Explainer: What is artificial rain, will it help curb pollution in Delhi?

As Delhi braces for another smog-filled winter, the city is set to experiment with artificial rain — a technique that could bring temporary relief from hazardous pollution levels. On Thursday, the Delhi Government signed an MoU with the Indian Institute of Technology, Kanpur, to carry out cloud seeding trials as an emergency step to tackle worsening air pollution. The initial phase of the exercise is planned between October 7 and 11 in parts of North and North West Delhi.

How does it work?

Prof Maninder Agarwal, Director, IIT Kanpur, explains that cloud seeding works by dispersing substances such as silver iodide into moisture-rich clouds. These particles act as nuclei, helping water vapor condense and fall as rain. The rainfall, in turn, can temporarily “wash out” pollutants from the air, bringing them down to the ground and improving air quality.

However, the technique depends entirely on the right weather conditions — including the presence of dense clouds and favorable wind patterns. It also requires aircraft fitted with special spraying equipment to fly close to the clouds and release the seeding material, making flight availability and aviation clearances an equally critical factor in carrying out the operation.

Delhi officials said the approved aircraft, VT-IIT (a Cessna 206H), will operate under the supervision of the Directorate General of Civil Aviation (DGCA), with clearances from Air Traffic Control (ATC) and coordination with the Airports Authority of India (AAI) for issuing Notices to Airmen (NOTAMs). Flights will follow Visual Flight Rules (VFR), avoid restricted zones and prohibit aerial photography or the use of foreign crew.

Trials depend on weather

Weather data is being closely studied to time the trials for the days when clouds are present.

“The dates have been fixed, based on the weather data we have studied. For these three days, we are likely to witness cloud cover. But this may be adjusted as we approach the dates,” Prof Agarwal said.

Will it really help?

Artificial rain has been used elsewhere, including in the UAE and China, but results vary because cloud seeding depends on atmospheric conditions. “It is a common practice around the world,” Prof Agarwal said, adding that the aim is to refine the technology for Delhi’s needs.

However, experts caution that this is only a temporary fix. It does not address the root causes of Delhi’s pollution — vehicular emissions, stubble burning, industrial activity and construction dust. At best, it could provide short-lived relief during peak smog episodes.

As Prof Agarwal puts it, “Hopefully, by the time there is heavy pollution in Delhi, this technology may be of use.” The upcoming trials will determine whether artificial rain can become a part of Delhi’s clean-air toolkit.