Cloud Seeding to Reduce Air Pollution | 26 Nov 2024

Source: HT 

Why in News?

Recently, the proposal for cloud seeding as a measure to combat air pollution in Delhi has gained attention due to the acute air quality crisis with the Air Quality Index (AQI) exceeding 450.

What is Cloud Seeding?

• About:   
  • Cloud seeding, a weather modification technique, enhances precipitation by dispersing chemicals like silver iodide, potassium iodide, or dry ice into clouds, which serve as nuclei for water droplet formation, leading to rainfall. 
  • This process facilitates the formation of ice crystals in clouds, which can lead to artificial rain.  
    • The technique is being considered as a potential solution to combat severe air pollution, particularly during periods of high Air Quality Index (AQI) readings. 
• Types of Cloud Seeding: 
  • Static Cloud Seeding: 
    • This method involves introducing ice nuclei, such as silver iodide or dry ice, into cold clouds that have supercooled liquid water droplets. 
    • The ice nuclei can trigger the formation of ice crystals or snowflakes, which can grow at the expense of the liquid droplets and fall as precipitation. 
  • Dynamic Cloud Seeding: 
    • Dynamic cloud seeding is a technique to artificially stimulate rainfall by enhancing vertical air currents, thereby promoting the formation and growth of rain clouds. 
    • The process is considered more complex than static cloud seeding because it depends on a sequence of events working properly. 
  • Hygroscopic Cloud Seeding: 
    • This method involves spraying fine particles of hygroscopic materials, such as salts through flares or explosives into the base of warm clouds. 
    • The particles can act as cloud condensation nuclei and increase the number and size of the cloud droplets, which can enhance the reflectivity and stability of the clouds. 
  • Glaciogenic Cloud Seeding:  
    • It involves inducing ice formation in supercooled clouds by dispersing ice nuclei such as silver iodide or dry ice, leading to ice nucleation and precipitation. 
• Applications of the Technique: 
  • Cloud seeding is also used to enhance winter snowfall and increase mountain snowpack, supplementing the natural water supply for nearby communities. 
  • Cloud seeding can also be done to prevent hailstorms, dissipate fog, induce rainfall in drought-prone regions, or reduce air pollution.

What are the Challenges in Implementation of Cloud Seeding? 

• Environmental Impact: As artificial rain falls, seeding agents like silver iodide, dry ice or salt will also fall.  
  • Residual silver discovered in places near cloud-seeding projects is considered toxic. As for dry ice, it can also be a source of greenhouse gas that contributes to global warming (carbon dioxide). 
• Temporary Relief: While cloud seeding may provide short-term relief from air pollution by washing away particulate matter, it does not address the root causes of pollution such as vehicular emissions and industrial discharges. 
  • Example: Cloud seeding in Lahore, improved AQI from "poor" to "moderate." However, the effects were short-lived. 
• Availability Issues: Cloud seeding requires the presence of moisture-filled clouds, which are not always available or predictable. 
  • Specific cloud characteristics, including liquid water content and vertical motion, were used to identify clouds with potential for rainfall. 
• Costly: It involves processes such as delivering chemicals to the sky and releasing them into the air by flare shots or aeroplanes, which involves huge costs and logistic preparation. 
  • Example: Cloud seeding in Delhi requires Rs 13 crore to cover the entire aerial area of 1,300 square kilometers.