Ocean current El Niño. Natural phenomenon 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 in 1969 suggested that abnormal warming in the eastern Pacific Ocean may 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.
Virtki 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 may contribute to the sharper evolution leading to El Niño conditions through fluctuations in low-level winds and precipitation over the western and central regions. Pacific Ocean. The eastward propagation of oceanic Kelvin waves may be caused by MJO activity.
2. Southern Oscillation and El Niño
The Southern Oscillation and El Niño (Spanish El Niño - Baby, Boy) is a global ocean-atmospheric phenomenon. A characteristic feature of the Pacific Ocean, El Niño and La Niña are temperature fluctuations in surface waters in the tropical eastern Pacific Ocean. The names for these phenomena, borrowed from the native Spanish and first coined in 1923 by Gilbert Thomas Volcker, 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 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.
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 (Fig. 1)
Fig.1. 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. (NOAA/PMEL/TAO)
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:
1. Increase in air pressure over the Indian Ocean, Indonesia and Australia.
2. A drop in air pressure over Tahiti and the rest of the central and eastern parts of the Pacific Ocean.
3. Trade winds in the South Pacific are weakening or heading east.
4. Warm air appears near Peru, causing rain in the deserts.
5. 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 eastern 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.
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 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.
Traces of destruction caused by El Niño :
1.1525: First historical mention of El Niño in Peru.
2.1789-1793: El Niño killed 600,000 people in India and caused severe famine in South Africa.
3.1982-1983: This phenomenon caused the death of 2,000 people and caused damage, especially in tropical regions, amounting to US$13 billion.
4.1990-1995: Three incidents occurred one after another, making up one of the longest recorded El Niño events.
5.1997-1998: Despite early success in regional flood and drought forecasting, El Niño caused approximately 2,100 deaths and $33 billion in damages worldwide.
Typically, trade winds drive a layer of warm water from the American coast towards Asia. Around Indonesia, the current stops. The ocean surface level there at this time exceeds the mark off the Peruvian coast by 60 centimeters. Clouds form over the warming ocean and typically fall as monsoon rains over southern Asia. But when El Niño “shows character”, the trade winds weaken or do not blow at all. The heated water spreads to the sides and goes back to the American coast. Researchers now understand this phenomenon and call it the Southern Oscillation. They, as if in a bathtub, rock the heated ocean waters from west to east and back. Only in the ocean all this happens much more slowly than in a bath. Behind the swaying water, as if accompanying it, are rain clouds, which usually rained in September-October over Indonesia and Australia.
In the early spring of 1997, space satellites armed with infrared cameras showed that a patch of heated water had formed near the equator in the eastern Pacific Ocean. The 10-12 centimeter thick layer had a temperature of up to 30 degrees Celsius - 5 degrees higher than usual. This alerted meteorologists. The center of a tropical typhoon system could form here. Warmer water could weaken trade winds or reverse them, thereby increasing the destructive effects of El Niño, as was the case in 1982.
When then, in June, the difference in atmospheric pressure over the Australian port of Darwin and over the island of Tahiti changed significantly (southern oscillation), and Peruvian fishermen in their waters, to everyone’s surprise, caught a pair of hammerhead sharks (fish that live in very warm waters) , the weather service and the media sounded the alarm.
The reasons for this were: a change in atmospheric pressure over the equatorial region of the Pacific Ocean - a sign that the current there had reversed. That's why heat-loving sharks ended up off the coast of Peru.
Another month and a half passed, and new facts emerged confirming the worst fears: corals, creatures that are very sensitive to water temperature, began to die off the coast of Mexico and Costa Rica. In Chile, hungry cormorants have begun raiding fish markets. In Peru, due to a lack of raw materials, several factories that processed fish into flour had to be closed. Heavy rains hit Chile, followed by a rat infestation. Viruses brought by rats caused outbreaks of disease. The oldest buildings in South America - pyramids made of unfired brick - fell victim to the rains. Many of them are about 1500 years old. And now they may be washed away by water pouring from the sky. Scientists sounded the alarm. Roofs made of canvas and plastic are being urgently built over the monuments.
Some archaeologists are already saying that El Niño in the distant past could have been one of the reasons for the death of the highly developed cultures of the peoples of South America. Archaeologist Ricardo Morales suggested that in the years 550 - 600 A.D. the famous Pyramid of the Moon was washed away by rains caused, as he believes, by a super-strong El Niño. The village, located not far from the pyramid, according to the scientist, was washed away by streams of water.
