First-ever ARTIFICIAL RAIN in Delhi 

Why in News? 

Recently, Delhi initiated its first-ever artificial rain pilot via cloud seeding, scheduled from July 4 to 11, 2025. Authorities aim to reduce severe air pollution by injecting silver iodide and salts into clouds.

Complete Details of First-ever ARTIFICIAL RAIN in Delhi

• The Delhi government is set to conduct its maiden cloud seeding operation in July 2025.
• The initiative is called “Technology Demonstration and Evaluation of Cloud Seeding as an Alternative for Delhi NCR Pollution Mitigation”.
• Delhi Cabinet approved ₹3.21 crore for this pilot in May 2025, allocating ₹55 lakh per trial and ₹66 lakh for setup and equipment.
• Clearances came from 13 central agencies, including SPG, CPCB, IMD, DGCA, Defence, Home, Environment, AAI, BCAS, and the UP government
• IIT Kanpur leads scientific planning, including chemical formulation, aircraft modification, flight mapping, and post-seeding analysis.
• The Indian Meteorological Department shares real-time weather updates and identifies the right time for seeding. The Directorate General of Civil Aviation handles aircraft approvals and flight planning.
• The pilot will run five sorties between July 4–11, 2025, targeting non-sensitive zones in northwest and outer Delhi.
• Each sortie will last about 90 minutes, covering roughly 100 sq km per flight.
• The cloud-seeding agent is a proprietary mix of silver iodide nanoparticles, iodised salt, and rock salt, formulated by IIT Kanpur.
• The compounds will be dispersed via modified Cessna aircraft equipped with flare-based delivery systems.
• The trial will measure pollution levels before and after seeding using Continuous Ambient Air Quality Monitoring Stations (CAAQMS) focused on PM₂.₅ and PM₁₀ levels
• Delhi will become the first Indian city to attempt urban cloud seeding for pollution reduction.

What is Cloud Seeding?

• Introduction: 

• • • Cloud seeding is the method of adding chemicals to clouds with the goal of producing rainfall or snowfall artificially.
    • It uses particles that mimic natural ice‑forming nuclei. These particles act as a base where water droplets gather and increase in size until they become heavy enough to fall.
    • Organizations apply this method to supplement water supply, reduce hail damage, or clear fog. The goal always remains to influence clouds that already contain moisture.
    • Seeding does not create clouds—it enhances existing ones. It typically produces a 10–15% increase in precipitation in favorable conditions.

• Origin:

• • • Researchers at General Electric in 1946 first showed that cold surfaces and particles could trigger ice formation in clouds.
    • In November 1946, Vincent J. Schaefer introduced dry ice into a cloud in a lab and observed artificial snow for the first time.
    • Later in 1947, scientists launched “Project Cirrus,” using planes to spread dry ice into clouds as part of early testing.
    • Those early tests validated that clouds could respond to external stimuli.
    • This research laid the foundation for modern cloud‑seeding operations.

• Types:

• • In static cloud seeding, materials like silver iodide are introduced into cold clouds to help form snow or ice.
  • Dynamic seeding works by increasing cloud formation through stronger upward air flow and the release of stored heat.
  • Hygroscopic seeding relies on salt particles to amplify droplet growth in warm clouds.

Materials Used in Cloud Seeding Operations

• Silver Iodide (AgI): Silver iodide crystals mimic the structure of ice and help supercooled cloud droplets freeze. Technicians use AgI in tiny amounts—typically 10–50 grams per mission—to trigger ice nucleation. This substance has been used in cloud seeding for over 75 years.

• Potassium and Rock Salt: Granules of iodized salt and rock salt serve as alternate condensation nuclei. These salts attract water vapor and help droplets form around them. This technique supports mixed-phase (liquid and ice) cloud conditions.

• Dry Ice (Solid CO₂): Some cloud seeding methods deploy solid carbon dioxide (dry ice) directly into clouds. Dry ice cools the surrounding air rapidly, causing water to freeze into crystals. This method works in supercooled clouds below 0°C.

