The research confirms that even if induced rain occurs, pollution rebounds quickly due to persistent emissions, pointing to source control as the only permanent fix. (Image: Ref)
A recent study by the Indian Institute of Technology (IIT) Delhi has raised doubts about using cloud seeding to tackle Delhi’s winter pollution. The researchers found that the city’s weather conditions during peak pollution months are not suitable for “consistent” or “effective” cloud seeding, questioning its use as a main solution to the smog problem.
The core of the problem lies in the fundamental weather conditions during peak winter, particularly in December and January. The IIT report states there is a "fundamental lack of sufficient moisture and saturation" precisely when anti-pollution interventions are most desperately needed. Even when western disturbances bring cloudy days, a special Moisture Suitability Index (MSI) shows they frequently lack the necessary combination of deep moisture, saturation, and atmospheric lift required to make cloud seeding work. The study found that over the past decade, only 92 days had conditions comparable to a moderate-to-heavy rainfall day, making viable "windows of opportunity" exceptionally rare.
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The challenges go beyond just a lack of moisture. Delhi's heavily polluted environment itself creates complications. The report highlights that the shallow layer of aerosols (below 2 km) is vertically separated from the seedable cloud layers (2-5 km), presenting significant operational targeting challenges. Furthermore, Professor Shahzad Gani, a mentor for the study, pointed out that even when rain does naturally occur, "air quality typically rebounds within a day or two because emissions continue." This fast recovery rate of pollutants due to persistent emissions makes any cleansing effect from seeded rains short-lived.
The findings align with recent admissions from the Delhi government and the results of previous trials. On the same day the study was released, Delhi's Environment Minister Manjinder Singh Sirsa stated that cloud seeding was not a permanent solution but a temporary measure for alarming pollution levels. This was corroborated by three recent cloud seeding trials conducted in October, all of which failed to produce rainfall. IIT Kanpur, which executed the trials, cited unfavourable meteorological conditions with moisture content at a mere 15-20% against a requirement of around 50%.
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Given the numerous constraints, the IIT Delhi study firmly states that cloud seeding cannot be recommended "as a primary or reliable strategy for Delhi’s winter air pollution management." It should be viewed, at best, as a potential high-cost, emergency short-term measure. Professor Sagnik Dey, who leads the Centre for Atmospheric Sciences, concluded that cloud seeding is both ineffective and unsustainable under Delhi’s winter atmospheric conditions and high pollution levels. The study emphasizes that lasting improvement in air quality can only be achieved by addressing pollution at its source.
