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Impact of La-Nina on Indian Monsoon

Impact of La-Nina on Indian Monsoon

  • The La Niña phase of the equatorial Pacific Ocean may persist for 6 more months - one of the longest ever La Niña events in recorded history.
  • The third episode since 1950 to stretch into a third year.
  • May have wide-ranging implications across the world and can potentially aggravate both floods and droughts in regions.

El-nino and La-nina

  • The periodic warming and cooling of surface waters in the equatorial Pacific Ocean (El Niño Southern Oscillations/ ENSO) has a major influence on global weather patterns, including the Indian monsoon.
  • La Niña - ENSO phase in which sea-surface temperatures are cooler than normal.
  • Warmer phase - El Niño.
  • El Niño and La Niña have almost opposite impacts on weather events.
  • El Niño and La Niña episodes last for about 9 months to a year.
  • Usually develop in the March-June period
  • Strongest during winter (November-January in the northern hemisphere)
  • Weakens by March or April of next year.
  • However, sometimes they continue for much longer periods.

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‘Triple dip’ La Niña

  • The El Niño of 2015-16, spread over 19 months, was one of the longest on record.
  • The current La Niña episode has already surpassed that in length.
  • Started in September 2020
  • Set to continue for another six months
  • Classified as a ‘triple dip’ La Niña.

Impact of La Nina

  • In the Indian context, La Niña is associated with good rainfall during the monsoon season.
  • A continued spell of La Niña could lead to expectation of another year of good, or normal, rainfall during the monsoon.
  • The continuance of La Niña further into 2023 is not bad news from the Indian standpoint.
  • But it is not the same for many other regions where La Niña has very different impacts.

Climate change link

  • The occurrences of El Niño or La Niña are not very regular.
  • Sometimes they emerge every two years, at other times there has been a gap of even seven years.
  • So, the natural variability of ENSO is not understood very clearly.
  • Such events are also linked with global warming.
  • During La Niña, the colder surfaces allow the oceans to absorb more heat from the atmosphere.
  • Thus, the air temperatures decrease, producing a cooling effect.
  • However, this is not enough to reverse or neutralize the impacts of global warming.

Prelims Takeaway

  • El Nino
  • La Nina
  • ENSO

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