In Peru, according to archaeologist M. Moseli, 1100 years ago, a powerful El Niño, or rather, the natural disasters generated by it, destroyed the system of irrigation canals and thereby destroyed the highly developed culture of a large state.
3. Study of the El Niño phenomenon
The first European to swim across the largest ocean on the planet was Magellan. He called him "Quiet". As it soon became clear, Magellan was mistaken. It is in this ocean that most typhoons are born, and it produces three-quarters of the planet's clouds. Now we have also learned that the El Niño current emerging in the Pacific Ocean sometimes causes many different troubles and disasters on the planet.
The current stretches from the coast of Peru to the archipelago surrounding the Southeast of the Asian continent. In terms of El Niño, it is an elongated tongue of highly heated water. It is equal in area to the United States. Heated water evaporates more intensely and “pumps” the atmosphere with energy faster. El Niño supplies it with 450 million megawatts, which is equivalent to the power of 300,000 large nuclear power plants. It is clear that this energy, according to the law of conservation of energy, does not disappear. And now in Indonesia, disaster broke out in full force. First, there was a raging drought on the island of Sumatra, then the dried-out forests began to burn. In the impenetrable smoke that enveloped the entire island, the plane crashed upon landing, and a tanker and a cargo ship collided at sea. The smoke reached Singapore and Malaysia... El Niño is also to blame for all this.
And to the American Pacific coast the current brought prolonged rain and hurricanes with hail. A state of emergency had to be declared in Costa Rica, Bolivia and Peru. South Africa is threatened by drought, and in Australia it has already devastated farmers' fields and meadows. In many places on earth, crops were completely destroyed.
Lack of water has reached the latitudes of Central America. Because of it, Lake Gatuk, part of the Panama Canal route, became shallow. It is filled with the runoff of rivers flowing towards the Atlantic. Due to the large landmass, the rivers have become scarce, the lake has become shallow, and now only ships with a shallow draft can pass through the Panama Canal.
The phenomenon, the origin of which is still unknown, repeats itself every six or seven years.
During the winter of 1997-1998, images of flooded villages, reports of heavy rains in various parts of the planet and abnormal temperatures in the United States and South America became a common sight on television screens and the pages of all newspapers. These events were associated with a phenomenon called El Niño.
However, the appearance of El Niño in 1997 and 1998 did not come as a surprise to meteorologists and people interested in this phenomenon. Since 1923, it has been the subject of close study. His name, meaning "little boy", came from South American fishermen, as his appearance coincided with the advent of Christmas - the time of the birth of little Jesus. During El Niño, an unusually high temperature is observed in the equatorial waters of the Pacific Ocean, which under normal conditions does not exceed 0.5 C. Temperature changes are associated with changes in pressure, as a result of which the winds blowing here also change direction. Due to rising water temperatures, squally winds often occur, especially in the Pacific Ocean on both its western and eastern coasts.
Unlike other parts of the world, South America is most affected by El Niño. Summer here has become hot and humid, with heavy rainfall on the coasts of Peru and Ecuador. From December 1997 to February 1998, there were serious floods.
Three months later, similar phenomena could be observed in northern Argentina and southern Brazil. As for Brazil, Rio de Janeiro still cannot recover from the terrible consequences of the flood.
Chile and the Bolivian Altiplano, on the other hand, experienced an incredibly harsh winter with snow storms and temperatures below normal. Northern Amazonia, Colombia and Central America experienced an unusually dry summer.
In the opposite part of the Pacific Ocean, similar phenomena also occurred, but on a slightly smaller scale. Indonesia, the Philippines and Australia received less rainfall than in previous decades.
The United States and Canada have experienced rising and falling temperatures. The Midwest and Canada experienced warm winters, while Southern California, Northwest Mexico and several U.S. states suffered from persistent rain.
Africa also had to deal with climate changes caused by El Niño. December through February was unusually wet for Equatorial Africa and Southern Sahara. In contrast to these areas of the African continent, Zambia, Zimbabwe, Mozambique and Botswana were surprised by hot, humid weather. Incessant rains caused floods on the American continent, and landslides became more frequent, causing serious material damage and 800 casualties.
