What is El Niño? El Niño has been replaced by La Niña: what does it mean?

The Southern Oscillation and El Niño are a global ocean-atmospheric phenomenon. Being characteristic feature Pacific Ocean, El Niño and La Niña are temperature fluctuations surface waters in the tropics of the eastern Pacific Ocean. The names for these phenomena, borrowed from the native Spanish and first coined in 1923 by Gilbert Thomas Volker, mean "baby" and "little one," respectively. Their influence on the climate of the southern hemisphere is difficult to overestimate. The Southern Oscillation (the atmospheric component of the phenomenon) reflects monthly or seasonal fluctuations in the difference in air pressure between the island of Tahiti and the city of Darwin in Australia.

The circulation named after Volcker is a significant aspect of the Pacific phenomenon ENSO (El Nino Southern Oscillation). ENSO is many interacting parts of one global system of ocean-atmospheric climate fluctuations that occur as a sequence of oceanic and atmospheric circulations. ENSO is the world's best known source of interannual weather and climate variability (3 to 8 years). ENSO has signatures in the Pacific, Atlantic and Indian Oceans.

In the Pacific, during significant warm events, El Niño warms up and expands across much of the Pacific tropics and becomes directly correlated with SOI (Southern Oscillation Index) intensity. While ENSO events occur primarily between the Pacific and Indian Oceans, ENSO events in the Atlantic Ocean lag behind the former by 12 to 18 months. Most of the countries that experience ENSO events are developing ones, with economies that are heavily dependent on the agricultural and fishing sectors. New capabilities to predict the onset of ENSO events in three oceans could have global socioeconomic implications. Since ENSO is a global and natural part of the Earth's climate, it is important to know whether changes in intensity and frequency could be a result of global warming. Low frequency changes have already been detected. Interdecadal ENSO modulations may also exist.

El Niño and La Niña

Common Pacific pattern. Equatorial winds collect a warm pool of water to the west. Cold waters rise to the surface along the South American coast.

AND La Niña officially defined as long-lasting marine surface temperature anomalies greater than 0.5 °C crossing the central tropical Pacific Ocean. When a condition of +0.5 °C (-0.5 °C) is observed for a period of up to five months, it is classified as an El Niño (La Niña) condition. If the anomaly persists for five months or longer, it is classified as an El Niño (La Niña) episode. The latter occurs at irregular intervals of 2-7 years and usually lasts one or two years.
Increase in air pressure above Indian Ocean, Indonesia and Australia.
The drop in air pressure over Tahiti and the rest of the central and eastern parts Pacific Ocean.
Trade winds in the South Pacific are weakening or heading east.
Warm air appears near Peru, causing rain in the deserts.
Warm water spreads from the western part of the Pacific Ocean to the eastern. It brings rain with it, causing it to occur in areas that are usually dry.

Warm El Niño current , consisting of plankton-poor tropical water and heated by its eastern outlet in the Equatorial Current, replaces the cold, plankton-rich waters of the Humboldt Current, also known as the Peruvian Current, which contains large populations of game fish. Most years, the warming lasts only a few weeks or months, after which weather patterns return to normal and fish catches increase. However, when El Niño conditions last for several months, more extensive ocean warming occurs and its economic impact on local fisheries for the external market can be severe.

The Volcker circulation is visible on the surface as easterly trade winds, which move water and air heated by the sun westward. It also creates oceanic upwelling off the coasts of Peru and Ecuador, bringing cold plankton-rich waters to the surface, increasing fish populations. The western equatorial Pacific Ocean is characterized by warm, humid weather and low atmospheric pressure. The accumulated moisture falls in the form of typhoons and storms. As a result, in this place the ocean is 60 cm higher than in its eastern part.

In the Pacific Ocean, La Niña is characterized by unusual cold temperature in the eastern equatorial part compared to El Niño, which, in turn, is characterized by unusual high temperature in the same region. Atlantic tropical cyclone activity generally increases during La Niña. A La Niña condition often occurs after an El Niño, especially when the latter is very strong.

Southern Oscillation Index (SOI)

The Southern Oscillation Index is calculated from monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

Long-term negative values SOIs often signal El Niño episodes. These negative values typically accompany continued warming of the central and eastern tropical Pacific, decreased strength of the Pacific trade winds, and decreased rainfall in eastern and northern Australia.

Positive SOI values are associated with strong Pacific trade winds and warming water temperatures in northern Australia, well known as a La Niña episode. The waters of the central and eastern tropical Pacific Ocean become colder during this time. Together this increases the likelihood of more rainfall than normal in eastern and northern Australia.

El Niño influence

As El Niño's warm waters fuel storms, it creates increased precipitation in the east-central and eastern Pacific Ocean.

In South America, the El Niño effect is more pronounced than in North America. El Niño is associated with warm and very wet summer periods (December-February) along the coast of northern Peru and Ecuador, causing severe flooding whenever the event is severe. The effects during February, March, April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions, but mainly during the spring and early summer. The central region of Chile gets a mild winter with big amount rains, and the Peruvian-Bolivian Plateau sometimes experiences winter snowfalls unusual for this region. Drier and warmer weather is observed in the Amazon Basin, Colombia and Central America.

Direct effects of El Niño leading to decreased humidity in Indonesia, increasing the likelihood of forest fires, in the Philippines and northern Australia. Also in June-August, dry weather is observed in the regions of Australia: Queensland, Victoria, New South Wales and eastern Tasmania.

The western Antarctic Peninsula, Ross Land, Bellingshausen and Amundsen seas are covered with large amounts of snow and ice during El Niño. The latter two and the Wedell Sea become warmer and are under higher atmospheric pressure.

In North America, winters are generally warmer than normal in the Midwest and Canada, while central and southern California, northwestern Mexico and the southeastern United States are getting wetter. The Pacific Northwest states, in other words, dry out during El Niño. Conversely, during La Niña, the US Midwest dries out. El Niño is also associated with decreased hurricane activity in the Atlantic.

Eastern Africa, including Kenya, Tanzania and the White Nile Basin, experiences long periods of rain from March to May. Droughts plague southern and central Africa from December to February, mainly Zambia, Zimbabwe, Mozambique and Botswana.

