Shrinking of India’s Sunlight Hours

Context

According to a recent collaborative research with Nature in Scientific Reports, the hours of sunlight over India are reducing because of the pollution and cloud cover that is posing a threat to the solar energy aspirations of the country.

Solar Dimming

• Solar dimming is a process by which the surface sun radiation reaches the Earth and is diminished. It is mainly caused by:
  • Industrial emissions, vehicular emissions, and biomass burning are aerosol pollutants.
  • Continuous cloudiness, particularly in the monsoon months.
  • City Haze and humidity that scatter and reflect the sunlight.

Key Highlights

• Decrease in Sunshine Hours: The North Indian plains had the highest decrease and they lost an average of 13.1 hours per year of sunshine.
• Twomey Effect: The paper emphasized the Twomey effect whereby, as the level of anthropogenic aerosol emissions rises (factories, vehicles, biomass burning) a greater proportion of smaller cloud droplets are produced.
• Key Factor of Decay: The increase in the concentration of aerosols, especially through industrial activities, automobiles and biomass combustion is the main factor that causes the diminishing effect of the sun over a prolonged period.
  • The aerosols are the little scale of cloud compaction that makes the skies remain cloudy and minimizes the amount of sunlight that penetrates the ground.
  • Aerosols are of two kinds such as primary and secondary. Primary aerosols are the particles that are directly emitted such as sea salt, dust and soot, whereas secondary aerosols are formed in the atmosphere through the chemical reaction of gases such as SO2, NO2, and VOCs to sulphates, nitrates, or organic aerosols.

Implications

• Renewable Energy: Fewer sunrays endanger the solar power potential in India.
  • Up to 7 percent in the solar energy production, threatening the clean energy targets of 2030.
• Agriculture: Cultivated crops such as rice and wheat, which rely on photosynthesis, are responding by giving low yields because the light intensity is low.
• Environment: Fading sunlight contributes indirectly to the melting of Himalayan glaciers, and it interferes with the water cycles and ecosystems in the region.

Incoming Solar Radiation (Insolation)

• It can be defined as the solar energy that is received on the surface of the Earth as shortwave radiation.
• It is the main provider of heat and energy to our planet and it drives the processes of atmospheric and climatic.
• At the top of the atmosphere, Earth receives 1.94 calories per cm2 per minute.
• It changes slightly seasonally owing to the elliptical orbit of the Earth:
  • Aphelion (maximum distance): July 4. 
  • Perihelion (nearest to the Sun): January 3. 
• Daily weather and climate are influenced by the distribution of land and sea, atmospheric circulation and the angle of the solar rays.

Influencing Factors of Insolation

• The quantity and strength of insolation at the various places and times is determined by:
  • Earth’s rotation on its axis;
  • Tilting of the rays of the Sun;
  • Length of the day;
  • Atmospheric visibility (disturbed by clouds, dust, and pollution);
  • Land structure and topography.

Source: The Hindu

Prelims PYQ

(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 stratosphere? (2019)

(a) Creating 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 global warming

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