WMOD00438

• Title: HIPLEX: A Cooperative Program on Rain Augmentation in the High Plains
• Date: 6/1/1984
• Weather Modification - Doc Type: Report

uation of the experiments on High Plains convective
clouds that had been in progress for over a decade
as a part of Project Skywater. The results of some
of those experiments are mentioned below as an aid
to understanding of the HIPLEX approach.

2.3 Previous Skywater Experiments

The effects of several cloud seeding agents upon
convective rainfall were tested in the early years of
the Bureau's Project Skywater. A number of the
Skywater experiments of the 1 960's and early
1970's were directed at convective clouds in the
High Plains Region. North Dakota. Oklahoma. South
Dakota. and Texas were affected. The seeding
agents for the Skywater experiments included pow-
dered NaCl (sodium chloride. i.e.. common salt) to
induce the formation of large collector cloud drop-
lets and speed the coalescence process. and dry ice
and Agl (silver iodide) to hasten the appearance of
ice crystals in supercooled clouds. The results of the
Skywater experiments in the High Plains during the
1960's and early 1970's showed some promise for
all of the seeding methods tested.

In the Dakotas. evidence was obtained that salt seed-
ing hastened the formation of rain showers in con-
vective clouds (Biswas and Dennis. 1971; Dennis
and Koscielski, 1 972; Dennis et al.. 1 97 5a). More
extensive experimentation with Agl and dry ice indi-
cated that they lead to the formation of ice crystals
in supercooled clouds, and that some of the ice
crystals grow or combine into snowflakes (Dennis
and Miller. 1977). In summer. the snowflakes usually
melt as they fall so that the end result is additional
rainfall at the ground. Rainfall statistics showed that
these seeding agents could produce or intensify
local showers to increase the average precipitation
by 25 mm (1 in) or more per season (Dennis and
Koscielski. 1969; Dennis et al.. 1974. 1975a. b).

In 1970. the Bureau was directed by the Office of
Emergency Preparedness to seed clouds in several
mid we s t ern a nd so u t h w est ern S tat e s a san
emergency relief measure. Emergency seeding was
conducted in Arizona. Texas. Oklahoma. and Kansas.
and followed up with investigative studies and
experiments. Under the acronym of KANCUP (Kan-
sas Cumulus Project). an experimental program of
ice-phase and hygroscopic seeding was conducted
in Kansas during the summers of 1972 and 1973 to
determine whether existing technology could pro-
duce an increase in rainfall. The results gave some
qualitative evidence that Agl seeding. applied selec-
tively to cumulus clouds. produced useful rainfall
increases. The results also suggested that "warm
cumulus thicker than 2 km (1.2 mil produced rain
earlier and in greater amounts when seeded with salt
than when left unseeded.

2.4 The HIPLEX Approach

In order to develop a state-of-the-art design for
HIPLEX. the scientific community was involved
through planning meetings and a series of confer-
ences from the start of HIPLEX (fig. 2.2). In the
approach to the technical programs. it was deter-
mined to make full use of (1) experimental results
obtained previously in the High Plains I~egion;
(2) modern computer systems for acquisition. reduc-
tion. storage. and analysis of meteorological data;
and (3) numerical models of clouds and other
weather systems as an aid to interpretation of
experimental results. Advice was sought from
experts in such fields as cloud physics. instrumenta-
. tion. and statistical design of experiments.

Preliminary ideas were presented in the "Conceptual
Plan for a High Plains Cooperative Program,'" issued
in May 1973. Additional ideas were put forth in a
"Technical Plan:' which was the basis for discussion
at the Skywater VIII Conference in June 1973
(fig. 2.2). After Skywater VIII. planning became more
specific and moved to the selection of sites for field
experiments.

The HIPLEX managers resolved at the outset to
. address the social issues associated with adoption
of weather modification technology. as well as the
purely technical problems. The social issues to be
addressed included public attitudes. agricultural eco-
nomics. and environmental impacts. Of particular
importance in the early stages was a contract with
ISWS (Illinois State Water Survey). The ISWS scien-
tists develoyed a plan which addressed technical
and social studies in parallel (fig. 2.3). A three-step
comprehensive experiment design was prepared
advocating exploratory studies in step 1. single
cloud experiments in step 2. and eventually. in step
3. experiments involving many clouds over a wide
area. The experiments would seek to establish the
amount of additional precipitation resulting from
cloud seeding and a seeding induced physical
change in the cloud development which caused it.
Concurrent scioeconomic studies would indicate its
value.

19

lHO ltal 11&2

1173 1974 1975 77
1 , 1 . 5 6
HIP iEx~ COPE
0 0 . . . . . 0
0 0 0 0
0 . . . . 0 0 !

'$.. Below

UIIe. City, MT

Colby/GoodlolMll

811 $prlnl. TX
-Snyd.

o Observations Onll
. Experiment. I S..d'n,
. 1. OtIS DirectIve, 1/26/73 4. Hlplex Technlc'l Confllfone., Denve" 6/16-20/15
2. Sky..ter Vtll Conler.nce, O.n...., 5/25..25/73 5. Hlpl... Dulp WorkshOp, Dillon. CO. 12/5-8/77
3. Workshop.t Villi, CO, 7/74 6. "The Deslln of HIPLEX-l" published 4(79
Figure 2.2-Starting schedule of HIPLEX planning meetings
and conferences.

6