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Name: Alicia
Status: other
Grade: other
Location: N/A
Country: N/A
Date: 6/21/2005


Question:
Can you tell me about the technology know as cloud seeding?


Replies:
Alicia,

Cloud seeding is accomplished by adding something to saturated air (particularly non-precipitating clouds) that will serve as effective condensation nuclei (producing rain droplets) and/or will decrease the cloud temperature to the point where it will produce precipitation.

Typically, particles such as ice crystals, dry ice (solid carbon dioxide), silver iodide, and salt (sodium chloride) are used as condensation nuclei.

The results of cloud seeding experiments are not encouraging, as huge amounts of condensation nuclei are required to produce very little precipitation. This is made even worse by the fact that when precipitation is really needed, the air is often quite dry and does not produce clouds of enough extent to make seeding practical.

David R. Cook
Atmospheric Physics and Chemistry Section
Environmental Research Division
Argonne National Laboratory


Dear Alicia-

Cloud seeding is an effort to produce or increase rainfall from clouds. Condensation nucleii are added to clouds either from aircraft or from the ground, to increase the number of raindrops that form in the clouds. The effectiveness of different methods is not clear, and weather modification in this manner has mixed results.

Here is a link that explains the different processes of raindrop formation and how cloud seeding can assist or enhance these processes.

http://www.atmos-inc.com/weamod.html

Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO


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