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Encyclopedia > El Niño Southern Oscillation

This article is about Pacific ocean temperature anomalies.


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Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997

El Niño and La Niña (Spanish for "boy" and "girl", often written in English as El Nino and La Nina) are major temperature fluctuations in the tropical Pacific Ocean. They are Pacific signatures of the global ENSO phenomenon (El Niño-Southern Oscillation). Their effect on climate in the southern hemisphere is profound. Their role in global warming or cooling is an area of active research, with no clear consensus yet. Sergio García (born January 9, 1980 in Castellon, Spain), nicknamed El Niño, is a Spanish golfer who plays both on the United States PGA TOUR and the PGA European Tour. ... Chart of abnormal ocean surface temperatures [ºC] observed in December 1997 during the last strong El Niño (source: National Centers for Environmental Protection, US). ... Chart of abnormal ocean surface temperatures [ºC] observed in December 1997 during the last strong El Niño (source: National Centers for Environmental Protection, US). ... Global mean surface temperatures 1856-2004 Global warming is a term used to describe an increase over time of the average temperature of Earths atmosphere and oceans. ...

Contents

El Niño

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El Niño Conditions. Warm water pool approaches South American coast. Absence of cold upwelling increases warming. (NOAA / PMEL / TAO)
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Normal Pacific pattern. Equatorial winds gather warm water pool toward west. Cold water upwells along South American coast.
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La Niña Conditions. Warm water is further west than usual.

El Niño is officially defined as sea surface temperature anomalies greater than +0.5°C across the central tropical Pacific Ocean. The name comes from the Spanish name for the Christ child; the name was given to the phenomenon by fishermen working off the coast of Peru and Ecuador, who noticed it often occurs around Christmas. It occurs at irregular intervals of 2-7 years and usually lasts one or two years. The National Oceanic and Atmospheric Administration (NOAA) is an agency of the United States Department of Commerce. ... The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history, and in particular since 1850. ... This article is about the international language known as Spanish. ... The Child Jesus is a religious archetypical symbol of the infant Jesus, that recurs throughout history starting from the 3rd and 4th century with religious figurines and icons of the infant Jesus, usually with His mother, the Virgin Mary, and His father Joseph. ... Joseph and Mary with baby Jesus, at the first Christmas Christmas (literally, the Mass of Christ) is a holiday in the Christian calendar, usually observed on December 25, which celebrates the birth of Jesus. ...


El Niño's warm current of nutrient-poor tropical water replaces the cold, nutrient-rich surface water of the Humboldt Current which fish prefer. In most years the warming lasts only a few weeks or a month, after which the weather patterns return to normal and fishing improves. However, when El Niño conditions last for many months, more extensive ocean warming occurs and its economic impact to local fishing can be serious. The Humboldt Current (or Peru Current) is a cold ocean current that flows northward off the west coast of South America. ...


Recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, and 2002-2003. A new El Niño has been in effect since September 2004. The El Niño of 1997-1998 was particularly strong, while the period from 1990-1994 was unusual in that El Niños rarely occur in such rapid succession. They were generally weak, however. 1986 is a common year starting on Wednesday of the Gregorian calendar. ... 1987 is a common year starting on Thursday of the Gregorian calendar. ... 1991 is a common year starting on Tuesday of the Gregorian calendar. ... 1992 is a leap year starting on Wednesday of the Gregorian calendar. ... 1993 is a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003) Events Media:January January 1 - Czechoslovakia divides. ... 1994 was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ... 1997 is a common year starting on Wednesday of the Gregorian calendar, and was designated the International Year of the Reef. ... 1998 is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ... 2002 is a common year starting on Tuesday of the Gregorian calendar. ... 2003 is a common year starting on Wednesday of the Gregorian calendar, and also: The International Year of Freshwater The European Disability Year Events January January 1 - Luíz Inácio Lula Da Silva becomes the 37th President of Brazil. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ...


El Niño's effects

El Niño's weather effects depend on the location, time of year, and the location and strength of the particular episode.


Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean.


In South America, the effects of El Niño are rather direct and stronger than in North America. An El Niño is associated with warm and very wet summers (December-February) along the coasts of northern Peru and Ecuador causing major flooding whenever the event is strong or extreme. The effects during the months of February, March and April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions but mainly during the spring and early summer. Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts the Amazon River Basin, Colombia and Central America. December is the twelfth and last month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. ... February is the second month of the year in the Gregorian Calendar. ... The Altiplano (Spanish for high plain), where the Andes are at their widest, is the most extensive area of high plateau on earth outside of Tibet. ... Length 6,296 km Elevation of the source 5,597 m Average discharge 219,000 m³/ s Area watershed 6,915,000 km² Origin Nevado Mismi Mouth Atlantic Ocean Basin countries Brazil (62. ... Central America is the region of North America located between the southern border of Mexico and the northwest border of Colombia, in South America. ...


Direct effects of El Niño resulting in drier conditions occur in Indonesia, the Philippines, and northern Australia. Drier than normal conditions are also generally observed along the eastern half of Australia during June-August. June is the sixth month of the year in the Gregorian Calendar and one of four with the length of 30 days. ... August is the eighth month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. ...


In North America, typically, winters are warmer than normal in the upper midwest states and Canada, while central and southern California, northwest Mexico and the southeastern U.S., are wetter than normal. Summer is wetter in the intermountain regions of the U.S. The Pacific Northwest states, on the other hand, tend to be drier during an El Niño. During a La Niña, by contrast, the midwestern U.S. tends to be drier than normal. World map showing location of North America A satellite composite image of North America North America is the third largest continent in area and in population after Eurasia and Africa. ... State nickname: The Golden State Other U.S. States Capital Sacramento Largest city Los Angeles Governor Arnold Schwarzenegger Official languages English Area 410,000 km² (3rd)  - Land 404,298 km²  - Water 20,047 km² (4. ...


Finally, Africa experiences December-February wetter than normal conditions in the Sahel region, which is equatorial Africa) along the southern edge of the Sahara desert. There also are drier than normal conditions in south-central Africa, mainly in Zambia, Zimbabwe, Mozambique and Botswana. December is the twelfth and last month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. ... February is the second month of the year in the Gregorian Calendar. ... See also Sahel, Tunisia, a region of eastern Tunisia. ... World map showing location of Africa A satellite composite image of Africa Africa is the worlds second-largest continent in both area and population, after Asia. ...


Non-climate effects

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East Pacific fishing

Along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, that sustain abundant sea birds, whose droppings support the fertilizer industry. South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Upwelling is an oceanographic phenomenon that occurs when strong, usually seasonal, winds push water away from the coast, bringing cold, nutrient-rich deep waters up to the surface. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world. ... Fertilizers are chemicals given to plants with the intention of promoting growth; they are usually applied either via the soil or by foliar spraying. ...


The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño anchoveta reduction. During the 1982-83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward so some catches decreased while others increased. Horse mackerel have increased in the region during warm events. 1972 was a leap year that started on a Saturday. ... 1982 is a number and represents a common year starting on Friday of the Gregorian calendar Events January-February January 6 - William Bonin is convicted of being the freeway killer. January 8 - AT&T agrees to divest itself of twenty-two subdivisions January 11 - Mark Thatcher, son of the British... 1983 is an integer and composite number that represents a common year starting on Saturday of the Gregorian calendar. ... A mackerel is any one of a number of different species of fish, mostly in the family Scombridae. ... Genera Pecten Pedum Amusium Chlamys Decatopecten Argopecten Flexopecten Lissopecten Hyalopecten Nodipecten Patinopecten Semipallium Mimachlamys Equichlamys Mesopeplum Veprichlamys Notochlamys Delectopecten Cryptopecten Anguipecten Haumea Mirapecten Volachlamys Juxtamusium Annachlamys Gloripallium Excellichlamys Bractechlamys Minnivola Coralichlamys Serratovola Somalipecten Pseudohinnites Glorichlamys Scallops are the family Pectinidae of bivalve molluscs. ... The term hake refers to various fish in the families Gadidae (subfamily Phycinae) and Merlucciidae (both subfamilies Merlucciinae and Steindachneriinae). ... Suborders Not necessary complete list: Aristeidae Penaeidae Sergestidae Sicyoniidae Solenoceridae Nematocarcinidae Atyidae Pasiphaeoidae Rhynocinetidae Campylonotidae Palaemonidae Alpheidae Ogyrididae Hippolytidae Proussidae Pandalidae Crangonidae True shrimp are small, swimming, decapod crustaceans usually classified in the suborder Natantia, found widely around the world in both fresh and salt water. ... Sardines or pilchards are a group of several types of small oily fish related to herrings, family Clupeidae. ... A mackerel is any one of a number of different species of fish, mostly in the family Scombridae. ...

