Air Pollution

Aerosols Radiative Effects in the Himalayas

Note4Students

From UPSC perspective, the following things are important :

Prelims level : Aerosols

Mains level : Assessing the potential of aerosols in global warming

Indian researchers have found that the effect of anthropogenic aerosols is much higher over the high altitudes of western trans-Himalayas.

Try this question from CSP 2019:

Q. 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 the stratosphere?

(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

What are Aerosols?

  • An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas.
  • They can be natural or anthropogenic.
  • Examples of natural aerosols are fog, mist, dust, forest exudates and geyser steam. Examples of anthropogenic aerosols are particulate air pollutants and smoke.
  • The liquid or solid particles have diameters typically less than 1 μm; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut.
  • Technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and combustion technology.

Heat pump over the Himalayas

  • The transport of light-absorbing carbonaceous aerosols and dust from the polluted Indo-Gangetic Plain and desert areas over the Himalayas constitutes a major climatic issue due to severe impacts on atmospheric warming and glacier retreat.
  • This heating over the Himalayas facilitates the “elevated-hat pump” that strengthens the temperature gradient between land and ocean and modifies the atmospheric circulation and the monsoon rainfall.

Findings of the research

  • The monthly-mean atmospheric radiative forcing of aerosols leads to heating rates of 0.04 to 0.13 C per day.
  • Further, the temperature over the Ladakh region is increasing 0.3 to 0.4 degrees Celsius per decades from the last 3 decades.

How are aerosols fuelling the heat?

  • The atmospheric aerosols play a key role in the regional/global climate system through scattering and absorption of incoming solar radiation and by modifying the cloud microphysics.

Assessing the Aerosol potential

  • Despite the large progress in quantifying the impact of different aerosols on radiative forcing, it still remains one of the major uncertainties in the climate change assessment.
  • Precise measurements of aerosol properties are required to reduce the uncertainties, especially over the oceans and high altitude remote location in the Himalayas where they are scarce.
  • Researchers have analysed the variability of aerosol optical, physical and radiative properties and the role of fine and coarse particles in aerosol radiative forcing (ARF) assessment.
  • ARF is the effect of anthropogenic aerosols on the radiative fluxes at the top of the atmosphere and at the surface and on the absorption of radiation within the atmosphere.

Significance of ARF study

  • A scientific study of aerosol generation, transport, and its properties has important implications in our understanding and mitigation of climate change via atmospheric warming.
  • Aerosols impact the snow and glacier dynamics over the trans-Himalayan region.
  • The results from the study can help better understanding of aerosol effects in view of aerosol-climate implications.
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