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Despite past failures, weather modification endures

People used to believe that sonic waves would stop hail from forming, although studies have not proven its effectiveness. The cannons shown were supposedly fired to stop hail from forming.

For centuries there have been attempts to manipulate the weather, from ancient rituals designed to bring rain, to modern day cloud seeding. But where some past attempts were pseudo-scientific at best, weather modification continues to gain ground in an effort to solve some of the world's most devastating weather-related problems.

Weather modification includes attempts to create more rain, prevent rain, reduce hail, prevent fog, make snow, or reduce the severity of a hurricane. Although often used to create more precipitation in drought-prone regions, in some cases, weather modification has been a matter of convenience more than necessity. The Chinese government credited weather modification for assuring good weather for the 2008 Olympics. Rockets were used to induce rain by cloud seeding other areas in an attempt to keep the rain away from Beijing, specifically during the opening and closing ceremonies. In fact, the Beijing Meteorological Bureau has a Beijing Weather Modification Office dedicated to controlling the weather in the city and surrounding areas.

Cloud seeding was discovered by accident in July 1946 by scientist Vincent Schaefer, who was conducting a laboratory experiment at General Electric Research labs in New York. He was trying to produce a cloud in a chest freezer but it wasn't cold enough, so he put slabs of dry ice (solid carbon dioxide) in the freezer to cool it. To his surprise he found that when he breathed into the air, it created snow crystals.

Only a month later, his colleague, Bernard Vonnegut (older brother of writer Kurt Vonnegut) discovered another method for seeding using silver iodide crystals.

In November of that year, dry ice pellets were dropped by plane into a supercooled cloud (one that contains water in liquid form colder than the freezing point) over Massachusetts. Reportedly, it snowed only out of that portion of the cloud.

Today, silver iodide and dry ice are the most common chemicals used for seeding. The chemical is introduced into the cloud which induces the formation of ice crystals by providing the nuclei for water to condense. Liquid propane is sometimes also used, which turns into a gas at cold temperatures, freezing the surrounding air so that crystals form spontaneously out of the vapor.

Weather modification has been used in warfare. Between 1949 and 1952, Operation Cumulus was an attempt by the British government to learn to control the weather via cloud seeding, primarily for future military advantage. However, on August 16, 1952, a severe flood in the town of Lynmouth occurred after nine inches of rain fell in 24 hours. Infrastructure was damaged and 34 lives were lost. Although no evidence was found that Project Cumulus was to blame, the project was abandoned after the event.

From March 1967 to July 1972, Operation Popeye involved cloud seeding by the U.S. military in an attempt to extend the monsoon season over North Vietnam and Laos, specifically over the Ho Chi Minh Trail, which was used to funnel North Vietnamese soldiers and supplies to South Vietnam. The targeted areas reportedly saw a longer monsoon season by 30 to 45 days.

But all weather modification for warfare purposes was ordered to cease. In 1977, the United Nations banned all military or hostile use of environmental modification techniques.

Even before cloud seeding, hail cannons had been used since the early 20th century to prevent the formation of hail in approaching storms. It was thought that the shock waves disturbed the process, though any scientific evidence of such a cause and effect appears to be lacking.

As with hail prevention, attempts to prevent or weaken hurricanes has not met with great success. In 1947, a U.S. tropical hurricane that was moving west to east was seeded in an attempt to modify it. The hurricane then turned west and made landfall at Savannah, Georgia. This was blamed on the experiment, and the seeding of hurricanes was abandoned for over a decade.  

Between 1962 and 1971, Project Stormfury was undertaken by the U.S. to seed a hurricane's eyewall with silver iodide to weaken the storm. After what appeared to be some initial success with a noted drop in wind speed after seeding, it was determined that the results were inconclusive and such projects were again abandoned.  

In terms of current and future weather modification, several western states regularly practice cloud seeding to produce additional rain or snow. And in January 2011, it was reported that scientists in Abu Dhabi created over 50 artificial rainstorms between July and August of 2010 near Al Ain, which borders Oman. They used large ionizers to create fields of negatively charged particles which created clouds and rain — out of what had otherwise been a clear blue sky. Lightning, hail, and wind gusts even accompanied some of these storms. 

If drought conditions persist in the U.S. and other areas of the world, cloud seeding may be further utilized to produce additional rain in drought-stricken regions. This process relies, however, on there being clouds and humidity already present. If the results of the Abu Dhabi ionization project are valid, and rain can be created where it otherwise would not be, then such a process would be instrumental in bringing rain to arid regions thirsting for water. With an increasing need for water in the face of dwindling resources, such efforts may be seen as a future necessity.

Representative Image Caption
People used to believe that sonic waves would stop hail from forming, although studies have not proven its effectiveness. The cannons shown were supposedly fired to stop hail from forming.
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Susan Borowski

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