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El Niño

El Niño

El Niño (pronounced el-NEEN-yo) is the name given to a change in the flow of water currents in the Pacific Ocean near the equator. El NiñoSpanish for "the child" because it often occurs around Christmasrepeats every three to five years. Although El Niño takes place in a small portion of the Pacific, it can affect the weather in large parts of Asia, Africa, Indonesia, and North and South America. Scientists have only recently become aware of the far-reaching effects of this phenomenon.

What is El Niño?

The rotation of Earth and the exchange of heat between the atmosphere and the oceans create wind and ocean currents. At the equator, trade winds blow westward over the Pacific, pushing surface water away from South America toward Australia and Indonesia. These strong trade winds, laden with moisture, bring life-giving monsoons to eastern Asia. As warm surface water moves west, cold, nutrient-rich water from deep in the ocean rises to replace it. Along the coast of Peru, this pattern creates a rich fishing ground.

Every three to five years, however, the trade winds slacken, or even reverse direction, allowing winds from the west to push warm surface water eastward toward South America. This change is called the Southern Oscillation (oscillation means swinging or swaying), and it is brought about by a shifting pattern of air pressure between the eastern and western ends of the Pacific Ocean. The warm water, lacking nutrients, kills marine life and upsets the ocean food chain. The warm, moist air that slams into the South American coast brings heavy rains and storms. At the same time, countries at the western end of the PacificAustralia, Indonesia, and the Philippineshave unusually dry weather that sometimes causes drought and wildfires.

Another type of unusual weather that often follows an El Niño is called La Niña, which is Spanish for "the girl." El Niño and La Niña are opposite phases in the Southern Oscillation, or the back and forth cycle in the Pacific Ocean. Whereas El Niño is a warming trend, raising the water temperature as much as 10°F (5.6°C) above normal, La Niña is a cooling of the waters in the tropical Pacific, dropping the temperature of the water as much as 15°F (8°C) below normal.

Global effects of El Niño

Meteorologists believe the altered pattern of winds and ocean temperatures during an El Niño changes the high level winds, called the jet streams, that steer storms over North and South America. El Niños have been linked with milder winters in western Canada and the northern United States, as more severe storms are steered northward to Alaska. The jet streams altered by El Niño can also contribute to storm development over the Gulf of Mexico, which brings heavy rains to the southeastern United States. Similar rains may soak countries of South America, such as Peru and Ecuador, while droughts may affect Bolivia and parts of Central America.

El Niño also appears to affect monsoons, which are annual shifts in the prevailing winds that bring on rainy seasons. The rains of the monsoons are critical for agriculture in India, Southeast Asia, and portions of Africa. When the monsoons fail, millions of people are at risk of starvation. It appears that wind patterns associated with El Niños carry away moist air that would produce monsoon rains.

La Niña can bring cold winters to the Pacific Northwest, northern Plains states, Great Lakes states, and Canada, and warmer-than-usual winters to the southeastern states. In addition, it can bring drier-than-usual conditions to California, the Southwest, the Gulf of Mexico, and Florida, as well as drought for the South America coast and flooding for the western Pacific region.

Not all El Niños and La Niñas have equally strong effects on global climate; every El Niño and La Niña event is different, both in strength and length.

Words to Know

Jet streams: High velocity winds that blow at upper levels in the atmosphere and help to steer major storm systems.

Monsoon: An annual shift in the direction of the prevailing wind that brings on a rainy season and affects large parts of Asia and Africa.

Worst El Niños of the century

According the National Oceanic and Atmospheric Administration (NOAA), 23 El Niños and 15 La Niñas took place in the twentieth century. Out of those, the four strongest occurred after 1980. Scientists are unsure if this is an indication that human activity is adversely affecting the weather or if it is simply a meaningless random clustering.

The El Niño event of 198283 was one of the most destructive of the twentieth century. It caused catastrophic weather patterns around the world. Devastating droughts hit Africa and Australia while torrential rains plagued Peru and Ecuador. In the United States, record snow fell in parts of the Rocky Mountains; drenching rains flooded Florida and the Gulf of Mexico's coast; and intense storms brought about floods and

mud slides in southern California. French Polynesia in the South Pacific was struck by its first typhoon in 75 years. It is estimated this particular El Niño killed 2,000 people and caused $13 billion worth of property damage.