Conditions Required for Effective Cloud Seeding

• Suitable Cloud Types: Clouds must contain supercooled liquid water (SLW)—water droplets in liquid form below freezing. Ideal targets are mixed-phase clouds, which include SLW and ice crystals simultaneously. Clouds that contain only water or only ice without supercooled liquid water do not respond well to normal seeding techniques.

• Humidity Level: Absolute humidity must be high to support droplet growth and freezing processes. To allow water to collect around added particles, humidity at the bottom of the cloud should be close to 100 percent. Low ambient humidity may stall particle formation, making seeding ineffective.

• Ideal Temperature: Mixed-phase clouds with SLW occur when temperatures range from 0°C to –20°C. Warmer clouds may be seeded with hygroscopic salts like sodium chloride for inducing raindrop formation.

• Wind Conditions: Wind must be gentle enough to maintain cloud integrity during seeding flights. Strong turbulence or high wind speeds may quickly disperse seeding agents before they act. Optimal wind at seeding altitudes allows steady plume release and adequate dispersion into target areas.

• Water Content: Deeper cloud layers above 1 km with moisture content above 0.5 g/m³ yield better seeding results. Greater vertical depth provides more area for ice crystal formation and growth.

How Cloud Seeding Works

• Cloud Selection: Meteorologists monitor weather systems to spot clouds rich in supercooled liquid water (SLW). SLW droplets exist in clouds at temperatures between 0 °C and –20 °C. These droplets stay liquid despite being below freezing point and are ideal targets for seeding. Scientists use weather radars, satellite data, and balloon soundings to confirm ideal conditions.

• Airspace Coordination: Once target clouds form, pilots set routes that pass through the SLW regions. Flights typically happen at altitudes around –5 °C, where seeding is most effective. Flight paths are designed to maximize chemical coverage across the cloud area. Pilots also avoid severe turbulence and follow strict safety rules.

• Disperse Seeding Agents: SEeding chemicals are released once aircraft reach the SLW zone. Silver iodide is the chemical most often used in seeding because it helps cold clouds form ice. Agents disperse via flares that burn slowly to release microscopic particles. Particles act as “landing pads” for SLW to condense and freeze. These seeds kickstart the precipitation process inside clouds.

• Precipitation Formation: Once introduced, AgI provides tiny crystal structures that mimic ice. SLW droplets attach and freeze around these nuclei. Once ice forms, it gathers more water droplets as it moves, becoming large enough to fall as snow or rain. In warm clouds, hygroscopic salts help droplets coalesce into larger drops.

• Ground-Based Generators: Along mountain ridges, ground generators release AgI into updrafts. These generators burn AgI solutions to emit particles carried upward by wind. They complement aircraft seeding in orographically influenced areas. These systems operate remotely and activate during suitable weather events.

Pros and Cons of Cloud Seeding

• Pros:

• Enhanced Water Resource Management: Cloud seeding often elevates precipitation by 10–15%, as observed in multiple research sites since the 1940s. Such increases help to strengthen reservoirs, raise groundwater, and alleviate drought.

• Effective Drought Mitigation: Countries like the U.S. and Indonesia have used it to combat severe dry spells. In North Dakota, cloud seeding reduced hail damage and improved crop outcomes. These localized programs demonstrate real agricultural and economic gains from targeted interventions.

• Cost-efficient Alternative: Adding an acre-foot of water via seeding costs under USD 3, compared to over USD 3,000 for desalination. It helps optimize limited resources without need for large infrastructure investments.

• Cons:

• Uncertainty in Effectiveness: Success depends heavily on existing cloud conditions and moisture content. The U.S. GAO found precipitation gains ranging from 0–20%, with mixed evidence. 

• Environmental and Health Concerns: Silver iodide (AgI), the primary seeding agent, is classified as a hazardous substance. Though its environmental impact appears low at current doses, some studies suggest possible bioaccumulation and ecosystem effects. 

Unintended Weather Patterns: Cloud seeding could affect precipitation distribution and water availability regionally. In the UAE, aggressive seeding coincided with flooding, raising concern that targeting one region may deprive another.