TAHOE/TRUCKEE — Remember this past winter when instead of enjoying winter sports, people were riding bicycles and hiking well into the 2012 ski season? How different it would have been for the regional economy if we could have managed to temporarily change the stubborn dry weather pattern from calm to stormy.
Mankind's quixotic quest to influence weather is as old as civilization itself, but scientists today can be successful in coaxing enhanced precipitation from clouds when atmospheric conditions are favorable. Ground-based and aerial cloud seeding over the Sierra can increase precipitation from any given storm by up to 15 percent. That is not a trivial amount. During the El Nino-influenced winter of 1998, seed-dispensing aircraft and five ground-based generators were able to produce almost 15,000 acre feet of water in the Tahoe area before seeding was suspended in February — enough to supply 15,000 suburban households with a year's worth of water.
Private entrepreneurs, public utilities and government agencies have been seeding Sierra skies with dry ice, silver iodide, and other particulates since the 1950s and in the Lake Tahoe region since the 1960s. For seeding to be successful, clouds must contain supercooled water — water that has remained liquid at below-freezing temperatures. Introducing nuclei into the supercooled water accelerates the production of ice crystals that fall as snow or melt into rain drops. Increasing precipitation with cloud seeding is based on sound science and in the arid west is a far cheaper method of increasing water supplies than buying water on the open market.
One of the first Sierra cloud seeders was Bob Symons, based in Bishop, Calif. In 1946, a General Electric research scientist discovered how dry ice initiated precipitation in lab experiments. During a winter dry spell in 1948, executives at California Electric and Power Company were concerned about the lack of snowpack in the southern Sierra and the utility's hydroelectric energy commitments. Since no one had done cloud seeding in the region before, a Cal-Electric engineer secretly contacted Symons to see if he would be willing to try some “hush hush” weather modification. Ironically, several months before Symons had shaved a load of dry ice himself and tossed it from his plane. It snowed!
For two more years, Cal-Electric and Bob Symons worked in tight secrecy on the project. People in Bishop knew something was going on because virtually every time Symons flew his plane, it seemed to rain or snow. However, the whole town kept the experiment secret for two years, including the publisher of Bishop's newspaper, until March 1950 when the project was revealed as a well-documented success.
In addition to enhancing precipitation, modern-day weather modification efforts include using seeding to mitigate hailstorm formation, dissipating ground fog near airports, and, more controversially, weakening hurricanes by dosing cloud-tops to alter circulation. Historically, “rainmakers” have also included those who claimed they could protect farmers from destructive hailstorms. In the U.S. alone, crop losses from hailstorms average a half billion dollars annually, but it's a worldwide problem.
Using artillery to disrupt hailstorm formation has been around since 1890. Their use in the United States reached its heyday in the early 20th century when meteorologists debunked it, but in recent years several companies have reintroduced “anti-hail cannons” back into the market. The new cannons automatically load and reload, and can be remotely controlled and fired. Each gun costs about $60,000, and that doesn't include the recommended radar component. Most scientists are skeptical of their efficacy, but there are 20 cannon sites in California alone, and there is one in Mississippi where a Japanese automobile manufacturer has installed the cannons to protect new cars at their plant.
— Tahoe historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at www.thestormking.com. You can reach him at email@example.com.