IIT Delhi Study: Why Cloud Seeding Fails as a Solution for Delhi's Winter Air Pollution Crisis

The research indicates significant challenges associated with Delhi's high aerosol environment for cloud seeding operations.

New Delhi:

According to a comprehensive report from IIT Delhi, the winter atmospheric conditions in Delhi are fundamentally unsuitable for effective cloud seeding operations, primarily due to insufficient moisture and inadequate saturation levels, particularly during December and January when pollution levels peak.

This conclusion stems from extensive research conducted by IIT's Centre for Atmospheric Sciences, analyzing climatological data spanning from 2011 to 2021. The findings emerge following unsuccessful cloud-seeding experiments by the Delhi government in collaboration with IIT Kanpur at locations including Burari, north Karol Bagh, and Mayur Vihar, which failed to produce rainfall. While IIT Kanpur had previously achieved successful trials in 2017-18, these represented the first attempts in the Delhi-NCR region.

"Cloud seeding theoretically remains possible under specific conditions, but winter in Delhi presents significant practical limitations for consistent application as an air quality intervention. Suitable atmospheric conditions rarely occur and often coincide with natural precipitation events, minimizing potential additional benefits," the report states.

"Even when rainfall can be successfully induced, the resulting air quality improvements typically last only one to three days before pollution levels return to previous concentrations. Considering the high operational costs, scientific uncertainties in aerosol-dense environments, and no impact on underlying emission sources, cloud seeding cannot be recommended as a primary strategy for managing Delhi's pollution challenges."

"At most, it might serve as an expensive tactical measure during declared air quality emergencies, dependent upon weather forecasts meeting rigorous MSI-based suitability criteria. The research ultimately emphasizes that sustained emission reductions represent the only viable and sustainable solution to Delhi's persistent air pollution crisis," the report concludes.

The analysis highlights that the winter months of December and January consistently experience both the most severe pollution episodes and the driest climatological conditions over the studied decade.

"The core pollution months fundamentally lack adequate moisture and saturation precisely when intervention would be most beneficial. While Western Disturbances (WDs) provide the primary potential for seeding conditions, viable opportunities remain exceptionally rare and limited to specific anomalous weather events."

"Even on seemingly promising days with cloudy Western Disturbance conditions without rainfall, multi-criteria Moisture Suitability Index (MSI) analysis indicates they typically lack the necessary combination of moisture depth, saturation levels, and atmospheric lift required for successful cloud seeding operations," the report elaborates.

The study identifies additional complexities arising from Delhi's high-aerosol environment.

Elevated aerosol loading, characterized by high Aerosol Optical Depth (AOD) measurements, correlates with increased cloud cover and higher liquid/ice water content, particularly during precipitation events.

However, favorable microphysical conditions including low cloud base and high water content typically coincide with naturally occurring rainfall, limiting the potential added value of seeding interventions. The vertical separation between the shallow aerosol layer (below 2 km) and typical seedable cloud formations (2-5 km altitude) creates significant operational targeting challenges.

From a thermal perspective, glaciogenic seeding appears potentially viable during core winter months, though operational feasibility appears largely restricted to existing rainy conditions.

Regarding pollution removal effectiveness, the analysis confirms that heavy natural rainfall demonstrates high efficiency (exceeding 80-95% washout for PM2.5, PM10, and NOX), while light precipitation produces minimal impact. Importantly, even following significant washout events, air quality improvements remain short-lived, with pollutant concentrations typically returning to pre-event levels within one to five days due to ongoing emissions.

Ozone concentrations frequently increase following rainfall events. While dry Western Disturbances provide limited ventilation benefits, significant concerns persist regarding potential environmental and health impacts of seeding agents like silver iodide (AgI), high operational costs, and scientific uncertainties.

"Given these substantial constraints, cloud seeding cannot be recommended as a primary or reliable strategy for addressing Delhi's winter air pollution challenges. It should be considered, at most, as a potential high-cost emergency measure for short-term intervention, contingent upon meeting stringent forecasting criteria."

"The research ultimately emphasizes that sustained emission reduction remains the most viable and necessary long-term solution," concludes the report.