Warm Pool of the Western Hemisphere. A study of climate data showed that approximately half of the post-El Niño summers experienced unusual warming in the Western Hemisphere Warm Pool. This influences the weather in the region and appears to have a connection to the North Atlantic Oscillation.

Atlantic effect. An El Niño-like effect is sometimes observed in the Atlantic Ocean, where water along the equatorial African coast becomes warmer and water off the coast of Brazil becomes colder. This can be attributed to the Volcker circulation over South America.

Non-climatic effects of El Niño

Along the eastern coast of South America El Niño reduces the upwelling of cold, plankton-rich water that supports large fish populations, which in turn support an abundance of seabirds, whose droppings support the fertilizer industry.

Local fishing industry along coastline may experience fish shortages during prolonged El Niño events. The world's largest fisheries collapse due to overfishing, which occurred in 1972 during El Niño, led to a decline in the Peruvian anchovy population. During the events of 1982-83, populations of southern horse mackerel and anchovies declined. Although the number of shells in warm water increased, the hake went deeper into cold water, and shrimp and sardines went south. But the catch of some other fish species was increased, for example, the common horse mackerel increased its population during warm events.

Changing locations and types of fish due to changing conditions have presented challenges for the fishing industry. The Peruvian sardine has moved towards the Chilean coast due to El Niño. Other conditions have only led to further complications, such as the Chilean government creating fishing restrictions in 1991.

It is postulated that El Niño led to the extinction of the Indian Mochico tribe and other tribes of the pre-Columbian Peruvian culture.

Causes that give rise to El Niño

The mechanisms that may cause El Niño events are still being researched. It is difficult to find patterns that can reveal causes or allow predictions to be made.
Bjerknes suggested in 1969 that abnormal warming in the eastern Pacific Ocean could be attenuated by east-west temperature differences, causing weakening in the Volcker circulation and trade winds that move warm water westward. The result is an increase in warm water to the east.
Virtky in 1975 suggested that the trade winds could create a westerly bulge of warm waters, and any weakening of the winds could allow warm waters to move east. However, no bulges were noticed on the eve of the events of 1982-83.
Rechargeable Oscillator: Some mechanisms have been proposed that when warm areas are created in the equatorial region, they are dissipated to higher latitudes through El Niño events. The cooled areas are then recharged with heat for several years before the next event occurs.
Western Pacific Oscillator: In the western Pacific Ocean, several weather conditions could cause easterly wind anomalies. For example, a cyclone in the north and an anticyclone in the south result in an easterly wind between them. Such patterns can interact with the westerly flow across the Pacific Ocean and create a tendency for the flow to continue eastward. A weakening of the westerly current at this time may be the final trigger.
The equatorial Pacific Ocean can lead to El Niño-like conditions with a few random variations in behavior. External weather patterns or volcanic activity can be such factors.
The Madden-Julian Oscillation (MJO) is a critical source of variability that can contribute to the sharper evolution leading to El Niño conditions through fluctuations in the winds blowing on low levels, and precipitation over the western and central Pacific Ocean. The eastward propagation of oceanic Kelvin waves may be caused by MJO activity.

History of El Niño

Normal conditions along the western Peruvian coast are a cold southerly current (Peruvian Current) with upwelling water; plankton upwelling leads to active ocean productivity; cold currents lead to a very dry climate on earth. Similar conditions exist everywhere (California Current, Bengal Current). So replacing it with a warm northern current leads to a decrease in biological activity in the ocean and to heavy rains leading to flooding on land. The connection with flooding was reported in 1895 by Pezet and Eguiguren.

Towards the end of the nineteenth century there was increased interest in predicting climate anomalies (for food production) in India and Australia. Charles Todd suggested in 1893 that droughts in India and Australia occur at the same time. Norman Lockyer pointed out the same thing in 1904. In 1924, Gilbert Volcker first coined the term "Southern Oscillation."

For most of the twentieth century, El Niño was considered a large local phenomenon.

The Great El Niño of 1982-83 led to a sharp rise in the interest of the scientific community in this phenomenon.

History of the phenomenon

ENSO conditions have occurred every 2 to 7 years for at least the last 300 years, but most of them have been weak.

Major ENSO events occurred in 1790–93, 1828, 1876–78, 1891, 1925–26, 1982–83, and 1997–98.

Latest events El Niño occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998 and 2002-2003.

The 1997–1998 El Niño in particular was strong and brought international attention to the phenomenon, while what was unusual about the 1990–1994 period was that El Niño occurred very frequently (but mostly weakly).

El Niño in the history of civilization

The mysterious disappearance of the Mayan civilization in Central America could have been caused by strong climate change. This conclusion was reached by a group of researchers from the German National Center for Geosciences, writes the British newspaper The Times.

Scientists tried to establish why, at the turn of the 9th and 10th centuries AD, at opposite ends of the earth, the two largest civilizations of that time ceased to exist almost simultaneously. We are talking about the Mayan Indians and the fall of the Chinese Tang Dynasty, which was followed by a period of internecine strife.

Both civilizations were located in monsoon regions, the moisture of which depends on seasonal precipitation. However, at the indicated time, apparently, the rainy season was not able to provide the amount of moisture sufficient for the development Agriculture.

The ensuing drought and subsequent famine led to the decline of these civilizations, researchers believe. They associate climate change with the natural phenomenon "El Niño", which means temperature fluctuations surface waters of the eastern part Pacific Ocean in tropical latitudes. This leads to large-scale disturbances in atmospheric circulation, causing droughts in traditionally wet regions and floods in dry ones.

Scientists came to these conclusions by studying the nature of sedimentary deposits in China and Mesoamerica dating back to this period. The last emperor of the Tang Dynasty died in 907 AD, and the last known Mayan calendar dates back to 903.

In the World Ocean, special phenomena (processes) are observed that can be considered anomalous. These phenomena extend over vast water areas and are of great ecological and geographical significance. Such anomalous phenomena covering the ocean and atmosphere are El Niño and La Niña. However, a distinction must be made between the El Niño current and the El Niño phenomenon.

