What caused the recent rare freezing weather in China?

Interpretation of La Nina

La Nina means "La Nina"-in Spanish it means "little girl, saint", which is the opposite of El Ni? o phenomenon. It refers to the abnormal drop of water temperature in the eastern Pacific near the equator, which is characterized by obvious cooling in the eastern Pacific, accompanied by global climate chaos, and always appears after El Ni? o phenomenon.

Meteorologists and oceanographers use it to refer to the large-scale continuous abnormal cooling of seawater in the eastern and central equatorial Pacific (the surface temperature of seawater is lower than the climate average by more than 0.5℃ for more than 6 months). La Nina is also known as the anti-El Nino phenomenon.

El Nino and La Nina are abnormal manifestations of alternating sea surface temperature in the equatorial, Middle East and Pacific Ocean, forming a cycle. La Nina phenomenon after El Nino is not uncommon. Similarly, La Nina will be followed by El Nino. However, according to the records since 1950, the frequency of El Nino is higher than that of La Nina. Under the background of global warming, the frequency and intensity of La Nina phenomenon are slowing down. Especially in the 1990s, there were three consecutive El Ni? os from 199 1 to 1995, but there was no La Ni? a in the middle.

La Nina usually follows the El Ni? o phenomenon. La Nina will appear in the second year of El Ni? o, sometimes lasting for two or three years. During 1988-1989, 1998 -200 1 year, a strong La Nina phenomenon occurred, which made the seawater temperature in the eastern and central Pacific Ocean lower 1 ~ 2℃,1999. Some scientists believe that La Nina tends to weaken due to the trend of global warming.

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The last La Nina phenomenon appeared in 1998 and lasted until the spring of 2000. El Nino and La Nina usually appear alternately, which have roughly opposite impacts on the climate. Through the energy exchange between the ocean and the atmosphere, the atmospheric circulation is changed, thus affecting climate change. According to the monitoring data in recent 50 years, the frequency and intensity of El Nino are more than La Nina.

La Nina often happens after El Nino, but it doesn't always happen. It takes about four years for El Nino and La Nina to transform into each other.

Chinese oceanographers believe that the catastrophic flood disaster in China in 1998 was caused by "El Nino-La Nina phenomenon" and ecological deterioration in the Yangtze River basin.

Oceanographers and meteorologists in China noticed that last year's El Ni? o phenomenon (ocean warming) in the tropical Pacific turned into La Ni? a phenomenon (seawater cooling) within one month. This unprecedented situation is one of the reasons for the surge in rainfall in the Yangtze River basin.

The El Nino phenomenon made the climate in China abnormal. 1998 from June to July, there was frequent rainfall in the south of the Yangtze River and South China, and serious floods occurred in the Yangtze River basin and the two lakes basin. The water level of some rivers has exceeded the warning water level for a long time, and the rainfall in parts of Guangdong, Guangxi and Yunnan is also above 50%. Waterlogging also occurs in parts of North China and Northeast China. La Nina can also cause climate anomalies. Chao Jiping, academician of the China Academy of Sciences and honorary director of the National Marine Environmental Forecasting Research Center, said that the current situation is that the influence of El Ni? o has not completely disappeared, but the influence of La Ni? a has started again, which makes the climate state of China extremely complicated. Generally speaking, after the large-scale warm and humid air caused by El Nino moves to the higher latitudes in the northern hemisphere, it meets the cold air in the north and exchanges cold and warm, resulting in an increase in rainfall. But after June, when summer comes and the rain belt moves northward, the flood season in the Yangtze River basin should be over. But then La Nina appeared, the air in the south became cold and sank, and the warm and humid airflow that had moved northward returned to fill the vacuum. In fact, the subtropical high reached 30 degrees north latitude at 10 in July, and suddenly retreated southward to 18 degrees north latitude. This phenomenon has never happened in history.

La Nina is a modified transitional phenomenon after El Nino. This hydrological feature will cause the water temperature in the eastern Pacific to drop, which will lead to drought. On the contrary, the water temperature in the western Pacific will rise, and the precipitation will be significantly higher than normal. Scientists believe that La Nina, a hydrological phenomenon, will not have a significant impact on the world climate, but will bring more rainfall to Guangdong, Fujian, Zhejiang and even the entire southeast coast in a certain period of time.

