Watch | What are El Niño and La Niña?

Watch | What are El Niño and La Niña?

A video explainer on weather phenomena El Niño and La Niña.

February 28, 2023 03:45 pm | Updated 04:32 pm IST

Storm like weather conditions near Howrah Bridge due to formation of Cyclone Yaas in the Bay of Bengal, in Howrah, Monday, May 24, 2021.

Storm like weather conditions near Howrah Bridge due to formation of Cyclone Yaas in the Bay of Bengal, in Howrah, Monday, May 24, 2021. | Photo Credit: PTI

India is experiencing a colder winter than normal. This is due to the north-south winter flow set up by the weather phenomenon known as La Niña.

The La Niña is going on for a record-breaking third consecutive year. Now, forecasts for the 2023 fall and winter are predicting that its companion phenomenon, known as the El Niño, will occur with more than a 50% probability.

What do El Niño and La Niña refer to?

El Niño refers to a band of warmer water spreading from west to east in the equatorial Pacific Ocean. Similarly, a La Niña occurs when the band of water spreads east to west and is cooler.

Both phenomena affect the weather worldwide and can have drastic effects on economies that depend on rainfall. Together, El Niño and La Niña make up a cyclical process called the El Niño Southern Oscillation.

An El Niño year creates a global-warming crisis in miniature. This is because the warm water spreading across the tropical Pacific releases a large amount of heat into the atmosphere.

An El Niño this year could increase the planet’s average surface temperature by more than 1.5° C from pre-industrial levels.

What are the effects on the northern Indian Ocean?

A transition from a La Niña winter – which we are in currently – to an El Niño summer has historically tended to produce a largest deficit in the monsoon. This means that pre-monsoon and monsoon circulations tend to be weaker in an El Niño year.

The vertical shear, which is the change in intensity of winds from the surface to the upper atmosphere, tends to be weaker as well. This in turn can favour enhanced cyclogenesis, i.e. cyclone formation.

If an El Niño state does emerge by summer, India is likely to experience a deficit monsoon in 2023. The monsoon deficit will be accompanied by extreme wet and dry events. While overall seasonal total could be deficient, there are likely to be isolated pockets of heavy or very heavy rainfall.

Read more here

Reporting: Raghu Murtugudde

Voiceover & Production: Abhinaya Sriram

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