Tomorrow (November 7) will usher in the Beginning of Winter. The beginning of winter is the beginning of winter in terms of solar terms, but the beginning of winter in meteorology has certain temperature indicators. At present, multiple rounds of cold air are affecting us one after another. The temperature in most parts of the north has dropped rapidly, and many places have already felt like winter.
How to determine the winter standard?
The beginning of winter ≠ the beginning of winter. Solar terms are time-series nodes summarized by the ancients based on phenology, sunshine, etc. In meteorology, the beginning of winter is usually based on the five-day moving average temperature being stable below 10°C.
Zhou Ying, senior engineer at the Meteorological Publicity and Science Popularization Center of the China Meteorological Administration: The five-day sliding average temperature is a method of sliding forward and backward. Take the current day and the previous four days, and use the daily average temperatures of these five days to find an average value as the "five-day moving average temperature" for that day. Subsequent dates are also calculated in this way, forming a continuous smooth temperature sequence.
Zhou Ying: Why should we use this to define the season instead of the temperature on a certain day or at a certain time? Because the temperature of a single day is easily disturbed by a single cold air process or warm air or gusts of wind, if it is determined based on the temperature of a single day, there will be a recurring phenomenon of "spring begins today and winter returns tomorrow". However, using a sliding average can smooth out this short-term fluctuation, retain trend changes, and form a more stable seasonal date.
Our country has a vast territory, and winter generally advances gradually from north to south. The northern Northeast and northeastern Inner Mongolia are often the earliest areas to enter winter. The onset of winter in North China and the Huanghuai River generally occurs around early November.
Wang Yu, engineer of the Climate Service Office of the National Climate Center: At present, most areas in northern my country have officially entered winter. Compared with the normal time of winter, winter starts slightly earlier in Heilongjiang, Jilin and other places, and winter starts later than normal in most other areas in the north. Among them, the northern and central parts of Liaoning and the central part of the northwest region are 5 to 20 days later, and Shenyang is 11 days later than normal. Beijing usually enters winter on October 31st. This year it has not yet entered winter in the meteorological sense. However, the surrounding city of Qinhuangdao, Hebei Province has entered winter on October 31st. After the cold air passes this weekend, the temperature will drop significantly, and winter is expected to officially enter.
Cold air comes one after another. Is autumn in the north getting shorter?
Cold air comes one after another, and the temperature in northern my country also drops again and again. Many members of the public feel as if autumn has not yet had time to experience it, and they jump directly to winter. Is this feeling real or an illusion?
What is the standard for dividing the four seasons of the year that everyone often talks about? Scholars have divided the seasons based on the distribution of meteorological elements such as temperature and precipitation that are closely related to crop growth. The standard is: winter is defined as a five-day moving average temperature below 10°C, spring or autumn is defined as a temperature between 10°C and 22°C, and summer is defined as a temperature higher than 22°C.
According to this standard, compared with summer and winter, autumn in most parts of my country is generally shorter. Annual average statistics from the National Meteorological Information Center show that autumn lasts about 50 days in most places in Northeast and North China; autumn in Southwest China generally lasts 70 to 80 days.
Many scientists have studied seasonal changes in my country and found that the onset of autumn and winter has been delayed in many places, and the lengths of winter, spring and autumn are all getting shorter. From a regional perspective, the changes in the northern region are more obvious than in the southern region, and the changes in the eastern region are more obvious than in the western region. Among big cities, autumn in Changsha, Ningbo, Zhengzhou, Yinchuan and other places has also significantly "shrunk". Ningbo has shortened its autumn by 12 days since the 1990s, and Yinchuan, Hangzhou and Changsha have also lost 7 to 9 days.
Summer is extended and winter is advanced, and the autumn window period continues to be compressed
The physical sensation of "autumn passing by in a flash" is not a subjective illusion, but the result of long-term climate warming and atmospheric circulation anomalies. On the one hand, summer refuses to leave and the onset of autumn is delayed; on the other hand, the cold air is active and the onset of winter accelerates. Under the squeeze from both sides, the window period in autumn has been continuously compressed.
The shortening of autumn is usually seen from two aspects. One is that autumn begins later, and the other is that winter begins normally or earlier. Both of these may cause the entire autumn to be shorter. Meteorological data statistics show that since 1991, autumn has been delayed in many places in my country, especially in the eastern region. In addition, this year's strongest El Niño event has taken shape since monitoring records began, which will also have a significant impact on my country's climate.
Wang Yu, an engineer at the Climate Service Office of the National Climate Center: In the autumn of an El Niño development year, temperatures are relatively high across most of the country, with temperatures significantly higher in most of East China, most of Central China, and the eastern part of Southwest China. Autumn begins late in many places. Among them, autumn begins in Zhengzhou on September 28, 14 days later than normal. Autumn begins in Jinan on October 1, 12 days later than normal. In cities such as Guangzhou, autumn officially begins in early November.
How does public life “keep up” with the changing seasons?
The window period for changing seasons has become shorter, which makes many people feel that before they have time to change their clothes one by one, the temperature has already risen and fallen like a "roller coaster"; the agricultural season for autumn harvest and autumn planting has also been squeezed tighter.
The shortening of seasons has the most direct impact on health. The "extremely long standby" in summer, followed by the "one step" of cold air, and the sudden drop in temperature are the triggers for the high incidence of respiratory diseases and cardiovascular and cerebrovascular diseases. Experts suggest that we should pay special attention to the fact that there is a certain lag in the impact of low temperature weather on health. Sensitive people should continue to pay attention to their physical condition after the temperature drops. The traditional idea of "spring covers and autumn freezes" needs to be flexibly adjusted and cannot be carried on blindly.
The shortening of autumn also has an impact on agricultural production. According to meteorological experts, the heat accumulated late in autumn is conducive to autumn grain harvest and increased yield. However, early winter may cause insufficient accumulated temperature of winter wheat and other crops. If winter drought and frost damage are superimposed, the growth of the next spring will be deviated.
