A sudden freeze overnight! Snow scene floods the screen! Is this year destined to be a cold winter?

The first snow fell, and many parts of the country entered a state of rapid freezing overnight. Why is my country vulnerable to cold waves? Will the ice and snow disaster of 2008 reappear? What cold wave prevention suggestions do meteorological experts put forward?

Who would have thought that the strongest discount in November was not the "Double Eleven" event of major merchant platforms, but the temperature! This is a witty saying that has been popular on the Internet recently. Yes, the temperature is dropping sharply, and the cold wave is coming!

According to the Central Meteorological Observatory, this cold wave is very strong, with severe temperature drops, rain, snow and strong winds. On the afternoon of November 6, the Central Meteorological Observatory issued the first orange heavy snow warning this year.

Many places across the country entered a quick-freeze state overnight

Climate change in 2021 is like a roller coaster, cold for a while, hot for a while, and then cold again. At the beginning of this year, affected by the fission of the Arctic polar vortex, many countries and regions in the northern hemisphere experienced extremely cold weather, and some cities turned into "ice cities" overnight. In June this year, the climate suddenly reversed, and many countries and regions experienced extremely high temperatures, and tens of millions of people suffered in the rolling heat wave. Now, the cold wave has begun to sweep across China again.

Affected by the cold wave, from 08:00 on November 5 to 08:00 on November 8, my country will continue to experience strong winds and cooling weather from northwest to southeast: the temperature in most areas will drop by 8-10℃ successively, and the temperature in parts of northwest China, most of Inner Mongolia, North China, Huanghuai, western Jianghuai, and southern Northeast China may drop by 12-14℃, and above 16℃ in some places. Many places in northern my country entered a quick-freeze state almost overnight.

This cold wave not only brought a sharp drop in temperature and strong winds, but also rain and snow in many parts of the country. From 8:00 on November 5 to 8:00 on November 6, a heavy snowstorm occurred at a station in Xiwuzhumuqin Banner, Xilinguole League, with a snowfall of 20.8 mm. A heavy snowstorm occurred in Mandula, Darhanmaomingan United Banner, Baotou City, with a snowfall of 15.1 mm. On November 7, there will be heavy snowfall in eastern North China and Northeast China. Parts of southeastern Inner Mongolia, eastern Hebei, Tianjin, northwestern Shandong, central and western Liaoning, western Jilin, and southwestern Heilongjiang will have heavy to heavy snow. There will be heavy or extremely heavy snowstorms in some parts of eastern Hebei, northwestern Shandong, southeastern Inner Mongolia, central and western Liaoning, and western Jilin. Affected by the strong development of the northeastern cold vortex and ground cyclones, on November 8, the heavy snowfall will shift to the Northeast. Parts of southeastern Inner Mongolia, central and northern Liaoning, western Jilin, central and western Heilongjiang, etc. will experience heavy snow to torrential snow, and local torrential snow. Some areas will even be accompanied by strong cold waves and strong winds.

Zhang Linna, chief forecaster of the Beijing Meteorological Observatory, said in her analysis that in the Beijing area, there was rain, snow, strong winds and a sharp drop in temperature on November 6 and 7. Because this cold wave process has the characteristics of complex rain and snow phases, a large drop in temperature and strong winds, the general public needs to pay attention to the latest forecasts and warning information in a timely manner.

Meteorological experts warned that snowfall in Northeast China and eastern Inner Mongolia will last for a long time, and the wind will be strong due to the influence of the cold vortex. It is necessary to pay attention to the adverse effects of snowfall and strong winds and cooling on transportation and daily life.

This wave of cold waves covers an area of ​​90.1% of the country's land area.

According to the strength of cold air, domestic meteorological circles divide it into four levels: weak cold air, relatively strong cold air, severe cold air and cold wave, among which cold wave is the "king". Cold air from high latitudes will rapidly strengthen under certain weather conditions and invade low and middle latitudes, causing a large-scale sharp drop in temperature, strong winds, rain and snow in the areas along the way. This kind of cold air invading southwards to a certain standard is called a cold wave.

Yang Shunan, deputy chief forecaster of the Central Meteorological Observatory, said that according to the national standard for cold air, a cold wave is defined as a cold air activity that causes the daily minimum temperature in a certain place to drop by 8°C or more within 24 hours, or by 10°C or more within 48 hours, or by 12°C or more within 72 hours, and causes the daily minimum temperature in that place to be ≤4°C. Of course, the standards for cold waves vary from place to place due to the influence of geographical environment and climate conditions.

