What is the impact of El Nino and La Nina on nature? How does it protect the natural environment? What are the reasons?

It often refers to the phenomenon that the seawater temperature in the central and eastern tropical Pacific Ocean rises abnormally in a large range, resulting in global climate anomalies and a large number of fish deaths. El Nino means "El Nino" in Spanish. This phenomenon first appeared near the Pacific coast of Ecuador and Peru in South America, mostly around Christmas, hence the name. Generally speaking, the surface water temperature in the tropical western Pacific is higher, while the sea surface temperature in the eastern Pacific is lower. This sea surface temperature gradient between the east and west Pacific Ocean, together with the trade winds, constitutes a quasi-equilibrium state of the air-sea coupling system. Every 2-8 years, this quasi-equilibrium state will be broken, and the warm air flow in the western Pacific will move eastward with thunderstorms, making the water temperature in the whole Pacific warm and the climate abnormal for one year or more. In the months before El Nino, the warm water in the equatorial Pacific moved from west to east on a large scale. Around Christmas, the warm water on the east coast of the equatorial Pacific went south along the coasts of Ecuador and Peru, and the water temperature was abnormally high, with the highest being 5-6℃ higher than normal. Due to the rapid expansion of the warm water area to the west, the tropical rainy belt also goes south. The precipitation in the equatorial eastern Pacific, which was originally dry, increased sharply, and the river flooded; The western equatorial Pacific, which was originally a rainy season, is dry and rainless. In addition, the climate around the world has been seriously affected, causing serious natural disasters.

La Nina phenomenon: After El Ni? o, the tropical Pacific sometimes has the opposite state, which is called La Nina phenomenon. La Nina means "little girl" in Spanish. La Nina phenomenon is characterized by obvious cooling of sea surface temperature in the central and eastern Pacific Ocean, accompanied by global climate anomalies. It is used for the phenomenon that the sea surface temperature in the eastern and central equatorial Pacific is abnormally cold in a large range. The average sea surface temperature in the equatorial Pacific from 5 degrees north latitude to 5 degrees south latitude, and from 150 degrees west longitude to 90 degrees west longitude has been higher or lower than the normal value of 0.5℃ for more than 6 months, respectively, which is El Nino and La Nina.

Concept map of El Nino phenomenon

2. Approaching El Nino-Study on the Causes

How is the El Nino phenomenon formed and why does it affect the state and change of the atmosphere? This has always been an important topic in international marine and meteorological science research. The World Meteorological Organization formulated the Tropical Ocean and Global Atmosphere Plan (TOGA), which lasted for ten years from 65438 to 0985. One of its purposes is to improve the ability to predict El Nino and abnormal climate by studying the air-sea interaction. Chinese and American scientists have also carried out the "Joint Study on Air-Sea Interaction in the Tropical Western Pacific between China and the United States".

It is now known that under normal circumstances, a stable and strong easterly trade wind prevails on both sides of the equator of the Pacific Ocean, which blows warm surface seawater away from the coast of South America, flows westward, and accumulates in the equatorial western Pacific Ocean, and its sea surface is 30-40 cm higher than that on the east side; At the same time, the upwelling (called upwelling area) formed to compensate the seawater to the west has also appeared on the coast of South America. The upturned seawater comes from the deep layer and is rich in plankton, which provides a lot of food for fish. What is more significant is that its temperature is relatively low, so it finally forms a water temperature distribution pattern in the equatorial Pacific region, which is warm in the west and cold in the east. For the atmosphere, seawater is like a heat engine. The sea temperature in the west is high, the heated atmosphere rises, and turns east after reaching high altitude. The sea surface temperature in the east is low, and the air cools and sinks. After reaching the sea surface, it turns to the west (that is, the southeast trade wind), thus forming a complete zonal vertical circulation circle over the equator, which meteorologists call "Wacker circulation". It's like this all year round. As a result, the east coast of the equatorial Pacific has become a famous equatorial arid area because of the prevalence of downflow. The annual precipitation is only about 500mm in the range of 00- 100 south latitude east of international date line, and even less in the coastal areas of Peru and Chile near the cold water coast. On the contrary, in the Philippines and the western part of Indonesia, the convective updraft is strong, forming a humid and rainy climate zone, and the conventional precipitation is above 2000 mm. Wakak circulation is also the link to produce the Southern Oscillation.