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Fishing in warm water for cold-loving fish.

Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for artisanal fishermen and industrial fleets. Sardines or pilchards are a group of several types of small oily fish related to herrings, family Clupeidae. ... 1991 is a common year starting on Tuesday of the Gregorian calendar. ...


The ENSO variability may contribute to the great success of small fast-growing species along the Peruvian coast, as periods of low population removes predators in the area. Similar effects benefit migratory birds which travel each spring from predator-rich tropical areas to distant winter-stressed nesting areas. Migration occurs when living things move from one biome to another. ...


Causes of El Niño

The mechanisms which might cause an El Niño event are still being investigated. It is difficult to find patterns which may show causes or allow forecasts.


Major theories:

  • Bjerknes in 1969 suggested that an anomalously warm spot in the eastern Pacific can weaken the east-west temperature difference, causing weakening in the Walker and trade wind flows which push warm water to the west. The result is increasingly warm water toward the east.
  • Wyrtki in 1975 proposed that increased trade winds could build up the western bulge of warm water, and any sudden weakening in the winds would allow that warm water to surge eastward. However, there was no such buildup preceding the 1982-83 event.
  • Recharge oscillator: Several mechanisms have been proposed where warmth builds up in the equatorial area, then is dispersed to higher latitudes by an El Niño event. The cooler area then has to "recharge" warmth for several years before another event can take place.
  • Western Pacific oscillator: In the western Pacific, several weather conditions can cause easterly wind anomalies. For example, a cyclone to the north and anticyclone to the south force easterly winds between. Such patterns may counteract the westward flows across the Pacific and create a tendency toward continuing the eastward motion. A weakening in the westward currents at such a time may be the final trigger.
  • Equatorial Pacific Ocean may tend to be near El Niño conditions, with several random variations affecting behavior. Weather patterns from outside the area or volcanic events may be some such factors.
  • The Madden-Julian Oscillation (MJO) is an important source of variability that can contribute to a more rapid evolution toward El Nino through related fluctuations in low-level winds and precipitation over the western and central equatorial Pacific. Eastward-propagating oceanic Kelvin waves can be produced by MJO activity.

1969 was a common year starting on Wednesday (the link is to a full 1969 calendar). ... 1975 was a common year starting on Wednesday (the link is to a full 1975 calendar). ... 1982 is a number and represents a common year starting on Friday of the Gregorian calendar Events January-February January 6 - William Bonin is convicted of being the freeway killer. January 8 - AT&T agrees to divest itself of twenty-two subdivisions January 11 - Mark Thatcher, son of the British... 1983 is an integer and composite number that represents a common year starting on Saturday of the Gregorian calendar. ... A Kelvin wave is a wave in the ocean or atmosphere that balances the Earths Coriolis force against a topographic boundary such as a coastline. ...

