The Art of Cloud Seeding

Cloud Seeding (also known as weather modification) is a strategy used to increase and/or change the type of precipitation in certain geographical areas, with goals to increase water supplies, decrease fog and hail, and augment snowfall. However, success stories using cloud seeding are somewhat limited which has caused much debate over the effectiveness of the idea.

Within one month of each other in the summer of 1946, Vincent Schaefer and Bernard Vonnegut discovered the first two methods for cloud seeding. Schaefer discovered a method using dry ice, which in general changes the amount of heat in the cloud and allows snow to fall at higher temperatures. While Vonnegut found the more popular technique using silver iodide, which alters the structure of crystals in the clouds, changing cloud vapor or hail into water or snow. Other methods using liquid propane and mixtures of salt compounds have also been used, and continue to be used depending on the type of cloud being seeded and the desired outcome.

The North American Weather Modification Council helps control cloud seeding programs throughout the Western United States and Canada. One such program encompasses a large region of the Sierra Nevada mountain range – stretching from north of Lake Tahoe all the way south past Mount Whitney – and seen great success over the past few years. Last year in particular (2010/2011 winter season) the Sierra Nevada’s saw the largest snowfall in over a decade, with levels more than 160% above normal.

Could these methods slow the effects of climate change? Probably not since cloud seeding can only be done of preexisting clouds which already have potential to produce precipitation. In other words, cloud seeding most likely would not help a region come out of drought since there are so few water-producing clouds in such a situation to begin with. Additionally, there is very little or no research to prove that cloud seeding can actually change weather patterns in the long run. Therefore, it could be a great short term solution to increase snowfall for ski resorts or decrease fog and hail for airports, but it is very unlikely to change weather patterns as a whole.

On the topic of using cloud seeding to increase albedo, the current technologies would again make a very insignificant impact. As discussed above, the current methods in use are simply meant to change temperatures and crystalline structures rather than actually increase the size and breadth of clouds. However, in a time when water supply is shrinking rapidly, cloud seeding could become vital (if it is not so already) to the sustainability of our current lifestyles.