LA Officials to Force Rain with Cloud Seeding
Cloud seeding is the process of spreading either dry ice (or more commonly, silver iodide aerosols) into the upper part of clouds to try to stimulate the precipitation process and form rain. Since most rainfall starts through the growth of ice crystals from super-cooled cloud droplets (droplets colder than the freezing point, 32 deg. F) in the upper parts of clouds, the silver iodide particles are meant to encourage the growth of new ice particles. The history of cloud seeding has seen uncertain results because even if a cloud rains after seeding, it is not known whether the cloud would have rained anyway. [Roy Spencer, Weather Questions]
"It's a bit of a sign of desperation," Peter Gleick at the nonprofit Pacific Institute said to the LA Times. "They've been doing cloud seeding for decades, but we've never clearly been able to show if it's what we've done or what nature has provided." Gleick thinks the money would be better spent on promoting water conservation to the public. There are also worries it could trigger mud slides, one reason the cloud seeding program was stopped years ago.
Photo by Oracio Alvarado via Flickr