Cloud Seeding
What is Cloud Seeding?
It is a weather modification technique aimed at inducing artificial rainfall.
Involves spraying a salt mixture (like silver iodide, potassium iodide, or calcium chloride) into clouds using aircraft or rockets.
These particles act as nuclei, helping water vapor condense into droplets, which can then fall as rain when they become heavy enough.
Simple science:
Cloud + salt nuclei → condensation → water droplets → rain (if cloud moisture is sufficient).
Global History
1940s (USA):
Discovered by William Schaefer and Bernard Vonnegut of General Electric.
First artificial snow reported over Pittsfield, Massachusetts.
Led to Project Cirrus, aiming to modify weather and even control hurricanes (unsuccessful).
1950s–60s:
Widespread experiments globally.
US: Project Skywater (silver iodide used over Rockies).
Soviet Union: Used cloud seeding to clear skies over Leningrad during parades.
China (2008): Used it before Beijing Olympics to ensure clear skies.
India’s Experience with Cloud Seeding
Early Experiments
1952: First trials in Kolkata under S.K. Banerji (IMD).
Used salt and silver iodide released via hydrogen balloons and rockets.
1962: Attempted in Delhi — failed due to unsuitable cloud conditions.
Developments (1970s onwards)
Aircraft began to be used to reach cloud tops and spray salt mixtures.
Several drought-prone states (Maharashtra, Karnataka, Andhra Pradesh, Tamil Nadu) experimented, but results were inconsistent.
Challenges included:
Difficulty verifying if rainfall was due to seeding or natural causes.
High costs (aircraft, chemicals, pilots, radar).
Unpredictable outcomes and unclear cost-benefit ratio.
CAIPEEX Programme
Full Form: Cloud Aerosol Interaction and Precipitation Enhancement Experiment
Launched: 2009 by Indian Institute of Tropical Meteorology (IITM), Pune.
Objective:
To scientifically test whether cloud seeding increases rainfall and to study cloud microphysics.
Key Findings (Solapur, Maharashtra):
Conducted between 2017–2019.
Used calcium chloride instead of silver iodide.
Seeded vs. unseeded clouds comparison:
46% more rainfall from seeded clouds.
18% more rainfall across 100 sq km area downwind.
About 867 million litres of additional water generated.
Provided India’s first quantitative evidence that cloud seeding can enhance rainfall under the right conditions (especially monsoon clouds).
Delhi Cloud Seeding Trials
When and Who
Conducted by IIT Kanpur in October 2025.
Two flights on October 28, marking the first trials in Delhi in nearly 50 years.
Objective
To induce rainfall and settle smog and particulate matter to improve air quality.
Outcome
No significant rainfall; only a light drizzle in some areas.
Minor temporary improvement in air quality.
Reason for Failure
Post-monsoon clouds over Delhi lack sufficient moisture and vertical development.
Cloud seeding works better with monsoon-type cumulonimbus clouds, which were absent.
Challenges and Limitations
Cloud quality dependence – works only with moisture-rich clouds.
Verification issues – difficult to prove if rainfall was due to seeding or natural process.
High operational cost – aircraft, chemicals, radar monitoring.
Short-lived impact – not a permanent or scalable solution for drought or pollution.
Ethical/environmental questions – potential unintended weather impacts elsewhere.
Significance for India
Potential tool for drought mitigation and urban pollution management.
But requires scientific validation, precise cloud targeting, and cost-benefit assessment before large-scale use.
Ongoing research by IITM Pune and IIT Kanpur could help develop indigenous cloud seeding technology.
Prelims Practice MCQ
Q. With reference to the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX), consider the following statements:
It was launched by the Indian Institute of Tropical Meteorology (IITM), Pune to study the impact of aerosols on cloud formation and precipitation.
The CAIPEEX experiments used calcium chloride instead of silver iodide to avoid toxic effects.
The experiment conclusively proved that cloud seeding can increase rainfall by at least 50% in all drought-prone regions.
Which of the above statements is/are correct?
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2, and 3
Answer: (b)
Explanation:
CAIPEEX was launched in 2009 by IITM Pune, focusing on the interaction between aerosols and precipitation processes. (Statement 1 – Correct)
The experiment used calcium chloride, a safer alternative to silver iodide. (Statement 2 – Correct)
The project showed positive but variable results (46% increase in rainfall in certain clouds near Solapur), not a universal 50% increase everywhere. (Statement 3 – Incorrect)
Q. Consider the following statements regarding cloud seeding experiments in India:
The first cloud seeding experiment in India was conducted in 1952 using hydrogen balloons to release silver iodide and salt over Kolkata.
Delhi’s first cloud seeding attempt in 1962 succeeded in inducing rainfall.
Recent trials by IIT Kanpur failed mainly because post-monsoon clouds lacked sufficient moisture.
Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2, and 3
Answer: (b)
Explanation:
The first experiment (1952) was indeed done in Kolkata under IMD’s S.K. Banerji. (Statement 1 – Correct)
The Delhi trial in 1962 failed due to unsuitable cloud conditions. (Statement 2 – Incorrect)
The IIT Kanpur (2025) trial also failed because Delhi’s winter clouds are thin and moisture-deficient. (Statement 3 – Correct)
Q. Consider the following statements:
Cloud seeding artificially increases condensation by providing nuclei for droplet or ice formation.
The process can alter large-scale weather systems such as monsoons or cyclones.
The efficiency of cloud seeding depends on atmospheric humidity, temperature, and updraft strength.
Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 3 only
(c) 2 only
(d) 1, 2, and 3
Answer: (b)
Explanation:
The scientific principle is correct — seeding introduces condensation/ice nuclei to enhance rainfall. (Statement 1 – Correct)
Cloud seeding can modify local weather but cannot influence large-scale systems like monsoons or cyclones. (Statement 2 – Incorrect)
Success depends on the microphysical structure of clouds, humidity levels, and updraft velocity. (Statement 3 – Correct)