Less than 15 years later, another destructive El Niño pattern developed. This one, however, was much more devastating than the 1982-83 event. In fact, it was the worst in recorded history. Beginning in late 1997, heavy rain and flooding overwhelmed the Pacific coast of South America, California, and areas along the Gulf Coast. Eastern Europe and East Africa were affected, as well. Australia, Central America, Mexico, northeastern Brazil, Southeast Asia, and the southern United States were all hit hard by drought and wildfires. In the United States, mudslides and flash floods covered communities from California to Mississippi. A series of hurricanes swept through the eastern and western Pacific. Southeast Asia suffered through its worst drought in fifty years. As a result, the jungle fires used to clear lands for farming raged out of control, producing smoke that created the worst pollution crisis in world history. At least 1,000 people died from breathing problems. By the time this El Niño period ended some eight months later in 1998, the unusual weather patterns it had created had killed approximately 2,100 people and caused at least $33 billion in property damage.

[See also Atmospheric pressure; Ocean; Weather; Wind ]

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El Niño–Southern Oscillation

El Niño–Southern Oscillation (ENSO) (ĕl nēn´yō), large-scale climatic fluctuation of the tropical Pacific Ocean. The El Niño [Span.,=the child] itself is a warm surface current that usually appears around Christmas in the Pacific off Ecuador and Peru and disappears by the end of March, but every two to seven years it persists for up to 18 months or more as part of an ENSO, but the term El Niño is often used more broadly as a synonym for ENSO. An ENSO results from the dynamic and thermodynamic interactions among the atmosphere, oceans, and land surfaces, but exactly what initiates an ENSO is unclear. It seems certain that pressure changes and wind currents play a vital role. Some researchers have implicated the greenhouse effect (see global warming), while others have attributed it to activity occurring on the ocean floor, such as underwater earthquakes.

In a typical ENSO, the strong easterly winds of the equatorial Pacific weaken, which allows warm eastward-flowing subsurface waters to rise, increasing surface temperatures 1–2°C (2–3.5°F), and sometimes as much as 4–6°C (7–11°F), in the central and E Pacific. Along the W coast of South America, El Niño's warm waters persist and deepen, and cold, upwelling, nutrient-rich waters fail to reach surface waters; the resulting warm, nutrient-poor waters devastate coastal fisheries. Heavy rain falls along the South American coast, and heavy rainfall also moves from the western to central Pacific, causing drier than normal conditions in Indonesia and nearby areas. An ENSO also affects the climate of the northern latitudes, particularly North America, which experiences warmer temperatures along the Pacific coast, increased rainfall in the Gulf states, and weaker Atlantic hurricanes. A recent study suggests that some of these effects depend on whether the warming in the Pacific is stronger in its eastern or central waters.

Severe ENSO events can be economically disruptive worldwide. Of the 29 ENSOs that occurred between 1700 and 1999, the 1982–83 El Niño was the strongest and most devastating. It caused droughts in Africa, Australia, India, Indonesia, and the Philippines, flooding in Peru and Ecuador, and devastating coastal storms in California. The ENSO was blamed for 1,300–2,000 deaths and more than $13 billion in damage to property and livelihoods.

The effects of El Niño were documented in Peru as early as the Spanish conquest in 1525. By the end of the 19th cent. the phenomenon was being studied by Peruvian oceanographers, although the effects were thought to be limited to the W coast of South America. It was not until the systematic studies of the International Geophysical Year of 1957–58 that the extent of the meteorological impact of El Niño was recognized.

La Niña, a similar climatic fluctuation, involves the abnormal cooling of the waters off Ecuador and Peru. Penetrating westward, the cold current is believed to affect weather in areas in the middle latitudes in the western Pacific Ocean and to cause extremely hot summers in Japan. A La Niña in 2011–12 led to a prolonged dry spell in the South Pacific that created serious water shortages in several island nations; it also contributed to increased rainfall and significant flooding in E Australia.