However, when the easterly airflow weakens for some reason, the surge of deep cold water in the Middle East and the Pacific Ocean is greatly weakened. Even due to the appearance of the westerly airflow near the equator, the warm seawater originally accumulated in the west flows eastward, blowing the equatorial countercurrent seawater with higher water temperature to the south against the ocean current in the direction of the Peruvian cold current, and transforming the Peruvian cold current into a warm current. This calm and unstable warm current is called El Nino warm current. In this way, the original sea surface temperature distribution pattern is destroyed, the sea surface temperature on the west side of the Pacific Ocean decreases, and the sea surface temperature in the equatorial Middle East Pacific Ocean increases. When the temperature rises above 0.5℃ for several months to half a year, a new El Ni? o phenomenon is formed. Usually, warming not only occurs on the sea surface, but sometimes affects the depth of 200 meters. 1997 After the start of El Ni? o, it was observed that the warm water area in the central and eastern Pacific Ocean expanded by 300%, and the water temperature in the Middle East Pacific Ocean was 5℃ higher than normal in June and February of 5438. The anomaly of SST will inevitably affect the wacker circulation.

Why is it abnormal for the temperature to rise by 0.5℃? Seawater has high specific heat and strong ability to absorb solar radiation, so the vast ocean is usually considered as an important thermal reservoir of the atmosphere. According to the calculation, at the depth of 100 meters, the heat used to change the seawater temperature by 0. 1℃ is enough to raise the atmospheric temperature above 5000 meters by 6℃. The equatorial Pacific Ocean accounts for 1/4 of the global sea area, so the abnormal warming of sea surface temperature there will immediately affect the intensity and direction of Wako circulation. In nature, continuous updraft means continuous water vapor condensation and heavy rainfall, while continuous downdraft is correspondingly sunny and dry. Because the original downflow prevalent area near the coastal warming place in South America has become a strong upwelling convection area, it is extremely rainy and flooded. The seeds of flowers and plants accumulated for many years in arid areas bloom as soon as it rains, and the desert suddenly becomes an oasis. In the west, the tropical rain forests in Indonesia, Hiran Island and northern Australia are weakened due to the decrease of sea surface temperature, which leads to the decrease of rainfall and the development of drought. It is against this background that fires broke out in Indonesia for several months last year. At the same time, in the ocean, the weakening or loss of upwelling makes plankton in the water drop sharply, fish die because of the sharp drop in food, and seabirds who feed on fish starve to death or migrate in batches. For example, during El Nino in 1925, Peru not only lost a lot of fish and birds, but also observed 394.4 mm of precipitation in March, while the total precipitation here in the first five years was only 17.9 mm.

It has also been found that the occurrence of El Nino does not follow strict laws. Generally, it is formed in the winter and spring season and ends in the winter and spring season of the following year, lasting about one year, with an average of 2-7 years. Size occurred more than 30 times in 100 year. Since 1950s, there have been 13 ENSO events in the world, and 1997 is 14, which is the fourth strong ENSO phenomenon in recent years.

The formation of El Nino phenomenon, each symptom and the location of abnormal warming are different.

What caused the sudden change of easterly airflow in the first place? Unfortunately, this veil has not been completely lifted. Some experts in China have suggested that the earth movement and some internal changes, such as the continuous deceleration of rotation rate, volcanic eruption in the Pacific Ocean, submarine earthquake and solar activity, may all lead to the formation of El Ni? o. Apart from these "pure natural factors", are they related to the deterioration of the natural environment caused by human activities? These speculations need further argumentation. However, the weakening of the trade winds in the central Pacific is the direct cause of the formation of El Nino. It is summer in the southern hemisphere from June 6, 65438 to March of the following year. The water temperature in the southern hemisphere is generally warming. The equatorial countercurrent flowing eastward is strengthened. At this time, the global pressure belt and wind belt move south, and the northeast trade wind passes through the equator and is deflected into the northwest monsoon by the rotation of the southern hemisphere. The northwest monsoon weakens the near sea breeze on the west coast of Peru-the southeast trade wind, and even forms a westerly airflow. It leads to the abnormal warming of the equatorial sea area in the Middle East, which heats the atmosphere abnormally, affects the Wakefield circulation in the equatorial region, destroys the normal balance, and then causes climate anomalies in other regions. This view has been accepted by many experts.

