El Niño

Warm equatorial water which flows southward along the coast of Peru and Ecuador during February and March of certain years. It is caused by poleward motions of air and unusual water temperature patterns in the Pacific Ocean , which cause coastal downwelling, leading to the reversal in the normal north-flowing cold coastal currents. During many El Niño years, storms, rainfall, and other meteorological phenomena in the Western Hemisphere are measurably different than during non- El Niño years.

A warm current that usually appears around Christmas off the coast of Ecuador and Peru . It is often used to refer to episodic (3-5 year) events when the current is particularly intense and dominates the local population of organisms (the abundance of fish in particular). Such events lead to wider regional or global ocean-atmospheric perturbations whose manifestations range from increased sea surface temperatures in the tropical East Pacific to aberrant rainfall patterns. (see also ENSO ).