Cloud seeding is the attempt to modify weather by changing the amount or type of precipitation that falls from clouds. This is done, by dispersing substances into the air that serve as cloud condensation or ice nuclei. These substances alter the microphysical processes within the cloud. The intent is to increase rain or snow, and to suppress hail and fog at the airports.
It was the American chemist Vincent Schaefer (1906–1993) who discovered the principle of cloud seeding in July 1946 through a series of fortunate events. Based on his experiments and those of others, the united states military in 1960s started a project to modify hurricanes in the Atlantic basic by using cloud seeding, this project was codenamed ‘Stormfury’.
Using an aircraft or dispersion devices located on the ground (generators, firing canisters from anti-aircraft guns or even rockets) the chemicals are dispersed in the atmosphere. If an aircraft is being used, the silver iodide flares are ignited and dispersed as the plane flies through the cloud. If ground based devices are used, then chemicals are simply fired at the cloud.
Common chemicals used for cloud seeding include silver iodide and dry ice (solid carbon dioxide), Liquid propane (which expands into a gas). The use of table salt is becoming more popular.
The impact of cloud seeding on the environment has been proved to be minimal. Several detailed ecological studies that showed negligible environmental and health impact because the toxicity of silver and silver iodide is of low order.
Cloud Seeding in India
In India, cloud seeding operations were conducted during the years 1983, 1984–87,1993-94 by Tamil Nadu Govt. due to severe drought. In 2003 and 2004 Karnataka government initiated cloud seeding. Cloud seeding operations were also conducted in the same year through U.S. based Weather Modification Inc. in the state of Maharashtra. In 2008, there are plans for 12 districts of state of Andhra Pradesh.
Importance and Comment
India and the rest of Asia are dependent on the monsoons for rains therefore cloud seeding makes sense to the people here. Experiments conducted by the Indian Institute of Tropical Meteorology in Pune reported to show an indication of 24 per cent enhancement in precipitation in targeted areas.
Earlier considered a fringe science, Cloud seeding is now a mainstream tool to improve rain and snow. It has produced reliable results that make it a dependable and affordable water-supply practice for many regions lacking in water.
During the 2008 Summer Olympics in Beijing, clouds were seeded using rockets, so that there would be no rain during the opening and closing ceremonies, although others dispute their claims of success.
Although it has been the focus of many theories based on the belief that governments manipulate the weather in order to control everything from global warming, populations, and military weapons testing, to public health, cloud seeding has come of age and is going to be a major tool in environmental adjustment policy and practices. Further development of this technique and its adoption may help India in water management and fulfill needs left by the monsoon-dependence of our irrigation systems.