El Niño current - a constant current, small on an oceanic scale, off the northwestern coast of South America. It can be traced from the Gulf of Panama area and follows south along the coasts of Colombia, Ecuador, Peru to about 5 0 S However, approximately once every 6 - 7 years (but it happens more or less often), the El Niño current spreads far to the south, sometimes to northern and even central Chile (up to 35-40 0 S). The warm waters of El Niño push the cold waters of the Peru-Chile Current and coastal upwelling into the open ocean. Ocean surface temperatures in the coastal zone of Ecuador and Peru rise to 21–23 0 C, and sometimes up to 25–29 0 C. The anomalous development of this warm current, which lasts almost six months - from December to May and which usually appears around Catholic Christmas, is called "El Niño" - from the Spanish "El Nico - the baby (Christ)." It was first noticed in 1726.

This purely oceanological process has tangible and often catastrophic environmental consequences on land. Due to the sharp warming of water in the coastal zone (by 8-14 0 C), the amount of oxygen and, accordingly, the biomass of cold-loving species of phyto- and zooplankton, the main food of anchovies and other commercial fish of the Peruvian region, significantly decreases. A huge number of fish either die or disappear from this water area. Peruvian anchovy catches fall 10 times in such years. After the fish, the birds that feed on them also disappear. As a result of this natural disaster, South American fishermen are going bankrupt. In previous years, the abnormal development of El Niño led to famine in several countries on the Pacific coast of South America. . In addition, during the passage of El Niño weather conditions in Ecuador, Peru and northern Chile are deteriorating sharply, where powerful downpours occur, leading to catastrophic floods, mudflows and soil erosion on the western slopes of the Andes.

However, the consequences of the anomalous development of the El Niño current are felt only on the Pacific coast of South America.

The main culprit for the increasing frequency of weather anomalies in recent years, which have covered almost all continents, is called El Niño/La Niña phenomenon, manifested in a significant change in the temperature of the upper layer of water in the eastern tropical Pacific Ocean, which causes intense turbulent heat and moisture exchange between the ocean and the atmosphere.

Currently, the term "El Niño" is used to refer to situations where abnormally warm surface waters occupy not only the coastal region near South America, but also most of the tropical Pacific Ocean up to the 180th meridian.

Under normal weather conditions, when the El Niño phase has not yet arrived, the warm surface waters of the ocean are held by eastern winds - trade winds - in the western zone of the tropical Pacific Ocean, where the so-called tropical warm pool(TTB). The depth of this warm layer of water reaches 100-200 meters, and it is the formation of such a large heat reservoir that is the main and necessary condition for the transition to the El Niño phenomenon. At this time, the water surface temperature in the west of the ocean in the tropical zone is 29-30°, while in the east it is 22-24°C. This difference in temperature is explained by the rise of cold deep waters to the surface of the ocean off the west coast of South America. At the same time, in the equatorial part of the Pacific Ocean, a water area with a huge reserve of heat is formed and equilibrium is observed in the ocean-atmosphere system. This is a situation of normal balance.

Approximately once every 3-7 years, the balance is disrupted, and the warm waters of the western Pacific Ocean move east, and over a huge area of water in the equatorial eastern part of the ocean, a sharp increase in the temperature of the surface layer of water occurs. The El Niño phase begins, the beginning of which is marked by sudden heavy westerly winds (Fig. 22). They reverse the usual weak trade winds over the warm western Pacific and prevent cold deep waters off the west coast of South America from rising to the surface. Related El Niño atmospheric phenomena were called the Southern Oscillation (ENSO - El Niño - Southern Oscillation) because they were first observed in the Southern Hemisphere. Due to the warm water surface, intense convective rise of air is observed in the eastern part of the Pacific Ocean, and not in the western part, as usual. As a result, the area of heavy rainfall shifts from the western to the eastern Pacific Ocean. Rain and hurricanes hit Central and South America.

Rice. 22. Normal conditions and the onset phase of El Niño

Over the past 25 years, there have been five active El Niño cycles: 1982-83, 1986-87, 1991-1993, 1994-95 and 1997-98.

The mechanism for the development of the La Niña phenomenon (in Spanish, La Niça - “girl”), the “antipode” of El Niño, is somewhat different. The La Niña phenomenon manifests itself as a decrease in surface water temperature below the climate norm in the eastern equatorial zone of the Pacific Ocean. The weather is unusually cold here. During the formation of La Niña, easterly winds from the west coast of the Americas increase significantly. Winds shift the warm water zone (WWZ), and the “tongue” of cold waters stretches for 5000 kilometers in exactly the place (Ecuador - Samoa Islands) where during El Niño there should be a belt of warm waters. This belt of warm waters moves to the western Pacific Ocean, causing powerful monsoon rains in Indochina, India and Australia. At the same time, the countries of the Caribbean and the United States suffer from droughts, dry winds and tornadoes.

La Niña cycles occurred in 1984-85, 1988-89 and 1995-96.

Although the atmospheric processes that develop during El Niño or La Niña mostly operate in tropical latitudes, their consequences are felt throughout the planet and are accompanied by environmental disasters: hurricanes and rainstorms, droughts and fires.

El Niño occurs on average once every three to four years, La Niña - once every six to seven years. Both phenomena bring with them an increased number of hurricanes, but during La Niña there are three to four times more storms than during El Niño.

The occurrence of El Niño or La Niña can be predicted if:

1. Near the equator in the eastern part of the Pacific Ocean, an area of warmer water than usual (El Niño phenomenon) or colder water (La Niña phenomenon) forms.

2. The atmospheric pressure trend between the port of Darwin (Australia) and the island of Tahiti (Pacific Ocean) is compared. During El Niño, pressure will be low in Tahiti and high in Darwin. During La Niña it is the other way around.

Research has established that the El Niño phenomenon is not only simple coordinated fluctuations in surface pressure and ocean water temperature. El Niño and La Niña are the most pronounced manifestations of interannual climate variability on a global scale. These phenomena represent large-scale changes in ocean temperature, precipitation, atmospheric circulation, and vertical air movements over the tropical Pacific Ocean and lead to abnormal weather conditions around the globe.