See M. H. Glantz, Currents of Change: El Niño's Impact on Climate and Society (1996); B. Fagan, Floods, Famines, and Emperors: El Niño and the Fate of Civilizations (1999).

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El Niño

El Niño (Sp. (Christ) ‘child’) Warm surface current that flows in the equatorial Pacific Ocean towards the South American coast. It occurs around Christmas time. An easing or reversing of the trade winds over the s Pacific Ocean, causes warm surface waters that have ‘piled-up’ in the w Pacific to flow back and warm the coastal waters of South America by 2 to 3°C. It has a dramatic effect on climate patterns in Australia and Southeast Asia, and may affect rainfall as far away as Africa. In normal years, trade winds blow e to w along the Equator, dragging warm surface waters into a pool off n Australia and monsoon rains to Indonesia. In the w Pacific, the Humboldt Current pushes the surface waters away from the coast of Peru, bringing cold water to the surface. This upwelled, nutrient-rich water stimulates phytoplankton production and swells the population of anchovies, a mainstay of the Peruvian fishing industry. In an El Niño year, the upwelling ceases and the biological productivity of the area collapses. In 1982–83, the anchovy catch fell by 600%. In addition, mean sea-level along the coast of Latin America may increase by as much as 50cm (20in), causing widespread flooding. Some scientists believe that the frequency (presently every 2–10 years) and effects of El Niño may be increasing.

http://www.elnino.noaa.gov

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El Niño

El Niño A weakening of the Equatorial Current, allowing warm water to accumulate off the S. American Pacific coast; it is associated with a change in the atmospheric circulation known as a southern oscillation, the two together comprising an El Niño—Southern Oscillation (ENSO) event. Its climatic effects are felt throughout the Pacific region. (A similar phenomenon may occur in the Atlantic.) About once every 7 years, during the Christmas season (midsummer in the southern hemisphere), prevailing trade winds weaken, the Equatorial counter-current strengthens, and warm surface waters that are normally driven westwards by the wind to form a deep layer off Indonesia flow eastwards to overlie the cold waters of the northward-flowing Peru current. In exceptional years (e.g. 1953, 1972–3, 1982–3, and 1997–8) the severity with which the upwelling of nutrient-rich cold water is inhibited causes the death of a large proportion of the plankton population and a consequent decline in the numbers of fish.

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El Niño

El Niño A warm-water current which periodically flows southwards along the coast of Ecuador. It is associated with the Southern Oscillation (these effects are collectively known as an El Niño—Southern Oscillation, or ENSO, event) and with climatic effects throughout the Pacific region. A similar phenomenon may also occur in the Atlantic. Approximately once every seven years, during the Christmas season (the name refers to the Christ child), prevailing trade winds weaken and the Equatorial countercurrent strengthens. Warm surface waters, normally driven westward by the wind to form a deep layer off Indonesia, flow eastwards to overlie the cold waters of the Peru current. In exceptional years, e.g. 1891, 1925, 1953, 1972–3, 1982–3, 1986–7, 1994–5, and 1997–8 the extent to which the upwelling of the nutrient-rich cold waters is inhibited causes the death of a large proportion of the plankton population and a decline in the numbers of surface fish.

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El Niño

El Niño A weakening of the Equatorial Current, allowing warm water to accumulate off the S. American Pacific coast; it is associated with the southern oscillation (these two effects are known collectively as an El Niño–Southern Oscillation or ENSO event) and with climatic effects throughout the Pacific region. A similar phenomenon may also occur in the Atlantic. Approximately once every seven years, during the Christmas season (the name refers to the Christ child), prevailing trade winds weaken and the Equatorial Countercurrent strengthens. Warm surface waters, normally driven westward by the wind to form a deep layer off Indonesia, flow eastwards to overlie the cold waters of the Peru Current. In exceptional years (e.g. 1953, 1972–3, 1982–3, and 1997–8) the extent to which the upwelling of the nutrient-rich cold waters is inhibited causes the death of a large proportion of the plankton population and a consequent decline in the numbers of surface fish.

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Niño, El

Ni·ño, El • see El Niño.

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El Niño

El Niño •bagnio •dal segno, jalapeño •cursillo, Trujillo •caudillo • El Niño • yo-yo

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