Yesterday (2nd) at 3pm, in the consultation room of Beijing Meteorological Bureau, all kinds of cloud pictures and data were constantly switched on the big screen, and several analysts told their forecast views one by one before going on stage. Since the beginning of winter, except for two small-scale snowfalls in the outer suburbs in December 2008, almost no snow has fallen in Beijing, which makes the Spring Festival in 2009 less of a landscape and adds a little disappointment to people who are looking forward to the snowy scene.
Tomorrow is beginning of spring, and the Lantern Festival will be held in a few days. Will there be a "timely snow" coming to Beijing? Why is it difficult to snow in Beijing this winter? Our reporter interviewed Sun Jisong, the chief forecaster of Beijing Meteorological Bureau, to dispel doubts and doubts about snow.
Northwest airflow sings "one-man show"
Cause a winter without snow
Cloudy and sunny-the sky over Beijing is still calm. According to the forecast of Beijing Meteorological Observatory, the weather will be mainly sunny to cloudy this week, and the highest temperature will reach 10 degrees Celsius. Tomorrow will be beginning of spring, and in the more than 100 days since October 24th last year, there have been only two snowfalls in Yanqing in the north and Pinggu in the northeast-December 10th and 23rd, 2008. In the urban area of Beijing, there is still no effective snowfall. Only sporadic snowflakes appeared on December 10 last year, but they were fleeting and the precipitation was only 0.1 mm.
"This year’s situation is rare, but it is also normal." Sun Jisong, chief forecaster of Beijing Meteorological Observatory, said that historically, the winter precipitation in Beijing has not been large, and the precipitation from December to February of the following year is usually about 10 mm, so it cannot be said that there is no precipitation in winter. Tracing back to history, the last winter with almost no precipitation was in 1970. However, since October 24, 2008, there has been no precipitation in the urban area this winter, which is really rare.
A report in Sun Jisong’s hand shows that water shortage is not confined to Beijing. This winter, droughts occurred in Hebei, Shanxi, Henan and other places. According to media reports, the current drought has a wide range and a long duration, which is basically rare for many years.
"It should be said that there is no direct connection between no snow and warm winter." The computer in the consultation room shows that daily maximum temperature in some urban areas of Beijing has exceeded 10 degrees Celsius in the past two days. However, Sun Jisong said that in addition to cold air, the formation of snowfall must have water vapor transportation and appropriate ground temperature, and several factors are indispensable. However, there is no snow this winter, and the main reason is water shortage-the water vapor transportation has been "broken".
Sun Jisong introduced that from the perspective of Beijing, water vapor mainly comes from two channels. One is the water vapor brought by the southwest warm and humid airflow from the south of the Yangtze River, especially the snowfall, which often has the characteristics of large snowfall and long snowfall time, and often becomes the "main force" factor of snowfall in Beijing; The other source of water vapor is the water vapor brought by the easterly airflow from the Bohai Sea and the Yellow Sea. However, due to its short transport length, its snowfall is characterized by a small amount of snow.
Since December last year, there have been four cold waves sweeping the city, but all of them are mainly cooled by strong winds. "This winter, the northwest wind is mainly prevalent in Beijing, which is not conducive to the transportation of these two streams of water vapor. However, the easterly wind or southwest wind formed occasionally through the change of atmospheric circulation has basically not formed this year, so the water vapor transportation has basically been broken. " Sun Jisong said that the Chibi-style "sudden change of the wind and cloud" is pitiful, and it has not been encountered once this winter, which can be said to be "reasonable and unexpected".
Investigate and dispel doubts
Four conjectures about "No Snow"
Conjecture 1
Is it possible to snow on the fifteenth day of the first month?
On the sixth day of the Lunar New Year’s Eve, in a ski resort in Mentougou, Mona Lee skated with several friends. The only thing that made him regret was that the mountains beside the ski resort were bare. "I can’t even take a picture of Zhang Xuejing. There is no snow outside the slide. It is artificial at first glance."
In many people’s minds, snow and Chinese New Year are inseparable. If there are no snowflakes, the taste of the year will be much less. In the snow-free winter, can we make up for everyone’s regrets at the Lantern Festival? Sun Jisong, chief forecaster of Beijing Meteorological Observatory, said that such a wish may be difficult to realize. From the analysis of the current data, it is unlikely that it will snow in the next ten days or so, that is, during the Lantern Festival.
"But we can’t say that there is no hope at all." Sun Jisong said that due to the rapid change of atmospheric circulation, there may be changes, but from the whole circulation background, it is difficult for water vapor in the south to reach Beijing. There may be a small amount of precipitation in central and southern Hebei and southwestern Shanxi. "But if snowfall wants to come to Beijing, I am afraid it is still difficult to achieve."
