The prevailing La Ninã conditions over the equatorial Pacific Ocean have entered the third consecutive year. The current La Ninã phase has been prevailing since September 2020.
Key points
- Since the 1950s, La Ninã lasting for more than two years has been recorded only on six instances.
- There is a 70 per cent possibility that the La Niña will persist from September to November 2022 and a slightly lower chance of 55 per cent between December and February, stated the WMO.
- If it lasts that long, it would be a 30-month-long La Niña and one of the longest on record.
- The longest La Niña on record was 37-month-long, from the spring of 1973 to the spring of 1976, according to NOAA.
ENSO
- The El Niño Southern Oscillation (ENSO) is one of the key climate drivers for which the sea surface temperatures (SST) along the central and equatorial Pacific Ocean are constantly observed.
- It has three phases — El Niño, neutral and La Ninã.
El Nino
- El Niño means Little Boy, or Christ Child in Spanish. South American fishermen first noticed periods of unusually warm water in the Pacific Ocean in the 1600s.
- The full name they used was El Niño de Navidad, because El Niño typically peaks around December.
- El Niño is when the SSTs along the central and equatorial Pacific Ocean are abnormally warmer than normal.
La Niña
- La Niña, on the other hand, is when cooler SSTs prevail over these regions.
- La Niña means Little Girl in Spanish.
- During a La Niña event, the sea surface temperatures over the central and eastern Pacific oceans become cooler than normal. This makes the trade winds and associated storms blowing above them stronger than usual.
- These strong trade winds and storms cause more rainfall over some regions such as southeast Asia, especially Indonesia and many parts of Australia, but drastically reduce rainfall in other areas such as the Horn of Africa and western United States.
- In the Indian context, El Niño years have seen below normal monsoon rainfall and caused extreme heat, even though it may not be the single factor or have direct relations.
- In 2014, India received 12 per cent deficient rainfall during June to September.
- La Niña years, on the other hand, are known to favour the Indian summer monsoon.
