This Diwali, the National Capital Region experienced its worst air pollution in the past three years. This raised the question of why the Delhi government’s cloud seeding plan has not been implemented yet. Officials say the conditions are still not right.
Understanding Cloud Seeding
Cloud seeding is a method that has been around for 75 years. It works by adding special particles, usually silver iodide, to clouds. These particles attract water vapor and help form bigger droplets that eventually fall as rain. To release these particles, aircraft or drones are used. In India, flares attached to planes are commonly used to spray the seeding material into clouds, according to the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEE).
Ideal Conditions for Cloud Seeding
Cloud seeding can only work if clouds are already present. Rain cannot be created from nothing. The clouds must have enough moisture, proper thickness, and favorable wind conditions. CAIPEE notes that clouds should be at least 1 km thick for seeding. Strong horizontal winds can disrupt the process by preventing clouds from rising. Low winds at lower heights are also important. Clouds with strong upward currents are best because rising clouds cool down, allowing moisture to condense into rain. Seeding can be done in both cold and warm months. For low clouds, seeds are sprayed at the bottom or middle, while for high clouds with sub-zero temperatures, seeds are dropped on top.
Effectiveness of Cloud Seeding in India
Not all clouds in India can be seeded. Whether Delhi’s clouds can produce rain through this method is still being tested. The planned operation in Delhi is a trial rather than a proven technique. India’s first cloud seeding experiment was in 1972 by the Indian Institute of Tropical Meteorology, which showed some increase in rainfall by 17% but no definite conclusions. Several states, including Gujarat, Maharashtra, Karnataka, Andhra Pradesh, and Tamil Nadu, have tried cloud seeding in certain areas, but the results remain unverified.
Distinguishing Natural and Artificial Rain
It is difficult to tell if rain is natural or created artificially. However, modern models using data from clouds can simulate seeding effects. Observations from the ground and air help verify these models and understand how cloud seeding influences rainfall.