During El Niño years in the tropics, precipitation increases over areas east of the central Pacific Ocean and decreases over northern Australia, Indonesia and the Philippines. In December-February, above-normal precipitation is observed along the coast of Ecuador, in northwestern Peru, over southern Brazil, central Argentina and over equatorial, eastern Africa, during June-August in the western United States and over central Chile.

El Niño is also responsible for large-scale air temperature anomalies around the world.

During El Niño years, energy transfer into the troposphere of tropical and temperate latitudes increases. This is manifested in an increase in thermal contrasts between tropical and polar latitudes, and intensification of cyclonic and anticyclonic activity in temperate latitudes.

During El Niño years:

1. The Honolulu and Asian anticyclones are weakened;

2. The summer depression over southern Eurasia is filled, which is the main reason for the weakening of the monsoon over India;

3. The winter Aleutian and Icelandic lows are more developed than usual.

During La Niña years, precipitation increases over the western equatorial Pacific Ocean, Indonesia, and the Philippines and is almost completely absent in the eastern part of the ocean. More precipitation falls in northern South America, in South Africa and south-eastern Australia. Drier than normal conditions are observed along the coast of Ecuador, northwestern Peru and equatorial eastern Africa. There are large-scale temperature excursions around the world, with the largest number of areas experiencing abnormally cool conditions.

Over the past decade, great strides have been made in the comprehensive study of the El Niño phenomenon. This phenomenon does not depend on solar activity, but is associated with features in the planetary interaction of the ocean and atmosphere. A connection has been established between El Niño and the Southern Oscillation (El Niño-Southern Oscillation - ENSO) of surface atmospheric pressure in southern latitudes. This change in atmospheric pressure leads to significant changes in the system of trade winds and monsoon winds and, accordingly, surface ocean currents.

The El Niño phenomenon is increasingly affecting the global economy. So, this phenomenon of 1982-83. provoked terrible rainfalls in the countries of South America, caused enormous losses, and the economies of many countries were paralyzed. The effects of El Niño were felt by half of the world's population.

The strongest El Niño of 1997-1998 was the strongest during the entire observation period. It caused the most powerful hurricane in the history of meteorological observations, sweeping over the countries of South and Central America. Hurricane winds and downpours swept away hundreds of houses, entire areas were flooded, and vegetation was destroyed. In Peru, in the Atacama Desert, where rains generally occur once every ten years, a huge lake with an area of tens of square kilometers has formed. Unusually warm weather was recorded in South Africa, southern Mozambique, Madagascar, and unprecedented drought reigned in Indonesia and the Philippines, leading to forest fires. India experienced virtually no normal monsoon rains, while arid Somalia received significantly above normal rainfall. The total damage from the disaster amounted to about 50 billion dollars.

El Niño 1997-1998 significantly affected the average global air temperature of the Earth: it exceeded normal by 0.44°C. In the same year, 1998, the highest average annual air temperature was recorded on Earth for all years of instrumental observations.

The collected data indicate the regular occurrence of El Niño with an interval ranging from 4 to 12 years. The duration of El Niño itself varies from 6–8 months to 3 years, most often it is 1–1.5 years. This great variability makes it difficult to predict the phenomenon.

The influence of the climatic phenomena El Niño and La Niña, and therefore the number of unfavorable weather conditions on the planet, according to climate specialists, will increase. Therefore, humanity must closely monitor and study these climate phenomena.

El Niño

Southern Oscillation And El Niño(Spanish) El Niño- Baby, Boy) is a global ocean-atmospheric phenomenon. Being a characteristic feature of the Pacific Ocean, El Niño and La Niña(Spanish) La Nina- Baby, Girl) represent temperature fluctuations of surface waters in the tropics of the eastern Pacific Ocean. The names for these phenomena, borrowed from the native Spanish and first coined in 1923 by Gilbert Thomas Walker, mean "baby" and "little one," respectively. Their influence on the climate of the southern hemisphere is difficult to overestimate. The Southern Oscillation (the atmospheric component of the phenomenon) reflects monthly or seasonal fluctuations in the difference in air pressure between the island of Tahiti and the city of Darwin in Australia.

The circulation named after Walker is a significant aspect of the Pacific phenomenon ENSO (El Niño Southern Oscillation). ENSO is many interacting parts of one global system of ocean-atmospheric climate fluctuations that occur as a sequence of oceanic and atmospheric circulations. ENSO is the world's best known source of interannual weather and climate variability (3 to 8 years). ENSO has signatures in the Pacific, Atlantic and Indian Oceans.

El Niño and La Niña

El Niño and La Niña are officially defined as long-lasting marine surface temperature anomalies greater than 0.5°C crossing the central tropical Pacific Ocean. When a condition of +0.5 °C (-0.5 °C) is observed for a period of up to five months, it is classified as an El Niño (La Niña) condition. If the anomaly persists for five months or longer, it is classified as an El Niño (La Niña) episode. The latter occurs at irregular intervals of 2-7 years and usually lasts one or two years.

The first signs of El Niño are as follows:

Increase in air pressure over the Indian Ocean, Indonesia and Australia.
A drop in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean.
Trade winds in the South Pacific are weakening or heading east.
Warm air appears near Peru, causing rain in the deserts.
Warm water spreads from the western part of the Pacific Ocean to the eastern. It brings rain with it, causing it to occur in areas that are usually dry.

The warm El Niño current, composed of plankton-poor tropical water and heated by its easterly flow in the Equatorial Current, replaces the cold, plankton-rich waters of the Humboldt Current, also known as the Peruvian Current, which supports large populations of game fish. Most years, the warming lasts only a few weeks or months, after which weather patterns return to normal and fish catches increase. However, when El Niño conditions last for several months, more extensive ocean warming occurs and its economic impact on local fisheries for the external market can be severe.

In the Pacific Ocean, La Niña is characterized by unusually cold temperatures in the eastern equatorial region compared to El Niño, which in turn is characterized by unusually warm temperatures in the same region. Atlantic tropical cyclone activity generally increases during La Niña. A La Niña condition often occurs after an El Niño, especially when the latter is very strong.