In South America, climate change has caused the spread of cholera, dengue, malaria, encephalitis and leptospirosis, which, combined with poor health conditions, often cause high mortality rates in developing countries. Just like it happened in 1991, when during another El Niño visit there was an outbreak of cholera that claimed 12,000 lives.
The fishing industry is experiencing the most negative consequences of weather changes. With the advent of El Niño, cold currents rich in food for fish and birds are displaced. The decline in bird populations in the coastal zone poses certain dangers, as their excrement is used in the production of fertilizers. El Niño has a corresponding negative impact on the situation of fish processing enterprises. Surprisingly, while the fishing industry is in decline, life in the suburbs is improving significantly. The warm climate has a beneficial effect on the harvest, and local farmers can relax a little.
The El Niño phenomenon is nothing more than the southern oscillation, which is a significant fluctuation in water and air temperature in the South Pacific Ocean, off the coast of South America. Such fluctuations (oscillations) occur very irregularly - once every three, four, or even five years. The maximum development of the southern oscillations usually occurs in December, on Christmas Eve, and is accompanied by a strong increase in fish catch. That is why South Americans, especially Peruvians, are looking forward to the next oscillation with great impatience.
The El Niño phenomenon, as already mentioned, is characterized by a high degree of uncertainty. However, in recent years, there has been an opinion that they have already learned how to predict El Niño. The last cases of El Niño in 1986-1991 were predicted in advance and with a sufficient degree of accuracy by S. Zebiak. Together with M. Capel, S. Zebiak developed a forecast according to which the arrival of El Niño in 1993 was not expected.
Some scientists admit that this course of events has dealt a serious blow to mathematical modeling.
US President Clinton convened a council in October 1997 that examined all aspects of the unfolding environmental disaster. A task was formulated: all industrial enterprises in the country that discharge greenhouse gases into the atmosphere should reduce their emissions by the year 2000 to the 1990 level.
Meteorologists' predictions have been confirmed: catastrophic events associated with the El Niño current are hitting the earth one after another. Of course, it is very sad that all this is happening now. But still, it should be noted that for the first time humanity is encountering a global natural disaster, knowing its causes and the course of further development.
The El Niño phenomenon is already quite well studied. Science has solved the mystery that plagued Peruvian fishermen. They did not understand why sometimes during the Christmas period the ocean becomes warmer and the shoals of sardines off the coast of Peru disappear. Because the arrival of warm water coincided with Christmas, the current was called El Niño, which means "baby boy" in Spanish.
Fishermen, of course, are interested in the immediate reason for the departure of the sardines. The fact is that sardines (and not only them) feed on phytoplankton, a component of which is microscopic algae. And algae need sunlight and nutrients - primarily nitrogen and phosphorus. They are present in ocean water, and their supply in the upper layer is constantly replenished by vertical currents going from the bottom to the surface. But when the El Niño current turns back towards South America, its warm waters “block” the exit of deep waters. Biogenic elements do not rise to the surface, and algae reproduction stops. The fish leave these places - they do not have enough food.
Even in those years when El Niño does not bring great trouble, it is worth keeping an eye on it, since it contains and encodes the future development of the atmosphere: what to expect from the next winter, whether spring will be early or late, whether there is a threat of summer drought.
Factors such as wind, clouds, rain, sunny skies help predict the weather only for the near future. Several days will pass, and new winds and new clouds will determine the weather. Only the oceans have a long-term influence on the atmosphere. And they are the ones who determine the weather on Earth.
For more than 15 years, the joint work of climatologists, meteorologists, and oceanologists from around the world has continued, trying to find the basis for long-term weather forecasts. They installed buoys with instruments in the oceans, sank them to depth, and monitored the behavior of sea waters from satellites. The entire mass of extracted digital material was loaded into computers... The warning received from scientists that catastrophic weather changes were possible at the end of 1997 shows that all this complex and expensive research was not carried out in vain. German meteorologist M. Latif states: “We understand the essence of the phenomenon.”
Droughts, storms, floods, and colds have significantly influenced the fate of entire nations in all centuries. Stories about these very real events of distant times gradually turned into legends and myths. And now many of them are receiving a scientific explanation.
El Niño, a warm seasonal flow of surface water of low salinity in the eastern Pacific Ocean. Distributed in the summer of the Southern Hemisphere along the coast of Ecuador from the equator to 5-7° south. w. In some years, E. - N. intensifies and, penetrating far to the south (up to 15° S), pushes cold waters away from the coast. A thin layer of warm waters from the E. - N. stops the supply of oxygen to the subsurface layers, which has a detrimental effect on the plankton and fish of the richest Peruvian productive region; heavy rainfall causes catastrophic flooding on the normally dry coast.
