El Niño
What is El Niño?
El Niño occurs when the trade winds weaken and cause the “tongue” of cold water near the coast of South America to shrink and become warmer water (picture). This warmer water lacks the nutrients that the cold water brings in. This causes problems for the fishermen off the coasts of Ecuador and Peru. El Niño causes unusually high atmospheric pressures in the western tropical Pacific Ocean and Indian Ocean and unusually low pressures in the southeastern tropical Pacific (picture). Not only do these changes in pressure affect the weather of the areas in which the change occurs, but it also affects the rest of the world (see map).
El Niño also affects the Polar Jet Stream. Changes in the jet stream often cause many changes in temperature and precipitation globally. Certain areas receive more precipitation or less precipitation, see map inset for global affects.
El Niño's are not quite predictable. They occur irregularly between 2-7 years with an average of 3-4 years, but have been known to occur 4 years in a row (in the 1990s). When El Niño's occur they are sometimes followed by a La Niña (but not always). By following up a year of extra warm water with a year of extra cold water, the balancing act is being continued by forces on Earth.