Why didn't it snow in Beijing in 2009?

Why has Beijing not seen snow for the first time this winter since 1970?

February 3, 2009 14:25:44 Source: Beijing Evening News

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Yesterday (2nd) at 3pm, in the consulting room of Beijing Meteorological Bureau, various cloud pictures and data were constantly switched on the big screen, and several analysts told their forecast views one by one before taking the stage. Since the beginning of winter, except for two small-scale snowfalls in the outer suburbs in June 5438+February, 2008, there has been almost no snow in Beijing, which makes the Spring Festival in 2009 lack a trace of scenery and adds a trace of disappointment to people who are looking forward to a snow scene.

Tomorrow is beginning of spring, and the Lantern Festival will be celebrated in a few days. Will Beijing have a "timely snow"? Why is it difficult to snow in Beijing this winter? Our reporter interviewed Sun, the chief forecaster of Beijing Meteorological Bureau, to solve the problem of 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. From last year1October 24th 10, it snowed only twice in Yanqing in the north and Pinggu in the northeast-June 5438+February 10 and 23rd, 2008. In downtown Beijing, there is still no effective snowfall. Sporadic snowflakes only appeared in June 65438+February 10 last year, but they were fleeting and the precipitation was only 0. 1 mm.

"This situation is rare this year, but it is also normal." Sun, chief forecaster of Beijing Meteorological Observatory, said that historically, the winter precipitation in Beijing has not been large, and the precipitation from 12 to February of the following year is usually around 10 mm, so it cannot be said that there is no precipitation in winter. Looking back, the last winter with almost no precipitation was 1970. However, since 2008124 October 65438, there has been no precipitation in the urban area this winter, which is really rare.

A report in Sun's hand shows that water shortage is not limited to Beijing. This winter, droughts occurred in Hebei, Shanxi and Henan. 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 consulting room shows that the daily maximum temperature in some urban areas of Beijing in these two days exceeded 10 degrees Celsius. However, Sun said that in addition to cold air, the formation of snowfall must also have water vapor transport and suitable ground temperature, and several factors are indispensable. However, there was no snow this winter, mainly because of water shortage-the water vapor transportation has been "cut off".

Sun introduced that from the perspective of Beijing, water vapor mainly comes from two channels. One is that the water vapor brought by the warm and humid airflow in the southwest of Jiangnan, especially snowfall, often has the characteristics of large snowfall and long snowfall time, and often becomes the "main force" factor of snowfall in Beijing; Another source of water vapor is the water vapor brought by the easterly airflow in Bohai Sea and Yellow Sea. However, due to the short conveying length, its snowfall is characterized by less snow.

From 65438+February last year to now, four cold waves have swept through the city, but all of them are mainly cooled by strong winds. "The northwest wind prevailed in Beijing this winter, which is not conducive to the transportation of these two streams of water vapor. However, the easterly wind or southwest wind occasionally formed through the change of atmospheric circulation has basically not formed this year, so the water vapor transportation has basically been broken. " Sun said that the "sudden change of the situation" in Chibi style is pitiful, and it has not been encountered once this winter. It can be said that it is "reasonable and unexpected".

Investigate and dispel doubts

Four conjectures about "No Snow"

Guess 1

Is it possible to snow on the fifteenth day of the first month?

On the sixth day of Lunar New Year's Eve, Mona Lee skated with some friends at a ski resort in Mentougou. The only thing he regrets is that the mountain next to the ski resort is bare. "I can't even take a picture. There is no snow outside the slide. At first glance, it is artificial. "

In many people's minds, snow and Chinese New Year are inseparable. If there were no snowflakes, the taste would be much less in a year. In the snowy winter, can we make up for everyone's regrets on the Lantern Festival? Sun, chief forecaster of Beijing Meteorological Observatory, said that such a wish may be difficult to realize. From the current data analysis, 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 said that due to the rapid change of atmospheric circulation, it may change, 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 will still be difficult to achieve."

Conjecture 2

"Sequela" of Meteorological Intervention?

"In order to eliminate the rain, more than 1000 rockets were launched at the opening ceremony of the Olympic Games. It won't take a year's rain away, will it? " Some netizens questioned whether large-scale artificial intervention in the weather would have a "sequela" on the overall climate. For such a problem, Sun 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 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 artificial precipitation enhancement operations, and this snowfall process is no exception. If there is snowfall, artificial "snow increase" measures will be taken. According to media reports, from February/KLOC-0 to February 2, the weather modification department of Luoyang City, Henan Province seized the opportunity of weak cold air transit and successfully implemented artificial precipitation enhancement. "But only if there is water in the sky can 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 word "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 described the Three Gorges as a small "puddle". If there is such a puddle, it is difficult to have any impact on the overall climate.

"At present, most climatologists believe that global warming will lead to 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 it be dry?

Is there any scientific reason behind poetic folk proverbs such as "It snows on August 15th in Yun Zheyue, and it snows on the 15th of the first month" and "It doesn't snow in cold weather, but the fields crack in summer"?

"Folk proverbs are more similar to statistical induction, and some of them have some truth," Sun said. The prediction in folk proverbs is not necessarily correct, and winter drought does not mean that summer drought will last. "The weather on a certain day is not necessarily related to the weather on a certain day in a few months."

"However, insufficient snowfall will increase the possibility of pests and diseases and have a negative impact on the growth of overwintering crops. From this perspective, if it doesn't snow in winter, it will really have a certain impact on agriculture. " Snow-free winter not only loses its flavor, but also the lack of snow will cause many problems. Pan Jiahua, director of the Urban Development and Environment Research Center of China Academy of Social Sciences, said in an interview with the media that precipitation will worsen the living environment and seriously restrict social production. "Although heating in winter can shorten the heating time and reduce related expenses, the disadvantages still outweigh the advantages."

Investigation reminder

Be careful of catching a cold when the weather is dry and snowy.

During the Spring Festival, Dr. He, who works in a community hospital, is very busy. Due to the dry air, the number of patients with sudden respiratory diseases suddenly increased during the Spring Festival. The hospital accepts dozens of patients with infusion bottles every day, and the top three hospitals are overcrowded. Experts said that due to the low air humidity, some viruses are easy to reproduce and easily cause a series of diseases. During the Spring Festival in Beijing Children's Hospital, an average of nearly 5,000 children came to see a doctor every day. On the first normal outpatient day after the holiday, the number of outpatients exceeded 4000 in the morning alone. Among them, children with respiratory tract infection are the most.

"No snow 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, the elasticity will be reduced, and dust and bacteria will be produced. Easy to attach to mucous membrane, irritate throat and cause cough.

However, due to the accelerated reproduction of influenza virus in dry environment and its survival on floating dust, the spread of cold will be accelerated. However, due to the failure of "wet deposition", urban air pollution will be very serious, which will easily lead to respiratory diseases such as asthma and pneumonia.

"The method of preventing diseases is a cliche, but many people always ignore it." Experts say that opening windows regularly to keep indoor humidity is helpful to prevent diseases. At the same time, try to avoid going to crowded places. People with respiratory diseases should wear masks when they go out. Our reporter Wu Nan.