‘Double-dip’: La Nina has formed for second year in a row, says NOAA

What is the News?

The National Oceanic and Atmospheric Administration (NOAA) has declared that La Niña has re-developed. 

What is Double Dip La Nina?

La Nina is one part of the El Nino Southern Oscillation (ENSO) cycle. But when two La Ninas happen one after the other (with a transition through ENSO neutral conditions in between) is not uncommon. This is usually referred to as a ‘double-dip’. 

In 2020, La Nina developed during the month of August and then dissipated in April 2021 as ENSO-neutral conditions returned.

What is La Nina?

La Niña is a weather pattern that can occur in the Pacific Ocean every few years. 

Source: NASA

In a normal year, winds along the equator push warm water westward. Warm water at the surface of the ocean blows from South America to Indonesia. As the warm water moves west, cold water from the deep rises up to the surface. This cold water ends up on the coast of South America.

Source: NASA

In the winter of a La Niña year, these winds are much stronger than usual. This makes the water in the Pacific Ocean near the equator a few degrees colder than it usually is. Even this small change in the ocean’s temperature can affect weather all over the world.

Impact of La Nina

La Niña results in heavy or better monsoon rains in India, droughts in Peru and Ecuador, heavy floods in Australia, and high temperatures in the Indian Ocean and Western Pacific. 

What’s the difference between El Niño and La Niña?

Both events start in the Pacific Ocean, but they are opposites in almost every other way. La Niña causes the water in the eastern Pacific to be colder than usual. In the same region, El Niño can cause the water to be warmer than usual. So, areas that are hit with drought during La Niña years can get lots of rain in El Niño years!

Source: This post is based on the article‘Double-dip’: La Nina has formed for second year in a row, says NOAApublished in Down To Earth on 22nd October 2021.

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