El Niño The term El Niño now refers to the coupled ocean- atmosphere phenomenon characterized by, Abnormally warm sea surface temperatures from the date line (180W) east to the South American coast , Changes in the distribution of tropical rainfall from the eastern Indian Ocean east to the tropical Atlantic , Changes in sea level pressure throughout the global Tropics (low-index phase of the Southern Oscilla- tion) , Large-scale atmospheric circulation changes in the Tropics and portions of the extratropics in both hemispheres. Other terms commonly used for the El Niño phenomenon include “Paci c warm episode” and “El Niño/ Southern Oscillation (ENSO) episode.”
La Niña. La Niña is characterized by anomalously cool water in the central and east-
central equatorial Pacifc. It also results in changes in
the intensity and distribution of rainfall in the Tropics and in changes in the patterns of sea level pressure (corresponding to the “high-index” phase of the Southern Oscillation) and atmospheric circulation that affect many areas worldwide. Another term commonly used for the La Niña phenomenon is “Pacifc cold episode.”
