The power of humans to control the weather is growing, but the weather control can never be total, according to a Chinese meteorological expert.

The power of humans to control the weather is growing. Cloud seeding to create artificial rain has become an almost routine procedure. Chinese weather scientists have also produced artificial snow, prevented hail showers, and dispersed rain and fog.

Airplanes, antiaircraft guns, rockets and ground-based silver iodide generators can all be used to prevent, or reduce the impact of, extreme weather events. This helps guarantee food safety, conserve water resources, promote ecological protection, extinguish or prevent forest fires, as well as guaranteeing good weather for important social events.

Earlier this year, southwest China experienced a severe drought. From late February through to the end of April airplanes flew more than 100 cloud seeding missions. Finally on the afternoon of March 27, 10 counties in Yunnan Province saw their first significant rainfall in three months.

However, according to Wang Guanghe, a researcher with the China Meteorological Administration, the weather control can never be total. There are definite limits and its roles can never be exaggerated, he warned. Take artificial rain for example; clouds suitable for seeding must be more than 2 kilometers thick and contain cold, but not freezing, water. There also have to be upward-flowing currents inside the cloud so that the antiaircraft gun, rocket or airplane can fire the catalyst into the right section of the cloud.

He also noted that the catalysts used to seed clouds do not pollute the environment. Dry ice and liquid nitrogen vaporize into carbon dioxide and nitrogen, and become natural components of the atmosphere. The silver in silver iodide is admittedly a heavy metal but it is used in very small quantities, he explained.