Southern oscillation and the El-Nino is a global Oceanography atmospheric phenomenon. Being a characteristic feature of the Pacific Ocean, El Nino and La Nina are temperature fluctuations of surface waters in the tropical Eastern Pacific. The names of these phenomena, borrowed from the Spanish locals and introduced into scientific circulation in 1923 by Gilbert Thomas Walker, means "baby" and "baby", respectively. Their impact on climate of the southern hemisphere it is difficult to overestimate. Southern oscillation (atmospheric component of the phenomenon reflects the monthly or seasonal fluctuations in the air pressure difference between the island of Tahiti and Darwin in Australia.

Named after the Walker circulation is the significant aspect of the Pacific phenomena ENSO (El Nino Southern Oscillation). ENSO is a set of interacting parts of a global system Oceanography, atmospheric climatic fluctuations that occur as a sequence of oceanic and atmospheric circulations. ENSO is the most famous in the world source of interannual variability of weather and climate (from 3 to 8 years). ENSO has a signature in the Pacific, Atlantic and Indian Oceans.

In the Pacific ocean during a significant warm El Nino events, warming, is extended to a large part of the tropical Pacific and is in direct connection with the intensity of the SOI (southern oscillation index). While ENSO events are mainly between the Pacific and Indian Oceans, ENSO events in the Atlantic Ocean behind the first 12-18 months. Most of the countries that are ENSO events are developing, with the economy, which is heavily dependent on the agricultural and fishing sectors. New capabilities for predicting the beginning of ENSO events in the three oceans can have a global socio-economic importance. As ENSO is a global and natural part of the Earth's climate, it is important to know whether a change in the intensity and frequency of the result of global warming. Low-frequency changes have already been discovered. Middecade modulation of ENSO may also exist.

El Nino and La Nina


Ordinary Pacific template. Equatorial winds gather a warm water pool to the West. Cold water rises to the surface along the South American coast.

El Nino and La Nina officially defined as long sea surface temperature anomaly to a value greater than 0.5 °C, crossing the Pacific Ocean in the Central tropical parts. When there is a condition +0.5 degrees C (-0.5 °C) in the period up to five months, it is classified as a condition El Nino (La Nina). If the anomaly is retained for five months or longer, it is classified as an episode of El Nino (La Nina). The latter happens at irregular intervals 2-7 years and usually lasts one or two years.

The first signs of El Nino following:

Increase air pressure above the Indian Ocean, Indonesia and Australia.

The drop in air pressure over Tahiti and the rest of the Central and Eastern parts of the Pacific Ocean.

The trade winds in the southern part of the Pacific Ocean weaken or heading East.

Warm air appears next to Peru, causing rain in the desert.

Warm water is distributed from the Western part of the Pacific Ocean to the East. She brings the rain, calling him in those regions where it is usually dry.

Warm during El Nino, consisting of depleted plankton tropical water and heated its Eastern passage to the Equatorial Current, replaces cold, rich waters of the Humboldt Current, also known as the Peruvian Current, which contains a large population of commercial fish. A large part of years heat lasts only a few weeks or months, after which the weather patterns return to normal and increased fish catch. However, when conditions El Nino last few months, is more extensive oceanic warming, and can be a serious economic impact on the local its fishery for the export market.

Circulation Volcker visible on the surface as East trade winds that move to the West to water and air, warmed by the sun. It also creates oceanic upwelling off the coast of Peru and Ecuador and cold water, rich in plankton, is coming to the surface, increasing the population of fish. The Western Equatorial Pacific Ocean characterized by a warm, wet weather and low atmospheric pressure. Stored water falls as typhoons and storms. As a result, in this place the ocean at 60 cm higher than in the Eastern part.

In the Pacific, La Nina is characterized by unusually cold temperatures in the Eastern Equatorial part compared to El Nino, which, in turn, is characterized by unusually high temperatures in the same region. The activity of Atlantic tropical cyclones in the General case amplified during La Nina. Condition La Nina often occurs after El Nino, especially when the latter is very strong.

The southern oscillation index (SOI)

The southern oscillation index is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

Long-lasting negative values of the SOI often signal about the episodes of the El Nino. These negative values are usually accompanied by sustained warming of the Central and Eastern tropical Pacific, reducing the strength of the Pacific trade winds and the reduction of rainfall in the East and North of Australia.

