Context: 

Forecasts for the 2023 fall and winter are predicting that there is a 50% possibility for its companion phenomenon, the El Niño to occur. 

• India is experiencing a colder than normal winter thanks to the north south winter flow set up by the climate phenomenon known as La Niña. 

About El Niño Southern Oscillation (ENSO) cycle:

• El Niño and La Niña are atmospheric patterns that influence warming and cooling of sea surface temperatures in the Central and Equatorial Pacific. 
• The two opposing patterns occur in an irregular cycle called the El Niño Southern Oscillation (ENSO) cycle.
• The phenomenon was discovered by Sir Gilbert Walker.

El Niño 

• El Niño is a loose translation of “little boy” or even “Christ child” in Spanish.
• El Niño  is the warming of sea waters in the Central-east Equatorial Pacific that occurs every few years.
• During El Niño, surface temperatures in the equatorial Pacific rise, and trade winds — east-west winds that blow near the Equator — weaken.
• Normally, easterly trade winds blow from the Americas towards Asia. Due to El Niño , they falter and change direction to turn into westerlies, bringing warm water from the western Pacific towards the Americas.

La Niña

• La Niña, or “the girl/little girl”, is the opposite of El Niño. 
• La Niña is cooler than average SST in the equatorial Pacific region. Trade winds are stronger than usual, pushing warmer water towards Asia. 
• On the American west coast, upwelling increases, bringing nutrient-rich water to the surface.
• Pacific cold waters close to the Americas push jet streams — narrow bands of strong winds in the upper atmosphere — northwards. 
• This leads to drier conditions in the Southern U.S., and heavy rainfall in the northwest and Canada. La Niña also makes winter temperatures warmer in the south and cooler to the north of the U.S.

Impact on India’s monsoons

• In India, El Niño causes weak rainfall and more heat, while La Niña intensifies rainfall across South Asia , particularly in India’s northwest and Bangladesh during the monsoon.

News Source: The Hindu