La Niña

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A schematic diagram of the quasi-equilibrium and La Niña phase of the southern oscillation. The Walker circulation is seen at the surface is seen as easterly trade winds which move water and air warmed by the sun towards the west. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms. The ocean is some 60 cm higher in the eastern Pacific as the result of this motion. The water and air are returned to the east. Both are now much cooler, and the air is much drier. An El Niño episode is characterised by a breakdown of this water and air cycle, resulting in relatively warm water and moist air in the eastern Pacific.

In the Pacific, La Niña is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the same area. The La Niña condition often follows the El Niño, especially when the latter is strong. Strong La Niñas occurred in 1988-1989 and 1998-2001, and weakly in 1995-1996. 1988 is a leap year starting on a Friday of the Gregorian calendar. ... 1989 is a common year starting on Sunday of the Gregorian calendar. ... 1998 is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ... 2001 is a common year starting on Monday of the Gregorian calendar. ... 1995 was a common year starting on Sunday of the Gregorian calendar. ... 1996 is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ...


SOI

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SOI index, 1876-2004

The Southern Oscillation (SO) is a global-scale seesaw in atmospheric pressure between Indonesia/North Australia, and the southeast Pacific. Its measure is through the Southern Oscillation Index (SOI). The SOI is the normalised difference in surface pressure between Tahiti and Darwin.


ENSO

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Regional impacts of warm ENSO episodes (El Niño).
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Regional impacts of cold ENSO episodes. (La Niña)

ENSO (El Niño, Southern Oscillation) is a set of interacting parts of a single global system of climate fluctuations that come about as a consequence of atmospheric circulation. ENSO is the most prominent known source of interannual variability in weather and climate around the world (~3 to 8 years), though not all areas are affected. Global ENSO has signatures in the Pacific, Atlantic and Indian Oceans. In the Pacific, during major warm events El Niño warming extends over much of the tropical Pacific and becomes clearly linked to the SOI intensity. While ENSO events are basically in phase between the Pacific and Indian Oceans, ENSO events in the Atlantic Ocean lag those in the Pacific by 12-to-18 months. Many of the countries most affected by ENSO events are developing countries within main continents (South America, Africa...), with economies that are largely dependent upon their agricultural and fishery sectors as a major source of food supply, employment, and foreign exchange. New capabilities to predict the onset of ENSO events in the three oceans can have global socio-economical impacts. While ENSO is a global and natural part of the Earth's climate, whether its intensity or frequency may change as a result of global warming is an important concern. Low-frequency variability has been evidenced. Interdecadal modulation of ENSO might exist. Atmospheric circulation is the large-scale movement of air, and the means (together with the ocean circulation, which is smaller [1]) by which heat is distributed on the surface of the Earth. ...


Western Hemisphere Warm Pool

Study of climate records has found that about half of the summers after an El Niño have unusual warming in the Western Hemisphere Warm Pool (WHWP). This affects weather in the area and seems to be related to the North Atlantic Oscillation. The North Atlantic oscillation (NAO) is a complex climatic phenomenon in the North Atlantic Ocean (especially associated with fluctuations of climate between Iceland and the Azores). ...


Atlantic effect

An effect similar to El Niño sometimes takes place in the Atlantic Ocean, where water along equatorial Africa's Gulf of Guinea becomes warmer and eastern Brazil becomes cooler and drier. This may be related to El Niño Walker circulation changes over South America. The gigantic Gulf of Guinea is the part of the Atlantic southwest of Africa. ...


Related images

External links

  • The El Nino Theme Page (http://www.pmel.noaa.gov/tao/elnino/) Explains El Nino and La Nina, provides realtime data, forecasts, animations, FAQ, impacts and more.
  • NOAA El Nino Page (http://www.elnino.noaa.gov)
  • The El Nino Story (http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html)
  • ENSO events 1951 - present (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml)
  • NOAA announces 2004 El Niño (http://www.noaanews.noaa.gov/stories2004/s2317.htm)
  • The Climate of Peru (http://www.limaperunet.com/climate/climateall.html)
  • Southern Oscillation Index (SOI) (http://www.bom.gov.au/lam/glossary/soid.htm)

 
 

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