News Highlights:
- El Nino forecast: Recently, the US National Oceanic and Atmospheric Administration (NOAA) forecast that an El Niño was likely to brew in the tropical eastern Pacific Ocean, triggering drought and a deficient monsoon in India.
- El Niño is a weather phenomenon that creates abnormal warming of the Pacific Ocean and has been known to affect monsoons in India negatively.
Key Takeaway:
- NOAA is forecasting a 50 per cent likelihood of an El Niño setting later this year, which means it is more likely than a neutral prevailing condition.
- State governments in India are already on alert.
El Nino and La Nina:
- About El Nino:
- El Nino means ‘little boy’ or ‘Christ child’ in Spanish.
- The phenomenon was thus named because South American fishermen first recognised it in the early part of the 17th century.
- El Nino refers to the large-scale ocean-atmosphere climate interaction linked to periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific.
- It is associated with high pressure in the western Pacific.
- El Nino adversely impacts the Indian monsoons and hence, agriculture in India.
- La Nina:
- La Nina means ‘little girl’ in Spanish and is also known as El Viejo or ‘cold event’.
- Here, the water temperature in the Eastern Pacific gets colder than normal.
- As a result of this, there is a strong high pressure over the eastern equatorial Pacific.
- Now, there is low pressure in the Western Pacific and off Asia.
- La Nina causes drought in Peru and Ecuador, heavy floods in Australia, high temperatures in Western Pacific and Indian Ocean off the Somalian coast and good monsoon rains in India.
- A La Nina is beneficial for the Indian monsoon.
- Generally, El Nino and La Nina occur every 4 – 5 years. El Nino is more frequent than La Nina.
- Typically, the episodes last for nine to twelve months.
El Nino and La Nina Effects on India:
- Droughts Faced in India:
- Since 1950, out of the 13 droughts India faced, 10 have been during El Nino years and one during a La Nina year.
- This is because an El Nino generally means lesser than average rains for India.
- Indian agriculture is heavily dependent on the monsoons, and because of this, lesser rainfall during the monsoons generally translates to below-average crop yields.
Recent Findings on La Nina and El Nino:
- Atmospheric carbon dioxide:
- Increasing atmospheric carbon dioxide can cause a weakening of future simulated El Nino-Southern Oscillation (ENSO) sea surface temperature variability.
- Temperature extremes
- Future El Nino events will lose heat to the atmosphere more quickly due to the evaporation of water vapour.
- Also, in the future, there will be a reduced temperature difference between the eastern and western tropical Pacific, inhibiting the development of temperature extremes during the ENSO cycle.
- Weakening of Tropical Instability Waves
- There can be a weakening of Tropical Instability Waves (TIWs) in the projected future which can disrupt the La Nina event.
- TIWs are a dominant feature of monthly variability in the equatorial Pacific and Atlantic Oceans.
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Content Source: The Hindu