Delhi conducts two cloud seeding trials to tackle pollution, sees light rain and slight drop in PM levels

New Delhi: Delhi witnessed two consecutive cloud seeding trials on Tuesday in an ambitious bid to fight rising air pollution levels, marking another chapter in the city’s ongoing battle with toxic winter air. Conducted by the Indian Institute of Technology (IIT) Kanpur in collaboration with the Delhi government, the trials aimed to trigger artificial rainfall over selected areas, including Burari, North Karol Bagh, Mayur Vihar, Sadakpur, Bhojpur, and nearby regions.

The sorties, each lasting about 90 minutes, were carried out using a Cessna aircraft fitted with silver iodide and salt-based chemical flares. These flares, weighing about half a kilogram each, were fired into the clouds for about two to two-and-a-half minutes per flare to encourage precipitation. According to the Delhi government, humidity levels during the trials hovered between 15 and 20 per cent, significantly lower than the ideal 50 per cent required for cloud seeding to be effective.

Environment Minister Manjinder Singh Sirsa said the trials were part of Delhi’s broader “science-first” approach to improving air quality. “Delhi has taken an unprecedented, science-first step by adopting cloud seeding as a tool to control air pollution,” Sirsa said in a statement. “Our focus is to assess how much rainfall can be triggered under Delhi’s real-life humidity conditions. With every trial, science guides our actions, for the winter and all year round.”

The minister added that initial radar readings and ground observations indicated very light showers — around 0.1 to 0.2 mm — at the Delhi-Noida border on Tuesday evening. “According to expert forecasts, rain after seeding could occur anytime within the next 24 hours depending on cloud moisture,” Sirsa said.

Preliminary data from 20 air quality monitoring stations across the city showed slight but measurable reductions in particulate matter levels after the trials. PM2.5 concentrations at Mayur Vihar, Karol Bagh, and Burari dropped from 221, 230, and 229 µg/m³ respectively before the first sortie to 207, 206, and 203 µg/m³ after seeding. Similarly, PM10 levels declined from around 207–209 µg/m³ to 163–177 µg/m³. Officials attributed this modest improvement to the increase in cloud moisture and partial settling of pollutants.

Sirsa said that a comprehensive scientific report is expected soon. “Each data point from our air quality tracking brings us closer to building a clean, green capital,” he noted. “Scientists will now closely study all pre- and post-seeding data from all 20 locations, and a full report will be published tomorrow to guide our winter pollution response. Depending on the results, we are prepared for further cloud seeding sorties in the coming weeks.”

Cloud seeding is a weather modification technique that involves dispersing substances such as silver iodide or salt particles into moisture-bearing clouds to induce rainfall. These particles serve as nuclei for condensation, helping water droplets form and fall as rain if meteorological conditions are favourable.

Delhi Chief Minister Rekha Gupta has previously called cloud seeding “a necessity for the national capital,” describing it as a “pioneering step toward addressing the city’s persistent environmental challenges.”

However, some environmental experts remain cautious. They argue that while artificial rain may temporarily suppress pollution, it does not tackle the root causes, vehicular emissions, industrial pollution, and stubble burning.

Despite these concerns, officials maintain that the trials represent a milestone in using science and innovation to manage Delhi’s worsening air crisis. As Sirsa put it, “This is among India’s biggest scientific steps for urban air quality control, proving Delhi’s resolve to confront legacy pollution challenges head-on.”

While the immediate rainfall was limited, the government believes the data collected will help refine future interventions, marking what could be a turning point in Delhi’s experiment with weather-based pollution control. Meanwhile, Aam Aadmi Party termed the Delhi BJP government’s cloud seeding experiment a “big fraud” and said it might attempt to steal the credit of (Hindu rain god) Lord Indra if actual rain happens. There was no immediate reaction from the BJP.