El Nino
D1. Physical and chemical oceanography and marine meteorologyDefinition
Warm phase of ENSO with weakened trade winds and warming of the eastern tropical Pacific.
El Nino is the warm phase of ENSO: trade winds slacken, the equatorial Pacific thermocline flattens, and warm water and convection shift east, raising sea surface temperatures off South America and suppressing coastal upwelling. Strong events (1982-83, 1997-98, 2015-16) reorganize global rainfall, cut Peruvian fisheries, and warm global mean temperature. The Oceanic Nino Index tracks event strength from eastern-Pacific SST anomalies.