On the contrary, when the trade winds continue to strengthen, the warm water in the eastern equatorial Pacific is scraped away, and the deep cold water is turned up as a supplement, and the sea surface temperature is further cooled, which is easy to form La Nina.

The simplified model of El Nino shows the role of different fluctuations in the process of ocean energy transfer. In this simplified model, waves in the ocean, called Rossby waves, travel westward from the unusually warm sea near the equator. When it reaches the western boundary of the ocean, it will be reflected into a different wave called kelvin wave. This fluctuation spread eastward, offsetting or changing the original signs of abnormal temperature in the warm sea, and causing cooling events. The time required for this half cycle in the whole El Ni? o event is determined by the propagation speed of these waves, which takes about 2 years.

This phenomenon is essentially driven by ocean dynamics, and the corresponding atmospheric change is determined by sea surface temperature (in turn, atmospheric change will strengthen the distribution pattern of ocean temperature), and the distribution of sea surface temperature is determined by ocean dynamics, so the El Ni? o phenomenon represented by the above simplified model is predictable in nature.

Influence of El Ni? o and La Nina: When El Ni? o occurs, countries in the western Pacific, such as Indonesia and Australia, are prone to drought, while countries along the coast of South America, such as Peru and Ecuador, have heavy rains. On the contrary, when La Nina occurs, Australia and Indonesia are prone to floods, while Peru and Ecuador are prone to droughts. Generally speaking, when the El Ni? o phenomenon occurs, the global average temperature will rise. In recent 10 years, the frequency of El Nino phenomenon has accelerated, resulting in the warmest average temperature in the last three years after 1990, of which 1998 is the warmest year since 186 1 year. Since 1980s, in the short period of 17, there have been six El Nino events and three La Nina events. Among them, 1982- 1983, 1997- 1998 was the strongest El Ni? o event in the 20th century, which brought incalculable disasters to Latin America, Asia-Pacific and Africa, and initially estimated that it caused a loss of $25 billion to the world economy.

El Nino and La Nina events also have a great influence on the climate in China. For example, from June to August in the summer of 1998, catastrophic floods occurred in the Yangtze River basin, Nenjiang River basin and Songhua River basin in China, especially in the Yangtze River basin, which caused another basin-wide flood in the Yangtze River since 1954. According to statistics, during the period of 1998, 29 provinces and cities in China suffered from different degrees of rainstorm and flood disasters, with 230 million people affected, 3656 people killed, 7.33 million houses collapsed,13.79 million houses were damaged, 25.44 million crops were affected, and the direct economic loss was 264.2 billion yuan.

3. What are the impacts of El Nino and La Nina on the climate in China?

In El Nino year, the East Asian monsoon weakened, and the main monsoon rain belt in China was southward in summer, so it was more likely to be rainy in the Jianghuai Basin, while the northern region, especially from North China to Hetao, was less rainy and dry. La Nina year is just the opposite.

In autumn and winter of El Nino, most of the precipitation in the north is less than normal, most of the precipitation in the south is more than normal, and the Qinghai-Tibet Plateau is snowy in winter. The distribution of precipitation in autumn and winter in La Nina in China is more in the north and less in the south.

In El Nino year, it is often warm in winter and cool in summer in China, especially in Northeast China, where the summer temperature is low, and the possibility of chilling injury is greater. In La Nina years, China is prone to winter Leng Xia fever.

During El Nino, the number of typhoons generated in the western Pacific and South China Sea and landed in China was less than normal, while during La Nina, it was more than normal.

4. What is the impact of El Nino and La Nina on the global climate?

The rapid rise of SST in the tropical central and eastern Pacific directly leads to abnormal rainfall and even floods in the countries along the central and eastern Pacific and South American Pacific. It also reduced precipitation in the tropical western Pacific, causing severe drought in Indonesia and Australia. El Nino often leads to droughts in southeastern Africa and northeastern Brazil, warm winters in western Canada and northern United States, and wet and rainy winters in southern United States. It is also related to the low summer temperature in Japan and Northeast China and the precipitation in Japan and China. In addition, El Nino tends to inhibit the formation of tropical storms in the western Pacific, but it will increase hurricanes in the northeast Pacific. La Nina's climate impact is completely opposite to that of El Ni? o, but its impact is less than that of El Ni? o ... When La Nina appeared, Indonesia, eastern Australia, northeastern Brazil, India and southern Africa had more rainfall, but the eastern and central equatorial Pacific, Argentina, equatorial Africa and the southeastern United States were prone to drought.