El Nino and La Nina are far from the tropics.

A few days ago, NASA said that in the past three years, El Nino and La Nina caused abnormal weather.

They will no longer affect the tropics, but other regions will also be affected by them. The temperature and water level in tropical Atlantic and Pacific have returned to normal levels. The water level in the central Pacific Ocean is higher14 ~ 32cm than normal, and the water level in Bering Sea and gulf of alaska is 5 ~13cm lower than normal. William Patzelt, an oceanographer at the agency's Jet Propulsion Laboratory, said that the current calm began with the disappearance of La Nina three months ago. He believes that the global climate system has returned to the state of three years ago.

La Nina phenomenon is decreasing.

The following content was published in 2007, but the facts have overturned this theory. It can be seen from the snowstorm in the south in early 2008 that La Nina has not disappeared.

———2008.0 1

The latest ocean observation data sent back by Poseidon satellites in France and the United States show that the La Nina phenomenon affecting the Pacific Ocean has obviously weakened in the past two years, and the world's largest ocean will restore its former "tranquility".

"La Nina" literally means "girl" and refers to a phenomenon of abnormal water temperature change in the eastern Pacific Ocean near the equator. La Nina phenomenon is formed after the huge cold water area caused by El Nino surfaced in the East Pacific Ocean. Because of its characteristics, it is also called "anti-El Nino" phenomenon. La Nina phenomenon is marked by hurricane, rainstorm and severe cold, which, together with El Ni? o phenomenon, will cause serious global climate anomalies.

According to French experts, "La Nina" usually appears after "El Nino". Usually, these two phenomena each last for about a year. However, the "La Nina" phenomenon, which started at 1998, lasted for two years and didn't begin to weaken until June this year (2007). They said that the current research could not explain why the La Ni? a phenomenon and the previous El Ni? o phenomenon were extremely strong, nor could it explain why the La Ni? a phenomenon lasted for one year longer than before.

Researchers observed signs of "La Nina" weakening twice in June and June last year, but later results proved that these were just illusions. After a little breathing, "La Nina" made a comeback again. French experts stressed that the latest data sent back by this satellite shows that the phenomenon of "La Nina" has obviously weakened, and this time the "girl" is really old.

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So, how was La Nina formed? El Nino is related to the warming of sea surface temperature and the weakening of trade winds in the equatorial Middle East Pacific, while La Nina is related to the cooling of sea surface temperature and the strengthening of trade winds in the equatorial Middle East Pacific. So La Nina is actually the product of the interaction between tropical ocean and atmosphere.

Trade winds refer to the winds blowing from tropical regions to equatorial regions in the lower atmosphere, which are called "northeast trade winds" in the northern hemisphere and "southeast trade winds" in the southern hemisphere. The Spaniards who lived in South America a long time ago used this continuous easterly wind to sail to Southeast Asia for business activities. So trade winds are also called trade winds.

The motion of the ocean surface is mainly constrained by the sea surface wind. Because of the existence of trade winds, a large amount of warm water is blown to the equatorial western Pacific Ocean and blown away in the equatorial eastern Pacific Ocean, which is mainly supplemented by cold water below the sea surface. The SST in the equatorial eastern Pacific is obviously lower than that in the western Pacific. When the trade winds strengthen, the upwelling phenomenon of deep seawater in the equatorial eastern Pacific becomes more intense, resulting in abnormally low sea surface temperature, which makes the airflow in the equatorial eastern Pacific sink, while the upward movement of the airflow in the equatorial western Pacific intensifies, which is conducive to the strengthening of the trade winds, thus further aggravating the development of cold water in the equatorial eastern Pacific and triggering the so-called La Nina phenomenon.

La Nina also has an impact on the climate. La Nina is the opposite of El Ni? o. With the disappearance of El Ni? o and the arrival of La Ni? a, the weather and climate disasters in many parts of the world will also change. Generally speaking, La Nina is not very gentle and will bring disaster to many parts of the world. Its climate impact is roughly opposite to that of El Nino, but its intensity and impact are not as good as that of El Nino.

June 5438+October 2007 10, La Nina affected the north, causing a large area of sea ice phenomenon.

