Category : UPSC / STATE PCS

CLOUD SEEDING

Recently Delhi Government tried to use cloud seeding technique to bring down the pollution levels.

What is cloud Seeding and why it is also called Artificial Rain?

Cloud Seeding is a weather modification technique which involves spraying of a salt mixture into the clouds (with the help of aircraft). This induces ice or water vapour within the clouds to form water droplets. When lots of such water droplets come together they pour down as rain . Hence it is also called Artificial Rain.

History of Cloud Seeding –

General Electric scientists William Schaefer and Bernard Vonnegut in 1940’s were the first to successfully make snow over Pittsfield in Massachusetts USA, using clod seeding.

China used cloud seeding for clear skies fir inaugural ceremony of 2008 Olympics.

India’s first cloud seeding experiment was done in drought prone area of Solapur, Maharashtra. Once the clouds were identified flares of calcium chloride (Silver Iodide was not used) was fired on some clouds and others were left unseeded, using air craft.

In terms of rainfall measured on the ground – seed cloud gave an average of 46% more rain in seeded locations as compared to unseeded ones.

Over 100 square kilometre area down there was an increase of 18% more rain in seeded versus unseeded.

Chemicals used for cloud seeding –

1. Silver Iodide (AgI)
2. Sodium Iodide (NaI)
3. Potassium Iodide (KI)

These chemicals act as seed particles or Condensation Nuclei around which water vapour condenses to form raindrops.

The seeding mix used contains both materials i.e. Nanoparticle AgI is primarily Glaciogenic seeding materials where as micro sized rock/sea salt is Hygroscopic material.

Requirements –

Sufficient moisture must be present in the clouds else this technique will not be able to generate artificial rain.

Cloud seeding cannot create rain clouds , it only help in adding more water to the clouds with minimum quantity of water vapour called ‘warm clouds’ and hence it can only enhance rainfall.