Firm footing for cloud seeding

Abstract

The pilots at Weather Modification Inc. were standing by on alert on Aug. 12, 2012, when they got word from their staff meteorologist to jump in their planes and head toward a budding thunderstorm just west of Calgary, Alberta. Their mission: to prevent the formation of crop-destroying, car-denting hail by shooting flares loaded with silver iodide into cumulus clouds. Some of the pilots headed for the smooth, rain-free base of the clouds at 2,000 meters, where updrafts could pull the inorganic compound in. Other pilots flew to 5,500 meters, penetrating the tops of the billowy formations. Once in position, the aviators ejected the flares mounted on their planes. Theoretically, the silver iodide particles that spewed forth would catalyze supercooled water droplets in the clouds to freeze at a warmer temperature and more abundantly than they might have otherwise. The pilots hoped that this maneuver would redistribute the water vapor in