Cloud Seeding Trials in Delhi to Combat Air Pollution

Delhi conducted cloud seeding trials with the Indian Institute of Technology Kanpur (IITK) after nearly 50 years. The aim was to induce rainfall to reduce severe smog and particulate pollution. Despite efforts, the trials yielded limited rain due to unsuitable cloud conditions. This renewed interest marks the evolving role of weather modification in urban air quality management.

What Is Cloud Seeding?

Cloud seeding is a weather modification technique. It involves spraying salt or chemical mixtures into clouds. Aircraft equipped with flares release these substances. The chemicals encourage water vapour to form droplets. When droplets merge, they fall as rain. This method aims to increase precipitation artificially.

Historical Background

Cloud seeding began in the 1940s. Scientists William Schaefer and Bernard Vonnegut discovered that dry ice could form ice crystals in clouds. Early experiments caused snow over Massachusetts. The U.S. initiated Project Cirrus to explore weather control. The Soviets and later China used cloud seeding for specific events. The technique became popular globally during the 1950s and 1960s.

Cloud Seeding in India

India’s first cloud seeding experiments started in 1952 under S.K. Banerji of the India Meteorological Department. Early attempts used rockets and hydrogen balloons to release chemicals. Results were inconclusive as natural rain could not be ruled out. From the 1970s, aircraft-based seeding began. Various states used cloud seeding during droughts with mixed success. High costs and uncertain outcomes limited widespread adoption.

The CAIPEEX Experiment

The Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) started in 2009. It was led by the Indian Institute of Tropical Meteorology. CAIPEEX studied cloud physics and precipitation in drought-prone Solapur, Maharashtra. From 2017-2019, they seeded clouds with calcium chloride. Results showed seeded clouds produced 46% more rain locally and 18% more rain downwind. This was scientific breakthrough in quantifying cloud seeding benefits.

Delhi’s 2025 Cloud Seeding Trials

Recently, IIT Kanpur conducted two seeding flights over Delhi. The trials failed to generate substantial rainfall. Some light drizzle and minor air quality improvements were reported. The failure was due to the absence of moisture-rich monsoon clouds. Delhi’s post-monsoon atmosphere does not favour effective cloud seeding. Despite this, IITK plans to continue trials in winter seasons.

Scientific and Practical Challenges

Cloud seeding success depends on cloud type and moisture content. Monsoon clouds are more suitable. Winter and post-monsoon clouds in Delhi lack enough moisture. Verification of rain caused by seeding remains difficult. Seeding operations are costly due to aircraft, chemicals, and technical staff. Effective deployment requires precise meteorological data and timing.

Future Prospects

Renewed trials show interest in weather modification for pollution control. Advances in cloud physics and radar technology improve targeting. More research is needed to optimise seeding in different climates. Collaboration between meteorological institutes and government agencies is crucial. Cloud seeding may become part of integrated air quality management strategies.

Questions for UPSC:

1. Taking example of cloud seeding, discuss the ethical and environmental concerns related to weather modification technologies.
2. Examine the role of India Meteorological Department in disaster management and climate adaptation with suitable examples.
3. Analyse the impact of air pollution on urban health and economy. How can technology and policy interventions be integrated to address this challenge?
4. Discuss in the light of recent climate trends, the challenges and opportunities of using artificial rainfall techniques in drought-prone regions of India.

Answer Hints:

1. Taking example of cloud seeding, discuss the ethical and environmental concerns related to weather modification technologies.

1. Weather modification can alter natural precipitation patterns, potentially depriving downwind regions of rain (rain shadow effect).
2. Unintended ecological impacts may arise, such as changes in local biodiversity and water cycles.
3. Ethical concerns include consent and equity—affected populations may not agree or benefit equally.
4. Long-term environmental consequences are uncertain due to limited scientific understanding.
5. Potential for misuse or militarization of weather control technologies raises geopolitical risks.
6. Transparency and regulation are often lacking, complicating accountability for adverse effects.

2. Examine the role of India Meteorological Department in disaster management and climate adaptation with suitable examples.

1. IMD provides early warnings for cyclones, floods, heatwaves, aiding timely disaster response (e.g., Odisha cyclone warnings).
2. Monitors and forecasts weather patterns critical for agriculture and water resource planning.
3. Conducts climate research and supports climate adaptation policies through data and modeling.
4. Leads initiatives like cloud seeding experiments to mitigate drought and air pollution effects.
5. Collaborates with international agencies for improved disaster risk reduction and climate resilience.
6. Developed specialized bulletins and mobile apps to disseminate real-time weather alerts to the public.

3. Analyse the impact of air pollution on urban health and economy. How can technology and policy interventions be integrated to address this challenge?

1. Air pollution causes respiratory, cardiovascular diseases, increasing healthcare burden and mortality in cities.
2. Economic losses include reduced workforce productivity, higher medical costs, and damage to infrastructure.
3. Technological tools like air quality monitoring, cloud seeding, and pollution control devices help track and reduce pollution.
4. Policy measures include stricter emission norms, promoting clean energy, and vehicular restrictions (e.g., odd-even scheme in Delhi).
5. Integration requires data-driven policymaking, public awareness, and coordination between urban planning and environmental agencies.
6. Investment in green infrastructure and sustainable transport complements technological and regulatory efforts.

4. Discuss in the light of recent climate trends, the challenges and opportunities of using artificial rainfall techniques in drought-prone regions of India.

1. Climate change increases drought frequency and severity, intensifying water scarcity in vulnerable regions.
2. Cloud seeding offers potential to augment rainfall but depends heavily on suitable cloud conditions and timing.
3. Challenges include high operational costs, uncertain effectiveness, and difficulty in scientifically verifying results.
4. Opportunities lie in integrating cloud seeding with advanced meteorological tools and drought management strategies.
5. Successful experiments like CAIPEEX in Maharashtra provide a scientific basis for targeted interventions.
6. Requires policy support, capacity building, and community engagement to scale artificial rainfall efforts sustainably.