WMOD00376

• Contract/Permit #: 14-06-D-5640
• Project Name: Park Range Atmospheric Water Resources Program
• Title: Park Range Atmospheric Water Resources Program - Phase II - Parts A and B
• Date: 10/6/1967
• Weather Modification - Doc Type: Report

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An initial inspection of the first seeding period would indicate that
winds are from the wrong direction, but examination of the origina.l data
from Emerald Mountain shows a wind shift from 190 to 310 degrees occur-
red just after 0100 MST. Perfect alignment of the Emerald and Me Harris
11,000 ft. winds is not nece s sary for pulsing to be detected at Rabbit Ear s.
Mt. Harris winds of 250 to 360 degrees, with proper Emerald winds (270-
3500) have given pulse s at Rabbit Ears,

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The next simplest case occurs when Emerald Mountain is under an

inversion; it was found during 22% of the observation times, In Figure 14,

an inversion is definitely present as indicated by the moderate westerlies

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at 11, 000 ft. and the light southe rlie s (changing to northerly) at Emerald.

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The interesting point is that the nuclei concentration is on the order of

1 per liter during periods of no seeding. Evidently, some of the seeding

agent doe s reach the counter at Rabbit Ear s even when the top of an in-

version is between Emerald Mountain and Rabbit Ears Pass elevationso

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When the IlK ft. MSL wind from Mt. Harris is between 270 and 360

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degrees, the nuclei count usually ran 1-2 nuclei per liter; when that wind
was between 180 and 270 degrees, the count was less than, 8e,} per liter.

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Another type of nuclei concentration variation is shown in Figure
15, An inversion exists up to about 1230 hours on 25 January, but then
there was a wind shift and speed increase at Emerald -- indicating a
dissipation of the inversion. High nuclei concentrations were subse-

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quently measured between 1310 and 1600, This suggests that high con-

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centrations of ice nuclei were built up under the inversion, and were

released during the first few hours after the stable layer was destroyedo

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The most difficult case to explain occurred during 18% of the ob-
servation times, Both Mt. Harris and Enlerald winds are favorable for

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detection, but the nuclei concentration rer.nains near 1 per liter, This

case is demonstrated in Figure 16 where, the winds above ridge level are

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