As Delhi continues to grapple with hazardous air quality levels, the city's Environment Minister, Gopal Rai, has proposed a bold measure—artificial rain. On November 19, 2024, Rai wrote to the Centre seeking clearance for cloud seeding to bring rain to the region. He also urged the Centre to convene a meeting with experts from IIT Kanpur and Union government agencies to deliberate on the feasibility of this approach.
While artificial rain has been considered a potential short-term solution to air pollution, its effectiveness remains a topic of debate. Here’s an in-depth look at the concept of cloud seeding, its mechanics, and the reasons why it may not be the silver bullet for Delhi’s air pollution crisis.
The Current State of Delhi’s Air Pollution
Delhi’s air quality has been in the ‘severe plus’ category for several consecutive days. On November 19, the average Air Quality Index (AQI) in the city stood at a staggering 492, with areas such as Alipur, Anand Vihar, Bawana, Narela, Pusa, and Sonia Vihar recording the maximum index value of 500, according to the Central Pollution Control Board (CPCB).
Despite the implementation of Stage IV of the Graded Response Action Plan (GRAP), which includes emergency measures like halting construction activities and imposing restrictions on vehicular movement, the pollution levels remain unabated.
What is Artificial Rain or Cloud Seeding?
Cloud seeding, commonly referred to as artificial rain, is a weather modification technique aimed at inducing or enhancing rainfall. It involves introducing specific substances into clouds to accelerate the natural process of rain formation.
How Does it Work?
- Formation of Rain: In nature, water vapor condenses around small particles to form droplets, which collide, grow, and eventually fall as rain when they become heavy enough.
- Cloud Seeding Process: In cloud seeding, salts such as silver iodide, potassium iodide, or sodium chloride are dispersed into clouds. These act as nuclei around which additional cloud droplets form. This process is facilitated using aircraft or ground-based generators.
The two primary substances used in cloud seeding are:
- Cloud Condensation Nuclei (CCN): Facilitates the formation of water droplets.
- Ice Nuclei: Promotes the formation of ice crystals, which grow rapidly and fall to the ground as precipitation.
Conditions Required for Cloud Seeding
1. Presence of Clouds
Cloud seeding is contingent on the presence of a specific type and depth of clouds with adequate water content. Without these conditions, the process is futile. Clear skies, such as those often seen in winter over Delhi, make cloud seeding impossible.
2. Winter Challenges
In winters, cloud formation in Delhi depends largely on western disturbances—storms originating in the Caspian or Mediterranean Sea that bring non-monsoonal rainfall to northwest India. Even when these disturbances occur, the suitability of the clouds for seeding must be assessed on parameters such as:
- Cloud height
- Liquid water content
- Stability of the atmosphere
Can Artificial Rain Fix Delhi’s Air Pollution?
Temporary Relief at Best
Research on cloud seeding has shown mixed results. A 2003 study by the National Academy of Sciences highlighted significant uncertainty regarding its efficacy. Similarly, a synthesis by the World Meteorological Organization (WMO) found that the increase in precipitation through cloud seeding typically ranges between 0% and 20%. The higher end of this range occurs only when clouds are already primed for natural precipitation.
Cloud seeding can help wash out particulate matter like PM2.5 and PM10 to some extent, providing temporary respite. However, other pollutants like ozone and sulfur dioxide remain largely unaffected.
Environmental and Ethical Concerns
- Impact on Ecosystems:
- The chemicals used, such as silver iodide, may accumulate in the soil and water, potentially harming agriculture and ecosystems. The long-term environmental impact of these chemicals is not fully understood.
- Redistribution of Rainfall:
- Artificial rain can alter natural weather patterns, potentially depriving other regions of rainfall. This manipulation could inadvertently cause droughts in areas that would have otherwise received this precipitation.
Why Cloud Seeding is a Long Shot for Delhi
Several technical, logistical, and ethical challenges make cloud seeding an impractical solution for addressing Delhi’s air pollution crisis:
- Limited Cloud Cover:The atmospheric conditions in Delhi, especially during winter, do not always favor the formation of clouds suitable for seeding.
- Uncertain Results:Even under optimal conditions, the efficacy of cloud seeding remains debatable, with results varying widely across regions and circumstances.
Environmental Risks:
The potential harm caused by chemical accumulation in the environment outweighs the temporary benefits of pollution reduction.Short-Term Solution:
At best, cloud seeding offers a temporary reprieve, addressing symptoms rather than the root causes of air pollution.
Conclusion
While cloud seeding may seem like an innovative approach to tackling air pollution, it is far from a viable long-term solution for Delhi. Addressing the root causes of pollution—such as industrial emissions, vehicular pollution, and crop residue burning—requires coordinated policy measures, stricter enforcement of environmental regulations, and a shift toward sustainable practices.
Artificial rain can provide momentary relief, but the associated environmental risks and logistical challenges highlight the need for more holistic and sustainable strategies to combat air pollution in the national capital.
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