Aerosol ( UPSC Prelims)

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News Context

Researchers have linked the phenomenon of solar dimming, or the reduction in Sunshine Hours (SSH) over the past three decades, to increased emissions of anthropogenic aerosols.

Aerosol and its types

• Tiny solid or liquid particles are suspended in the atmosphere (gas medium).
 • Types:
    o Primary Aerosols: These are particles emitted directly, such as sea spray, dust, smoke, and volcanic ash.
    o Secondary Aerosols: These form from gases through chemical reactions, like sulfates from industrial emissions or biomass burning.
 • Impact of Aerosol:
    o They act as condensation nuclei, leading to smaller and longer-lived cloud droplets, which can cause skies to remain overcast for longer periods.
    o They influence climate and weather by affecting heating, cooling, and cloud formation through the absorption or scattering of sunlight.
    o Dust provides nutrients that impact ecosystems, such as the fertilization of the Amazon rainforest.
    o They are associated with the Twomey Effect, which describes how increased anthropogenic aerosol emissions make clouds brighter by creating more tiny droplets, reflecting more sunlight and cooling the climate.

Urban Wind Stilling Effect

A research study has discovered that the Urban Wind Stilling Effect leads to the formation of Urban Aerosol Clean Islands in North India.

About Urban Wind Stilling Effect

 ● Weakened surface winds caused by urban structures create invisible barriers that slow the entry of long-range dust and pollutants.  
      ○ In 43% of cities in the northwest and northern Indo-Gangetic Plain, urban aerosol clean islands were observed, where aerosol levels were lower than in nearby rural areas because city infrastructure blocked aerosol pollution carried by the winds.