Why has it been "frozen to purple" recently?

Goose feathers and heavy snow, plummeting temperatures, splashing water into ice, shivering... Recently, most areas of China have experienced "freezing to purple" weather, and the local temperature is significantly lower than usual. The Central Meteorological Observatory predicts that in the next 5 days, the temperature in most parts of China will continue to be low.

Why has the weather been so cold lately? What is the weather trend for the latter part of the winter? How can I prepare for cold waves?

Why has it been so cold lately?

The Central Meteorological Observatory forecast on the 18th that in the next five days, the temperature in most parts of China will continue to be low.

It is expected that from 12:18 on December 08 to 21:08 on the 5st, the daily minimum temperature in some areas of northern Xinjiang, central and eastern Northwest China, Inner Mongolia, North China, Northeast China, Huanghuai, Jianghuai, Jianghan, northern Jiangnan, Guizhou and other places will be more than 0 °C lower than the same period in history, and the minimum temperature 12 °C line will be located in the area from southern Guizhou to northern Jiangnan. The Central Meteorological Observatory continued to issue a yellow warning for low temperatures at 18 o'clock on December 6.

Why have temperatures continued to be low recently?

Xu Jun, chief forecaster of the Central Meteorological Observatory, said in an interview with a reporter from China News Service that it was mainly affected by the continuous superposition of strong cold waves and strong cold air.

She said that from the 13th to the 16th, China was hit by a strong cold wave, with temperatures of 6 to 12 degrees Celsius in most areas, and some areas reaching more than 14 degrees Celsius. Around the 14th, the cold wave process caused the daily average temperature or daily minimum temperature to be lower than that of the same period in normal years in some areas of northern Xinjiang, eastern Northwest China, Inner Mongolia, North China, Northeast China, Huanghuai, eastern Jianghuai, and eastern Jiangnan.

"After the end of the strong cold wave from the 13th to the 16th, most of China is still controlled by cold air masses, and the cold tone continues." Xu Jun said that although there were slight signs of warming on the 17th, from the 18th to the 20th, a new round of stronger cold air will affect the central and eastern parts of China, and most of the central and eastern regions will have a cooling of 4 to 8 °C, and the local cooling of Liaoning, Shanxi, and central Inner Mongolia may reach more than 10 °C, and this round of cooling will not only affect the north, but also most of the central and eastern regions will be affected, and the temperature in the south of the Yangtze River and the eastern part of South China will drop by more than 4 °C.

"Recently, China has been continuously affected by strong cold waves and strong cold air, so the temperature in most areas has continued to be low." Xu Jun said.

Recently, many people feel that the weather is "unusually cold", what is the particularity of this cold air process compared with normal years?

Xu Jun said that the cold wave is the cold air from the polar regions or cold zones in winter, which is a common disastrous weather in China, which occurs more frequently and has a wide range of activities, and the cold wave will cause a sharp drop in temperature when it hits, accompanied by strong winds and rain and snow weather, which has a more serious impact on industrial and agricultural production, people's lives and human health. From the 13th to the 16th, there was a strong cold wave.

"Strong cold spells are uncommon compared to normal cold air and cold wave processes, but they have occurred in the past." Xu Jun said that for example, at the beginning of 2016, China also experienced a once-in-a-century cold wave, which also brought widespread cooling, rain and snow to China.

Xu Jun said that affected by the strong cold wave from the 13th to the 16th, the daily minimum temperature of many weather stations in North China fell below the historical extreme value in December since the establishment of the station, and on the 12th, the minimum temperature in Daxing, Beijing was -17.18 °C, Datong, Shanxi -8.31 °C, and Tianjin Beichen -9.21 °C.

How does an "El Niño year" affect this winter's weather?

In people's impression, El Niño is often associated with warm winters, and in the context of global warming, the frequency of warm winters in China is increasing.

