WMOD00525

• Title: A Proposed Wintertime Weather Modification Research Program for Colorado
• Date: 1/1/1980
• Weather Modification - Doc Type: Report

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snow in one area decrease them l.n nearby areas."l Many in-
dividuals, both scientists and nonscientists, continue to
question these issues,
To the ordinary citizen it seems reasonable that as YOtl
remove additional moisture from the atmosphere in one area, the
precipitation downwind of the area will be decreased, It has
been estimated that approximately 20 billion tons of atmospheric
water vapor flows over the continental united States daily, borne
by the prevailing west-to-east winds, On the average, eight to
ten percent of that moisture is deposited as rain or snow on the
land areas, and that eight to ten percent frequently is unevenly
distributed. 8 The precipitation for any given area ranges widely
with years of surplus and years of deficit. Because of the
extremely high percentage of water that remains in the atmosphere
each day and the natural variability in precipitation, it is
highly speculative that a winter orographic cloud seeding operation
in the Colorado Rockies would have an observable effect dOWTlwind
of the seeded area,
In addition to the question of a possible decrease in
precipitation downwind of the seeded area, there are the fol,1owing
related questions: (1) Do seeding agents persist to the extent
that they affect precipitation amounts in other areas? (2) Does
an increase in overall precipitation in one area cause more
precipitation in an adjacent area because increased evaporation
may cause possible stimulation of the hydrologic cycle? These
questions demonstrate the need to make meteorological observations
not only wi thin the target area for cloud seeding activities but
also in adjacent and downwind areas,
In order to seed winter orographic clouds with beneficia1
results, the seeding opportunity must be forecast enough in
advance or conditions recognized rapidly enough during a storm
to allow for efficient treatment. Some uncertainties sti11
exist in the area of opportunity recognition. Vardiman and
Moore 6 reanalyzed the results of seven similar winter seeding
programs in an effort to identify and generalize the key para-
meters into seedabi1i ty criteria. In general, they found that

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