Why in News?
- The World Meteorological Organization (WMO) has warned that the ongoing 2026–27 El Niño could become one of the strongest on record — a potential Super El Niño.
- Niño 3.4 sea surface temperature (SST) anomalies are projected to reach approximately +3.7°C during October–December 2026.
- While El Niño generally weakens India's Southwest Monsoon (June–September), Tamil Nadu can experience enhanced Northeast Monsoon (October–December) rainfall, increasing the risk of extreme rainfall and flooding.
What is a 'Super El Niño'?
El Niño
- It is the warm phase of the El Niño–Southern Oscillation (ENSO) — a recurring coupled ocean–atmosphere phenomenon in the central and eastern tropical Pacific Ocean, occurring every 2 to 7 years.
- Threshold: El Niño is identified when SSTs in the Niño 3.4 region remain at least +0.5°C above normal for five consecutive overlapping three-month periods, as measured by the Oceanic Niño Index (ONI).
- Mechanism: Easterly trade winds weaken or reverse into westerlies, pushing warm surface water toward the South American coast (Peru/Ecuador) and suppressing cold-water upwelling (the Peruvian/Humboldt Current).
Super El Niño
- 'Super El Niño' is an informal, popular term — not a formal WMO/NOAA classification — referring to an extreme El Niño event with Niño 3.4 SST anomalies of +2.0°C or higher, with some eastern Pacific areas exceeding +3.0°C.
- Such events significantly alter global atmospheric circulation and weather patterns.
Historical Context in India
| Event | Impact |
|---|---|
| 1876–78 (strongest recorded) | Triggered the catastrophic Great Madras Famine in British India — extreme drought across the Deccan and millions of fatalities |
| 1997–98 (Super El Niño) | India received normal Southwest Monsoon rainfall because it was counterbalanced by a strong Positive Indian Ocean Dipole (+IOD) |
| 2015–16 | Caused back-to-back Southwest Monsoon droughts across interior India, while simultaneously triggering the devastating December 2015 Chennai floods during the Northeast Monsoon |
Factors Influencing El Niño's Impact on India
- Shift in the Walker Circulation — The ascending (rain-bearing) limb shifts to the central/eastern Pacific, while its descending limb (high pressure, dry sinking air) settles over the Indian Ocean and Indian subcontinent, suppressing Southwest Monsoon cloud formation.
- Indian Ocean Dipole (IOD) — Called the 'Indian Niño', it is the SST gradient between the Western Equatorial Indian Ocean (Arabian Sea) and the Eastern Equatorial Indian Ocean (near Indonesia).
- Positive IOD (warmer Arabian Sea): strengthens the monsoon and neutralises El Niño droughts.
- Negative IOD: compounds the drought.
- Location of Pacific Warming
- Canonical (Standard) El Niño: warming in the Eastern Pacific (off Peru) — typically suppresses the Southwest Monsoon across India.
- El Niño Modoki: warming in the Central Pacific, flanked by cooler water on both east and west — splits the atmospheric wind loop into two cells, increasing cyclones in the Arabian Sea while reducing them in the Bay of Bengal.
- Madden-Julian Oscillation (MJO) — Unlike El Niño (which stays anchored in the Pacific), the MJO is a moving band of rain clouds and winds that travels eastward around the equator every 30 to 60 days. When its active (wet) phase passes over the Indian Ocean during the monsoon, it triggers heavy rainfall bursts, helping revive the monsoon even in an El Niño year.
Why Does Tamil Nadu Encounter El Niño Differently?
- Reliance on the Northeast Monsoon (Oct–Dec): Tamil Nadu lies in the rain-shadow of the Western Ghats during the Southwest Monsoon and derives nearly 48–50% of its annual rainfall from the retreating Northeast Monsoon.
- The 'Wind Tunnel' Effect: During strong El Niño events, pressure differences between the Bay of Bengal and the Arabian Sea can channel moisture-laden winds towards coastal Tamil Nadu, potentially intensifying Northeast Monsoon rainfall.
- Warmer Bay of Bengal & High Evaporation: Weakened winds and clear skies allow sunlight to heat the southern Bay of Bengal (up by ~1°C). The Bay's shallow mixed layer and salinity stratification retain heat near the surface, increasing moisture available to developing rain-bearing systems.
- Supercharged Cyclones & Depressions: When retreating northeasterly winds and low-pressure depressions pass over these abnormally warm Bay waters in November–December, they absorb massive heat and moisture and release it as intense, localized downpours and cyclones along the Tamil Nadu coast.
- Role of the East India Coastal Current (EICC): Along the Tamil Nadu coast, the EICC undergoes a unique seasonal reversal between February and November (changing from northward to southward flow), altering coastal SSTs and helping low-pressure systems form and intensify.
- Additionally, equatorial ocean currents in the western Indian Ocean that normally flow eastward have reversed westward in 2026, pushing even more warm water toward the Indian coast.
Significance for India
- Monsoon variability and agriculture: El Niño years threaten kharif output, rural incomes and food inflation; Tamil Nadu's case shows the risk can shift to the rabi/NE monsoon window instead.
- Disaster risk: The 2015 Chennai floods demonstrate that a Super El Niño can simultaneously produce drought in one season and deluge in another — demanding a dual-mode preparedness strategy.
- Cyclone and coastal management: Warmer Bay waters intensify cyclogenesis, with implications for coastal infrastructure, fisheries and storm-surge planning.
- Policy linkage: Relevant to NDMA guidelines on drought and flood management, monsoon forecasting by IMD, and India's Mission Mausam push for improved modelling.
Related Concepts to Remember
- ENSO = El Niño + La Niña + Southern Oscillation (pressure difference between Tahiti and Darwin).
- La Niña: the cold phase, generally favourable for the Indian monsoon.
- Oceanic Niño Index (ONI): 3-month running mean of SST anomalies in the Niño 3.4 region.
- El Niño Modoki (Japanese for 'similar but different'): central Pacific warming.
Frequently Asked Questions
- What is El Niño? The warm phase of ENSO, identified by SST anomalies of at least +0.5°C in the Niño 3.4 region for five consecutive overlapping three-month periods.
- What is a Super El Niño? An informal term for an exceptionally strong El Niño, commonly associated with Niño 3.4 anomalies of +2.0°C or higher.
- Why does El Niño affect Tamil Nadu differently? Tamil Nadu receives a substantial share of its annual rainfall from the Northeast Monsoon (Oct–Dec), which can bring heavy rainfall even during El Niño years.
- What is the IOD? A difference in sea surface temperatures between the western and eastern equatorial Indian Ocean. A Positive IOD can partly offset El Niño's adverse impact on the Indian monsoon.
- How does the MJO influence the Indian monsoon? It is an eastward-moving system of clouds, rainfall and winds that can trigger active monsoon phases and intense rainfall over the Indian Ocean and India.
Previous Year Questions
Prelims 2017: With reference to 'Indian Ocean Dipole (IOD)', which of the following statements is/are correct? (i) It is characterised by a difference in SST between the tropical Western Indian Ocean and the tropical Eastern Pacific Ocean. (ii) It can influence El Niño's impact on the monsoon. Ans: (b) 2 only
Prelims 2011: La Niña is characterised by unusually cold ocean temperature in the equatorial Indian Ocean… Ans: (d) Neither 1 nor 2
Mains 2014: Discuss the mechanisms for preparedness to deal with likely El Niño and La Niña fallouts in India, with a focus on NDMA guidelines.
Mains 2014: Most of the unusual climatic happenings are explained as an outcome of the El Niño effect. Do you agree?