WHAT IS THE ENVIRONMENTAL IMPACT? ALBERTA’S TOP 10 COSTLIEST HAIL STORMS Location Date Estimated Damage Calgary September 1991 Calgary August 2012 500 Calgary July 2010 400 Edmonton July 1987 317 Calgary July 1996 139 Calgary July 1996 119 Calgary July 1995 102 Calgary July 1998 86 Red Deer July 1991 59 Calgary July 1992 55 In millions of dollars, and normalized to 2011 dollars 1,281 Source: Public Safety Canada - Canadian Disaster Database (http://cdd.publicsafety.gc.ca/) Radar Station WHICH AREAS ARE PROTECTED? Thunderstorms are seeded as they develop along the foothills from the west of High River, all the way to Rocky Mountain House, AB. The seeding aircraft follow the bigger storms as they move off the foothills and threaten communities. Priority is assigned to storms depending on their severity and the size of the community. Only those storms threatening populated areas are seeded. Seeding thunderstorms does not present any environmental or health hazards because silver iodide is a non-toxic chemical at the concentrations used in cloud seeding. Silver is actually already present in Canadian soil and many of our foods; it is also naturally found in our water supplies. In fact, the amount of silver iodide used for cloud seeding is minimal compared to the large quantities of water that storms produce. Average seeding rates are about 10 grams per minute, which would be equivalent to putting a spoonful of silver iodide over the Niagara Falls every minute. Rain samples collected from seeded Alberta storms have been found to contain levels of silver similar to most surface and tap water supplies, and much less than what would be present in a cup of water stirred with a silver teaspoon. FOR FURTHER INFORMATION CONTACT: Dr. Terry Krauss Project Director [email protected] Todd Klapak President [email protected] Alberta Severe Weather Management Society c/o 128 Chancery Point Sherwood Park, Alberta T8H 1Z4 Severe Storm Rolling In ALBERTA SEVERE WEATHER MANAGEMENT SOCIETY HAIL SUPPRESSION 2 1 Aircraft seed clouds with silver iodide particles 3 Silver iodide particles cause cloud moisture to freeze and create ice crystals Ice crystals grow and fall as rain/snow ALBERTA HAIL STORMS: THE BREAKDOWN In the months of June, July and August, thunderstorms occur on 55-75% of days. • Of these days, hail falls 50% of the time • 15% of the time that it hails, hailstones will be greater than the size of a walnut • Rainfall has been observed to increase minimally due to cloud seeding DID YOU KNOW? Over 40 major hail storms rumble through Alberta every summer. Over the past decade, these hail storms have caused over $1 billion in damage. WHO ARE WE? HOW DOES IT WORK? HOW IS IT CONDUCTED? WHO BENEFITS? The Alberta Severe Weather Management Society (ASWMS) is a private, non-profit organization that was established by the Property and Casualty insurance companies of Alberta to administer the cloud seeding program. The actual cloud seeding operations are outsourced and performed under contract by Weather Modification Inc. (WMI), a private atmospheric and cloud seeding company based in Fargo, North Dakota. Hail suppression works by seeding thunderstorms with billions of microscopic silver iodide particles. These particles act as artificial ice nuclei which freeze the supercooled water drops in the storm’s updraft. Cloud seeding is conducted with five twinengine, high performance aircraft equipped to dispense silver iodide. Three seeding aircraft are stationed at Springbank Airport and two are stationed at Red Deer Airport. Every year from June 1st through to September 15th, these aircraft remain on stand-by for immediate launch to seed storms. Cloud seeding has been found to reduce the size/frequency of hailstones, which in turn reduces damage to people’s gardens, crops, homes, cars and businesses. IS HAIL ELIMINATED? For these reasons, a hail suppression program makes good economic sense for everyone. WHAT IS CLOUD SEEDING? Cloud seeding is a form of intentional weather modification that involves the process of dispersing a particular substance (we use silver iodide) into developing clouds. The intention is to alter the cloud’s micro-physical properties which results in a change of the type of precipitation that will fall. Seeding results in the formation of billions of additional ice crystals that compete for excess cloud water, thus producing smaller ice particles. Many of these ice crystals melt completely as they fall through warmer subcloud air on their way down, but even those that don’t are still significantly smaller than the “bruisers” that smash windows, dent cars, and wreck roofs and siding. Cloud seeding also helps to control insurance company losses, which in turn helps to stabilize insurance rates throughout the province. No, cloud seeding does not eliminate hail, but it does reduce the size of hailstones which results in less damage. Cloud Seeding Aircraft
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