Cloud Seeding

Cloud seeding:

  • Cloud seeding is a form of weather modification
  • It is a way of changing the amount or type of precipitation that falls from clouds
  • How? by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud
  • Why? The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports
  • Chemicals used: In cloud seeding, either dry ice, or more commonly, silver iodide aerosols are sprayed into the upper part of clouds to try to stimulate the precipitation process and form rain
  • Cloud seeding also occurs due to ice nucleators in nature, most of which are bacterial in origin
  • Mechanism: Since most rainfall starts through the growth of ice crystals from super-cooled cloud droplets (droplets colder than the freezing point, 32 deg. F or 0 deg. C) in the upper parts of clouds, the silver iodide particles are meant to encourage the growth of new ice particles
  • The history of cloud seeding has experienced uncertain results because it can never be known whether a cloud that rains after seeding might have rained anyway
  • This is because seeding is performed on clouds that look like they have some potential for producing rain

 

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Why in News?
The state government of Karnataka has recently launched ‘Project Varshadhari’, an ambitious cloud seeding project but denial of clearance from Air Traffic Controller makes it difficult for aircraft to chase ‘seedable’ clouds.
 
Uses of Cloud seeding
  • In agriculture, crop loss can be prevented.
  • In water management, floods and droughts can be managed (Indonesia is known to use it to prevent risk of floods).
 
Cloud seeding in India
  • In India, Tamil Nadu became the first state in the country to attempt cloud- seeding as early as 1983-1984.
  • Karnataka and Maharashtra followed in 2003 and 2008 respectively when drought situations prevailed.
  • As Indian socio-economic setup is vitally linked with Monsoon (which is highly erratic leading to agrarian and economic crises), many states are experimenting in cloud seeding projects.