Chao News Client Reporter Zhu Yan Zou Guaner Design Huang Chunzi Correspondent Ren Lu
Today is the first day that the province has entered the meteorological sense of winter, and the winter has come directly to a dismount, and it is frozen enough to choke. In the morning, the Zhejiang Provincial Meteorological Observatory issued a cold wave and low temperature report.
Compared with normal years, this year's winter in many places in Zhejiang is generally late, among which Hangzhou, Jiaxing, and Shaoxing have broken the record of the latest winter in history.
Meteorologically, we define winter as a meteorological winter when the moving average temperature is less than 10°C for 5 consecutive days. On December 14, the highest temperature in Hangzhou was 25.3 °C, breaking the record in mid-to-late December.
In the context of global warming, warm winters occur frequently, but when strong cold air comes, we can't help but ask - isn't it getting warmer and hotter, and why is it still so cold?
Will this winter be cold or warm? The Chao News reporter counted the average winter temperature data of the whole country and Zhejiang in the past 10 years, and found that the trend of warming is obvious.
Warm ≠ warm winter How to determine "cold winter" and "warm winter"?
"Cold winter" and "warm winter" have always been hot topics that people pay attention to in winter, however, there are different opinions on the definition of the two, so what is the scientific definition standard of "cold winter" and "warm winter"?
"A warmer winter is when the average winter temperature is higher than normal for the same period of the year. According to the national standard, the current average annual temperature is the average temperature of the 30 years from 1991 to 2020, and the 'warm winter' is the average temperature of the winter is higher than the average temperature of the past 30 years, reaching more than 0.5°C. Mao Yanjun, a senior engineer at the Zhejiang Provincial Climate Center, said that a cold or warm winter is not the same thing as a cold or warm winter.
According to the national standards "Warm Winter Grade" and "Cold Winter Grade", the determination of cold winter and warm winter is based on the average temperature of three months in winter as the basic element of judgment, and is judged by the difference (anomaly) and standard deviation (the statistical describing the deviation of the series from its average condition) between the average winter temperature and its normal value.
Taking the warm winter as an example, it is divided into a single-station warm winter and a national warm winter. When the average winter temperature anomaly of a station is greater than or equal to 0.43 times of its standard deviation, it is defined as a single station warm winter, and the national warm winter is defined by the percentage of the national warm winter area in the national effective area (also known as the warm winter index), and the warm winter index ≥ 50%, which is defined as the national warm winter.
In the context of global warming, winters are getting warmer
Under the influence of El Niño and global warming, the continent has experienced its warmest autumn. According to the monitoring released by the National Climate Center a few days ago, in the autumn of 2023 (September to November), the average temperature of the country will be 11.3 °C, 1.1 °C higher than the same period of the year, the warmest autumn since 1961, and the temperature in most parts of the country will be 0.5 to 2 °C higher, of which the northern and eastern parts of Xinjiang will be 2 to 4 °C higher. The average temperature in Guizhou, Liaoning, Sichuan, Tianjin, Xinjiang, Yunnan and Zhejiang has been the highest in the same period since 1961, while Gansu, Henan and Shandong are the second highest.
The World Meteorological Organization (WMO) predicts that 2023 is likely to break the record for the warmest year in 2016 and become the warmest year since 1850, with the warmest monthly record since May 2023.
Looking forward to the weather on the mainland this winter, Jia Xiaolong, deputy director of the National Meteorological Center, said that the peak period of the El Niño event is expected to be from November 2023 to January 2024, with moderate intensity, and will last until the spring of 2024. Affected by the El Niño event, the East Asian winter monsoon is expected to be weak, and the temperature in most parts of the central and eastern part of the continent is higher than normal for the same period of the year.
According to the winter natural disaster risk situation released by the Ministry of Emergency Management, a comprehensive analysis shows that this winter, the mainland will be warmer in the first winter and close to normal in the second winter.
According to information provided by the Zhejiang Provincial Climate Center, in the past decade, Zhejiang has had eight years with average winter temperatures above the average of 1991-2020, and reached a peak of 9.3°C in the winter of 2019 – a clear trend of warming from the data. However, this does not mean that the temperature has been in an upward channel.
"In this trend, the temperature will also fluctuate more and more. Lei Yuan, a senior engineer at the Zhejiang Provincial Climate Center, believes that global warming will allow the atmosphere to accumulate more energy, and when it is released, it will be more violent.
Will El Niño be a "super warm winter" this year?
It is worth noting that in the context of global warming, the frequency of continental warm winters is increasing. Of the 20 national warm winters that occurred between 1951 and 2018, 18 occurred after 1985.
The occurrence of El Niño will inevitably cause regional or global climate anomalies. In the context of global warming, extreme abnormal weather and climate events have intensified, lasted longer, and had a more obvious impact. The last super El Niño occurred between the fall of 2014 and the spring of 2016, during which 2015 and 2016 set the world's warmest record since 1850.
Under the influence of El Niño events, the probability of a warm winter on the continent is also increasing. According to statistics, there were 14 El Niño events in the 51-year period from 1950 to 2000, and 13 continental winters had warm winters.
Mao Yanjun said that El Niño is only a climatic factor that causes the temperature to be warm in winter, and the strength of the winter monsoon is the direct cause of the cold and warm winter on the mainland. The results show that in the winter of El Niño years, the location of the East Asian polar front is often more northerly than normal, and the cold air activity is also northerly and weaker, while the warm air mass in the south is relatively strong, so the probability of warmer temperature increases, but it is the combined effect of the climate system that affects the winter that ultimately determines the cold and warm winter.
The climate types of the continent are complex and diverse, and there are many influencing factors, even in the warm winter, there will be phases of cold, cold waves and heavy snowfall scenes will not be absent. Regarding the impact of this year's El Niño event, Mao Yanjun believes that El Niño will make South Asia, Southeast Asia, southern China and Northeast Asia warmer in winter, and southern China may be wetter. Therefore, the southern region may need to be wary of rainy weather this winter.