The penetration of warm waters into the south is associated with the weakening of the action of trade winds and the cessation of the rise of cold subsurface waters to the surface in the coastal part of the ocean. Usually this catastrophic phenomenon is observed in late December - early January. It manifested itself especially sharply in 1891, 1925, 1941, 1953, 1957-58 and 1972-73. During the years of development of E. - N., fish (anchovy) either die or leave coastal waters, which causes a high mortality rate of seabirds feeding on fish and reduces the amount of guano used as food. - X. fertilizers
An analysis of historical oceanographic, meteorological, heliogeophysical and geodynamic data was performed. Main results obtained:
Large-scale phenomena in the ocean and atmosphere of the Earth are closely related to each other, being direct factors of weather and climate fluctuations. In turn, these factors are a reflection of external (cosmic) influences: solar activity, interplanetary magnetic field and dissymmetry of the solar system, the latter being the guiding factor, affecting the influx of light radiation from the Sun to the Earth, changes in the speed of the Earth’s orbital and axial rotation, and precession of the earth's axis.
The speed of rotation of the Earth is associated with the magnitude of the angular momentum of the motion of the atmosphere in relation to the earth's surface (circulation index according to E.I. Blinova). It is shown that with an increase in the circulation index, the centers of atmospheric action over the oceans (the Azores and Honolulu anticyclones) shift southward.
As a result of the displacement of anticyclones to the south, the atmospheric pressure gradient between them and the equatorial zone increases (an increase in the Southern Oscillation index in the Pacific Ocean and the North-South Oscillation in the subtropical Atlantic zone). In these zones of increased atmospheric pressure gradients, trade winds intensify, drawing the surface waters of the oceans in the western and northwestern directions and, as a consequence, the appearance of low temperatures on the surface of the Pacific Ocean near the equator in its central and eastern parts.
The US National Oceanic and Atmospheric Administration (NOAA) has declared an El Niño (Spanish for "boy") in the Pacific Ocean. As reported, the climate phenomenon is characterized by an increase in the temperature of the surface layers of water by at least 0.5 degrees Celsius.
Currently, temperatures in this region of the Pacific Ocean are almost a degree above average for this time period. NOAA promises that El Niño will last until the spring of 2010. Officially, the last time El Niño occurred was in 2006.
Possible climate effects caused by El Niño include harsh winters in California, accompanied by snow storms, and drought in Indonesia. In addition, "Boy" can lead to floods in South and Central America. However, not all climate effects of El Niño are negative. Thus, among the advantages of this phenomenon are weaker hurricane seasons (the first hurricane of the new season recently formed).
Most recently, the American Space Agency provided Internet users with the opportunity to observe changes in the temperature of the oceans in real time using the Sea Level Viewer website. When you visit this resource, made using Flash technology, an interactive globe appears, which displays data on water temperature. In particular, the presence of El Niño is separately displayed there.
As previously reported, the earth has warmed by 0.4 degrees Celsius over the past 30 years, according to data obtained from NASA satellites and the American weather agency NOAA.
A map of temperature changes since December 1, 1978, when satellites began collecting data, shows that the level of warming has not been the same across the planet. Half the globe warmed by at least 0.3 degrees Celsius during this period, while a quarter of the Earth became 0.6 degrees warmer.
The strongest warming occurred in the North Atlantic and Arctic. The temperature rose the highest in one of the regions of Greenland - by more than 2.5 degrees.
One of the most prominent features of the 30-year temperature curve is the warming in 1997-1998 associated with El Niño, an anomalous warming of surface water in the eastern Pacific Ocean that affects the climate of the entire Western Hemisphere. The opposite phenomenon, La Niña, is associated, on the contrary, with anomalous cooling of water.
Conclusion
Unfortunately, the causes of El Niño still remain unknown, as are the consequences caused by global climate change. The repetition of this phenomenon is observed every six or seven years. Its duration depends on a number of factors, which meteorologists are currently studying.
The events of 1997-1998 caused La Niña. This natural phenomenon occurs when climate changes caused by El Niño become particularly noticeable. La Niña is the exact opposite of El Niño. Where one causes temperatures to rise, the other causes them to fall. While El Niño brings rain, La Niña brings drought.
