Cloud Seeding – Mechanism, Applications, Challenges in India
In an attempt to combat the severe air pollution in Delhi, Indian scientists are planning to use cloud seeding for the first time to induce heavy rain. The project, led by the Indian Institute of Technology at Kanpur, aims to tackle the smog that has been enveloping the world’s most polluted capital. The process involves spraying a mix of salts, including silver iodine, into clouds to trigger rainfall, which is expected to wash away pollutants.
What is Cloud Seeding?
Cloud seeding is a weather modification technique that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air. These substances serve as cloud condensation or ice nuclei, altering the microphysical processes within the cloud. There are three main cloud seeding methods:
- Static Cloud Seeding: Involves spreading chemicals like silver iodide, potassium iodide, or dry ice into clouds. These chemicals provide a crystal around which moisture can condense, making rain clouds more effective at dispensing their water.
- Dynamic Cloud Seeding: Aims to boost vertical air currents, encouraging more water to pass through the clouds and translating into more rain. This method is more complex than static cloud seeding and depends on a sequence of events working properly.
- Hygroscopic Cloud Seeding: Disperses salts through flares or explosives in the lower portions of clouds. The salts grow in size as water joins with them, promoting the formation of raindrops.
How does it work?
Here is the step-by-step explanation of how Cloud Seeding works:
- Identify Suitable Clouds: Not all clouds are suitable for cloud seeding. The clouds must have enough water vapor and be at the right temperature.
- Seeding Material: The most commonly used seeding material is silver iodide, which has a structure similar to natural ice crystals. Other materials like dry ice (solid carbon dioxide), regular salt, and other salt compounds can also be used.
- Dispersal of Seeding Material: The seeding material is dispersed into the clouds either by aircraft that drop the particles from above or by ground-based generators that shoot particles into the sky. In some cases, drones are used to cast an electric charge into the clouds.
- Formation of Ice Crystals: The seeding material acts as a nucleus around which supercooled water vapor in the clouds condenses to form ice crystals. This process is similar to how natural snowflakes form around dust or pollen particles in the atmosphere.
- Precipitation: As more and more water vapor condenses around the seeding material, the ice crystals grow in size. Once they become heavy enough, they fall to the ground as precipitation (rain or snow).
It’s important to note that cloud seeding can’t create clouds; it can only enhance the precipitation process in existing clouds. The effectiveness of cloud seeding is still a matter of academic debate, with contrasting results depending on the study in question.
Applications of Cloud Seeding
Cloud seeding is a weather modification technique that aims to enhance precipitation, such as rain or snow, by dispersing substances into the air. Here are some of its applications:
- Enhancing Winter Snowfall: Cloud seeding is used to enhance winter snowfall and increase mountain snowpack, supplementing the natural water supply available to communities in the surrounding area.
- Drought Management: Cloud seeding has been increasingly used in drought management strategies. It can help increase precipitation in areas experiencing drought, thus contributing to the replenishment of water resources.
- Agriculture: In some regions, cloud seeding is used to help irrigate fields for farmers, providing necessary water for crop growth.
- Reducing Hail and Fog: Cloud seeding can be used to reduce the size of hailstones that form in thunderstorms, potentially minimizing damage to crops and property. It is also used to reduce the amount of fog in and around airports, improving visibility for aircraft.
- Enhancing Water Storage: Cloud seeding is most valuable over mountains, where the water is essentially stored as snow until the spring runoff. This stored water can then be used for various purposes, such as irrigation and drinking water supply.
- Fighting Forest Fires: In some cases, cloud seeding has been used to lessen the effects of haze and fight forest fires.
- Ski Resorts: Cloud seeding is occasionally used by major ski resorts to induce snowfall, providing better conditions for winter sports.
It’s important to note that while cloud seeding can enhance precipitation, it is not a cure-all solution for water scarcity or drought. The effectiveness of cloud seeding can vary based on a range of factors, including weather conditions and the specific techniques used.
Cloud Seeding Applications in India
Cloud seeding has been used in India for various purposes, including:
- Mitigating Air Pollution: In recent years, cloud seeding has been considered as a method to combat the severe air pollution in Delhi. The idea is to induce artificial rain to wash away the pollutants in the air.
- Alleviating Drought Conditions: Cloud seeding has been used in India to bring rainfall to drought-prone areas. This has been attempted during the monsoon season in places such as Karnataka, Maharashtra, and Tamil Nadu. For instance, the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX-IV) conducted in drought-prone Solapur in Maharashtra during the monsoon seasons of 2018 and 2019 resulted in a relative enhancement of 18% in rainfall.
- Agriculture: Cloud seeding has been used to induce rainfall in areas suffering from drought, thereby benefiting agriculture. For example, the Karnataka government launched “Project Varshadhari” in 2017, under which an aircraft was used to spray chemicals to induce rainfall in Bengaluru, Gadag, and Yadgir districts.
- Power Generation: While not specific to India, cloud seeding has been shown to augment the production of hydroelectricity, as seen in Tasmania, Australia.
- Water Pollution Control: Cloud seeding can maintain minimum river flows and dilute the impact of treated wastewater discharges from industries.
- Fog Dispersal and Cyclone Modification: Cloud seeding can be used to disperse fog and modify cyclones. This application is not specific to India but has been used in other countries like the US.
Challenges for Cloud Seeding in India
- Temporary relief: Cloud seeding provides only short-term relief from air pollution, and it does not address the root causes of the problem.
- Weather conditions: For cloud seeding to work, significant cloud cover with reasonable moisture content is required, which Delhi generally lacks during the winter.
- Pollution: Rain resulting from cloud seeding may contain seeding agents such as silver iodide, dry ice, or salt, which can be toxic.
- Secondary particulate matter formation: If cloud seeding produces only drizzle, humidity may rise, potentially leading to secondary aerosol formation.
- Abnormal weather patterns: Cloud seeding may lead to changes in climatic patterns, potentially causing drought conditions in areas that usually receive rain.
- High cost: Cloud seeding involves dispersing chemicals using aircraft or flare shots, which requires significant financial and logistical resources.
- Regulatory framework: India currently lacks a comprehensive regulatory framework to address legal ambiguities and potential issues related to weather modification.
Way Forward
Based on the current state of cloud seeding in India and the challenges faced, here are some suggestions:
- Research and Development: Invest in further research to better understand the effectiveness, environmental impact, and long-term consequences of cloud seeding in the Indian context.
- Collaboration: Encourage collaboration between government agencies, research institutions, and international partners to share knowledge, expertise, and best practices in cloud seeding.
- Regulatory Framework: Develop a comprehensive regulatory framework to ensure transparency, accountability, and environmental safety in cloud seeding operations.
- Public Awareness: Increase public awareness about cloud seeding, its potential benefits, and limitations, to address misconceptions and concerns.
- Addressing Root Causes: Focus on addressing the root causes of water scarcity and air pollution, such as improving water management, promoting sustainable agriculture, and reducing emissions from industries and vehicles.
- Monitoring and Evaluation: Implement robust monitoring and evaluation mechanisms to assess the impact of cloud seeding operations on precipitation, air quality, and ecosystems.
- Adaptive Management: Adopt an adaptive management approach, adjusting cloud seeding strategies based on the latest scientific evidence and local conditions.
- Explore Alternative Solutions: Continue exploring alternative solutions to address water scarcity and air pollution, such as water conservation, rainwater harvesting, and pollution control measures.
Practice Question for Mains
Explain Cloud Seeding and Evaluate the effectiveness of cloud seeding as a solution to mitigate air pollution in urban areas. (250 words)
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