302 THE FUTURE OF ARID LANDS 
Since it is such cloud systems which produce the Kona Storms 
of Hawaii, the ‘‘blow down” storms of Central America, the hurri- 
canes of the Caribbean and Atlantic seaboard regions, and the 
major rain-producing storms of regions like the southwestern 
United States, it is of great importance to learn the techniques 
for “taking away”’ the effects of natural atmospheric nuclei and 
replacing them with controlled amounts of more dominant arti- 
ficially introduced nuclei. Until we learn how to do this effectively, 
any talk of weather control is unrealistic. 
Importance of Ice Nuclei in Regions Like New Mexico 
Starting in 1948 and continuing for three years, cloud-seeding 
studies were conducted in New Mexico by Project Cirrus. The 
flight studies were primarily of an exploratory nature and were 
not planned to attempt to produce economical amounts of rain. 
That some of the seeding flights were followed by substantial 
amounts of precipitation in the seeded regions was incidental to 
the primary objective, which was to establish the nature of the 
clouds and the effects that might be induced by using various 
amounts and varieties of seeding materials (16). 
For the New Mexico studies dry ice, silver iodide and water 
ice, water and gaseous ammonia were used. A total of twenty 
seeding experiments were conducted in 1948, 1949, and 1950 (27). 
Since these were experimental studies, the experiences resulting 
from each flight were used to modify each subsequent flight study. 
Based on the results obtained, the following general conclusions 
were established. 
1. Cumulus clouds in New Mexico commonly contain large 
amounts of supercooled cloud masses. 
2. The bases of such clouds under summer conditions vary 
between 12,000 and 14,000 feet msl. 
3. The freezing level commonly occurs at 16,000 feet. 
4. The most spectacular effects of seeding with dry ice or silver 
iodide occurred on days when the first clouds appeared over the 
cloud breeding spots not later than 1000-1100 o’clock. 
5. The most striking seeding effects by aircraft occurred in 
clouds which were growing vigorously and were seeded when their 
