NOAA hurricane mitigation cloud seeding experiments over Carribbean and Florida.
The Departement of Commerce's National Oceanic and Amtospheric Administration (NOAA) supports precipitation modification research on summer cumulus clouds and winter storm clouds under its National Cumulus Modification Project and its Great Lakes Snow Redistribution Project, respectively. In contrast with Interior's Project Skywater, which involves orographic clouds, these projects concern tropical cumulus clouds and winter stratus clouds, which are produced by interactions of water and air over lakes.
The National Cumulus Modification Project is aimed at increasing rainfall from tropical cumulus clouds. Experimental seedings of such clouds with silver iodide were conducted initially over the Carribbean Sea in 1963 and 1965. Since 1968 such experiments have been conducted over Florida. Seeding under the project is done with silver iodide flares which are dropped directly into suitable clouds from airplanes. Project costs for fiscal years 1968 trhough 1972 are estimated to total about $2.1 million.
The results of these experiments, according to NOAA, indicate that seeded clouds, ont he average, yield more than three times as much rain as unseeded clouds. NOAA has estimated that seeding individual clouds yields 100 to 250 acre-feet of additional water for each cloud and htatseeding two single clouds which merge can yield approximately 20 times as much water as two singly seeded clouds which do not merge. However, it hasnot been determined whether the seeding techniques developedfor tropical cumulus clouds in Florida would be applicable in other parts of the country. 
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