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Indian Ocean Dipole (IOD)

Published: 29th Jun, 2023


With the El Nino phenomenon almost certain to affect the Indian monsoon this year, high hopes are pinned on the development of a positive Indian Ocean Dipole (IOD) and its ability to counterbalance the El Nino effect.

About Indian Ocean Dipole:

  • The IOD is an ocean-atmosphere interaction very similar to the El Nino fluctuations in the Pacific Ocean, playing out, as the name shows, in the Indian Ocean.
  • It is also a much weaker system than El Nino, and thus has relatively limited impacts.
  • A positive IOD helps rainfall along the African coastline and also over the Indian sub-continent while suppressing rainfall over Indonesia, Southeast Asia and Australia.
  • The impacts are opposite during a negative IOD event.
  • IOD, sometimes referred to as the Indian Nino, is a similar phenomenon, playing out in the relatively smaller area of the Indian Ocean between the Indonesian and Malaysian coastline in the east and the African coastline near Somalia in the west.

The El Nino phenomenon:

  • An El Nino event is the result of a weakening of wind systems that leads to lesser displacement of warmer waters.
  • This results in the eastern side of the Pacific becoming warmer than usual. During La Nina, the opposite happens.
  • Both these conditions, together called El Nino Southern Oscillation or ENSO, affect weather events across the world.
  • Over India, the El Nino has the impact of suppressing monsoon rainfall.

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