Chao News client reporter Xiao Nuannuan
When I woke up, the temperature plummeted.
The Central Meteorological Observatory issued a cold wave blue warning at 6 o'clock on December 16, and due to the cold wave weather, many places in the mainland will cool down sharply from the 16th to the 17th. At 8 o'clock on the 16th, the Central Meteorological Observatory issued a weather reminder that a strong cold wave arrived in southern Jiangnan, and the minimum temperature of 0 °C line will be pressed south to southern Qiannan and northern Jiangnan.
The national warning signal for this strong cold wave Source: @中央气象台
At 8 o'clock in the morning, the temperature in many places in Zhejiang Province dropped below 5 °C.
Source: @浙江天气
Cold, cold, cold!
The strong cold wave exerted force, and the temperature dropped sharply, as if the "quick-freezing mode" was turned on, and the cold air of Siberia once again brushed up on its presence.
Can we see the invasion of cold air? How does the cold air of Siberia, the "old actor" of the cold winter season, affect the temperature of the mainland? What is the sacred place of the cold wave that has been frequently warned in the past two days?
The Chao News reporter interviewed Zhu Guangliang, a professor at Zhejiang University of Foreign Chinese and vice chairman of the Zhejiang Geographical Society, and Ge Yongfeng, a senior geography teacher at Zhuji Xuemian Middle School.
A "visible" invasion of cold air?
With the great cooling in many places across the country, a popular video of "Siberian cold air invading Kanas on the mainland" shot by netizens has once again attracted attention. In the video, it can be seen that the white airflow is quite strong along the terrain over the mountains and mountains, driving straight in, like a white dragon. Some netizens sighed, "After listening to the cold Siberian air all my life, I finally saw it today." ”
Screenshot of the video of "Siberian cold air invasion" taken by netizen Chen Wuji
Can the human eye really see cold air intrusion?
Zhu Guangliang and Ge Yongfeng told Chao News reporters that the normal atmosphere is colorless and transparent, and from a scientific point of view, the human eye generally cannot see cold air.
Zhu Guangliang said that the white air flow in the video should be a "cloud", and the water vapor in the air will form a "cloud" or "fog" when it condenses. "If there happens to be cold air entering the country on the day of the video shooting, then this white air flow actually indicates the direction of movement of the cold air, allowing people to feel and experience the flow of cold air more concretely. From a popular point of view, it is understandable to say that you have 'seen' cold air. ”
Ge Yongfeng introduced, "The white airflow in the video is actually formed by the warm and humid airflow when it is cold. Considering that the filming location was in Kanas, it should have been that the cold air from Siberia was moving southward at that time, and the local water vapor was abundant and condensed, so that the white color could be seen with the naked eye and move forward with the air current. The effect in the video needs to be windy, but not too fast. This situation is similar to the heat in a pot turning white when it is cold, or seeing white gas when you open the refrigerator door. ”
How does the cold Siberian air "wield"?
What is the sacredness of the cold Siberian air that begins to "brush up its presence" in winter, and how does it affect the temperature of the continent?
Ge Yongfeng introduced that after the autumn equinox, as the direct point of the sun moved to the southern hemisphere, the sunshine time in the northern hemisphere gradually shortened, and the temperature gradually decreased. Siberia is located in the middle and high latitudes of the Northern Hemisphere, coupled with the invasion of cold polar air and favorable topographic conditions, cold air continues to accumulate here, making it the coldest place in the Northern Hemisphere in winter. The density of cold air is high, and the atmospheric cooling contraction and sinking, forming the strongest and most extensive high pressure in the Northern Hemisphere, that is, the Mongolian-Siberian high (Asian high).
He said that the Mongolian-Siberian high is one of the four main seasonal atmospheric activity centers in the northern hemisphere, and the center of the high pressure is located in the Mongolian-Siberian region in winter, moving eastward in spring and disappearing in midsummer. Since the region is north of the Arctic Ocean and the winter temperature is very low, the pressure difference between the two places is small, so the northward flow is not very obvious. At the same time, the latitude of Siberia is mainly controlled by the prevailing westerly wind belt, so the westward flow is not obvious, while the eastward and southward flow from the Siberian high is very strong, and the northwest monsoon is formed in East Asia under the influence of geostrophic deflection forces. "The northwest monsoon from the Siberian high is the main factor affecting the significant cooling of the continent in the winter half of the year, and it is also what we often call 'cold air'. ”
Source: @中国天气
Zhu Guangliang told reporters that according to the results of many years of observations, the cold air intrusion in Siberia is divided into several paths: the northwest road, the north road and the west road.
Among them, the cold air from the northwest road moved from the Barents Sea west of Novaya Zemlya to the south of the mainland through Siberia and central Mongolia to the middle and lower reaches of the Yangtze River and South China. "Cold spells on this path can affect most of the continent and occur more often. In addition, there is a cold wave on the north and west roads. After the cold air enters the mainland, it mainly affects the south of the Yangtze River and South China along the eastward and southward directions. ”
The northwest path of cold air Courtesy of the interviewee
The cold air on the northern route enters northern Asia from the Kara Sea or Novosibirsk east of Novaya Zemlya, enters the Mongolian People's Republic from north to south, then moves to the north and northeast of the mainland, and then spreads south along the lower reaches of the Yellow River. The cold wave usually only affects the area north of the Yangtze River on the mainland. Photo courtesy of the interviewee
The cold air from the west road passes through Xinjiang from west to east in the Eurasian continent south of 50°N, and then moves south along the Hexi Corridor and the east side of the Qinghai-Tibet Plateau. The cold wave of this path has the greatest impact on the northwest and southwest of the mainland, south of the Yangtze River, and southern China. Photo courtesy of the interviewee
After the cold air enters the mainland, the cold air from the north road goes south from the lower reaches of the Yellow River, and the cold air from the west road goes south from the eastern part of Qinghai. The two often converge in the Yangtze River area south of the Yellow River, and then move southward, affecting the south of the Yangtze River and South China. Photo courtesy of the interviewee
Whenever the cold air from the Mongolian-Siberian high moves south, the continent will experience a cooling phenomenon from north to south, and the power of the northwest monsoon can be clearly felt from Northeast China, North China, the middle and lower reaches of the Yangtze River, and even South China.
Cold wave, the highest level of cold air
What exactly is the cold wave that makes the meteorological station issue frequent warnings?
Ge Yongfeng said that the geographical definition of a cold wave is the invasion of cold air from the polar regions or cold zones into lower latitudes on a large scale like a tide.
"Cold air can be divided into cold waves, strong cold air, strong cold air, moderate intensity cold air, and weak cold air according to the degree of intensity. Therefore, we can colloquially understand a cold wave as the highest level of cold air. Zhu Guangliang added.
He pointed out that due to the vast size of the continent and the large difference between the climate of the north and the south, when discussing cold waves, the criteria are slightly different, but the sharp cooling is the core feature of cold waves.
Ge Yongfeng introduced that the cold wave standard stipulated by the mainland meteorological department is that the cold air invasion causes a temperature drop of more than 10 °C within 24 hours (or more than 12 °C within 48 hours), and the minimum temperature drops below 5 °C. ”
Source: @中国天气
"As a large-scale strong cold air event, a cold wave is accompanied by strong winds, rain and snow. Depending on the region and the time of day, there may be sand blows, sandstorms, thunderstorms, hailstorms, etc. Zhu Guangliang said that the first frost, final frost and frost caused by the cold wave are very harmful to agricultural production, and will also bring inconvenience to people's work and life, so we must pay attention to the early warning of the cold wave in time and do a good job of keeping warm and protecting.
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