Cloud Seeding in Delhi

Source: DH

Context: For the first time in over five decades, the Delhi government, in collaboration with IIT-Kanpur, has conducted a cloud seeding trial to induce artificial rain and combat the city’s severe air pollution.

• The experiment involved a Cessna 206H aircraft dispersing flares loaded with seeding material over north and east Delhi.

About Cloud Seeding in Delhi:

What it is?

• Cloud seeding is a weather modification technique aimed at artificially inducing rainfall by dispersing certain chemicals into clouds to enhance precipitation. It is being tested in Delhi as a scientific measure to reduce air pollution by settling suspended pollutants through rainfall.

Organizations Involved: The project is a joint initiative between the Delhi Government and the Indian Institute of Technology (IIT) Kanpur.

Chemicals Used:

• Silver iodide (AgI)

• Potassium iodide (KI)

• Sodium chloride (NaCl)

These act as “seed particles” or condensation nuclei around which water vapour condenses to form raindrops.

How Cloud Seeding Works?

• Identification of Suitable Clouds: Meteorologists first monitor weather conditions using radar and satellite data to identify clouds with sufficient moisture content and depth. Only these clouds can sustain the process of artificial rain formation.

• Deployment of Aircraft/Drones: A small aircraft or drone (in Delhi’s case, a Cessna 206H) carries seeding flares containing specific chemical agents such as silver iodide, potassium iodide, or sodium chloride.

• Release of Seeding Agents: Once the aircraft reaches the targeted altitude, flares are ignited and released into the base or interior of the clouds. Each flare, weighing around 2–2.5 kg, contains fine particles that act as condensation or ice nuclei.

• Nucleation and Condensation Process: The released particles attract surrounding water vapour. In warm clouds, water droplets form and grow around the salt particles; in cold clouds, ice crystals form around silver iodide. These microphysical processes increase droplet size and density.

• Droplet Growth and Coalescence: As more droplets collide and merge, they become heavier and larger, accelerating their downward fall due to gravity. This process eventually results in precipitation—either rain or snow, depending on temperature.

• Artificial Rainfall and Pollution Washout: The induced rainfall helps settle airborne pollutants such as PM2.5, PM10, and dust particles, temporarily improving air quality and visibility.

• In Delhi’s case, eight flares (2–2.5 kg each) were fired into clouds with 15–20% humidity, targeting areas such as Burari, Karol Bagh, and Mayur Vihar.

Result: Attempts to induce rain through cloud seeding in parts of Delhi on Tuesday were “not completely successful” because the moisture content in the clouds was low.

Limitations:

• Dependence on weather: Requires sufficient cloud cover and moisture, which are often lacking in Delhi’s dry winter months.

• Short-term relief: Even if successful, rainfall offers only temporary pollution reduction, without addressing root causes like emissions and stubble burning.

• Environmental concerns: Residual silver iodide may pose toxicity risks to soil and water ecosystems.