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,” explains JR Kulkarni, a retired scientist from the IITM, Pune, in a conversation with Down to Earth. On the question of whether it can affect air quality, he is rather sceptical.
“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,” he adds.
For the experiment in the Delhi-NCR region, the aircraft will be procured from the National Remote Sensing Agency, a body affiliated with ISRO.
“There is a western disturbance forming in Jammu & Kashmir…. that will not be enough as we need clouds in the plains. Such seeding is routine in Russia and other cold countries when they need to disperse fog at airports…In this case, we need to create clouds. It is a completely different challenge,” said IMD Director-General KJ Ramesh, to The Hindu.
The task of forecasting the weather conditions that will enable the formation of these clouds, will be undertaken by the Indian Meteorological Department.
“Cloud Seeding can only be done if the meteorological conditions for this are suitable, and if the moisture content in the local atmosphere meets the requisite criteria. Having spoken to weather experts, it has been pointed out that the NCR region is unlikely to have favourable conditions for cloud seeding in the immediate future. Further, artificial rainfall can only provide immediate symptomatic relief in terms of suppressing the pollutants present in the air,” says Polash Mukherjee, Senior Research Associate under the Clean Air and Sustainable Mobility Unit at the Centre for Science and Environment, speaking to The Better India.
“Ultimately, if the sources of the pollutants, i.e. vehicles, industry, construction etc. are allowed to emit unabated, artificial rains through cloud seeding will have only a limited and temporary impact. We must decide if we want to focus our efforts on controlling the structural causes of air pollution-medium- and long-term action on the sources, or on end of the pipe solutions such as cloud seeding and ambient air purifier,” adds Polash.
Despite conducting 30 successful instances of cloud seeding over the past four years in India, authorities will also likely struggle with clearing out skies beyond an area measuring a football field.
It’s evident that the IIT-Kanpur researchers have massive challenges ahead of them. Nonetheless, the fact that the centre has approved the project, only shows the gravity of the situation.
(Edited by Gayatri Mishra)