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Why in the News?
La Ninã conditions prevailing over the equatorial Pacific Ocean since September 2020 have entered the third year.
Key Points:
About El Niño-Southern Oscillation (ENSO) Cycle
- El Nino and La Nina are the exact opposite phases of a climatic phenomenon called the El Niño-Southern Oscillation (ENSO) cycle.
- ENSO takes place in the Pacific Ocean.
- Generally, El Nino and La Nina occur every 4 -5 years.
- El Nino is more frequent than La Nina.
What is La Nina?
- La Niña means “little girl” in Spanish. It is also known as ‘El Viejo’ or a cold event.
- La Nina is caused by the build-up of cold water on the ocean surface dropping the temperature.
- It mostly occurs in the tropical Pacific region, between the Tropic of Cancer and the Tropic of Capricorn.
- La Niña is characterized by lower-than-normal air pressure over the western Pacific.
- These low-pressure zones contribute to increased rainfall.
- For Example, The 2010 La Niña event correlates with one of the worst floods in the history of Queensland, Australia.
- These low-pressure zones contribute to increased rainfall.
- It is considered to be the counterpart to El Nino, which is characterized by unusually warm ocean temperatures in the equatorial region of the Pacific Ocean.
Impact of La Nina:
- La Nina causes:
- drought in the South American countries of Peru and Ecuador
- high rainfall and tropical cyclones across countries in the Pacific region.
- high temperatures in the Western Pacific, and the Indian Ocean.
- During La Niña, waters off the Pacific coast are colder and contain more nutrients than usual which support more marine life.
- La Niña usually has a positive impact on the fishing industry of western South America.
La Nina & India:
- La Nina has a cooling influence in India even as it recorded a very unusual spring and summer dominated by extreme record-breaking heat spells.
- La Niña influences the Indian subcontinent by piping in cold air from Siberia and South China, which interacts with the tropical heating to produce a north-south low-pressure system.
- In the ‘La Nina year’, rainfall associated with the summer monsoon in Southeast Asia tends to be greater than normal, especially in northwest India and Bangladesh.
La Niña years are infamous for frequent and intense hurricanes and cyclones in the Atlantic Ocean and the Bay of Bengal.
