EL NINO

The cyclical warming of East Pacific Ocean sea water temperatures off the western coast of South America that can result in significant changes in weather patterns in the United States and elsewhere. This occurs when warm equatorial waters move in and displace the colder waters of the Humbolt Current, cutting off the upwelling process.

The cyclical warming of East Pacific Ocean sea water temperatures off the western coast of South America that can result in significant changes in weather patterns in the United States and elsewhere. This occurs when warm equatorial waters move in and displace the colder waters of the Humbolt Current, cutting off the upwelling process. Related terms: ENSO and Dave's Dictionary

Southern Oscillation (ENSO) refers to the combined effects of El Ninõ (see above) and a global-scale shift in atmospheric pressure called the Southern Oscillation. In the warm phase of ENSO, El Ninõ warming extends over much of the tropical Pacific and becomes clearly linked to the SO pattern. Many of the countries most affected by ENSO events are developing countries with economies that are largely dependent upon their agricultural and f:ishery sectors as a major source of food supply, employment and foreign exchange. New capabilities to predict the onset of ENSO events can thus have important human impacts. While ENSO :is a natural part of Earth's climate variability, whether its intensity or frequency may change as a result of global warming :is a concern.

A complex state of the equatorial ocean-atmosphere system associated with anomalously warm ocean temperatures in the central and eastern Pacific Ocean, anomalously cold ocean temperatures in the western Pacific Ocean, and a weakening of the southeasterly trade winds. Changes in the ocean temperatures result in increased convection over the warmer waters of the central and eastern Pacific and decreased convection over the western Pacific. Weather patterns are also affected in other regions of the world. [See teleconnection.] El Niño occurs every three or four years.