WMOD00299

• Title: Physical Structure of Northern Colorado River Basin Cloud Systems
• Date: 9/1/1985
• State: CO
• Weather Modification - Doc Type: Report

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
1
\
,
~
1

21

specifically focused on natural cloud systems, since seeding operations
associated with the operational program are routinely performed.
Hill (1982b) found that low level inversions were frequently
present over the valley west of the southern Wasatch, even during storm
periods. These inversions severely complicated the nuclei dispersion
characteristics. The distribution of supercooled water was found to be
closely associated with the topography. Liquid water contents were
maximum over the range and minimum over the valley. Few events occurred
where liquid water was observed during the two month study. However,
according to Hill, the period of observation was generally
uncharacteristic of storms which affect the area based on climatology.
Cloudsonde data reported by Hill indicated that the maximum liquid water
contents were at the elevation of the barrier crest. Observations of
rime on crystals at the radiometer site during the program generally

supported the radiometric measurements of liquid water described above.

Aircraft observations of ice particles during the experiment indicated

that ice particles grew rapidly in regions of high liquid water content,

that riming substantially steepened ice particle trajectories, and that

the maximum precipitation rate lags the maximum liquid water content

from 0-20 minutes.

Long (1984) confirmed the findings of Hill (1982b) concerning

nuclei entrapment by inversions. Long's study of liquid water structure

using radiometric data also confirmed that liquid water contents were

greatest over higher topography. Long presented climatological values

of integrated liquid water content based on radiometric data. These

were categorized according to precipitation echo type based on C-band

radar operations. Rauber and Grant (1985) reported that shallow

i~