Urban Aerosol Clean Islands

 Urban Aerosol Clean Islands : Recently, a 17-year satellite-based study (2003–2020) of 141 Indian cities found that several cities in the north and northwest Indo-Gangetic Plain have lower aerosol levels than nearby rural areas. Researchers from IIT Bhubaneswar have dubbed these cities "Urban Aerosol Clean Islands“.

• Key Highlights : 57% of cities (mainly in south & southeast India) had higher aerosol levels than nearby rural areas, termed Urban Aerosol Pollution Islands.

o 43% of cities (mainly in north & northwest Indo-Gangetic Plain) had lower aerosol levels than surrounding areas, termed Urban Aerosol Clean Islands.

• About Urban Aerosol Clean Islands : Cities acted as barriers that resisted or redirected incoming aerosols.

o Clean island effect was most visible during pre-monsoon due to dust transport; disappears during monsoon and less prominent in winter.

o Wind Stilling Effect: Caused by urban structures slowing surface winds, creating atmospheric stagnation zones.

ü These act as invisible barriers, blocking long-range dust and pollution, especially from the Thar Desert and biomass burning.

• Global Context: Similar clean island effects have been noted in Shanghai, Atlanta, and some European cities, though attributed to suburban emissions.