What Is Cloud Seeding ?
What Is Cloud Seeding?
- Seeding involves spraying chemicals into clouds. Cloud seeding is a form of weather modification.
- It is a way of changing the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud.
- The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports.
How Does It Work?
- The most common chemicals used for cloud seedings include silver iodide, potassium iodide and dry ice (solid carbon dioxide).
- Liquid propane, which expands into a gas, has also been used. This can produce ice crystals at higher temperatures than silver iodide.
- After promising research, the use of hygroscopic materials such as table salt, is becoming more popular.
- Introduction of a substance such as silver iodide, which has a crystalline structure similar to that of ice, induces freezing nucleation (molecules gathering in clusters).
- In mid-latitude clouds, the usual seeding strategy has been based on the fact that the equilibrium vapour pressure is lower over ice than over water.
- The formation of ice particles in super-cooled clouds allows those particles to grow at the expense of liquid droplets.
- If sufficient growth takes place, the particles become heavy enough to fall as precipitation from clouds that otherwise would produce no precipitation. This process is known as ‘static’ seeding.
Beginning of Cloud Seeding
- China used this technique during the 2008 Olympics to veer rain away from the inaugural venue and now it has a full-fledged department that blasts rockets into clouds to induce rain and control pollution.
Cloud Seeding in India
- The Government of Maharashtra has decided to respond to frequent droughts in Vidarbha with a three-year cloud seeding experiment.
Cloud Seeding Experiment
- During monsoon 2017, weather scientists sprayed silver iodine over clouds. Airplanes were used to spray the chemical.
- However, the cloud seeding experiment failed to increase rainfall. Government has decided to continue with the experiment to get insights into cloud seeding technique.
- The programme coordinated by the Indian Institute of Tropical Meteorology, was the first controlled experiment to quantify the extent to which clouds form water drops large enough to make rain