Aerosols
Also called: Dust particles · Topic: Atmosphere: Composition, Structure and Elements of Weather · NCERT: Class 11, Ch 7 "Composition and Structure of Atmosphere"; Class 11, Ch 11 "World Climate and Climate Change"
Meaning
Aerosols are very tiny solid bits floating in the air. They include sea salt, fine soil, smoke-soot, ash, pollen, dust and pieces of burnt-up meteors. NCERT calls them "dust particles". Most stay in the lower layers of the atmosphere, but rising air currents (convection) can carry them higher. They gather most in subtropical and temperate regions, where winds are dry, and there are fewer near the equator and the poles. Dust and salt act as hygroscopic nuclei, which are specks that attract water. Water vapour condenses on them, so clouds could hardly form without them. Aerosols also scatter and absorb sunlight.
Example
Over the Arabian Sea, breaking waves throw sea-salt particles into the air. Moist monsoon air condenses on these salt specks and forms clouds before it reaches the Western Ghats.
Don't confuse with
- Particulate matter (PM10, PM2.5): this is a way of sorting airborne particles by size for air-quality limits. It is usually discussed as pollution, while "aerosols" covers natural particles too.