News | Why is it so cold this winter?

Will the new cold air really accompany us during the New Year?

　　Since December 23, there has been a new round of cold air in many parts of the country, and the weather that has just been warmed for two days has cooled down again. At the same time, sayings such as "the New Year's Eve may encounter a major cold wave" have appeared on the Internet, and let people Worry: Why is it so cold this winter?

Will a new wave of cold air really accompany us New Year's Eve?

Since December, temperatures in many parts of the country have been lower than the same period in previous years

　　On December 24, Niu Ruoyun, chief of the Central Meteorological Observatory's mid-term weather forecast, told The Paper that according to weather monitoring data, since December, the temperature in many parts of the country has indeed been lower than the same period in previous years.

　　It can be seen from the national average temperature anomaly map from December 1 to 22 that, except for the northeast of Inner Mongolia, the west and north of Heilongjiang, Tibet, most of Qinghai, the west of Sichuan, and Yunnan, the temperature is higher than normal in the same period in my country. The temperature in most areas is close to the same period of normal year or low, and the number of provinces accounts for about 80% of the country.

　　Among them, the temperature in northern Xinjiang, northern Northwestern China, most of Inner Mongolia, northern and western North China, southeastern Southwest China, western Jiangnan, and western South China is 2°C to 4°C lower.

　　"What is the concept of a 2°C to 4°C lower temperature? Imagine that an air-conditioned room at 26°C in summer has a significant difference in body perception compared with air-conditioned rooms at 24°C and 22°C. The same is true in winter. Not only that , The low 2°C to 4°C is only an average state, and the local extreme situation is more serious." Niu Ruoyun said.

　　According to Niu Ruoyun, since December, the temperature in many parts of the country has fluctuated due to the influence of cold air forces. For example, from 9 to 13 the average temperature in most parts of the country was slightly higher than in previous years.

Under such circumstances, when the cold air comes, the public will feel the chill more intensely.

　　Taking Erlianhot, Inner Mongolia as an example, the city’s average temperature in the past 10 days was -22.5°C, which was 7.5°C lower than usual. The lowest temperature on December 15 was -36.4°C, which was the extreme value for the same period in December since 1968.

The 10-day average temperature of Tongliao Huolin Gol Meteorological Station reached -20.8℃, which broke through the lowest extreme value (-20.5℃) of the station’s historical average temperature during the same period.

The temperature is obviously low, and affected by snowfall, some pastoral areas are very likely to form "winter snow", which is not good for foraging and overwintering of livestock in pastoral areas. At the same time, lambs and calves are prone to freeze to death. situation.

　　In Guiyang City, Guizhou Province, the temperature in the city in mid-December was generally 3.4°C to 4.8°C lower than normal.

Especially during the low-temperature and snow-condensing weather from 14 to 17, the lowest temperature in some towns and villages in Guiyang dropped to -6°C (average temperature 0.7°C to 3.5°C), roads were frozen in many road sections, and transmission lines were icy.

　The lack of sea ice in La Niña and the Arctic is an important background for the coldness, which may continue to be cold in the future

　　Yuan Yuan, a researcher at the Climate Prediction Office of the National Climate Center, said that high or low temperatures for a period of time belong to the climate category, and are mainly the result of the interaction of the atmosphere, ocean, land surface, ice and snow and other spheres.

If the sun heats the ocean and the sea temperature rises by 0.5°C, the warming and evaporation of seawater will affect the atmospheric circulation.

For our country, tropical sea temperature, Arctic sea ice, and snow cover in Europe and Asia are all important factors affecting the winter climate.

　　Yuan Yuan believes that the main reason for the low temperature in many places since December is the "four strong"-in December, there was a strong meridional circulation in the middle and high latitudes of Europe and Asia, the Ural high pressure ridge was strong, and Lake Balkhash-Baikal The wide low-pressure trough of the lake is also stronger, and the Siberian high pressure is also obviously stronger on the sea-level pressure field. These are all favorable factors that make the cold air affect my country from north to south from the northwest.

From a large climatic background, the development of La Niña and the lack of anomalous sea ice in the Arctic are the two main external forcing factors.

　　Yuan Yuan further explained that the La Niña phenomenon refers to a phenomenon in which the sea surface temperature of the equatorial Central and Eastern Pacific continues to be abnormally cold.

In the winter during the heyday of most La Niña, the meridian of the Eurasian mid-high latitude circulation is relatively large, and the cold air activity is also relatively strong. The temperature in most of the central and eastern parts of my country is likely to be low.

　　This autumn, the Arctic sea ice was unusually low. In September, the Arctic sea ice was the second least in history. October and November were also the least in history and the second least.

"Less sea ice is also conducive to the strong ridge of the Ural Mountains in winter, and the strong East Asian winter monsoon. The temperature in most of the central and eastern parts of my country is likely to be lower than normal." But Yuan Yuan also pointed out that under the current global warming background, the impact The factors of anomalous climate in winter in my country are more complicated. Specific to a certain cold stage or a certain strong cooling process, it is mainly a direct result of the abnormal atmospheric circulation. It is difficult to say which factor or several factors are responsible.

　　At present, La Niña is still in a developing state, and the National Climate Center predicts that it may reach its peak at the end of this month, and the intensity may be moderate.

The sea ice in the Arctic is low and difficult to change.

Therefore, in the near future, the overall colder temperature in my country will continue.

　　"In late December this year, the cold air force has increased significantly. From the 26th to the 28th and the 30th, there will be two cold air invading our country." Niu Ruoyun said, from the perspective of weather trends, more "cold air accompany crossover" "Year" is not impossible, but the exact temperature should be subject to nowcasting.

　　Diao Fanchao, chief reporter of The Paper