Southern Oscillation Index (SOI)

The Southern Oscillation Index is calculated from monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

Long-lasting negative SOI values often signal El Niño episodes. These negative values typically accompany continued warming of the central and eastern tropical Pacific, decreased strength of the Pacific trade winds, and decreased rainfall in eastern and northern Australia.

Extensive influence of El Niño conditions

As El Niño's warm waters fuel storms, it creates increased precipitation in the east-central and eastern Pacific Ocean.

In South America, the El Niño effect is more pronounced than in North America. El Niño is associated with warm and very wet summer periods (December-February) along the coasts of northern Peru and Ecuador, causing severe flooding whenever the event is severe. The effects during February, March, April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions, but mainly during the spring and early summer. The central region of Chile receives mild winters with plenty of rain, and the Peruvian-Bolivian Plateau sometimes experiences winter snowfall, which is unusual for the region. Drier and warmer weather is observed in the Amazon Basin, Colombia and Central America.

The direct effects of El Niño are reducing humidity in Indonesia, increasing the likelihood of wildfires, in the Philippines and northern Australia. Also in June-August, dry weather is observed in the regions of Australia: Queensland, Victoria, New South Wales and eastern Tasmania.

Warm Pool of the Western Hemisphere

A study of climate data showed that approximately half of the post-El Niño summers experienced unusual warming in the Western Hemisphere Warm Pool. This influences the weather in the region and appears to have a connection to the North Atlantic Oscillation.

Atlantic effect

An El Niño-like effect is sometimes observed in the Atlantic Ocean, where water along the equatorial African coast becomes warmer and water off the coast of Brazil becomes colder. This can be attributed to Volcker circulations over South America.

Non-climatic effects

Along the east coast of South America, El Niño reduces the upwelling of cold, plankton-rich water that supports large populations of fish, which in turn support an abundance of seabirds, whose droppings support the fertilizer industry.

Local fishing industries along coastlines may experience shortages of fish during prolonged El Niño events. The world's largest fisheries collapse due to overfishing, which occurred in 1972 during El Niño, led to a decline in the Peruvian anchovy population. During the events of 1982-83, populations of southern horse mackerel and anchovies declined. Although the number of shells in warm water increased, hake went deeper into cold water, and shrimp and sardines went south. But the catch of some other fish species was increased, for example, the common horse mackerel increased its population during warm events.

It is postulated that El Niño led to the extinction of the Mochico Indian tribe and other tribes of the pre-Columbian Peruvian culture.

Causes that give rise to El Niño

The mechanisms that may cause El Niño events are still being researched. It is difficult to find patterns that can reveal causes or allow predictions to be made.

History of the theory

The first mention of the term "El Niño" dates back to the year when Captain Camilo Carrilo reported at the Congress of the Geographical Society in Lima that Peruvian sailors called the warm northerly current "El Niño" because it was most noticeable around 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 are a cold southerly current (Peru Current) with upwelling water; plankton upwelling leads to active ocean productivity; cold currents lead to a very dry climate on earth. Similar conditions exist everywhere (California Current, Bengal Current). So replacing it with a warm northern current leads to a decrease in biological activity in the ocean and to heavy rains, leading to flooding, on land. An association with flooding was reported in Pezet and Eguiguren.

Towards the end of the nineteenth century there was increased interest in predicting climate anomalies (for food production) in India and Australia. Charles Todd suggested that droughts in India and Australia occur at the same time. Norman Lockyer pointed out the same thing in Gilbert Volcker who first coined the term "Southern Oscillation".

For most of the twentieth century, El Niño was considered a large local phenomenon.

History of the phenomenon

ENSO conditions have occurred every 2-7 years for at least the last 300 years, but most of them have been weak.

Large ENSO events occurred in - , , - , , - , - and - 1998 .

The last El Niño events occurred in -, -, , , 1997-1998 and -2003.

The 1997-1998 El Niño in particular was strong and brought international attention to the phenomenon, while the 1997-1998 El Niño was unusual in that El Niño occurred very frequently (but mostly weakly).

El Niño in the history of civilization

Scientists tried to establish why, at the turn of the 10th century AD, the two largest civilizations of that time ceased to exist almost simultaneously on opposite ends of the earth. We are talking about the Mayan Indians and the fall of the Chinese Tang Dynasty, which was followed by a period of internecine strife.

Both civilizations were located in monsoon regions, the moisture of which depends on seasonal precipitation. However, at this time, apparently, the rainy season was not able to provide enough moisture for the development of agriculture.

The ensuing drought and subsequent famine led to the decline of these civilizations, researchers believe. They link climate change to the natural phenomenon El Niño, which refers to temperature fluctuations in the surface waters of the eastern Pacific Ocean in tropical latitudes. This leads to large-scale disturbances in atmospheric circulation, causing droughts in traditionally wet regions and floods in dry ones.

Scientists came to these conclusions by studying the nature of sedimentary deposits in China and Mesoamerica dating back to this period. The last emperor of the Tang dynasty died in 907 AD, and the last known Mayan calendar dates back to 903.

Literature

Cesar N. Caviedes, 2001. El Niño in History: Storming Through the Ages(University Press of Florida)
Brian Fagan, 1999. Floods, Famines, and Emperors: El Niño and the Fate of Civilizations(Basic Books)
Michael H. Glantz, 2001. Currents of change, ISBN 0-521-78672-X
Mike Davis Late Victorian Holocausts: El Niño Famines and the Making of the Third World(2001), ISBN 1-85984-739-0

Climate, Climatology
Changing of the climate	Paleoclimatology El Niño Geochemical carbon cycle Proterozoic glaciation, Ice Age, Little Ice Age Thermal maximum (

The first time I heard the word “El Niño” was in the United States in 1998. At that time it a natural phenomenon was well known to Americans, but almost unknown in our country. And it’s not surprising, because El Niño originates in the Pacific Ocean off the coast of South America and greatly influences the weather in the southern states of the United States. El Niño(translated from Spanish El Niño- baby, boy) in the terminology of climatologists - one of the phases of the so-called Southern Oscillation, i.e. fluctuations in the temperature of the surface layer of water in the equatorial Pacific Ocean, during which the area of heated surface water shifts to the east. (For reference: the opposite phase of oscillation - the displacement of surface waters to the west - is called La Niña (La Nina- baby, girl)). The El Niño phenomenon, which occurs periodically in the ocean, greatly affects the climate of the entire planet. One of the largest El Niño events occurred in 1997-1998. It was so strong that it attracted the attention of the world community and the press. At the same time, theories about the connection of the Southern Oscillation with global climate change spread. According to experts, the warming phenomenon El Niño is one of the main driving forces of natural variability in our climate.