Influence of La Nina on Climate in China

The following year refers to 2007.

In the first half of the year, the national climate showed a diversified trend. After research and analysis, climate experts initially believe that La Nina phenomenon is the main reason that affects China's climate in the first half of the year.

Zhao Zhenguo, a researcher at the National Climate Center, believes that this year, due to the La Ni? a phenomenon, the water temperature in the equatorial eastern Pacific is low and the meridional circulation in East Asia is abnormal, resulting in the northerly airflow prevailing in northern China since the spring, while the warm and humid airflow in the southeast is relatively weak. It leads to frequent strong cold waves and strong winds in the north, but the rainfall continues to be less and the temperature remains high.

According to statistics, sandstorms occurred frequently in northern China this spring. From March to April, a large-scale sandstorm 12 occurred, affecting northwest, north, northeast, Huanghuai and even Jianghuai areas. In May, there were three regional or local sandstorms in northwest China, which were rare in the same period of nearly 50 years. Chen Yu, a climate expert, said that in the past 50 years, the frequency of dusty weather in northwest China has increased year by year.

Lu, a senior engineer of the National Climate Center, said that since 300 AD, there have been five frequent sandstorms in China, each lasting about 90 years. In the past 10 years, sandstorms have shown a significant increase trend.

Talking about the causes of sandstorms, Chen Yu believes that the formation and scale of sandstorms depend on two factors: environment and climate. From the environmental point of view, the increasingly serious desertification problem can not be ignored. However, "there is no smoke without fire". From the climate point of view, the temperature in the northern region has risen rapidly since February this year, with a high range of 2 to 3 degrees Celsius, which led to the early thawing of soil and the emergence of a large number of dry soil layers. At this time, the rainy season has not yet arrived. Affected by La Ni? a phenomenon, windy weather occurred continuously in the northern region, and the gale immediately formed a sandstorm.

High temperature and little rain in the north are also hot topics. From March to May this year, the national average temperature reached 196 1, which was the highest in the same period, especially in the north. Since February, there has been less precipitation in most areas north of the Yangtze River. For four consecutive months, the total precipitation was less than 100 mm, and less than 50 mm in North China and Northwest China, which was more than 50% less than normal. Especially from February to April, the average precipitation in the northern region was only 23 mm, which was the least since the founding of the People's Republic of China. The combined effect of high temperature and little rain led to the rapid decline of soil water content in the northern region, and the worst spring drought occurred since the 1990s.

Zhao Zhenguo said that since 1992, except 1998, the precipitation in North China from February to April in other years was lower than the multi-year average, especially since June last year, the precipitation in North China has been less and the soil moisture has been very poor. At this time, under the influence of La Nina phenomenon, the northerly airflow prevails in northern China, while the warm and humid airflow in the southeast is relatively weak. Coupled with the unfavorable cooperation of cold and warm air, the ideal rainfall conditions in the northern region have not been formed, resulting in continuous lack of rain and drought.

During the drought-resistant period in the north, heavy rains occurred frequently in some areas south of the Yangtze River. In this regard, Lu pointed out that the heavy rain in the south is the result of local strong convective weather, and the precipitation is normal in a wide range of river basins.

When talking about the overall climate characteristics and development trend of China, Lu said that from the global climate change trend in recent years, the overall trend is diversified, which is mainly the result of the alternating effects of El Ni? o and La Ni? a phenomena under the background of global warming. In this environment, China cannot be a peaceful "Xanadu". He said that the national meteorological department is paying close attention to the future atmospheric climate changes and making timely forecasts to minimize the losses caused by disastrous climate.

Relationship between Climate Anomaly and La Nina in 2008

We are in La Nina state this year, that is, the SST in the equatorial eastern Pacific is 0.5 degrees lower than normal, which has a very obvious impact on China's climate. Under the influence of La Nina phenomenon, the meridional circulation in East Asia is abnormal, which is very beneficial to the southward movement of cold air in northern China. It has given us a cold winter, so we can see that this cold winter has already appeared this year.

