A report finds Delhi’s cold, dry winter air unsuitable for effective cloud seeding, warning that only emission control—not artificial rain—can bring lasting relief from smog

Delhi’s winter atmosphere is climatologically unfit for consistent and reliable cloud seeding due to a chronic lack of moisture and saturation during the peak pollution months of December and January, according to a new report by the Indian Institute of Technology (IIT) Delhi.

The study, conducted by the Centre for Atmospheric Sciences at IIT-Delhi, analysed a decade of climatological data from 2011 to 2021. It found that while cloud seeding is scientifically possible under specific conditions, those conditions are rare during Delhi’s smog season and often coincide with natural rainfall events, offering little additional benefit.

The findings come after the Delhi government conducted two experimental cloud-seeding trials in Burari, Karol Bagh, and Mayur Vihar, in collaboration with IIT-Kanpur. Unlike earlier successful trials in Kanpur in 2017–18, the recent efforts in the capital failed to produce rain.

“Cloud seeding could, at best, serve as a high-cost emergency intervention when very specific atmospheric conditions align,” the report stated. “Even then, any improvement in air quality would likely last only one to three days before pollution levels rebound.”

The analysis found that Delhi’s core winter months coincide with its driest climatological phase, leaving too little ambient moisture for cloud formation. Western Disturbances occasionally create brief windows for seeding, but these events are uncommon and hard to predict.

The report also highlighted operational challenges arising from Delhi’s heavy aerosol concentration. High aerosol loading increases cloud cover but rarely produces ideal microphysical conditions for artificial rain. Moreover, the separation between the pollution layer (below 2 km) and potential seeding clouds (2–5 km) complicates targeting efforts.

Thermally, glaciogenic seeding may appear possible during the cold season, but only during existing rainfall, the researchers noted. When natural rain does occur, it already washes out 80-95 per cent of particulate matter (PM2.5, PM10, NOx), though the relief is temporary, lasting no more than five days before pollutants return to previous levels.

The study further cautioned against the environmental risks of silver iodide (AgI) and other seeding agents, as well as the high operational costs involved.
“Given these constraints, cloud seeding cannot be recommended as a primary or reliable strategy for Delhi’s winter air pollution management,” the report concluded. “Sustained emission reduction remains the only viable and durable solution to the city’s chronic air-quality crisis.”

By drawing attention to the limitations of technological fixes, the IIT-Delhi report underscores the need for a long-term, emission-focused approach to restoring clean air in the capital.