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ASIAN DESERT DUST AND INDIAN SUMMER MONSOON

Context:

A new study has shown how dust coming from the deserts in the West, Central and East Asia plays an important role in the Indian Summer Monsoon.

The researchers also explain how the Indian Summer Monsoon has a reverse effect and can increase the winds in West Asia to produce yet more dust.

Relevance:

GS-I: Geography (Climatology, Important Geographical Phenomena, Indian Geography)

Dimensions of the Article:

  1. What is Monsoon?
  2. Causes of Monsoon
  3. What the recent research finds?

What is Monsoon?

  • Monsoon connotes the climate associated with seasonal reversal in the direction of winds. India has hot monsoonal climate which is the prevalent climate in south and southeast Asia.
  • The Indian summer monsoon typically lasts from June-September with large areas of western and central India receiving more than 90% of their total annual precipitation during the period, and southern and northwestern India receiving 50%-75% of their total annual rainfall.
  • Overall, monthly totals average 200-300 mm over the country as a whole, with the largest values observed during the heart of the monsoon season in July and August.
See the source image

Causes of Monsoon

  • During the summer months, sunlight heats the surfaces of both lands and oceans, but land temperatures rise more quickly due to a lower heat capacity.
  • As the land’s surface becomes warmer, the air above it expands and an area of low pressure develops.
  • Meanwhile, the ocean remains at a lower temperature than the land and so the air above it retains a higher pressure.
  • Since winds flow from areas of high-pressure area to low, this deficit in pressure over the continent causes winds to blow in an ocean-to-land circulation (a sea breeze).
  • As winds blow from the ocean to the land, moist air is brought inland. This is why summer monsoons cause so much rain.

What the recent research finds?

  • Dust swarms from the desert when lifted by strong winds can absorb solar radiation and become hot.
  • This can cause heating of the atmosphere, change the air pressure, wind circulation patterns, influence moisture transport and increase precipitation and rainfall.
  • A strong monsoon can also transport air to West Asia and again pick up a lot of dust.
  • Also, the hot air over the Iranian Plateau can heat the atmosphere over the plateau, strengthen the circulation over the deserts of the Arabian Peninsula and increase dust emission from the Middle East.

Aerosols transported

  • The dust aerosols from deserts in West China such as the Taklamakan desert and the Gobi Desert can be transported eastward to eastern China and can influence the East Asia summer monsoon. And in the southwest United States, we have some small deserts that influence the North African monsoon.
  • Some studies have found that the anthropogenic aerosols emitted from the Indian subcontinent can decrease summer monsoon precipitation, while others found that absorbing aerosols such as dust can strengthen the monsoon circulation.
  • Many studies have shown that the dust emission scheme is extremely sensitive to climate change and the team writes that understanding these mechanisms and effects of dust will help understand our monsoon systems in the face of global climate change.

-Source: The Hindu

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September 2022
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