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What is El Niño

El Nino complex weather pattern resulting from variations in ocean temperatures in the Equatorial Pacific Region. Itis opposite phase of what is known....

What is El Nino : It is a complex weather pattern resulting from variations in ocean temperatures in the Equatorial Pacific Region. It is opposite phase of what is popular as the El Nino-Southern Oscillation (ENSO) cycle.

  • It is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean.
    • It is the “warm phase” of a larger phenomenon and is popular as the El Nino-Southern Oscillation (ENSO).
    • It occurs more frequently than La Nina.
  • 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 this, 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.
Effects of the El Nino
  • Weather – It 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 the event is strongly linked to suppressed rainfall in the monsoon season.
  • Marine resource – 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.

El Nino’s Impact on India

The pressure distribution in a typical monsoon year (without El Nino) is as follows.

  • The pressure along Peru’s coast in South America is higher than in the region bordering northern Australia and South East Asia
  • As the Indian Ocean is warmer than the surrounding oceans, it has lower pressure. As a result, moisture-laden winds blow from the western Pacific to the Indian Ocean. 
  • As the pressure on India’s landmass is lower than that on the Indian Ocean, moisture-laden winds go farther from the ocean to the lands. The monsoons are disturbed if this typical pressure distribution is disrupted for any cause.

El Nino causes the chilly surface water off the Peruvian coast to warm. The regular trade winds are lost or alter their direction when the ocean is warm. As a result, moisture-laden winds from the western Pacific are steered towards Peru’s coast (the region near northern Australia and South East Asia). It creates significant rainfall in Peru, during the El Nino, depriving the Indian subcontinent of its typical monsoon rains. The greater the temperature and pressure differential, the greater is the rainfall deficit in India.

Monitoring El Nino and La Nina
  • Scientists, governments, and non-governmental organizations (NGOs) collect data about El Nino using a number of technologies such as scientific buoys.
  • The Oceanic Nino Index (ONI) is usually measure as deviations from normal sea surface temperatures.

Read more: La Niña

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