In 2015 The World Meteorological Organization reported that the emerging ahead of schedule and dubbed the "Bruce Lee" El Niño could be one of the strongest since 1950. Its appearance was expected last year, based on data on rising air temperatures, but these models did not materialize, and El Niño did not manifest itself.

In early November, the American agency NOAA (National Oceanic and Atmospheric Administration) released a detailed report on the state of the Southern Oscillation and analyzed the possible development of El Niño in 2015-2016. The report is published on the NOAA website. In conclusions of this document It is said that currently there are all the conditions for the formation of El Niño, the average surface temperature of the equatorial part of the Pacific Ocean (SST) has increased values and continues to rise. The probability that El Niño will develop throughout the winter of 2015-2016 is 95% . A gradual decline of El Niño is predicted in the spring of 2016. The report published an interesting graph showing the change in SST since 1951. The blue areas correspond to low temperatures(La Niña), orange shows elevated temperatures (El Niño). The previous strong increase in SST of 2°C was observed in 1998.

Data obtained in October 2015 indicate that the SST anomaly at the epicenter already reaches 3 °C.

Although the causes of El Niño are not yet fully understood, it is known that it begins with trade winds weakening over several months. A series of waves move across the Pacific Ocean along the equator and create a body of warm water off South America, where the ocean normally has low temperatures due to the rise of deep ocean waters to the surface. Weakening trade winds coupled with strong westerly winds could also create a pair of cyclones (south and north of the equator), which is another sign of a future El Niño.

While studying the causes of El Niño, geologists noticed that the phenomenon occurs in the eastern part of the Pacific Ocean, where a powerful rift system has formed. American researcher D. Walker found a clear connection between increased seismicity on the East Pacific Rise and El Niño. Russian scientist G. Kochemasov saw another curious detail: the relief fields of ocean warming almost one to one repeat the structure of the earth's core.

One of interesting versions belongs to the Russian scientist - Doctor of Geological and Mineralogical Sciences Vladimir Syvorotkin. It was first expressed back in 1998. According to the scientist, powerful centers of hydrogen-methane degassing are located in hot spots of the ocean. Or simply - sources of constant release of gases from the bottom. Their visible signs are exits thermal waters, black and white smokers. In the area of the coast of Peru and Chile, during El Niño years there is a massive release of hydrogen sulfide. The water is boiling and there is a terrible smell. At the same time, an amazing power is pumped into the atmosphere: approximately 450 million megawatts.

The El Niño phenomenon is now being studied and discussed more and more intensively. A team of researchers from the German National Center for Geosciences has concluded that the mysterious disappearance of the Mayan civilization in Central America may have been caused by strong climate changes caused by El Niño. At the turn of the 9th and 10th centuries AD, the two largest civilizations of that time ceased to exist on opposite ends of the earth almost simultaneously. We are talking about the Mayan Indians and the fall of the Chinese Tang Dynasty, which was followed by a period of internecine strife. Both civilizations were located in monsoon regions, the moisture of which depends on seasonal precipitation. However, a time came when the rainy season was unable to provide sufficient moisture for the development of agriculture. The drought and subsequent famine led to the decline of these civilizations, researchers believe. Scientists came to these conclusions by studying the nature of sedimentary deposits in China and Mesoamerica dating back to this period. The last emperor of the Tang Dynasty died in 907 AD, and the last known Mayan calendar dates back to 903.

Climatologists and meteorologists say that El Niño2015, which will peak between November 2015 and January 2016, will be one of the strongest. El Niño will lead to large-scale disturbances in atmospheric circulation, which could cause droughts in traditionally wet regions and floods in dry ones.

A phenomenal phenomenon, which is considered one of the manifestations of the developing El Niño, is now observed in South America. The Atacama Desert, which is located in Chile and is one of the driest places on Earth, is covered with flowers.

This desert is rich in deposits of saltpeter, iodine, table salt and copper, there has been no significant precipitation here for four centuries. The reason is that the Peruvian current cools the lower layers of the atmosphere and creates temperature inversion which prevents precipitation. Rain falls here once every few decades. However, in 2015, the Atacama was hit by unusually heavy rainfall. As a result, dormant bulbs and rhizomes (horizontally growing underground roots) sprouted. The faded plains of the Atacama were covered with yellow, red, violet and white flowers - nolans, beaumaries, rhodophials, fuchsias and hollyhocks. The desert first bloomed in March, after unexpectedly intense rains caused flooding in the Atacama and killed about 40 people. Now the plants have bloomed for the second time in a year, before the start of the southern summer.

What will El Niño 2015 bring? A powerful El Niño is expected to bring welcome rainfall to dry areas of the United States. In other countries, its effect may be the opposite. In the western Pacific Ocean, El Niño creates increased Atmosphere pressure, bringing dry and sunny weather to large areas of Australia, Indonesia, and sometimes even India. The impact of El Niño on Russia has so far been limited. It is believed that under the influence of El Niño in October 1997, temperatures in Western Siberia reached above 20 degrees, and then they started talking about the retreat of permafrost to the north. In August 2000, Emergencies Ministry specialists attributed the series of hurricanes and rainstorms that swept across the country to the impact of the El Niño phenomenon.

La Nina - « baby, girl»).

