Why in the News
A Indian Institute of Technology Madras led study published in Science Advances shows that air pollution aerosols are making winter fog over north India denser and longer lasting, worsening visibility and health impacts.
About Aerosols
- Aerosols are tiny solid or liquid particles suspended in the atmosphere.
- They strongly influence air quality, weather and climate.
- Natural sources: desert dust, sea spray, volcanic ash, forest fires
- Human sources: vehicle emissions, industrial pollution, biomass burning, coal and diesel use
- Primary aerosols are emitted directly.
- Secondary aerosols form in the air from gases like sulphur dioxide and nitrogen oxides.
Key Features
- Extremely small size: penetrate deep into lungs and remain airborne easily
- Persistence: stay suspended for days to weeks, travel long distances
- Condensation nuclei: provide surfaces for water vapour to condense, aiding fog and cloud formation
- Radiative effects:
- Scatter sunlight: reflective aerosols cool the surface
- Absorb heat: black carbon warms the atmosphere
How Aerosols Affect Winter Fog
- Increase number of fog droplets, making fog thicker
- Reduce sunlight reaching the surface, causing cooling that sustains fog
- Slow fog dissipation, leading to prolonged low visibility episodes
Prelims Pointers
- Aerosols act as condensation nuclei for fog and clouds
- Black carbon absorbs heat while sulphate aerosols reflect sunlight
- Human sources significantly amplify winter fog over north India
- Aerosols influence health, visibility, weather and climate simultaneously
| [2019] In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosol into stratosphere?Â
(a) Creating the artificial rains in some regions (b) Reducing the frequency and intensity of tropical cyclones (c) Reducing the adverse effects of solar wind on the Earth (d) Reducing the global warming |
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