◎Intern reporter Pei Chenwei
The large fluctuation of spring temperature is mainly related to the adjustment and transformation of the atmospheric circulation situation in the westerly wind belt. In spring, the atmospheric circulation at middle and high latitudes changed from high pressure control to northeast cold vortex.
The occurrence of spring cold wave weather in northern China will not only be affected by climate change in the equatorial region, but also by climate change in the middle and high latitudes.
The sudden spring cold a few days ago made people who had already worn short sleeves on the street have to put on their coats again.
Affected by the cold wave and cold air, the temperature in northern China dropped sharply some time ago, and the local area cooled by more than 10 degrees Celsius, and even snowy weather appeared.
If the spring cold has chilled some people, the following news may feel a little "warm": The World Meteorological Organization pointed out earlier this month that La Niña, which has caused global temperatures in recent years, is coming to an end, and there will be an El Niño that will raise temperatures in the coming months.
As soon as this news came out, the related topic sparked widespread discussion. Netizens wondered that the La Niña phenomenon has lasted for 3 years, but why is the winter in many areas still dominated by warm winters in the past 3 years? In mid-spring, there is such a violent cold wave "visiting", is this contradictory to El Niño? The La Niña phenomenon and El Niño phenomenon quickly "connect", how can the weather "change face" so quickly? In response to the above problems, the reporter interviewed relevant experts from the Beijing Climate Center.
The appearance of La Niña is not contradictory to warm winters
So, what exactly is La Niña?
The reporter learned that La Niña refers to the phenomenon of continuously unusually low sea surface temperatures in the eastern and central equatorial Pacific Ocean. The so-called "persistently abnormally low" means that the surface temperature of seawater in key areas is above 0.5 degrees Celsius below the average value of previous years, and lasts for more than 5 months. The phenomenon is the product of a combination of tropical oceans and atmosphere, occurring approximately every 3 to 5 years, but sometimes at intervals of more than 10 years.
Zhang Yingjuan, senior engineer at the Beijing Climate Center, said that the La Niña phenomenon, which is coming to an end, is related to the weakening of the easterly trade wind.
The surface movement of the ocean is mainly controlled by the winds on the surface of the ocean. Under normal conditions, in the equatorial Pacific region, perennial easterly trade winds "blow" high warm water from the surface of the equatorial eastern Pacific Ocean to the equatorial western Pacific Ocean. To "replenish" the blown-out seawater, the cooler deep waters of the eastern equatorial Pacific Ocean turn over.
When easterly trade winds become stronger, the surface water blown away by the eastern equatorial Pacific Ocean increases, causing a large amount of cooler deep seawater to turn up, causing the surface water temperature of the eastern Pacific Ocean to be low, causing La Niña phenomenon.
La Niña lasts for about 3 years, but why is winter still dominated by warm winters in many areas in recent years?
La Niña does cause global temperatures to drop, but specific to a region, whether its winter is cold or warm depends on the specific analysis.
"Take my country as an example. Whether China's winter is cold or warm winter is not only related to La Niña phenomenon, but also related to atmospheric circulation conditions, Arctic sea ice thickness, snow cover in Eurasia and natural variability within the atmospheric circulation system. Zhang Yingjuan said, "Therefore, it can only be said that the year in which La Niña occurs has a greater probability of cold winter, but it cannot be said that there will be a cold winter during this period." ”
El Niño has a very limited impact on spring temperatures
As soon as La Niña is over, El Niño is coming, and the "face" of the weather is really changing. This has sparked some fears: Is the global climate anomaly exacerbating?
"El Niño phenomenon refers to a phenomenon in which the sea surface temperature of the equatorial Middle East Pacific Ocean is abnormally high, and the occurrence of this phenomenon will have a certain impact on China's weather and climate. Historically, shortly after the end of each El Niño event, the equatorial Middle East Pacific Ocean has experienced abnormally low sea surface temperatures, which is what we call La Niña, and vice versa. Na Ying, a senior engineer at the Beijing Climate Center, said in an interview that in general, El Niño and La Niña will alternate.
Many people are puzzled, since the El Niño phenomenon is coming, the temperature should rise, why did it cool down sharply a few days ago?
In this regard, Dr. Karen Gao of the Beijing Climate Center said in an interview with reporters that whether it is the spring cold or the rapid warming this spring, it is not directly related to the upcoming El Niño phenomenon.
Karen Gao said that the large fluctuations in spring temperatures are mainly related to the adjustment and transformation of the atmospheric circulation situation in the westerly wind belt. In spring, the atmospheric circulation at middle and high latitudes changed from high pressure control to northeast cold vortex.
Karen Gao further said: "The occurrence of spring cold wave weather in northern China will not only be affected by climate change in the equatorial region, but also by climate change in the middle and high latitudes. The La Niña phenomenon, which is already in the "decay period", and the El Niño phenomenon, which is still in the "gestation period", have a very limited impact on the temperature in northern China. (Science and Technology Daily)