How "cold" is the cold wave? Big data tells you!
Tell everyone a "cold" news, the strongest cold wave since the winter of this year is coming soon! It is predicted that from November 26th to 30th, the cold wave will sweep across China, and the temperature will plummet in most areas.
Speaking of the cold wave, many people have memories dominated by it. As the "strongest" cold air, how "cold" is the cold wave? What is the strongest cold wave in history? The reporter interviewed Ye Dianxiu, a senior engineer under research at the National Climate Center and the chief expert of meteorological services at the China Meteorological Bureau, and asked him once and for all.
1. What is the standard of cold wave? Is there a difference between the north and the south of China?
Cold wave is a kind of cold air and a kind of disastrous weather. According to the national standard of cold air grade in China (GB/T 20484-2017) formulated in 2017, the cold air activity that makes the daily minimum temperature in a certain place lower than or equal to 8℃ within 24 hours, or lower than or equal to 10℃ within 48 hours, or lower than or equal to 12℃ within 72 hours is called cold wave.
2. How strong is the "ability" of cold wave cooling?
Monitoring shows that the average cooling rate of each cold wave in most parts of China is above 10℃. The average cold wave cooling rate in most parts of Northeast China, Jianghuai, eastern Jianghan, Jiangnan and southern China, as well as most parts of Inner Mongolia and northern Xinjiang can reach 12.℃To 14℃, more than 14℃ in most areas of Guangdong and Guangxi.
The maximum cooling range of cold waves in Northeast China, most of North China, most of Northwest China, most of Huanghuai, most of Jianghuai, southern Jiangnan and most of Inner Mongolia and Tibet is above 20℃. Among them, the maximum cooling rate in most parts of Northeast China and Inner Mongolia, northern Xinjiang, northwestern Tibet and southwestern Qinghai can reach 25.℃To 30℃, more than 30℃ in some areas; The maximum cooling range of cold wave in Sichuan basin, most of Yunnan and Hainan is below 15℃, and that in other parts of the country is generally below 15℃℃To 20℃.
3. How many cold waves occur on average every year in China?
In China, cold waves mostly occur in late autumn, winter and early spring. In the past 30 years (1991-2020), cold waves have occurred 5.4 times a year on average in China.
Since 1991, the most frequent cold wave occurred in 2021, with 11 times. Followed by 2009, there were 8 times, and the least number of cold waves was in 2017, only 2 times.
4. Where did the cold wave affect our country come from?
The cold air affecting China can be roughly divided into the following four paths:
① Northwest route: Cold air enters China from the White Sea and Barents Sea west of Xindi Island via Siberia and Mongolia in the west.
② Northern route: Cold air enters northern Asia from Kara Sea or Novosibirsk Sea east of Xindi Island, and enters China from north to south via Mongolia.
③ Western route: Cold air affects eastern China from west to east in Eurasia south of 50 degrees north latitude via Xinjiang.
④ Northeast route: Cold air from the Sea of Okhotsk or eastern Siberia affects the northeast of China.
more thanPath,The first three paths are more common, while the last path is less frequent and less intense.
5. What are the cold waves with large temperature drop in history?
According to the monitoring results of cold air process, since 1991, the top five cold waves with comprehensive cold air intensity in China have appeared on November 4-9, 2021, March 11-14, 2006, March 18-22, 1998, February 14-17, 2020 and April 11-17, 2006.
Cold waves often bring a wide range of severe cooling, strong winds and snowfall. Taking the cold wave process from November 4 to 9, 2021 as an example, the land area with the temperature drop exceeding 8℃ is 7.709 million square kilometers, accounting for about 80.3% of the national land area. Among them, there are 1.011 million square kilometers whose temperature drop exceeds 16℃.
The daily minimum temperature of 172 national meteorological stations in Xinjiang, Gansu, Qinghai, Ningxia, Shaanxi, Shanxi and other places reached or exceeded the historical extreme value in early November.
The daily precipitation of 151 national weather stations in Liaoning, Jilin, Heilongjiang, Inner Mongolia, Hebei, Tianjin, Shanxi, Shandong and other places exceeded the historical extreme in November. There is obvious snow in many places in the north, and the depth of snow in Inner Mongolia, Jilin and Liaoning is more than 40 cm.
The cold wave process cooled downAmplitude forecast chart (26-30 November) Photo courtesy of Central Meteorological Observatory
6. Where is the place most favored by the cold wave in China?
In China, the frequency of cold wave is characterized by more in the north and less in the south. The areas most favored by cold waves include: Northeast China, western and northern parts of North China, northern and central parts of Northwest China, most of Tibet, Inner Mongolia and other places, with an average annual cold wave frequency of more than 4 times. Among them, there are generally 10 to 15 times in the eastern and northern parts of Northeast China, most of Inner Mongolia and parts of northern Xinjiang, and there are more than 15 times in some areas.
7. In cold winter, are there more cold waves than in warm winter?
The answer is no.
There are obvious differences in judging factors and time periods between cold winter and cold wave, and the annual cumulative cold wave frequency is not necessarily related to cold and warm winter. Cold winter is a kind of climate concept based on the temperature condition of the whole winter, and the basic element of judging cold and warm winter is the average temperature of winter (December to February) for three months. The basic factors to judge the cold wave process are the daily minimum temperature (≤4℃) and the 24-hour (or 48-hour, 72-hour) cooling range (≥8℃, 10℃ or 12℃).
Therefore, the number of cold waves in cold winter is not necessarily more than that in warm winter. For example, both 1998 and 2019 were strong warm winters, and the number of cold waves was 6, which was more than that of strong cold winters in 1983 (3 times), 1984 (2 times) and 1985 (2 times).
(Author: Zhang Juan Cartography: Fu Lei Editor: Yan Hong)