▲The ground weather map at 14:00 Beijing time on November 5 shows that a cold front stretches thousands of miles from northwest to northeast my country, and the strong cold high pressure on its north side is the main body of the cold wave. (Image source: China Meteorological Administration)

According to China Weather Network, affected by this cold wave, the area with a temperature drop of more than 6°C accounts for 90.1% of the country's land area, affecting 1.18 billion people. Xue Jianjun, deputy director of the National Meteorological Center, said at a press conference on November 4 that the reason why this cold wave is so wide is that on the one hand, it is affected by the cold air from Western Siberia, and on the other hand, the atmospheric circulation in Eurasia has changed recently, with obvious north-south movement, and the cold air from the polar region has moved all the way south to replenish Western Siberia.

Around October 30, a high-altitude warm high-pressure ridge formed on the west side of the Ural Mountains. On the coast of the Arctic Ocean on the northeast side of the high-pressure ridge, there is a low vortex carrying a strong cold air mass moving, which is the predecessor of the cold wave that is affecting my country. The high-pressure ridge of the Ural Mountains is stable and strong. The high-pressure ridge extends northward to the poles, which is conducive to the transfer of cold air from the poles to the south. In front of the high-pressure ridge, there is a stable east-west trough in the Siberian region. After the cold air is transferred to Siberia, it is blocked by the trough and accumulates here. The cold air continues to sink, causing the air pressure to rise, and finally forms a powerful, deep and broad cold high-pressure air mass. When the cold high pressure strengthens to a certain extent, the trough that blocks the cold air turns vertical and collapses, and the cold air moves eastward and southward in a big way. On the one hand, the cold air accumulated in Siberia quickly invades eastward and southward; on the other hand, the high-pressure ridge extending to the poles can still continue to guide the polar cold air down.

▲ Weather map of the middle troposphere in the Northern Hemisphere at 8:00 Beijing time on October 31. The circles represent atmospheric disturbances triggered by storms on the west coast of North America. The black circle is the warm high-pressure ridge on the west side of the Ural Mountains; the white circle is the low vortex that carries the initial cold air mass, which can be regarded as the source of the cold wave. (Image source: Easterlywave)

Why is our country vulnerable to cold waves?

Fang Chong, chief forecaster of the Central Meteorological Observatory, said that according to the forecast of the Central Meteorological Observatory, the minimum temperature of 0℃ will be pressed to the central part of Shandong, central Henan and northern Sichuan on the morning of November 8, and the minimum temperature in the northern part of South China will drop to around 10℃. The impact of the cold wave is coming to an end. However, there will still be weak cold air continuously replenished, and the temperature in my country will rise slowly and will continue to be low. In addition, we must also be vigilant against the multiple cold waves that hit my country in the winter of 2021-2022.

Why is China vulnerable to cold waves? This has a lot to do with China's geographical location. Because in the northern hemisphere, the Arctic Ocean and Siberia are the birthplaces of cold air. Cold air originally comes from the Arctic Ocean region and then strengthens in the Siberian region. Due to the high latitudes of these regions, the days are short and the nights are long, the sunshine is less, and the temperature is low in autumn and winter, which makes it easy for cold air masses to form. As time goes by, the air mass becomes colder and drier. When this cold air mass accumulates to a certain extent and the air pressure increases to a level far higher than that in the south, it is like a flood stored in the mountains. Once there is an opportunity, it will flood and pour to the south where the air pressure is lower. The range of cold air is usually thousands of kilometers long and wide. China, which is located in the lower reaches of Siberia, is the first to be hit, so it is very vulnerable to cold currents.

During this cold wave, the low vortex carried cold air across the Siberian wilderness, which had already entered winter, and its strength was further enhanced by the cooling of the ground. The warm high-pressure ridge on the west side of the Ural Mountains also moved eastward along the westerly belt and developed further. The northerly airflow on its east side pushed the low vortex further eastward and southward, allowing it to guide the cold wave toward my country. As a result, China's Great Wall and its north and south began to suffer from this strong cold wave.

