Besides the intense cold, the winters also bring a cloud of smog over the Delhi-NCR region, with slower winds and cooler temperatures doing the job of trapping pollutants closer to the ground. Considering the dire air quality prevalent in the Delhi-NCR region during the winters, authorities are almost willing to try anything and by any means necessary to mitigate its effects on public health.To this end, the Ministry of Environment, Forest and Climate Change has approved an IIT-Kanpur-developed project that could induce artificial rain through a process called cloud seeding.

So, what is cloud seeding?

• It is a method of weather modification with the stated objective of changing the amount or type of precipitation that falls from the clouds. This is done via dispersing chemicals into the air like silver iodide or dry ice into the upper part of clouds to stimulate the precipitation process and form rain.
• “They work to promote rainfall by inducing nucleation—what little water is in the air condenses around the newly introduced particles and crystallises to form ice,” says this explainer. This rain is expected to settle the volume of atmospheric dust by just enough to clear the sky.

How will authorities execute this exercise in the Delhi-NCR region?

• As per media reports, it will be done through an aircraft which will transport and disperse the necessary silver iodide, taking off from one of three airports in the region—the Safdarjung airport, the Indira Gandhi International Airport and the Hindon airport.
• This is not the first time Indian authorities have tried cloud seeding. First developed by General Electric’s Vincent Schaefer in 1946, it was only six years later that climatologist DR SK Banerji first tried this technique over Kolkata during the monsoon season.
• “The technique consisted of dispersing seeding agents like salt and silver iodide by means of hydrogen-filled balloons released from the ground,” says this report from the Indian Institute of Tropical Meteorology.
• Over 60 years, Indian authorities have used cloud seeding for primarily drought mitigation and raising water levels in dams across Karnataka, Andhra Pradesh and Maharashtra.
• However, this initiative has met mixed results. China has already tried cloud seeding and claims that it works well. Scientist in India are not content with the Chinese plan because they aren’t sure whether it is effective at times of extreme pollution. Moreover, the cloud seeding process will only be successful when there are enough clouds in the sky.
• 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.
• Air pollution is due to concentration or accumulation of particles in the lower troposphere. The accumulation is due to stable atmospheric conditions. In such conditions, the formation of vertical, convective clouds is not possible. Even if clouds are formed, they are of the horizontal, stratified type on which seeding will not have any effect.