El Nino and La Nina
26-08-2023
11:53 AM
1 min read
What’s in today’s article?
- Why in News?
- What are the Normal Climatic Conditions?
- What is El Nino and La Nina?
- News Summary Regarding Forecast about El Niño
- What can be the Probable Effects of El Nino on India?
Why in News?
- India is experiencing a colder than normal winter thanks to the north-south winter flow set up by the weather phenomenon known as La Niña, which is going on for a record-breaking third consecutive year.
- Now, forecasts for 2023 are predicting that its companion phenomenon - the El Niño - will occur with more than a 50% probability.
What are the Normal Climatic Conditions?
Image Caption: Normal Climatic Conditions
- Weather depends a lot on ocean temperatures and where the ocean is warm, more clouds form and more rainfall in that part of the world.
- In the Pacific Ocean, near the equator, the Sun makes the water especially warm on the surface.
- Normally, a surface low pressure system forms in northern Australia and Indonesia and a high-pressure system develops off the coast of Peru.
- As a result, the trade winds blow strongly from east to west over the Pacific Ocean, transporting warm surface waters westward.
- This leads to convective storms (thunderstorms) to Indonesia and coastal Australia.
What is El Nino and La Nina?
Image Caption: El Nino and La Nina
- El Nino and La Nina are two opposing climate trends that deviate from the normal conditions and normally run nine to twelve months, but can often extend.
- These events occur every two to seven years on average (El Nino is more frequent than La Nina), but not on a regular basis and together are referred to as the El Nino-Southern Oscillation (ENSO) cycle by scientists.
- El Nino is typically known as the warm phase (a band of warmer water spreading from west to east in the equatorial Pacific Ocean) and La Nina is identified as the cold phase (a band of cooler water spreads east-west) of ENSO.
- Both El Nino and La Nina can have global effects on weather, wildfires, ecosystems and economics.
News Summary Regarding Forecast about El Niño
- The first thing to note is that El Niño forecasts before spring tend to be notoriously unreliable due to a so-called ‘spring predictability barrier’.
- This is because the climate system is quite noisy in spring as the Sun transitions across the equator, from one hemisphere to the other.
- More importantly, in a La Niña year, the tropical Pacific Ocean soaks up heat like a sponge and builds up its volume of warm water.
- During the El Niño, this warm water spills from the western part of the Pacific Ocean to the eastern part.
- But the earth has had three straight La Niña years, which means the Pacific’s warm-water volume is fully loaded and is likely to birth an El Niño soon.
- But the question is ‘Will this be a strong El Niño, like the one in 2015-2016?’.
- An El Niño year creates a global-warming crisis in miniature, since the warm water spreading across the tropical Pacific releases a large amount of heat into the atmosphere.
- According to reports, an El Niño this year could increase the planet’s average surface temperature by more than 1.5° C from pre-industrial levels (a.k.a. the threshold of the Paris Agreement).
What can be the Probable Effects of El Nino on India?
- A transition from a La Niña winter to an El Niño summer has historically tended to produce a deficit in the monsoon.
- This means that pre-monsoon and monsoon circulations tend to be weaker in an El Niño year.
- The vertical shear (change in the 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.
- Some research has indicated that the Indian Ocean dipole - a seesawing of sea-surface temperature over the western Indian Ocean, could compensate for the negative effects of an El Niño.
- But it is not yet clear whether there is a robust relation between the dipole, the El Niño, and the summer monsoon, as the summer monsoon system is quite complicated.
- In all, India will have to wait for the El Niño forecast to be updated in the coming weeks.
Q1) What is the difference between El Nino and La Nina?
El Nino is typically known as the warm phase (a band of warmer water spreading from west to east in the equatorial Pacific Ocean) and La Nina is identified as the cold phase (a band of cooler water spreads east-west) of El Nino-Southern Oscillation (ENSO).
Q2) How does El Nino impact India?
A transition from a La Niña winter to an El Niño summer has historically tended to produce a deficit in the monsoon. The vertical shear (change in the 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.
Source: Why is India watching the El Niño forecast with unease? | NOAA | Tribune India | IE