A change in the condition of the tropical atmosphere and ocean that occurs somewhat regularly, generally every 3-4 years. An El Niño climate event usually begins with a weakening of the trade winds and changes in atmospheric pressure over the sub-tropical Pacific Ocean, followed by a warming of the eastern tropical Pacific. The cycle or oscillation is completed by a return to stronger trade winds and a cooler ocean. The phenomenon is sometimes referred to ENSO, a contraction of El Niño-Southern Oscillation
(ENSO): pattern of climate/ weather variation, known popularly as El Niño, that results from coupled atmosphere-ocean interactions, and recurs at two- to seven-year intervals. The ENSO pattern is characterized partly by alternating warmer(El Niño) and cooler surface waters (La Niña) of the sea surface in the eastern and central tropical Pacific Ocean, which in turn are caused by changes in subsurface termperatures. It affects precipitation and temperatures over a large portion of the globe, with drastic consequences to human activities like farming and fishing, which depend on weather and ocean currents.
A sporadic climatic phenomenon that occurs because of changes in the usual atmospheric pressure patterns and in the sea surface temperature in parts of the Pacific Ocean. The results include the substantial reduction of the normal upwelling off the Peruvian coast, failure of the anchovy fishery in the same area, excessive rain in western South America, and droughts in Australia and parts of Indonesia.