Overview of El Nino phenomenon

1. Performance: The sea water in the eastern and central South America and the equatorial waters of the Pacific Ocean (Peru and Ecuador) is unusually warm and flows eastward to the west coast of South America, which is called "El Ni? o" (Spanish means "the son of Christmas") because it originates from around Christmas every year.

The internationally recognized criterion for judging the El Ni? o phenomenon is that the monthly average temperature in the equatorial waters of the eastern and central Pacific Ocean has been above 0.5℃ for more than three consecutive months, even if the seawater temperature is abnormal. The reason is that seawater has high specific heat and strong ability to absorb solar radiation, so the vast ocean is usually considered as an important thermal reservoir of the atmosphere. According to calculation, the heat used to change the seawater temperature at a depth of 100 m by 0. 1℃ is enough to raise the atmospheric temperature at a thickness of 5000 m above it by 6℃. The equatorial Pacific occupies a quarter of the global sea area, so the abnormal warming of sea surface temperature there will cause global climate anomalies.

2. Regularity: The El Ni? o phenomenon occurs every 3 to 7 years, and the active period usually lasts for more than 1 year, and anti-El Ni? o phenomenon occurs at intervals (that is, the abnormal cooling of water temperature near the equator in the eastern Pacific-La Ni? a phenomenon).

3. Impact:

(1) Global climate anomaly. El Nino disturbs the ocean current model and atmospheric circulation, the southeast trade wind south of the equator weakens or disappears, the warm current south of the equator weakens or disappears, and the equatorial countercurrent strengthens. The water temperature in the eastern and coastal areas of the South Pacific is abnormally high, and precipitation increases. The western Pacific is dry with little rain, but the Sahara desert in Africa is extremely dry.

(2) Global warming. During the westward flow of the El Nino warm current, it collided with the Kuroshio warm current (that is, the Japanese warm current) and moved northward. The Kuroshio Warm Current is a warm current across the Pacific Ocean, which comes from near Japan and usually transports huge heat to the eastern Pacific Ocean. Its northward movement has raised the water temperature in the northern sea area and the temperature in the northern hemisphere.

(2) Marine biological disasters. The water temperature near the fishing ground in Peru rises, and the upwelling turns into downwelling, which destroys the marine ecology and threatens the survival of marine life. 1972- 1973 When a strong El Ni? o occurred, the surface water temperature in the sea area near the equator in the central and eastern Pacific Ocean and the west coast of South America was 4℃ higher than the normal value, which caused a large number of Peruvian fish to die or move southward, resulting in a large number of eel-eating birds to die. All kinds of biological bodies float on the sea, rotting and stinking, and the sea is dark.

(3) Extraordinary storm surge disaster. Oceanographers have found that the occurrence of severe storm surge disasters is directly related to the El Ni? o phenomenon.

(4) global plague epidemic. El Nino disturbed the original global climate pattern, induced this natural disaster, led to the migration of some creatures, and thus induced the spread of some epidemics and plagues around the world. Dengue fever and epidemic plague, which were prevalent in the Caribbean and Central America from 65438 to 0993, raged in Puerto Rico, Central America and northern Brazil. 1994 The spread of cholera in Bangladesh, hepatitis in South America and equine encephalitis in eastern Massachusetts is also directly related to El Ni? o..

(5) Joint economic losses. 1973 During the El Ni? o, a large number of anchovies in Peru died or moved southward, resulting in a large number of birds feeding on eels. This year, Peru's fishing catch dropped sharply from 6.5438+0.03 million tons to 6.5438+0.8 million tons. Exports have fallen, fishermen have no income, and fishermen are unemployed in large numbers. The fish meal industry with anchovy (sardine) as raw material is in a depression period, the factory closes down and the price of fish meal industry rises rapidly. Manufacturers who use fish meal as feed all over the world have to use soybeans as feed. As a result, the price of soybeans has soared, and even in Japan, which is far away from the Pacific Ocean, the price of tofu has also increased a lot. The strong El Nino warm current has brought extremely adverse effects on some aspects of the world economy.

