Cumulus Studies -45- 



The carrying out of successful ground-air operations on three dif- 

 ferent occasions, using lapse-time photographs as part of the ground 

 coverage, demonstrated conclusively to the members of the project the 

 value of carrying out such studies of clouds which develop in definite 

 cloud -breeding regions. Similar areas in the United States known to 

 possess such developments were Albuquerque, New Mexico, and Priest 

 River, Idaho. Schaefer had already visited Priest River, and arrange- 

 ments had been made for investigations and experiments there. And 

 a test mission had been conducted at Albuquerque the previous year, 

 details of which will be found in the next section of this report. (See 

 last paragraph on this page.) 



Despite the fact that no suitable clouds were found for testing out 

 water -seeding techniques during the period, many valuable results were 

 obtained which it was expected would lead to a much better understanding 

 of the formation of rain in tropical clouds. 



One of the very important results of the expedition was the obser- 

 vation of the important effect of salt nuclei on the formation of precipi- 

 tation in thin tropical clouds. Said one of the reports: "This seems, 

 on first sight, to be of great importance in explaining the rain showers 

 which are of daily occurrence and random distribution in the vicinity of 

 Puerto Rico. Rarely is rain observed from such clouds in the eastern 

 United States." Said Langmuir: 



"Observations in Puerto Rico in 1949 and in the Hawaiian 

 Islands in 1951 have shown that the rainfall depends on rela- 

 tively large particles of sea salt in the air, in accord with the 

 publications of A. H. Woodcock and Mary Gifford. Calcula- 

 tions of the rate of growth of salt particles indicate that it 

 should frequently be possible to induce heavy rainfall by 

 introducing salt into the trade wind at the rate of about one 

 tone per hour in the form of fine dust particles of about 25 

 microns in diameter. The heat generated by the condensation 

 may liberate so much heat as to produce profound changes 

 in the air flow and the synoptic conditions in neighboring 

 areas. "(24) 



EARLY WORK IN NEW MEXICO 



Although interest in cumulus clouds and thunderstorms was high 

 among the members of the Research Group in 1948, the cumulus season 

 passed in the vicinity of Schenectady without any significant flights 

 having been carried out. It was realized that the best results could be 

 obtained from the seeding of cumulus clouds in a region where storms 