Conjecture 2
"Sequela" of Meteorological Intervention?
"More than a thousand rockets were fired at the opening ceremony of the Olympic Games to eliminate the rain. It won’t eliminate all the rain in a year, will it?" Some netizens questioned whether large-scale artificial intervention in the weather would have a "sequela" to the overall climate. For such a question, Sun Jisong said that in the face of nature, the intervention that human beings can do is extremely small and it is impossible to have an impact on long-term climate change. "In fact, every time it rains, we basically carry out precipitation enhancement operations." Sun Jisong said that due to the long-term drought in the northern region, basically every precipitation process throughout the year, the relevant departments will carry out precipitation enhancement operations, and the snowfall process is no exception. If there is snow, artificial "snow increase" measures will be taken. According to media reports, from February 1 ST to February 2 nd, the weather modification department of Luoyang City, Henan Province seized the opportunity of weak cold air crossing the border and successfully implemented artificial precipitation enhancement. "But only when there is water in the sky can we make it fall to the ground as much as possible."
Guess 3
Is the Three Gorges Project the Source of Extreme Weather?
In recent years, the term "extreme weather" has appeared more and more in public, and the coincidence of these extreme weather occurrences and the completion time of the Three Gorges Dam also makes many people suspect that the Three Gorges Dam is the source of extreme weather.
"The problem of the Three Gorges is a cliche, but from a scientific point of view, the statement that the Three Gorges caused extreme weather is unfounded." Climate change often involves thousands of kilometers in Fiona Fang. Compared with this climate background, Sun Jisong described the Three Gorges as a small "puddle", and it is difficult to have any impact on the overall climate if there is such a puddle.
"At present, most climatologists believe that global warming will cause an increase in extreme weather." With global warming, the frequency of extreme weather is increasing, but how global warming affects the appearance of extreme weather and what is the inevitable relationship between them is still an unsolved mystery.
Guess 4
Beijing this summer
Will there be a drought?
Is there a scientific truth behind the poetic folk proverbs, such as "Yun Zheyue on August 15th, the lights on the fifteenth day of the first month when it snows" and "It doesn’t snow when it’s cold, and the fields crack when it’s summer"?
"Folk proverbs are more similar to statistical induction, and some of them have some truth," Sun Jisong said. The predictions in folk proverbs are not necessarily correct, and winter drought does not mean that summer drought will continue. "The weather on a certain day is not necessarily related to the weather on a certain day in a few months."
"However, the lack of snowfall will increase the possibility of pests and diseases, which will have a negative impact on the growth of overwintering crops. From this perspective, it will indeed have a certain impact on agriculture if it does not snow in winter." Snow-free winter not only has less flavor, but also lack of snow can cause many problems. In an interview with the media, Pan Jiahua, director of the Urban Development and Environment Research Center of China Academy of Social Sciences, said that precipitation will make the living environment worse and seriously restrict social production. "Although warming in winter can shorten the heating time and reduce related expenses, its disadvantages still outweigh its advantages."
Investigation reminder
Watch out for colds when it’s dry and snowy.
During the Spring Festival, Dr. He, who works in a community hospital, was busy. Due to the dry air, the number of patients with sudden respiratory diseases suddenly increased during the Spring Festival. Every day, the hospital received dozens of patients who had infusion bottles, and the top three hospitals were crowded. Experts said that due to the low air humidity, some viruses are easy to reproduce and easily lead to a series of diseases. During the Spring Festival in Beijing Children’s Hospital, an average of nearly 5000 children came to see a doctor every day. On the first normal outpatient day after the festival, more than 4,000 outpatient visits were made in the morning alone. Among them, children with respiratory tract infection are the most.
"It doesn’t snow, which is very bad for human health." Doctors at Chaoyang Hospital in Beijing said that because of the dry air, people are prone to chapped lips, bleeding nostrils and itchy throat. When the air humidity is lower than 40%, the respiratory mucosa of the nose and lungs will be dehydrated and the elasticity will be reduced, making dust, bacteria, etc. easily attached to the mucosa, stimulating the throat and causing cough.
However, the spread of cold will be accelerated because of the accelerated reproduction of influenza virus in dry environment and its survival on floating dust. However, due to the failure of "wet deposition", urban air pollution will be serious and respiratory diseases such as asthma and pneumonia will be easily caused.
"The way to prevent diseases is a cliche, but many people always pay no attention." Experts say that opening windows regularly to ventilate and maintain indoor humidity will help prevent diseases. At the same time, we should try to avoid going to crowded areas. People with respiratory diseases should wear masks when going out.
Reporter Wu Nan
Editor: Gao Song