0) P- Value
Climax I
o to < O. 7 S 24 S 24 NPl -36 .058 < -50 .0045
NS 21 NS 21 NP2 -46 .0314 < -50 .0071
(S17, NS19) PAR -40 .072
0, 7 to < 1. 3 S 76 S 76 NPl +4 . 371 +11 .284
NS 86 NS 86 NP2 +6 .334 +8 .274
(S6l, NS66) PAR +3 .401
1. 3 to < 2. 0 S 20 S 20 NPl +117 .0351 +53 .154
NS 24 NS 24 NP2 +171 .147 +100 .145 ~I
(S12, NS17) PAR +128 .0150

S 15 S 15 NPl -38 .147 < -50 .049
NS 12 NS 12 NP2 <-50 .0239 < -50 .0336
(S10, NS11) PAR -45 .134
S 36 S 36 NPl +7 .341 + 5 .397
NS 42 NS 42 NP2 -5 .452 +16 . 212
(S31, NS34) PAR +2 .468
S 10 S 10 NPl >+200 .0239 >+200 .0392
NS 12 NS 12 NP2 >+200 .082 >+200 . 142
(S8, NS8) PAR +145 .090

Climax II

o to < O. 7

O. 7 to < 1. 3.

1. 3 to < 2. 0

Wolf Creek Summit
o to < O. 8 S 33 S 30 NPl -21 .184 -20 . 187
NS 38 NS 34 NP2 -39 .074 --24 . 102
(S10, NS25) PAR -10 .238
O. 8 to < 1. 2 S 58 S 55 NPl +11 .394 -14 .370
NS 81 NS 80 NP2 +2 .448 -15 .284
(S36, NS53) 'PAR +20 .149
1. 2 to < 2.0 S 73 S 62 NP1 +128 .0202 >+200 .0025
NS 79 NS 67 NP2 >+200 .0021 >+200 .0012
(1lI40, NS43) pAR +-65' .0094

mountain barrier. This is apparent from the
influence the static stability term exerts in the wave
equatiffi s for flow over mountain barriers as
discussed by Scorer (1953). Thus, the static stability
helps to determine the orographically induced
vertical motion field over the mountain barrier. The
integrated effect of stability upon modification poten-
tial is therefore difficult to assess.

The distribution of seeding effects
with a convective stability index is shown in Table V.
The three independent samples are in agreement in
most respects. All three samples indicate snowfall
decreases when seeding the most stable categories.
The two Climax samples show snowfall increases
when seeding the most unstable events (less than
1. 0) and again in an intermediate range (4.0 to 8.0).
This double mode in evidence at Climax is not
repeated at Wolf Creek Summit, but instead a gradual

decr~~s(i; ~n positive seeding effects with increasing
stablhty lS noted. The increase in snowfall when
seeding the unstable events is significant at the 5%
level for some afth~ tests for Climax I and Wolf Creek
I samples.

The mean temperature advection in the 700-
500 mb layer has been computed and provides a
measure of the baroclinic state of the atmo sphere.
The distribution of seeding effects with the mean
temperature advection in the clou'd layer is shown in
Table VI. The three samples are again quite con-
sistent. It is seen that snowfall increases are
observed when seeding the moderate baroclinic
conditions (warm or cold advection), The snowfall
increases at Climax are spectacular when seeding
the moderate warm advection events. All tests
indicate significance at the 5% level in the Climax I
sample.

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