Why in news?
On 28 October 2025, a small aircraft (Cessna 206H) conducted a cloud‑seeding trial over parts of Delhi amid severe air pollution. The experiment, flown from IIT Kanpur to Delhi, aimed to induce light rain in order to reduce levels of particulate matter (PM 2.5 and PM 10) in the air. It was one of the first attempts in India to use cloud seeding as a pollution‑control measure.
Background
Cloud seeding is a weather‑modification technique developed in the 1940s. It involves introducing “seed” particles into suitable clouds to enhance rainfall or snowfall. Water vapour normally condenses around microscopic particles to form cloud droplets. By adding additional nuclei—commonly salts such as silver iodide, potassium iodide or sodium chloride—scientists hope to encourage droplet formation and trigger precipitation. Cloud seeding has been used in many countries to supplement rainfall during droughts, but its effectiveness varies depending on cloud conditions.
How it is carried out
- Seeding materials: Salts such as silver iodide, potassium iodide or sodium chloride act as cloud condensation nuclei (for water droplets) or ice‑nucleating particles (for ice crystals). These materials help water vapour condense or freeze more readily.
- Delivery methods: Seed particles can be dispersed from aircraft, rockets, drones or ground‑based generators. In the Delhi trial, flares containing the seeding material were attached to the aircraft’s wings and ignited as it flew through suitable clouds.
- Meteorological requirements: Successful cloud seeding requires clouds of sufficient thickness and moisture, with vertical updrafts and favourable wind conditions. Without adequate cloud cover, seeding has little effect.
Why use it for pollution?
- Rain washes pollutants: Raindrops can capture and remove airborne particles through a process called coagulation. As droplets fall, they attract particulate matter and gases, cleaning the air temporarily.
- Short‑term relief: Experts note that any reduction in pollution from artificial rain is likely to be temporary. Significant rainfall is required to meaningfully lower pollution levels, and winter cloud conditions over Delhi are often marginal for seeding.
- Underlying causes: Critics argue that cloud seeding treats the symptom rather than the cause. Long‑term improvement requires reducing emissions from vehicles, industry, construction dust and agricultural burning.
Conclusion
While cloud seeding offers a novel tool for weather modification, its role in air‑pollution control remains limited. Successful trials depend on favourable cloud conditions, and the effect is short‑lived. Comprehensive strategies to curb emissions and improve air quality remain the cornerstone of pollution management.
Source: The Indian Express