El Niño–Southern Oscillation (
ENSO) is an irregularly periodical variation in
winds and
sea surface temperatures over the tropical eastern Pacific Ocean, affecting much of the tropics and subtropics. The warming phase is known as
El Niño and the cooling phase as
La Niña.
Southern Oscillation is the accompanying atmospheric component, coupled with the sea temperature change:
El Niño is accompanied with high, and
La Niña with low air
surface pressure in the tropical western Pacific. The two periods last several years each (typically three to four) and their effects vary in intensity.
