The official announcement of the country! The peak of the El Niño event has passed, which can be said to be a good thing, but it can also be said that it is not a good thing, because there may continue to be big changes in the future, and La Niña may make a comeback!
What is La Niña.
Taking the equator as the dividing line, the earth can be divided into trade wind belts, westerly wind belts and polar easterly wind belts. Under the action of the Earth's rotational deflection force, the wind direction deviates, and the northeast trade wind is formed in the northern hemisphere. Southeast trade winds form in the southern hemisphere. The area where trade winds blow all year round is called the trade wind belt.
La Niña refers to the phenomenon of large-scale surface water temperature in the central and eastern equatorial regions of the Pacific Ocean continuously and abnormally cooling, and we all know that the presence of trade winds causes a large amount of surface warm water to be blown to the equatorial western Pacific region; In the eastern equatorial Pacific, warm water is swept away and is mainly replenished by cold water below the sea surface, and the SST in the eastern equatorial Pacific is significantly lower than that in the western Pacific.
Therefore, under normal conditions, the sea level along the equatorial Pacific Ocean is high in the west and low in the east, and this structure corresponds to the distribution of mean SST in the west and cold in the east.
When the trade winds intensify, the upward upturn of the deep sea water in the eastern equatorial Pacific becomes more intense, resulting in abnormally low sea surface temperatures and the sinking of airflow in the eastern equatorial Pacific. The upward movement of the airflow in the west is more intensified, which is conducive to the strengthening of the trade winds, which further exacerbates the development of cold water in the eastern equatorial Pacific Ocean, causing the so-called La Niña phenomenon.
La Niña's impact on the global climate as well as in China.
When La Niña occurred, due to the strengthening of the global pressure field, the northerly airflow prevailed in China in winter, cold waves and strong winds occurred frequently, the ice conditions in the Yellow Sea and the Bohai Sea were generally heavier, and the frequency of sand and dust was higher than in normal years.
Scientists have found that in La Niña years, China is prone to cold winters and hot summers, because in summer, in the low latitudes, the Pacific high pressure is also correspondingly strengthened at this time, and the location is northerly, and the tropical convergence zone close to the south side of the parachic is also northerly. Typhoons, on the other hand, mostly develop under low pressure or clouds in the convergence zone. In addition, the surface water temperature in the western Pacific Ocean is high. Tropical storms have abundant energy and strong convection over the sky, and under the action of the summer monsoon, more tropical cyclones have formed and landed in China in the western Pacific Ocean and the South China Sea than in normal years, when La Niña occurs. The frequent southward movement of cold air masses in winter and the strong Pacific subtract in summer make the summer monsoon strengthen and accelerate the northward movement, resulting in the distribution of precipitation in China in the north and in the south, and the temperature distribution in cold winter and hot summer.
Globally, when La Niña occurs, convective activity intensifies in Indonesia, the Philippines, eastern Australia, northeastern Brazil, and southern Africa, and there are more storms and rainfall processes. On the one hand, the drought situation in the above-mentioned areas, which had been ravaged by drought in the previous period, has been alleviated, and on the other hand, it is also prone to flooding. However, the eastern and central equatorial Pacific Ocean, Argentina, equatorial Africa, and the southeastern United States are prone to drought and little rainfall. La Niña will also significantly increase the activity of Pacific typhoons and Atlantic hurricanes. It can be seen that La Niña has the strongest impact on the climate in the tropics, especially in the tropical Pacific.
Among them, the "2008 China Snow Disaster" is still fresh in everyone's memory, which is related to a moderately strong La Niña phenomenon from July 2007 to May 2008, which caused 129 deaths, 4 missing people and 1,516 direct economic losses due to the extreme weather of low temperature, freezing, rain and snow500 million RMB.
El Niño is followed by La Niña, and humanity needs to be vigilant.
And after the El Niño phenomenon, La Niña may make a comeback, and humanity needs to be vigilant!
In 2018, due to the La Niña event, the northeastern United States was hit by a snowstorm and severe cold weather, and many places in New York State entered a state of emergency, and some areas were lower than the surface of Mars, with a minimum felt temperature of -69, resulting in 22 deaths.
At the time of the 2021 La Niña event, New York suffered extreme snowfall, and the Southern California region of the United States has been experiencing drought since the beginning of 2021.
And Chinese experts have also made a warning, beware of the arrival of extreme weather!
So how cold will China be under the influence of La Niña? Through the analysis of 15 La Niña events in history since 1951, it is found that there are 10 La Niña years with low winter temperatures and 5 La Niña years with high winter temperatures. That said, not every La Niña year has an average low winter temperature. After the occurrence of La Niña events, the probability of cold winter in China is indeed greater, about twice the probability of warming.
In addition, it is important to note that cold temperatures do not equal cold winters. "Cold" and "warm" are only compared to the average situation, while "cold winter" and "warm winter" are different, and there are strict standards. Therefore, we should still be vigilant, be wary of the "possible extreme weather" mentioned above, and make adequate preparations in agricultural production, energy**, transportation, etc.
Frequent La Niña events, global warming stopped?
At this time, some netizens will have questions, does the frequent trend of La Niña events mean that global warming has stopped?
Actually, no, although global warming has been the consensus of the global scientific community. However, there is still some uncertainty about the causes of this. The causes of climate state and change do not exist in isolation in the atmosphere, but depend on the interaction of the 'climate system' consisting of the atmosphere, hydrosphere, biosphere, lithosphere, cryosphere and intellect. In summary, it should include two aspects: natural climate fluctuations and the impact of human activities. Natural climate fluctuations include changes in solar radiation and the effects of volcanic eruptions; The impacts of human activities include the greenhouse effect, changes in land cover, changes in land use and the effects of sulphide aerosols.
La Niña events are just a small episode in the Earth's climate system, and in terms of overall trends, this warming trend is set to continue. Lasts for hundreds of years or more.