El Niño
Mechanism and the ENSO Cycle
El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO) cycle — a coupled ocean-atmosphere phenomenon centred on the equatorial Pacific Ocean. Under normal conditions, easterly trade winds push warm surface water westward, causing upwelling of cold deep water off the South American coast (La Niña-like conditions). During El Niño, trade winds weaken or reverse, causing warm surface water to spread eastward across the central and eastern equatorial Pacific, raising sea surface temperatures (SSTs) above normal by 0.5–2°C or more.
- ENSO index: Oceanic Niño Index (ONI) — measured as 3-month running average of SST anomaly in Niño 3.4 region (5°N–5°S, 120–170°W).
- El Niño threshold: ONI ≥ +0.5°C for at least 5 consecutive overlapping 3-month periods.
- La Niña (cool phase): ONI ≤ -0.5°C; typically associated with above-normal monsoon in India.
- ENSO cycle frequency: every 2–7 years; duration: typically 9–12 months.
- World Meteorological Organization (WMO) and NOAA monitor ENSO; ECMWF provides extended seasonal forecasts.
● Tracked since March 13, 2026 · last seen June 16, 2026 · updates as the daily brief publishes
16 Jun '26
Centre’s foodgrain reserves at record high as El Nino threatens kharif production
Economics
11 Jun '26
Modi asks states to harness AI, tackle social risks, prepare for El Nino impact
Polity & Governance
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