originally referred specifically to a warming of the sea off the coast of Peru, now more generally used for the unusual warming of a large area of the eastern equatorial Pacific Ocean. This is strongly linked to changes in the Walker Circulation and to negative phases of the Southern Oscillation.
The name given to warming of coastal waters off Peru around Christmas. Occasionally, this warming is exceptionally strong. It is these occasional extremes (once every 5-9 years) that are now called El Nino episodes. This strong warming of the eastern Pacific is linked to negative phases of the Southern Oscillation. Through this connection, episodes are generally periods of drought over eastern Australia. (from Spanish: the (Christ) child). See La Nina
A climatic phenomenon occurring irregularly, but generally every 3 to 5 years. El Ninos often first become evident during the Christmas season (El Nino means Christ child) in the surface oceans of the eastern tropical Pacific Ocean. The phenomenon involves seasonal changes in the direction of the tropical winds over the Pacific and abnormally warm surface ocean temperatures. The changes in the tropics are most intense in the Pacific region, these changes can disrupt weather patterns throughout the tropics and can extend to higher latitudes, especially in Central and North America. The relationship between these events and global weather patterns are currently the subject of much research in order to enhance prediction of seasonal to interannual fluctuations in the climate.