(6) Loss of life and property. The El Ni? o events from 1982 to 1983 caused floods in northern Peru and Ecuador, killing 600 people and losing 650 million dollars. At the same time, it caused severe drought in Indonesia, India and Australia, killing 400 people and losing $3 billion; From 1997 to 1998, El Ni? o caused hundreds of millions of dollars in economic losses around the world.

4. Impact on China:

(1) In the year of El Nino, the summer monsoon weakened, and the summer rain belt in China was located to the south, with little rain and drought in North China. 1997 The precipitation in the main flood season is the second year with little rain and drought in 46 years.

(2) The middle and lower reaches of the Yangtze River entered Meiyu late.

(3) In the autumn of El Ni? o, the eastern part of China is prone to precipitation distribution with less in the north and more in the south.

(4) Warm winters often occur in China.

(5) In the El Ni? o year, the number of tropical storms and typhoons generated in the Northwest Pacific and South China Sea is less than normal.

5. Causes of El Ni? o phenomenon:

(1) The weakening of equatorial trade winds in the Pacific Ocean may be an important reason for triggering El Ni? o..

(2) The slowdown of the angular velocity of the Earth's rotation may be an important reason for the formation of El Nino.

(3) Submarine volcanic eruption and earthquake may be important causes of El Nino.

6. Enlightenment:

(1) People's understanding is constantly improving. The process of people's understanding of El Nino phenomenon, from simple ocean phenomenon to air-sea interaction, to the signal of climate anomaly, has been expanding and deepening. From the beginning, Peruvian fishermen saw the temporary disappearance of marine life, the death of fish and the vitality in the desert on land, and gave the warm ocean current the reputation of "El Ni? o". However, according to the current statistics, every El Ni? o brings tens of billions of dollars in losses, but it is impossible to make a clear judgment on whether "warm winter" is good or bad.

(2) Things are generally related. It has also been noted that during El Ni? o, warm current replaces cold water, which directly leads to the disappearance of plankton, the decrease of fish, the death or migration of fish-eating birds, the decrease of fish meal and bird droppings, and the shortage of fertilizer and animal feed (fish meal). Subsequently, the prices of soybeans as feed substitutes and feed-dependent chickens and poultry soared. For example, two years after El Nino in 1982, the catch in Peru dropped sharply from10.3 million tons to1800,000 tons, and the soybean prices in Japan and the United States rose more than three times. If we consider the increase in coconut prices caused by the drought in the Philippines and the consequent shortage of soap and detergent raw materials, it will eventually go beyond the field of abnormal climate and enter the discussion of ecological environment and eco-economy.

(3) Look at the problem comprehensively. What we are facing now is an earth system, a system including atmosphere, ocean, biology and so on. On this basis, we can evaluate and study El Nino and other phenomena in this system more comprehensively. At this point, it is the advantage of geographers.

7. Benefits of global warming:

(1) makes China's agricultural climate heat resources richer, the accumulated temperature increases, the growth period is prolonged and the frost period is shortened. It will push the boundary between the existing agro-climatic zone and various cropping systems to the north, which is conducive to improving the multiple cropping index of cultivated land, alleviating the chilling injury that plagues the northern cold agricultural areas and improving the final yield of crops.

(2) It can make the world's large-scale grain yield high. For many developing countries on the edge of monsoon, it is possible to get wet and warm, which is not only beneficial to the development of agricultural production, but also to the improvement of ecological environment.

La Nina made Millennium extreme cold experts predict the winter climate in China this year.

Introduction to La Nina:

La Nina refers to the phenomenon that the sea surface temperature in the eastern and central equatorial Pacific Ocean continues to be abnormally cold (just the opposite of El Ni? o phenomenon), which is the product of the interaction between tropical ocean and atmosphere. . It can be seen from the snowstorm in the south in early 2008 that La Nina has not disappeared.

Times News This summer, not only China, but also the eastern United States, Europe and even the whole northern hemisphere experienced the hottest summer in recent years, but after autumn, the temperature began to plummet again. Some meteorologists predict that Europe may face a "once in a thousand years" new low temperature.

The climate of China this year is similar to that of 1998, which is likely to be a cold winter. This abnormal climate is related to a phenomenon called La Nina.