According to the monitoring of the National Climate Center, since the equatorial eastern Pacific Ocean entered an El Niño state in May this year, the SST index in key areas has shown a rapid and continuous increasing trend from May to October, and has exceeded 5.5°C for five consecutive months, reaching the standard for forming an El Niño event, with moderate intensity, and will continue until the spring of 10.

The recent widespread cold wave has hit most of China, is this a "slap in the face" of El Niño?

Lu Er, a professor at Nanjing University of Information Science and Technology, said that warm winter and cold winter refer to the overall temperature situation throughout the winter. The short-term cold wave cooling is only a "small episode", and the average cold and warm situation of the whole winter is the "main theme". Warm winters don't mean there are no cold spells, and even El Niño years don't rule out the possibility of cooler winters and strong cold spells.

"Cold spells and blizzards are weather processes, the immediate cause of which is anomalies in atmospheric circulation. A single cold spell and blizzard may not be too directly related to El Niño. ”

For example, in January 2016, during the Super El Niño event, China also ushered in an extreme cold wave, with the freezing line reaching the South China Sea, and snow falling in Guangzhou, Dongguan and even northern Shenzhen. In November 1, during the moderate El Niño event, the North China Plain ushered in an extreme snowstorm, and the Shijiazhuang snowstorm fell for three consecutive days, breaking the historical record for total precipitation and snow cover.

"The El Niño, which is currently forming over the tropical Pacific Ocean, is a big climatic backdrop." Overall, El Niño affects global atmospheric circulation, making many places vulnerable to extreme weather and climate events, Luer said. To some extent, the blizzard can be seen as a manifestation of the extreme climate in the context of El Niño.

According to statistics, there were 1951 El Niño events from 2000 to 14, and 13 of them had mild winters in China. For China, in the winter of El Niño, the precipitation in the Huai River, the Yangtze River, the Pearl River basin and other places is abnormally high, while the temperature in the northeast is abnormally high, that is, the winter in the south is rainy and the north is warm.

Looking ahead to the later part of this winter, according to the National Climate Center, the temperature in most parts of China this winter will be close to the same period of the year or high, with the first winter (December 2023) being warmer and the latter winter (January to February 12) close to normal, with a high probability of a warm winter in the north.

When will this round of cold weather end?

Xu Jun said that in the next 5 days, most parts of China will maintain a pattern of sustained low temperatures, and the northwest region will begin to warm up before the central and eastern regions, and the continuous low temperature in the central and northern parts of the northwest region, including Xinjiang, western Inner Mongolia and western Gansu, is expected to end around the 22nd, reaching a state close to normal;

The central and eastern regions are expected to start to warm up slowly on the 23rd, and it may not feel so cold around the 25th, and the temperature will reach a state that tends to be close to the same period of the year (late December).

The meteorological department predicts that the maximum temperature in Beijing will be -18 °C on the 4th, and by next Monday (25th), the maximum temperature in Beijing will rise to 4 °C; The maximum temperature in Nanjing was 18°C on the 1th, and it will rise to 26°C on the 10th.

Patients with cardiovascular diseases, respiratory diseases, chilblains, arthritis, rheumatoid arthritis and other diseases are more sensitive to cold, and these vulnerable and susceptible groups need to be protected. In addition, outdoor workers, especially food delivery workers and construction workers at night, have very low temperatures at night, so they should pay special attention to personal protection.

In addition to the cold weather, there will be rain and snow in the south in the near future, Nanjing, southern Jiangsu and other places have rain and snow on the 18th and 19th, and Guizhou and Hunan will have some freezing rain on the 18th. The rain and snow roads in the Jianghuai area are slippery, and the public should pay attention to travel safety.

For agriculture and animal husbandry, it is necessary to pay attention to the risk of low temperature chilling injury, do a good job in the windproof reinforcement of greenhouses related to facility agriculture, and adjust the temperature in the shed, so as to do a good job in the cold protection and warmth of crops and animals.

In addition, the cold air process from the 18th to the 21st will also bring windy weather to the northern region, and there will be northerly winds of level 4 to 6 in Beijing and northern Hebei. (Text/Chen Su)