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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01 , , I
o 1000 2000 3000 '
MAXIMUM CRYSTAL DIMENSION (MICRONS)

Figure 7. --Observed terminal velocities of various
crystal habits as a function of crystal size.

It is evident that the information
required to compute (1) the time to transport artificial
ice nuclei from the generator site to point of activa-
tion in the cloud system, (2) the growth and residence
period within the cloud system, and (3) the final set-
tling time from cloud base to mountain, is fragmen-
, tary and inconclusive. Modelling of these processes
will therefore by necessity be full of assumptions
and approximations.

It appears that due to the many
, uncertainties embodied in computing generator-
target seprration distances that equal consideration
should he given to experimental reBl)ltR, TnV8,
computed generator-target designs should be tempered
with experimental designs that have yielded success-
ful results.

'B. Experimental basis for a pilot proiect and
meteorological criteria for weather modific~
operations
: The programs of weather modification
! research carried out in the central Colorado Rockies
and the operational - type program
carried out in the Wolf Creek Pass area by the
State of Colorado provide the primary empirical type
information being utilized for the design of the pilot
program. This section of the report briefly discusses
these programs and presents some of the result!, in a
form that can be utilized in the design and operation
of a pilot proj ect.

1. Experimental Design

a. Climax experiment
The experimental design d the Climax
experiment has been presented in detail elsewhere
(Grant and Mielke, 1967), so only a brief synopsis is
pres ented below.

Randomization is employed in obtaining the
seeded and non-seeded samples. The randomi-
zation is restricted to t.he extent that large
blocks (20 to 40) have the same number of seeded
and non-seeded cases.

The sampling unit is a 24-hour interval of time.

Eight standard Weather Bureau stations located
southwest, west, northwest and north of the
experimental site are available for use as
control stations.

The criteria of an experimental day is that at
least. 01 inches of precipitation be forecasted
during 3. 24-hour sampling unit at Leadville,
Colorado, accompanied by a 500 mb wind
direction between 210 degrees and 360 degrees
inclusive. This forecast is prepared by the
United States Weather Bureau in Denver. The
forecasters have no access to the seeding
decision.

Generators are turned on t to 1 hour prior to
the beginning of the experimental day, and
shut off t to 1 hour prior to the end of the day
depending upon their respective distances from
the primary target area.

b. Wolf Creek experiment
The WQlf Creek Pass experiment is
inherently an operational program whose basic
purpose and objective was to augIJ;lent snowfall over
an area cf the San Juan Mountain Massif centered at
the summit of Wolf Creek Pass. In order to secure
useful data from this operational program eight snow-
boards were installed over the pass. Recording
precipitation gages were added such that hourly
precipitation amounts are available near the summit
and on the west and east sides of the pass. The
experimental design of the Wolf Creek experiment is
summarized below.

Randomization is employed in obtaining the
seeded and non-seeded samples. The randomi-
zation is restricted to entire winter seasons.
This resulted in the winter seasons of HH:i4-65
and 1966-67 being seeded periods while the
winter seasons of 1965-66 and 1967-68 were
left non-seeded.

The sampling unit is a 24-hour interval of time.

Seven standard Vv'eather Bureau statials
located south, southwest and west of the
experimental site are available for use as
control stations.

The criteria of an experimental day is that at
least. 01 inches of precipitation occurred
during a 24-hour sampling unit at one or more
of the recording precipitation gages on Wolf
Creek Pass, or at tJ::e control station.

The generator operations were controlled by a
private meteorological group from Denver
(Water Resources Development Corp.) du..-ring me

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