Artificial Rain

What is Artificial Rain? 

  • Clouds carry water, but sometimes water doesn’t reach where it’s needed on the ground. 

  • It happens because the water molecules are not dense enough to feel Earth’s gravity. When the molecules huddle together, they form larger, heavier droplets. Eventually, they become heavy enough to fall to the ground as precipitation.

  • The process of modifying the structure of clouds to increase the chance of rain is called cloud seeding. This rain is called artificial rain.

Cloud Seeding 

  • It involves modifying a cloud’s structure to increase the chance of precipitation. Cloud seeding adds small, ice-like particles to clouds. Usually, silver iodide particles are used.

    • The foreign particles which are drenched over these clouds can be Dry Ice(solid carbon dioxide), Silver Iodide, Salt powder etc.

  • These particles act as additional condensation nuclei. Unattached supercooled water vapour molecules in the clouds condense around these particles. Then, the condensed water vapour droplets group together. This process continues until the droplets are large enough to fall as rain.

  • There are two ways of adding particles to clouds: 

    • Using large cannons that shoot particles into the sky.

    • Using airplanes that drop the particles from above.

  • History: Cloud seeding first began in the mid 1940s when Dr. Vincent J. Schaefer was studying cloud formation for General Electric.


Stages of Cloud Seeding

  • Agitation : The first stage includes the use of chemicals to stimulate the air mass upwind of the target area to rise and form clouds. These chemicals absorb the water vapour and help in the process of condensation. Chemicals like - Calcium Oxide, compound of Urea and Ammonium Nitrate or Chloride Calcium Carbonate.

  • Building Up Stage : In the second stage the mass of the cloud is build up by urea, dry ice, kitchen salt etc to increase the density of the clouds.

  • Seeding : In the final stage of persuing the artificial rain, super cool chemicals (dry ice or iodide) are bombarded with the pressurized canister onto the base of the clouds to build the beads of water and make them fall as rain.


Types of Clouds Required

  • The clouds required for cloud seeding are of a typical type. They are called convective clouds, and they grow vertically. Only these can be seeded, not the other type, which are called stratified and grow horizontally. 

  • They work to endorse rainfall by inducing nucleation – whatever water is in the air condenses around the newly familiarised particles and crystallises to form ice


Negative effect of Artificial Rain

  • Risks or concerns like unwanted ecological changes, ozone depletion, continued ocean acidification, erratic changes in rainfall patterns, rapid warming if seeding were to be stopped abruptly, airplane effects, to name a few, may just not be bad enough to override the imperative to keep temperatures down.


Where all has it been tried earlier?

  • Cloud seeding is not new to India and it has earlier been attempted in Karnataka, Andhra Pradesh and Maharashtra to address drought.

    • Similar experiments of cloud seeding had earlier been tried in Australia, America, Spain and France. 

  • In United Arab Emirates, the cloud seeding technique led to the creation of 52 storms in Abu Dhabi.

  • Till last year, IMD had around 30 successful incidents of seeding. Also, such seeding is routine in Russia and other cold countries where the technique is used to disperse fog at the airports.


Artificial Rain and Pollution

  • Although artificial rain is tried and tested and is expected to help with the problem of air pollution, several environmental experts have raised concerns when it comes to the viability of the method in a long run.

  • Cloud-seeding might give relief from air pollution for a short span of time by washing down the pollutants from the air but for how long? In 2 or 3 days, the toxic smog will be back and then what?

  • It is nowhere near to a solution to pollution we need to trap pollutants at source and come up with a sustainable solution to curb air pollution.

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