El Niño and La Niña

El Niño and La Niña

El Niño and La Niña

#GS-01 Geography

For Prelims:

  • El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle.

El Niño:

  • El Nino means ‘little boy’ or ‘Christ child’ in Spanish.
  • El Nino is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean along the coast of Ecuador and Peru.
  • It is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).
  • The El Nino event is not a regular cycle, they are not predictable and occur irregularly at two- to seven-year intervals.
  • El Niño normally occurs around Christmas and usually lasts for a few weeks to a few months.
  • Sometimes an extremely warm event can develop that lasts for much longer time periods.
  • In the 1990s, strong El Niños developed in 1991 and lasted until 1995, and from fall 1997 to spring 1998.
  • It occurs more frequently than La Nina.

Impact of El Nino:

  • El Nino and Indian monsoon are inversely related.
  • The cool surface water off the Peruvian coast goes warm because of El Nino.
  • When the water is warm, the normal trade winds get lost or reverse their direction.
  • Hence, the flow of moisture-laden winds is directed towards the coast of Peru from the western Pacific (the region near northern Australia and South East Asia).
  • This causes heavy rains in Peru during the El Nino years robbing the Indian subcontinent of its normal monsoon rains.
  • The larger the temperature and pressure difference, the larger the rainfall shortage in India.

La Niña:

  • La Nina means ‘little girl’ in Spanish and is also known as El Viejo or ‘cold event’.
  • La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the tropical eastern Pacific.
  • La Nina events may last between one and three years, unlike El Nino, which usually lasts no more than a year.

Impact of La Nina:

  • La Nina is caused by a build-up of cooler-than-normal waters in the tropical Pacific, the area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn.
  • La Nina events are also associated with rainier-than-normal conditions over southeastern Africa and northern Brazil.
  • However, strong La Nina events are associated with catastrophic floods in northern Australia.
  • Drier-than-normal conditions are observed along the west coast of tropical South America, the Gulf Coast of the United States, and the pampas region of southern South America.

Source “Are El Niño-La Niña weather patterns changing?