Model Answer

Introduction

Cloud seeding is a weather modification technique aimed at enhancing precipitation by dispersing substances such as silver iodide, sodium chloride, or dry ice into clouds. These act as cloud condensation or ice nuclei, accelerating the formation of raindrops and inducing artificial rainfall. Recently, Delhi conducted a successful cloud seeding trial in collaboration with IIT Kanpur to explore its potential in combating severe air pollution.

Body

1. Scientific Principle of Cloud Seeding:
   • Cloud seeding works on the principle of nucleation, where chemical agents attract water vapour in clouds, forming larger droplets that eventually fall as rain.
   • Methods used include pyrotechnic flares or aircraft dispersal of agents like silver iodide and sodium chloride.
   • The success of cloud seeding depends on the availability of suitable clouds and favourable atmospheric conditions.
2. Role in Addressing Air Pollution in Delhi:
   • Temporary relief from pollution: Artificial rain can help wash out suspended particulate matter (PM2.5, PM10), dust, and other pollutants from the air.
   • Improved air quality: Rainfall increases wet deposition, thereby lowering the Air Quality Index (AQI) and visibility-related hazards.
   • Emergency response tool: It can serve as an immediate mitigation measure during peak pollution periods (October–November) when stubble burning and weather inversion worsen air quality.
   • Supports health protection: Cleaner air reduces respiratory problems and stress on public health systems.
3. Limitations and Challenges:
   • Dependence on cloud presence: Cloud seeding cannot be performed under clear skies; hence, it's weather-dependent.
   • Short-term impact: Artificial rainfall provides only temporary respite and does not address root causes like vehicular emissions, industrial pollution, and stubble burning.
   • Environmental concerns: Excessive use of chemicals such as silver iodide may have ecological side effects on soil and water.
   • Cost and coordination: It requires technical expertise, aircraft, and inter-agency coordination, making it expensive and logistically complex.

Conclusion/Way Forward

While cloud seeding can act as a supplementary and short-term measure to reduce pollution levels in Delhi, it cannot replace comprehensive solutions. Long-term strategies such as emission control, renewable energy adoption, sustainable transport, and better waste management are essential for lasting improvement in air quality. Artificial rain, therefore, should be viewed as a temporary relief mechanism within a broader pollution-control framework.