The Lower Arkansas Water Conservancy District heard a pitch for a potential cloud-seeding program at their last meeting

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From The Pueblo Chieftain (Chris Woodka):

Cloud-seeding, using silver iodide crystals fired from ground cannons, is already widely used in Colorado. Mainly using for increased snowpack in the mountains, the cannons are also used for hail suppression in some areas like the San Luis Valley. There are 111 generators in the state, said Joe Busto, who coordinates cloud-seeding for the Colorado Water Conservation Board. Programs have continued for decades and in the last six years, the state and cooperating agencies have spent $3.9 million for cloud-seeding programs…

Just over the state line, Kansas has been conducted summer cloud seeding to suppress hail and increase rainfall since 1975, said Walt Geiger, meteorologist for the Kansas program. He explained the Kansas program to the Lower Arkansas Valley Water Conservancy District last week, and suggested a similar approach could help Eastern Colorado…

Airplanes fly both into and below thunderstorms, using dry ice (frozen carbon dioxide) and silver iodide both to reduce the size of hail and increase rainfall. Updrafts allow silver iodide crystals to flow into the clouds from below. Dry ice is released into the clouds by planes flying near the edges of storms…

The theory behind cloud-seeding is that it increases precipitation by injecting trillions of nuclei into clouds. That encourages more rain or snow, and reduces the size of hail by creating more targets for loose droplets to cling to in the clouds. Large hailstones gain size as droplets attach to them as they move through clouds. Airplanes are are used on the plains because ground cannons are not effective in reaching the zone where hail forms — about 11,000-16,000 feet above ground, where there are freezing temperatures, even in summer. Above that zone, ice crystals don’t precipitate as easily.

More cloud-seeding coverage here and here.

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