On the coast of South America, La Nina is greeted with joy: with a decrease in the temperature of the current, more fish come and, consequently, catches increase. But in agriculture, the opposite is true: La Niña is not popular because the drop in temperature it causes has an adverse effect on crops.
In recent times, especially since 1982-1983, when the impact of El Niño was at its strongest, and also in 1990-1994, its longest period of influence, countries dependent on the vagaries of nature have relied entirely on weather forecasting.
Without a doubt, only an accurate forecast helps plan the harvest and the workload of the fishing fleet. And governments of different countries can develop plans for timely provision of financial assistance to various sectors of the economy.
So, an unusually complex and branched system of direct and feedback connections allows us to talk about the Earth as a single living organism in which everything is very finely balanced.
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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 are deteriorating sharply in Ecuador, Peru and northern Chile, 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, warm surface ocean waters are held by easterly winds - trade winds - in the western zone of the tropical Pacific Ocean, where the so-called tropical warm pool (TTB) is formed. 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. The atmospheric phenomena accompanying El Niño were called the Southern Oscillation (ENSO - El Niño - Southern Oscillation), as 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, South Africa and southeastern 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.
The first time I heard the word “El Niño” was in the United States in 1998. At that time, this 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 said the premature El Niño, dubbed the “Bruce Lee,” 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. The findings of this document state that the conditions for the formation of El Niño are currently in place, with the average surface temperature of the equatorial Pacific Ocean (SST) having elevated values and continuing 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. Blue areas correspond to low temperatures (La Niña), orange indicates high 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 the 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 thermal water outlets, 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 Mayans 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 nitrate, iodine, table salt and copper; for four centuries there has been no significant precipitation. The reason is that the Peruvian Current cools the lower layers of the atmosphere and creates a temperature inversion that 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 high atmospheric 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.
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.
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
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 eastern 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.
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 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.
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.
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.
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 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.
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 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 Mayans 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.
Links
- The El Nino Theme Page Explains El Nino and La Nina, provides real time data, forecasts, animations, FAQ, impacts and more.
- The International Meteorological Organization announced the detection of the beginning of the event La Niña in the Pacific Ocean. (Reuters/YahooNews)
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 | |
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Changing of the climate | Paleoclimatology El Niño Geochemical carbon cycle Proterozoic glaciation, Ice Age, Little Ice Age Thermal Maximum ( |
Introduction
3. Study of the El Niño phenomenon
Conclusion
Bibliography
Introduction
The first mention of the term "El Niño" dates back to 1892, when Captain Camilo Carrilo reported at the Geographical Society congress 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. A connection with flooding was reported in 1895. 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 in 1893 suggested that droughts in India and Australia occur at the same time. Norman Lockyer pointed out the same thing in 1904. In 1924 Gilbert Volker first coined the term "Southern Oscillation".
For most of the twentieth century, El Niño was considered a large local phenomenon.
Great El Niño in 1982-1983 led to a sharp rise in the interest of the scientific community in this phenomenon.
1. El Niño in the history of civilization
The mysterious disappearance of the Mayan civilization in Central America could be caused by severe climate changes. 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 Mayans 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.
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 in 1969 suggested that abnormal warming in the eastern Pacific Ocean may 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.
Virtki 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 may contribute to the sharper evolution leading to El Niño conditions through fluctuations in low-level winds and precipitation over the western and central regions. Pacific Ocean. The eastward propagation of oceanic Kelvin waves may be caused by MJO activity.
2. Southern Oscillation and El Niño
The Southern Oscillation and El Niño (Spanish El Niño - Baby, Boy) is a global ocean-atmospheric phenomenon. A characteristic feature of the Pacific Ocean, El Niño and La Niña are temperature fluctuations in surface waters in the tropical eastern Pacific Ocean. The names for these phenomena, borrowed from the native Spanish and first coined in 1923 by Gilbert Thomas Volcker, 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 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.
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 (Fig. 1)
Fig.1. 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:
1. Increase in air pressure over the Indian Ocean, Indonesia and Australia.
2. A drop in air pressure over Tahiti and the rest of the central and eastern parts of the Pacific Ocean.
3. Trade winds in the South Pacific are weakening or heading east.
4. Warm air appears near Peru, causing rain in the deserts.
5. 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 eastern 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.
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 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.
Traces of destruction caused by El Niño:
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