Positive values of the SOI are associated with strong Pacific trade winds and warming water temperatures in Northern Australia, is well known as an episode of La Nina. Waters of the Central and Eastern tropical Pacific Ocean become colder during this time. All this increases the probability of greater precipitation in the Eastern and Northern Australia than usual.

The extensive impact of El Nino

As the warm waters of the El Nino fuel the storm, it creates an increase in rainfall in East Central and Eastern parts of the Pacific Ocean.

In South America the effect of El Nino is more pronounced than in North America. El Nino is associated with a warm and very humid summer period (December-February) along the coast of Northern Peru and Ecuador, causing severe flooding whenever the event is strong. Effects during February, March, April, may become critical. Southern Brazil and Northern Argentina also experienced wetter than normal conditions, but mainly during spring and early summer. The Central region of Chile receives a soft winter with plenty of rain, and the Peruvian-Bolivian Highlands sometimes experiencing unusual for this region in winter snowfalls. More dry and warm weather is observed in the Amazon Basin, Colombia and Central America.

Direct effects of El Nino lead to decrease moisture in Indonesia, increasing the probability of occurrence of forest fires in the Philippines and in Northern Australia. Also in June and August, the weather is observed in the regions of Australia: Queensland, Victoria, New South Wales and Eastern Tasmania.

West of the Antarctic Peninsula, the land of the Ross sea, Bellingshausen and Amundsen covered lots of snow and ice during El Nino. The last two sea and the Weddell become warmer and are under a higher atmospheric pressure.

In North America, normal winter warmer than usual in the Midwest and Canada, while in the Central and southern California, in the Northwest of Mexico and the South-East of the USA becomes more humid. Pacific Northwest States, in other words, drained during El Nino. Conversely, during La Nina is drained the Average West of the USA. El Nino is also associated with a decrease in the activity of hurricanes in the Atlantic.

Eastern Africa, including Kenya, Tanzania and pool of the White Nile, have long rains from March to may. Drought pursue from December to February the southern and Central regions of Africa, mainly Zambia, Zimbabwe, Mozambique and Botswana.

A Warm Pool Of The Western Hemisphere

The study of climatic data showed that approximately half of the summer periods after El Nino observed an unusual warming of the Warm Pool of the Western Hemisphere. It affects weather in the region, and seem to have a connection with the North Atlantic Oscillation.

Atlantic effect

The effect is similar to El Nino, sometimes observed in the Atlantic Ocean, where the water along the Equatorial African coast is becoming warmer, and the coast of Brazil - colder. This can be attributed to the circulations Volcker over South America.

Non-climatic effects

Along the East coast of South America El Nino reduce the upwelling of cold, rich waters, which supports large populations of fish, which, in turn, support an abundance of marine birds, litter which supports the fertilizer industry.

The local fishing industry along the coastline may suffer from the lack of fish during a prolonged El Nino events. Most of the world's fisheries collapse from overfishing, which occurred in 1972, during El Nino, has reduced the population of Peruvian anchovy. During the events of 1982-83, the population of southern horse mackerel and anchovy decreased. Although increased the number of shells in warm water, but heck went in deep, cold water, and shrimp and sardines gone to the South. But the catch some fish species has been increased, such as the common mackerel increased its population during the warm events.

Change the location and types of fish because of changes in conditions ensured problems for the fishing industry. Peruvian sardines left for El Nino to the Chilean coast. Other conditions still only led to further complications, such as the government of Chile in 1991 created restrictions on fishing.

Postulated that El Nino has caused the disappearance of the Indian tribe of Machico and other tribes of Peruvian pre-Columbian culture.

Causes of El Nino

Mechanisms that can cause the events of the El Nino still investigated. It is hard to find templates that can show cause or allow to make predictions.

Main theories:

Bjerknes in 1969 suggested that the abnormal warming of the Eastern Pacific can be weakened the East-West difference of temperatures, causing a weakening in circulation Volcker and the trade winds that move the warm water to the West. The result is an increase of warm water to the East.

