Has Cloud Seeding Been Effective?, Pg 12

Key Highlights:

• Cloud seeding involves spraying a salt mixture (like silver iodide or calcium chloride) into clouds using aircraft to induce rainfall.
• The Delhi trials on October 28 by IIT-Kanpur were intended to improve air quality by precipitating pollutants.
• Results were disappointing, with no measurable rainfall triggered.
• India’s first systematic experiment, the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX), began in 2009 led by the Indian Institute of Tropical Meteorology (IITM).
• The CAIPEEX experiment in Solapur, Maharashtra (2017–2019) found that while some seeded clouds produced up to 46% more rain, results were inconsistent and weather-dependent.

Detailed Insights:

• Scientific Mechanism: Cloud seeding introduces fine particles (like salt or silver iodide) into existing moisture-rich clouds, providing condensation nuclei around which water vapor condenses to form droplets that can coalesce into rain.
• Historical Background:
  • Developed in the 1940s by General Electric scientists Vincent Schaefer and Irving Langmuir, cloud seeding gained popularity as a method to manage drought and enhance rainfall.
  • India first experimented in the 1950s, and later through projects like Project Cirrus and CAIPEEX in the 2000s.
• India’s Experience:
  • The CAIPEEX study (2009–2019) provided scientific data showing mixed results. Seeded clouds produced localized rain but were dependent on sufficient existing humidity.
  • The Delhi trials failed primarily because winter clouds lacked enough moisture to respond to seeding.
• Limitations:
  • Works only with moist, well-developed cumulus clouds; ineffective in dry or stable winter conditions.
  • Requires accurate meteorological timing and favorable wind conditions.
  • Even when successful, benefits are short-term and may not significantly reduce air pollution.
• Policy Context:
  • Delhi’s trials highlight ongoing technological interest in weather modification but also underline the need for scientific scrutiny and realistic expectations.
  • Experts caution that air pollution mitigation should rely on emission control rather than atmospheric manipulation.

Scientific/Technical Concepts Involved:

• Condensation Nuclei: Microscopic particles (like dust or salt) that facilitate the condensation of water vapor into droplets.
• Silver Iodide: A compound used as a seeding agent due to its structural similarity to ice crystals.
• CAIPEEX: A decade-long IITM program studying aerosol-cloud interactions and quantifying rainfall enhancement potential.
• Hygroscopic Seeding: Seeding method using salt particles that attract water vapor to enhance droplet formation.