Some Relationships of Experimental 
Meteorology to Arid Land 
Water Sources 
VINCENT J. SCHAEFER 
The Munitalp Foundation, Inc., 
Schenectady, New York 
Since the fall and early winter of 1946, when our first cloud 
seeding experiments were brought to a successful conclusion, 
many things have happened to clarify as well as confuse the pic- 
ture of the present state of experimental meteorology. With about 
eight and a half years of experience behind us, what conclusion 
can be drawn in relation to successes or failures? 
As in any other new science, advance has been rapid as well as 
slow. Startling new discoveries have occasionally emerged from 
the less spectacular plodding advance as new facts in atmospheric 
physics have become established. 
Variation in Concentration of Ice Nuclei 
With the 1946 demonstrations that extensive cloud systems not 
only exist for considerable periods as supercooled clouds (1) but 
may also be profoundly and rapidly modified by relatively small 
amounts of dry ice fragments (23), the question arose as to how 
variable the concentration of ice nuclei was in the natural atmos- 
phere. To gather statistical data in this regard three hourly 
observations of the concentration of ice nuclei were inaugurated 
at the Mt. Washington Observatory. These studies have been 
continued from January 1, 1948 to date. The more than 18,000 
observations show that natural ice nuclei concentration may vary 
300 