The characteristic oscillation time is from 3 to 8 years, but the strength and duration of El Niño in reality varies greatly. Thus, in 1790-1793, 1828, 1876-1878, 1891, 1925-1926, 1982-1983 and 1997-1998, powerful phases of El Niño were recorded, while, for example, in 1991-1992, 1993, 1994 this phenomenon , often repeating, was weakly expressed. The 1997-1998 El Niño was so strong that it attracted the attention of the world public and the press. At the same time, theories about the connection of the Southern Oscillation with global climate change spread. Since the early 1980s, El Niño also occurred in 1986-1987 and 2002-2003.

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✪ El Niño and La Niña (narrated by oceanographer Vladimir Zhmur)

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Description

Normal conditions along the western coast of Peru are determined by the cold Peruvian Current, which carries water from the south. Where the current turns to the west, along the equator, cold and nutrient-rich waters rise from deep depressions, which contributes to the active development of plankton and other life forms in the ocean. The cold current itself determines the aridity of the climate in this part of Peru, forming deserts. Trade winds drive the heated surface layer of water into the western zone of the tropical Pacific Ocean, where the so-called tropical warm pool (TTB) is formed. In it, the water is heated to depths of 100-200 m. The atmospheric Walker circulation, manifested as trade winds, coupled with low blood pressure over the Indonesia region, leads to the fact that in this place the level of the Pacific Ocean is 60 cm higher than in its eastern part. And the water temperature here reaches 29-30 °C versus 22-24 °C off the coast of Peru.

However, everything changes with the onset of El Niño. The trade winds are weakening, the TTB is spreading, and water temperatures are rising across a vast area of the Pacific Ocean. In the region of Peru, the cold current is replaced by a warm water mass moving from the west to the coast of Peru, upwelling weakens, fish die without food, and westerly winds bring moist air masses and rainfall to the deserts, even causing floods. The onset of El Niño reduces the activity of Atlantic tropical cyclones.

History of discovery

The first mention of the term "El Niño" dates back to 1892, when Captain Camilo Carrilo reported at the Congress of the Geographical Society in Lima that Peruvian sailors called the warm northerly current "El Niño" because it was most noticeable around Christmas. El Niño called the Christ Child). In 1893, Charles Todd suggested that droughts in India and Australia were occurring at the same time. Norman Lockyer pointed out the same thing in 1904. The connection between the warm northerly current off the coast of Peru and floods in that country was reported in 1895 by Peset and Eguiguren. The Southern Oscillation was first described in 1923 by Gilbert Thomas Walker. He introduced the terms “Southern Oscillation”, “El Niño” and “La Niña”, and examined the zonal convection circulation in the atmosphere in the equatorial zone of the Pacific Ocean, which now received his name. For a long time, almost no attention was paid to the phenomenon, considering it regional. Only towards the end of the 20th century did the connections between El Niño and the planet’s climate become clear.

Quantitative description

Currently, for a quantitative description of the phenomena, El Niño and La Niña are defined as temperature anomalies of the surface layer of the equatorial part of the Pacific Ocean lasting at least 5 months, expressed in a deviation of water temperature by 0.5 °C higher (El Niño) or lower (La Niña) side.

First signs of El Niño:

Increase in air pressure over the Indian Ocean, Indonesia and Australia.
A drop in pressure over Tahiti, over the central and eastern Pacific Ocean.
Weakening of the trade winds in the South Pacific until they cease and the wind direction changes to the westerly.
Warm air mass in Peru, rain in the Peruvian deserts.

In itself, an increase in water temperature off the coast of Peru by 0.5 °C is considered only a condition for the occurrence of El Niño. Typically, such an anomaly can exist for several weeks and then disappear safely. And only a five-month anomaly, classified as an El Niño phenomenon, can cause significant damage to the region’s economy due to a drop in fish catches.

The Southern Oscillation Index is also used to describe El Niño. It is calculated as the difference in pressure over Tahiti and over Darwin (Australia). Negative index values indicate the El Niño phase, and positive values indicate the La Niña phase.

Early stages and characteristics

The Pacific Ocean is a huge heat-cooling system that causes the movement of air mass systems. Changing Pacific Ocean temperatures affect weather on a global scale. Rain fronts are moving from the western ocean towards the Americas, while drier weather sets in in Indonesia and India.

Although not a direct cause of El Niño, the Madden-Julian Oscillation moves an area of excess precipitation west to east along the tropical belt with a period of 30-60 days, which can influence the rate of development and intensity of El Niño and La Niña in several ways. . For example, air flows from the west, passing between areas of low atmospheric pressure formed by the Madden-Julian oscillation, can trigger the formation of cyclonic circulations north and south of the equator. As these cyclones intensify, westerly winds within the equatorial Pacific also intensify and shift eastward, thus being an integral part in the development of El Niño. The Madden-Julian Oscillation may also be the source of eastward-propagating Kelvin waves. Kelvin wave), which in turn are strengthened by El Niño, leading to a mutually reinforcing effect.

Southern Oscillation

The Southern Oscillation is an atmospheric component of El Niño and represents fluctuations in air pressure in the surface layer of the atmosphere between the waters of the east and western parts Pacific Ocean. The magnitude of the oscillation is measured using the Southern Oscillation Index. Southern Oscillation Index, SOI). The index is calculated based on the difference in surface air pressure over Tahiti and over Darwin (Australia). El Niño was observed when the index took negative values, which meant a minimal difference in pressure between Tahiti and Darwin.

Low atmospheric pressure usually forms over warm waters, and high atmospheric pressure over cold waters, partly due to the fact that intense convection occurs over warm waters. El Niño is associated with prolonged warm periods in the central and eastern tropical Pacific. This is causing the Pacific trade winds to weaken and rainfall levels to fall over eastern and northern Australia.

Atmospheric Walker circulation

During the period when conditions do not correspond to the formation of El Niño, the Walker circulation is diagnosed near the surface of the earth in the form of easterly trade winds, which move masses of water and air, heated by the sun, to the west. It also promotes upwelling along the coasts of Peru and Ecuador, bringing rich nutrients water close to the surface, increasing the concentration of fish. In the western part of the Pacific Ocean during these periods there is warm, humid weather with low pressure, excess moisture accumulates in typhoons and thunderstorms. As a result of these movements, the sea level in the western part at this time is 60 cm higher.

