El Niño and La Niña
First published: 2014
Brief summary
NOAA overview of ENSO phases and global impacts.
Article
El Niño and La Niña are opposite phases of the El Niño–Southern Oscillation, a recurring pattern of tropical Pacific ocean and atmospheric variability. Episodes usually develop irregularly every two to seven years and commonly persist for several seasons.
During El Niño, trade winds weaken and unusually warm surface water extends eastward across the equatorial Pacific. Atmospheric convection and tropical rainfall shift eastward, changing jet streams and weather patterns across many parts of the world.
During La Niña, trade winds strengthen and cooler-than-average water occupies the central and eastern equatorial Pacific. Upwelling increases in the eastern Pacific, and tropical rainfall shifts westward relative to El Niño conditions.
ENSO affects drought, flooding, temperature, tropical cyclone activity, fisheries and ecosystems. Its regional impacts differ by season and event, so monitoring combines ocean temperatures, atmospheric pressure, winds and forecasts rather than relying on a single measurement.
Source details and credits
- Source / publisher: NOAA Climate.gov
- Source type: Educational portal
- URL type: WWW
- Credits: NOAA Climate.gov
- URL: https://www.climate.gov/enso