Cloud Seeding in Delhi: Science, Applications, and Challenges

Recently, the Government of the National Capital Territory (NCT) of Delhi conducted cloud seeding operations to induce artificial rain as an emergency measure to reduce air pollution.
This initiative has sparked interest in understanding the science behind cloud seeding, its applications, limitations, and its effectiveness as a temporary intervention for environmental challenges.

Definition: Cloud seeding is a weather modification technique aimed at enhancing precipitation by dispersing chemical agents into existing clouds.
Mechanism:
- Chemicals act as artificial condensation nuclei, promoting the formation of larger water droplets or ice crystals, which eventually leads to rainfall.
Seeding Agents:
- Silver iodide – Mimics ice crystal structures.
- Potassium iodide – Alternative nucleating agent.
- Dry ice (solid CO₂) – Rapidly cools the air.
- Sodium chloride (common salt) – Promotes droplet formation in warm clouds.
Dispersal Methods:
- Aircraft dispersal.
- Ground-based generators when wind conditions allow aerosol transport.
- Drones for targeted seeding operations.

Scientific Preconditions:

Moisture-rich clouds – Only existing clouds like cumulus and nimbostratus can be seeded; clear skies cannot generate rain.
Sufficient moisture content – Cloud must contain at least 50% water content.
Cloud characteristics:
- Vertical thickness of at least 1 km.
- Cold cloud seeding: requires “supercooled” droplets at −20°C to −7°C.
- Warm cloud seeding: requires temperatures above freezing.
Favourable wind conditions:
- Wind must transport seeding material to the target area.
- Speed should allow clouds to grow vertically without dispersing agents.
Vertical air currents: Strong updrafts help disperse agents and promote rainfall.

Relevance:

The Indian monsoon provides abundant moisture and widespread clouds, ideal for targeting rain-deficient areas.

Limitations:

Temporary relief: Mitigates severe droughts and supports agriculture and rural water security.
Air quality intervention: Artificial rain helps wash pollutants from the air, especially in cities like Delhi.
Agricultural stabilization: Supplements rainfall during delayed or weak monsoons.

Environmental risks: Chemical agents may contaminate soil and water, affecting biodiversity and soil fertility.
Limited effectiveness: Cannot induce rain without suitable clouds or moisture.
Ethical/legal concerns: Manipulating rainfall can affect neighboring regions, raising geopolitical and ethical issues.
Region-specific challenges (Delhi/Indo-Gangetic Plains):
- Winter pollution occurs under low humidity, limiting efficacy.
- Cloud seeding provides short-lived rainfall, lasting a few hours to a couple of days.

Historical Use: India has experimented with cloud seeding since the 1950s, initially for drought management.
State-level Initiatives: Tamil Nadu, Karnataka, Maharashtra, Andhra Pradesh have conducted operations in water-scarce regions.
Delhi’s Revival (2025):
- MoU with IIT Kanpur for five cloud-seeding trials in northwest Delhi.
- Approved by 23 departments, including DGCA, aiming to tackle winter pollution.
- IIT Kanpur will deploy own aircraft for the operations.

Scientific validation: Use satellite data, Doppler radar, and high-resolution meteorological models.
Standard Operating Procedures (SOPs): Develop protocols for execution, monitoring, and post-event assessment.
Regulatory framework: Ensure environmental safety, ethical governance, and transparency.
Long-term solutions: Cloud seeding should remain a supplementary intervention, not a primary pollution-control strategy.
Comprehensive analysis: Decisions should be based on meteorological assessments, transparent processes, and risk evaluation.

Short-term: Cloud seeding can serve as an emergency measure during extreme air pollution or droughts.
Long-term: India must focus on sustainable air-quality solutions, climate-resilient urban planning, and environmental management.
While scientifically plausible, cloud seeding is highly conditional and must be integrated into a broader, multi-layered environmental strategy rather than relied upon as a permanent solution.