Verdi in 1975 suggested that the trade winds could create a Western bulge of warm water, and any weakening of the winds could allow warm water to move to the East. Nevertheless, no bumps was not observed on the eve of the events of 1982-83 g.

Rechargeable Oscillator: Several mechanisms have been proposed, when warm areas are created in the Equatorial region, they are dispersed in higher latitudes with El Nino events. The cooled area then recharged warm for several years before the next event occurs.

Western Pacific Oscillator: In the Western part of the Pacific Ocean several weather conditions could cause the East wind anomalies. For example, a cyclone in the North and anticyclone in the South lead to an East wind between them. These templates can interact with the West over across the Pacific Ocean and to create a tendency of further movement to the East. The weakening Western groups at that time may be the final trigger.

Equatorial part of the Pacific Ocean may result in conditions close to El Nino with a few random variations of behavior. Weather templates from the outside or volcanic activity can become such factors.

Oscillation Madden-Julian (MJO - Madden-Julian Oscillation) is the most important source of variability that can contribute to a more dramatic evolution, leading to conditions of El Nino, through fluctuations winds blowing at low levels, and precipitation over the Western and Central parts of the Pacific Ocean. The East-the direction of propagation of oceanic Kelvin waves can be caused by MJO activity.

History theory

The first mention of the term "El Nino" refers to 1892, when the captain Camilo Carrillo said at the Congress of the Geographical Society in Lima that the Peruvian sailors called warm North for "El Nino", as it is most noticeable in the area of Christmas. However, even then the phenomenon was interesting only because of its biological impact on the efficiency of the fertilizer industry.

Normal conditions along the Western Peruvian coast is cold South for (Peruvian current) with the upwelling water; upwelling plankton leads to active oceanic productivity; cold currents lead to very dry climate on earth. Similar conditions exist everywhere (California current, Bengali). So replacing it with a warm Northern during leads to a decrease of biological activity in the ocean and downpours, leading to floods, --- on earth. The connection with the flooding was reported in 1895 by Peseta and Eguiguren.

By the end of the nineteenth century, a growing interest to the predictions of climate anomalies (for food production) in India and Australia. Charles Todd in 1893 suggested that droughts in India and Australia happen at the same time. Norman Lockyer pointed to the same thing in 1904.. In 1924 Gilbert Walker first introduced the term "southern Oscillation".

A large part of the twentieth century, El Nino was considered a local phenomenon.

Large El Nino in 1982-83, has led to skyrocketing interest of the scientific community to this phenomenon.

The history of the phenomenon

Conditions ENSO happen every 2-7 years at least the last 300 years, but most of them were weak.

Large ENSO events happened in 1790-93, 1828, 1876-78 it was, 1891, 1925-26, 1982-83 and 1997-98.

Recent developments El Nino occurred in 1986-1987, between 1991 and 1992, 1993, 1994, 1997 and 1998 and 2002-2003.

El Nino in 1997-1998, in particular, was strong and drew to the phenomenon of international attention, while in the period 1990-1994, was unusual that El Nino was manifested very often (but mostly poorly).

El Nino in the history of civilization

The mysterious disappearance of the Mayan civilization in Central America could be caused by climate change. To such conclusion the group of researchers from the German national center of Sciences about the earth, writes British newspaper the Times.

Scientists are trying to establish why at the turn of the IX and X centuries ad on opposite ends of the earth practically simultaneously stopped the existence of two major civilization of that time. We are talking about the Mayans and the fall of the Chinese Tang dynasty, followed was followed by a period of internecine strife.

Both civilizations were in the monsoon regions, moisturizing which depends on seasonal rainfall. However, at a specified time, to all appearances, the rainy season was not able to provide the amount of water sufficient for the development of agriculture.

The onset of the drought and the subsequent famine led to the decline of these civilizations, according to the researchers. They link climate change with natural phenomenon "El Nino", which implies temperature variations of the surface waters of the Eastern Pacific ocean in the tropical latitudes. This leads to large-scale circulation of the atmosphere, which causes drought in traditionally humid regions and flood - arid.

Scientists came to these conclusions after examining the nature of sediments in China and Mesoamerica belonging to the specified period. The last Emperor of the Tang dynasty died in 907 A.D. and the last known Mayan calendar dates back to the year 903.