306 THE FUTURE OF ARID LANDS 
A day and night study of air movements in the Rio Grande 
Valley of New Mexico during the month of July showed that 
mountain, valley, and drainage winds fit into a recurring diurnal 
pattern. These air motions may be studied by watching smoke 
plumes, smog patterns, zero lift balloons, and ordinary pilot 
balloons. 
The early morning situation is dominated by a drainage wind 
flowing down the river valley from the north. This continues until 
the mountain slopes become sufficiently heated to start convective 
movements, at which time the wind swings to a westerly and then 
a southwesterly direction. This wind then stops blowing in the 
evening. It is then followed by an easterly mountain wind which 
carries the cold air produced by radiative cooling down into the 
valley. These air movements are of sufficient magnitude to impress 
their pattern on a microbarograph. These traces are the most con- 
vincing evidence of the recurrent diurnal fluctuations in air flow of 
the area. 
On July 21, 1949, B. Vonnegut of the Project Cirrus group 
started a silver iodide smoke generator at 0530 and at the same 
time began releasing a series of zero lift balloons at the research 
station south east of Albuquerque. The air flow followed the de- 
scribed pattern. At about 0830, an isolated orographic cumulus 
cloud started forming about 25 miles south of the station. Visual 
and photographic observations of this cloud showed that its top 
grew at the average rate of 160 feet per minute between 0830 and 
0957. At 0957, the summit of the cloud was at 26,000 feet and its 
temperature about —23°C. At that time the top of the cloud 
started growing at the rate of 1,200 feet per minute. This rapid 
rate of growth continued for fifteen minutes. At 1012 it had 
reached an altitude of 44,000 feet, with a calculated temperature 
of —65°C. At this altitude, the rate of growth slowed down 
considerably. 
The first radar echo was observed at 1006 at 20,500 feet, where 
the temperature was —9°C. This echo occurred at 25 miles and 
an azimuth of 165°C. With the generator located at 5,600 feet 
msl, the smoke plume from the silver iodide generator moved 
toward the Manzano Mountains in such a manner that it was 
