Context:
The Delhi government, in partnership with IIT-Kanpur and the Department of Environment, is launching its first cloud seeding (artificial rain) pilot project to combat severe winter air pollution.
What is Artificial Rain?
- Definition: A weather modification technique to induce rainfall by dispersing chemicals into clouds.
- Chemicals Used: Silver iodide, potassium iodide, dry ice, rock salt.
- Purpose: Enhance condensation in clouds to trigger rainfall and wash out pollutants.
Why Delhi Needs It
- Pollution Spike: Delhi frequently records PM2.5 and PM10 levels in the ‘severe’ category.
- Sources of Pollution:
- Vehicle and industrial emissions
- Construction dust
- Crop stubble burning in neighbouring states
- Unfavourable meteorological conditions
- Health Risk: Hazardous air quality impacts respiratory and cardiovascular health.
Cloud Seeding
What is Cloud Seeding?
Cloud seeding is a scientific technique used to enhance precipitation by artificially dispersing chemical substances—such as silver iodide, potassium iodide, or dry ice—into clouds. These act as condensation or ice nuclei, encouraging the formation of raindrops or snowflakes.
- Purpose: To induce or increase rainfall/snowfall
- Common Chemicals: Silver iodide, potassium iodide, dry ice
- Mechanism: Enhances microphysical processes in clouds by accelerating droplet formation
Applications of Cloud Seeding
- Air Pollution Control: Helps settle airborne pollutants (like PM2.5 and PM10) by promoting rainfall, especially during high AQI periods
- Water Resource Management: Increases water availability in reservoirs, agriculture, and drought-prone areas
- Climate and Environmental Benefits: Contributes to ecosystem health, agricultural productivity, and weather stabilization
- Health Benefits: Improves air quality, reducing respiratory diseases linked to pollution
Types of Cloud Seeding
- Static Cloud Seeding
- Introduces ice-forming nuclei into cold clouds
- Converts supercooled water into ice crystals or snowflakes
- Typically used to induce precipitation in stable cloud systems
- Dynamic Cloud Seeding
- Aims to stimulate vertical air currents
- Enhances cloud growth and precipitation through energy amplification
- More complex and relies on meteorological conditions
- Hygroscopic Cloud Seeding
- Uses fine salt particles (e.g., sodium chloride) to attract moisture
- Increases cloud droplet size, making them heavy enough to fall as rain
- Effective in warm and moist cloud conditions
- Glaciogenic Cloud Seeding
- Induces ice formation in supercooled liquid clouds
- Leads to precipitation as snow or rain
- Commonly used in mountainous regions to increase snowpack, aid in drought relief, and combat pollution
UPSC Prelims PYQ 2025
Q. Artificial way of causing rainfall to reduce air pollution makes use of
(a) silver iodide and potassium iodide
(b) silver nitrate and potassium iodide
(c) silver iodide and potassium nitrate
(d) silver nitrate and potassium chloride
Ans: (a) silver iodide and potassium iodide