Rani, that's just one of the reasons. Another reason for the heavy snow is as follows:

Since 2008, the high pressure in Asia has been very active, forming a cold air mass in the south, affecting China, and there has been a large-scale gale and cooling weather. However, due to the active warm air mass in the south this year, a large number of warm and humid air currents from the Pacific Ocean and the Indian Ocean frequently patronize the southern region. When the powerful cold air mass from Mongolia and Siberia quickly moved south to meet the warm and humid air mass, the cold and warm air just merged into one. Affected by these two air currents, there have been more rainy and snowy weather recently, especially in the Yangtze River basin, and the low temperature weather has lasted for a long time. If there is only a strong cold air mass without a large amount of water vapor provided by warm and humid air mass, there will only be strong winds and cool weather in the south; If there is only a large amount of water vapor provided by warm and humid air masses, there will be no disastrous weather at all without the arrival of cold air masses. When both are ready, disaster comes.

At the same time, when China was severely hit by a snowstorm, the temperature in the central United States dropped by 20 degrees Celsius, and snowstorms appeared from time to time (2008+0); Central Asia, which has not snowed for a hundred years, suddenly snowed 10mm, setting a new record for Baghdad 100 (2007+02). In the summer of 2007, western Europe suffered severe floods, and Britain and France suffered huge losses (summer of 2007). Since the beginning of winter, the temperature in the northern edge of Russia has hit a new low, once reaching MINUS 50 degrees Celsius ... La Nina is still not over, and the situation is still grim. ...

La Nina phenomenon is also called anti-El Nino phenomenon.

La Nina-Where are you from?

Last year, after the "El Nino" phenomenon that lasted for more than a year quickly disappeared, "La Nina" immediately appeared in black and pink.

So what is 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 (similar to El Ni? o phenomenon).

Conversely). This is a new term used in meteorology and oceanography. It means "little girl", just as it means "El Nino"

On the contrary, El Nino is also called "anti-El Nino" or "cold event".

El Nino and La Nina are abnormal manifestations of alternating SST changes in the equatorial, Middle East and Pacific Ocean.

The process of cold and warm changes constitutes a cycle, and it is not uncommon for La Nina to appear after El Nino. Similarly, Rani

El Nino will appear after Nina. However, according to the records since 1950, the frequency of El Ni? o is higher than that of La.

Nina. Under the background of global warming, the frequency and intensity of La Nina phenomenon are slowing down. Especially in 1990.

From 199 1 to 1995, there were three consecutive El Ninos without La Nina.

So, how was La Nina formed? El Nino and SST warming and the trade winds in the equatorial Middle East and the Pacific Ocean

On the other hand, La Nina is related to the cooling temperature in the central equatorial and eastern Pacific and the enhancement of trade winds. Therefore,

In fact, La Nina is the product of the interaction between tropical ocean and atmosphere.

The trade wind refers to the prevailing wind in the lower atmosphere blowing from the tropical region to the equatorial region, which is called "Northeast Trade Wind" in the northern hemisphere.

The southern hemisphere is called the "southeast trade wind". The Spaniards who lived in South America a long time ago took advantage of this continuous eastward trend.

The wind sailed to Southeast Asia for commercial activities. So trade winds are also called trade winds.

The motion of the ocean surface is mainly constrained by the sea surface wind. The existence of trade winds makes a lot of warm water blown to the west of the equator.

In the Pacific, the warm water in the equatorial eastern Pacific is blown away, which is mainly supplemented by cold water below the sea surface.

The SST in the eastern Pacific is obviously lower than that in the western Pacific. When the trade winds strengthen, the upwelling phenomenon of deep seawater in the equatorial eastern Pacific becomes more serious.

Strong acceleration leads to abnormally low sea surface temperature, which makes the airflow in the eastern equatorial Pacific sink, while the airflow is on the western surface.

The strengthening of the ascending movement is conducive to the strengthening of the trade winds, thus further intensifying the development of cold water in the equatorial eastern Pacific Ocean, triggering the so-called

La Nina phenomenon.

La Nina also has an impact on the climate. La Nina and El Nino are opposite in nature. With the disappearance of El Nino, pull

With the arrival of Nina, the weather and climate disasters in many parts of the world will also change. Generally speaking, La Nina is not sex.

The situation is very mild, and it will also bring disasters to many parts of the world, and its climate impact is roughly the opposite of that of El Ni? o.

But its intensity and influence are not as good as that of El Nino.