WMOD00550

• Title: Scientific Weather Modification Experimentation in the United States
• Weather Modification - Doc Type: Report

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FIGURE 5 -- OBSERVATIONS MADE AT KINGVALE, CA
(l867m) SHOWING PASSAGE OF KATAFRONT FROM Ka
BAND RADAR TIME HEIGHT PROFILE (a), LIQUID
WATER (SOLID) AND VAPOR (DASHED) AS OBSERVED
BY DUAL CHANNEL RADI~lETER (b), PRECIPITATION
AT A NEARBY PRECIPITATION GAGE (c), AND
THIPERATURE AT THE SITE (d).

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60 80 100 120 .140
X IKM)
AVERAGE LIQUID WATER CONCENTRATION PROFILE IGlMn31

FIGURE 6 -- AVERAGE LIQUID WATER
CONCENTRATION PROFILE (GjM**3) DERIVED FROM
RADIOMETRIC OBSERVATIONS FOR SHALLOW
OROGRAPHIC CLOUDS OVER THE SIERRA.NEVADA
BARRIER. LOCATION OF MINIMUM ALTITUTE OF
.AIRCRAFT OBSERVATIONS IS DEPICTED.

As the storm further transitions into the
post frontal air mass, further destabiliza-
tion occurs and strong convective elements or
bands develop on the upwind edge of the
orographic cloud. The seedabi1ity then moves
to,the foothill region of the Sierra Nevada
~nere liquid water is being lost to entrain-
ment in convective clouds. This seedab1e
region translates down the barrier because,
as these convective clouds continue to deve-
lop and merge on the barrier, rapid develop-
ment of ice particles by a Hal1et-Mossop type
secondary ice crystal process effectively
removes the available condensate on the
barrier. The primary factor influencing
successful seeding of the convective clouds
is cloud lifetime. Although well documented
seeding signatures have been observed both oy
aircraft and conventional radar for these
convective cloud types, loss of liquid water
by entrai nment is substanti ally greater than
that used up in growing ice particles added
_. by seeding.

Given the above scenario, SCPP tends to con-
centrate on the warm, shallow orographic
cloud as the most treatable and most produc-
tive cloud type for producing additional" pre-
cipitation on the ground. Targeting of the
seeding effects will be at a fixed site high
on the barrier equipped with a dual channel
radjometer, Ka band radar, ground microphy-
sics observations, a rawinsonde unit and
other meteorological sensors to help measure
the magnitude of the seeding effect and with
the help of aircraft in-situ cloud physi~s
observations, document the physical links in
the chain of events leading to additional
precipitation on the ground.

5. CREST

OCIOO

The Bureau of Reclamation has proposed,but
not rEceived, funding for CREST (the Colorado
River Enhanced Snowpack Test) which is
designed to demonstrate an operational capa-
bility for increasing the flow of the
Colorado River through cloud seeding.
Current cloud seeding technology has the
potential to increase winter snowpack by 10
to 15 percent in many mountainous areas of
the ColoradO River Basin, and could produce
approximately 2.3 million acre-feet of ad~i-
tiona1 water in the Colorado and surroundlng
river basins. The increase would produce
economic benefits of $140 million annually
from increased power production, salinity
reduction and additional water supplies.

CREST is designed to address all aspects of
precipitation management through cloud
seeding and provide the basis for
establishing a fully operational program for
snowpack augmentation. The objectives pf
CREST are: 1) production of water to the
maximum extent possible during the demonstra-
, tion period, 2) demonstration of cloud
seeding technology to establish procedures
for an operational program, 3) quantification
of increases as a result of cloud seeding, 4)
assessment of impacts to ensure there will be
no adverse effects on the environment
resulting from cloud seeding, and 5) minimi-
zation of risks through the application of
.estab1ished suspension criteria to safeguard
against potential flood or avalanche con-
ditions.

160

Pending approval and funding of CREST, the
Bureau of Reclamation is conducting a winter-
tim~ research program, CRADP (the Colorado
River Augmentation Demonstration Program), on
the Grand Mesa of west central Colorado. The
program is designed to develop an improved
winter cloud seeding technology, improve the
already favorable benefit-to-cost ratio in
the Colorado River Basin and refine seeding
suspension criteria. This will be
accomplished by conducting studies which will
develop: 1) a more accurate climatology of
winter cloud seeding opportunities, 2)
improved methods of recqgniziny and treating
seedab1e conditions, and 3) a reliable and
consistent method of delivering seeding
materi a 1.

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i Field activities began in the winter of
I 19B2-83. Since that time efforts have ton-
i cent rated on observing winter storm behavior
! and making measurements of supercooled liquid
J water. A team of scientists and technicians
--- have established a year-round facility i~ the

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