Evening star. [volume] (Washington, D.C.) 1854-1972, 1952-12-28
Weitest Area in i. )
Is Selected for New
Rain.Making Tests


last night it will make new and
different attempt to see whether
man can make rain fall on a big
scale.
Instead of trying to make ap-
parently dry skies drop rain. the
bureau will go to the wettest place
in the United States-the Pacific
Northwest-and see how much. II
any, wetter it can make it.
The experiments will be con-
Quoted from the United States
Naval Air Station at Sand Point.
near Seattle, from late January
to May and again during the fall
and early winter of 1853. Ferguson
Hall, Weather Bureau specialist in
rain-making experiments, will be
in charge at Seattle.
At the start, a Weather Bureau
spokesman said, the cloud seeding
will take place over the southwest
corner of the State of Washing
ton, but the area may be extended
or changed.
Akin to Medical Experiment.
The idea is to carry out some
thing like a medical experiment,
where one group of patients is given
treatment and another group is
not. The untreated group is used
as a control" permitting better
scientific Judgment of the results.
Like the doctors, the Weather
Bureau wants to know not only
what happens under treatment,
but what would have happened
had there been no treatment.
That is why the rainy Pacific
Northwest was chosen for the
experiment. The area has more
rainy day than any other in the
United States. This, the announce
ment said, will give the rain
makers a choice Of many days
when it is raining or practically
certain to rain. On some of these
favorable" days planes on loan
from the Navy will go aloft to
seed rain clouds with the two
standard weapons of commercial
rain makers-dry ice pellets and
silver iodide fumes.
On other favorable days, nothing
will be done.
In this way. the Weather Bureau
spokesman said. it is hoped to dis
cover how much more rain falls,
If any, when clouds are seeded on
days when rainy conditions are
present.
AS a further control. the cloud
seeders will work only over small
areas at any one time. This will
allow comparison of rainfall from
seeded and unseeded clouds on the
same day.
The Weather Bureau conducted
rain-making experiments. mostly
near Wilmington, Ohio, In 1947
and 1913. It came up unconvinced
that rain making is practical. The
results, according to the Weather
Bureau, showed:
/. Seeding could cause changes
in cloud structure.
2. It apparently could cause some
rain to fall. but how much was
not clear.
3. Seeding only MIXED" clouds
of what rain moisture was2already
in them. That is, it did not set up
conditions in which new moist air
rushed in, building up new rain
cloud formations.
Differences in Areas.
These experiments were with
ordinary types of clouds and under
more ordinary conditions than
found in the Pacific Northwest,
where very thick rain clouds are
often present.
The Navy and several other gov
ernmental agencies are lending
the Weather Bureau a mass Of
equipment to make the new ex-
periments scientific and informa-
tive. Here are some details of the
attempt:
l. Special aircraft instruments
will measure changes in cloud for
nations after seeding.
2. An extensive series of rain
gauges, on the ground, will record
the amount of rain reaching the
ground.
8. Several experimental devices
for measuring raindrop sizes are
being installed. This is to check
claims Of commercial rain makers
that they produce gentler rain.
consisting Of smaller drops. Such
rain would not damage crops and
cause erosion as do hard rains Of
big drops.
1. Radar equipment will be used
to detect rain areas and cloud
formations and to guide the seed
ing planes to clouds selected for
seeding.