Impact on the climate of different regions

In South America, the El Niño effect is most pronounced. This phenomenon usually causes warm and very humid summer periods(December to February) on the northern coast of Peru and Ecuador. When El Niño is strong, it causes severe flooding. These, for example, happened in January 2011. Southern Brazil and northern Argentina also experience wetter than normal periods, but mostly in the spring and early summer. Central Chile experiences mild winters with plenty of rain, while Peru and Bolivia occasionally experience unusual winter snowfalls for the region. Drier and warmer weather is observed in the Amazon, Colombia and Central America. Humidity is falling in Indonesia, increasing the likelihood of forest fires. This also applies to the Philippines and northern Australia. From June to August, dry weather occurs in Queensland, Victoria, New South Wales and eastern Tasmania. In Antarctica, the western Antarctic Peninsula, Ross Land, Bellingshausen and Amundsen seas are covered with large amounts of snow and ice. At the same time, the pressure increases and becomes warmer. In North America, winters generally become warmer in the Midwest and Canada. Central and southern California, northwestern Mexico, and the southeastern United States become wetter, while the northwestern Pacific United States becomes drier. During La Niña, on the other hand, the Midwest becomes drier. El Niño also leads to a decrease in Atlantic hurricane activity. East Africa, including Kenya, Tanzania and the White Nile Basin, experiences long rainy seasons from March to May. Droughts plague southern and central Africa from December to February, mainly Zambia, Zimbabwe, Mozambique and Botswana.

An El Niño-like effect is sometimes observed in the Atlantic Ocean, where the water along the equatorial coast of Africa becomes warmer and the water off the coast of Brazil becomes colder. Moreover, there is a connection between this circulation and El Niño.

Impact on health and society

El Niño causes extreme weather conditions associated with epidemic disease frequency cycles. El Niño is associated with an increased risk of mosquito-borne diseases: malaria, dengue fever and Rift Valley fever. Malaria cycles are associated with El Niño in India, Venezuela and Colombia. There is an association with outbreaks of Australian encephalitis (Murray Valley Encephalitis - MVE) occurring in south-eastern Australia following heavy rainfall and flooding caused by La Niña. A notable example is the severe outbreak of Rift Valley fever that occurred due to El Niño following extreme rainfall events in northeastern Kenya and southern Somalia in 1997–98.

It is also believed that El Niño may be associated with the cyclical nature of wars and the emergence of civil conflicts in countries whose climate is influenced by El Niño. A study of data from 1950 to 2004 found that El Niño was associated with 21% of all civil conflicts during that period. At the same time, the risk of civil war in El Niño years is twice as high as in La Niña years. It is likely that the connection between climate and military action is mediated by crop failures, which often occur in hot years.

Recent cases

El Niño was observed from September 2006 to early 2007. The resulting drought in 2007 caused a spike in food prices and associated civil unrest in Egypt, Cameroon and Haiti.

In June 2014, the UK Met Office reported a high probability of El Niño developing in 2014, however, its forecast did not come true. In the fall of 2015, the World Meteorological Organization reported that, coming ahead of schedule and dubbed the “Bruce Lee,” El Niño could become one of the most powerful since 1950. Rain and floods accompanied the Christmas holidays in the USA (along the Mississippi River), in South America (along La Plata) and even in North-West England. In 2016, the influence of El Niño continued.

Notes

Scientific Network. El Niño phenomenon
Alena Miklashevskaya, Alena Miklashevskaya. The Pacific Ocean is waiting for a cold snap // Kommersant.
Tim Liu. El Niño Watch from Space (undefined) . NASA (September 6, 2005). Retrieved May 31, 2010.
Stewart, Robert (undefined) . Our Ocean Planet: Oceanography in the 21st Century. Department of Oceanography, Texas A&M University (January 6, 2009). Retrieved July 25, 2009. Archived May 11, 2013.
Dr. Tony Phillips. A Curious Pacific Wave (undefined) . National Aeronautics and Space Administration (5 March 2002). Retrieved July 24, 2009. Archived May 11, 2013.
Nova. (undefined) . Public Broadcasting Service (1998). Retrieved July 24, 2009. Archived May 11, 2013.
De-Zheng Sun. Nonlinear Dynamics in Geosciences: 29 The Role of El Niño-Southern Oscillation in Regulating its Background State . - Springer, 2007. - ISBN 978-0-387-34917-6. - DOI:10.1007/978-0-387-34918-3.
Soon-Il An and In-Sik Kang (2000). “A Further Investigation of the Recharge Oscillator Paradigm for ENSO Using a Simple Coupled Model with the Zonal Mean and Eddy Separated” . Journal of Climate. 13 (11): 1987-93. Bibcode:2000JCli...13.1987A. DOI:10.1175/1520-0442(2000)013<1987:AFIOTR>2.0.CO;2 . ISSN 1520-0442 . Access date 2009-07-24.
Jon Gottschalck and Wayne Higgins. Madden Julian Oscillation Impacts (undefined) . Center climate forecasting(USA) (English) Climate Prediction Center) (February 16, 2008). Retrieved July 24, 2009. Archived May 11, 2013.
Air-Sea Interaction & Climate. El Niño Watch from Space (undefined) . Jet Propulsion Laboratory California Institute of Technology (September 6, 2005). Retrieved July 17, 2009.

What is El Niño? El Niño has been replaced by La Niña: what does it mean?

El Niño and La Niña

Southern Oscillation Index (SOI)

El Niño influence

Non-climatic effects of El Niño

Causes that give rise to El Niño

History of El Niño

El Niño in the history of civilization

El Niño and La Niña

Southern Oscillation Index (SOI)

Extensive influence of El Niño conditions

Warm Pool of the Western Hemisphere

Atlantic effect

Non-climatic effects

Causes that give rise to El Niño

History of the theory

History of the phenomenon

El Niño in the history of civilization

Links

Literature

Encyclopedic YouTube

Subtitles

Description

History of discovery

Quantitative description

Early stages and characteristics

Southern Oscillation

Atmospheric Walker circulation

Impact on the climate of different regions

Impact on health and society

Recent cases

Notes

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