China's vulnerability to cold waves is also closely related to the westerly belt. In the Earth's mid-latitude troposphere, the westerly belt has always been strong, like a long river surrounding the Earth. However, in the Asian continent, the tall mountains and plateaus on the land cut off the westerly belt, resulting in weak westerly forces in the northern hemisphere, which also provides opportunities for cold waves to move southward and wreak havoc in China. Of course, in the northern hemisphere, for the same reason, European and American countries are also often suffering from the southward invasion of cold waves.

Is this going to be another cold winter?

Following the La Nina event in the autumn and winter of 2020-2021, there will be another La Nina event this winter. According to historical statistics, after the La Nina event, China is more likely to have a cold winter. In early 2008, ice and snow disasters occurred in southern China, and that year was also a La Nina year.

Given that La Niña is coming again this winter, people can't help but worry whether the ice and snow disaster in 2008 will reappear? According to the previous research and judgment of the China Meteorological Administration, it is expected that this winter (December 2021 to February 2022), the cold air activities affecting my country will be frequent and strong. The temperature in the central and eastern regions will be mainly cold, and the temperature will fluctuate greatly within the season. Jia Xiaolong, deputy director of the National Climate Center, said that the concepts of cold and cold winter are different. Cold winter is more of a comprehensive assessment and judgment of winter climate conditions or temperature conditions. It is expected that the temperature will be low this year, but whether it can meet the standard of cold winter still depends on the standard.

▲The National Climate Center's forecast of the temperature trend for this winter (December-February). (Image source: National Climate Center)

Although 2021 is considered by many in the meteorological community to be a "double La Nina year", many people are worried that this winter will be a cold winter. However, experts say that it is not just La Nina that affects my country's climate, but there are many other very important factors. There is indeed a higher probability of cold weather in La Nina years, but not every La Nina year has a low average winter temperature.

Recently, the National Climate Center released a forecast of my country's overall winter climate situation, predicting that this winter, except for the Qinghai-Tibet Plateau and Yunnan, most parts of the country will have low temperatures and be close to normal, with frequent extreme weather processes such as strong cold waves. However, this does not mean that this winter will be labeled as a "cold winter": we will have to wait until the end of the climatological winter in March of the following year, and then we can officially determine whether this winter is a cold winter based on the actual national average temperature from December to February.

However, the current large-scale strong winds, rain, snow and cold waves remind us that we cannot take the attacks of cold waves lightly. They will not only affect our personal lives, but will also bring great impacts and challenges to industry and agriculture. We need to take relevant precautions in advance.

Weather experts' advice on preventing cold waves

1. There will be significant snowfall from the night of the 6th to the morning of the 7th. The surface temperature will be low, which may easily cause snow accumulation and road icing. We need to guard against adverse effects on transportation, power transmission, and communications.

2. At present, the branches and leaves of the trees are still lush. Heavy snowfall and strong winds can easily cause branches to break and trees to fall. It is necessary to remove snow in time and take protective measures for ancient trees, roadside trees, etc.

3. Please do a good job in harvesting and frost prevention of open-field and facility vegetables, and promptly reinforce agricultural greenhouses and other facilities and clear snow to prevent the greenhouses from collapsing due to snow accumulation.

4. Reinforce makeshift houses, temporary structures, fences and other temporary facilities to ensure they can withstand snow pressure and wind, and clear snow on the top in a timely manner; transfer people from dangerous places to safe areas in a timely manner.

5. The temperature will drop significantly from the 6th to the 8th, which will bring certain pressure to the city's heating, electricity, gas supply, etc. Please ask relevant departments to do a good job in energy scheduling and supply guarantee.

6. The north wind will be strong from the 6th to the 7th. Relevant departments are requested to strengthen outdoor structures and billboards, and ensure the safety of outdoor high-altitude operations.

7. Rainy and snowy weather will cause poor visibility and slippery roads. The public is advised to take public transportation as much as possible. Drivers should drive carefully, understand road conditions in advance and pay attention to safety.

8. The wind chill effect is obvious and the body feels very cold. Please pay attention to keep warm and prevent colds and cardiovascular and cerebrovascular diseases. Children and the elderly, weak and sick people who are sensitive to temperature changes should avoid going out. In addition, residents who use coal for heating should pay attention to prevent carbon monoxide poisoning.

Written by reporter Li Peng New Media Editor: Lv Bingxin

Produced by: Science Central Kitchen

Produced by: Beijing Science and Technology News | Science Plus Client

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