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El Niño-La Niña Weather Patterns

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November 29, 2022

Why in news?

A new study projects that climate change will significantly impact El Niño-La Niña weather patterns approximately by 2030.

What are the findings of the study?

  • Study published in Nature journal – It has projected that climate change will impact El Niño-La Niña weather patterns approximately by 2030, a decade before what was earlier predicted.
  • If Central Pacific and Equatorial Pacific are not separated, sea surface temperature (SST) variability from ENSO will occur almost four decades earlier than previously suggested.
  • WMO prediction – In 2022, the World Meteorological Organisation (WMO) predicted the first “Triple dip” La Niña of the century.
  • This is only the third time since 1950 that a triple dip La Nina has been observed.

At present, India is witnessing an extended triple dip La Niña.

What is El Niño?

  • El Niño is a loose translation of “little boy” or “Christ child” in Spanish.
  • Earlier, it was also called “El Niño de Navidad” since it peaks around December.
  • El Niño is the warming of sea waters in Central-east Equatorial Pacific that occurs every few years (Warm phase off the coast of Peru).
  • During El Niño, surface temperatures in the equatorial Pacific rise
  • This weakens the trade winds — east-west winds that blow near the Equator.
  • Due to El Niño, easterly trade winds that blow from the Americas towards Asia change direction to turn into westerlies.
  • It thus brings warm water from the western Pacific towards America.

elnino

Effects of El Niño Phenomenon

  • Weather - El Niño causes dry, warm winter in Northern U.S. and Canada and increased flooding risk on the U.S. gulf coast and southeastern U.S.
  • It brings drought to Indonesia and Australia.
  • In India, an El Nino event is strongly linked to suppressed rainfall in the monsoon season.
  • Marine resource - Under El Niño, upwelling (deeper waters rise towards the surface) of deeper waters is reduced, thus reducing phytoplankton off the coast.
  • Fish that eat phytoplankton are affected, followed by other organisms higher up the food chain.
  • Warm water - Warmer water carries tropical species towards colder areas, disrupting multiple ecosystems.
  • Airflow above the ocean - Heat redistribution on the surface impacts airflows above the ocean.

What is La Niña?

  • La Niña or “Little girl” is the opposite of El Niño.
  • La Niña sees cooler than average sea surface temperatures in the equatorial Pacific region.
  • It is the “Cool phase”.
  • Trade winds are stronger than usual, pushing warmer water towards Asia.

lanina

Effects of La Niña Phenomenon

  • Weather - Pacific cold waters close to the Americas push jet streams (narrow bands of strong winds in the upper atmosphere) northwards.
  • La Niña leads to drier conditions in Southern U.S.
  • La Niña has been associated with heavy floods in Australia.
  • In the Indian context, La Niña is associated with good rainfall during the monsoon season.
  • Ocean water - On the American west coast, upwelling increases, bringing nutrient-rich water to the surface.

elnino-lanina

What about El Niño Southern Oscillation (ENSO)?

  • The combination of El Niño, La Niña, and the neutral state between the two opposite effects is called the El Niño Southern Oscillation (ENSO).
  • The phenomenon was discovered by Sir Gilbert Walker.

Quick facts

Triple dip La Nina - The extended spell of La Nina lasting across three winter seasons in the northern hemisphere is called ‘Triple dip La Nina’.

Walker circulation - The air circulation as a result of difference in surface pressure and temperature over the western and eastern tropical Pacific Ocean is known as Walker circulation.

 

References

  1. The Hindu│ El Niño, La Niña and changing weather patterns
  2. The Indian Express│ The ‘triple dip’ La Niña
  3. National Ocean Service│ What are El Niño and La Niña?
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