What kind of huge economic losses did the snowstorm bring?

Snow disaster, also known as white disaster, is a natural phenomenon caused by long-term heavy snowfall. It is a frequent meteorological disaster of animal husbandry in pastoral areas of China, mainly referring to animal husbandry areas that rely on natural grassland for grazing. Due to the excessive snowfall in winter for half a year, the snow cover is thick and lasts for a long time, which affects the normal grazing activities of animal husbandry. The harm to animal husbandry is mainly that snow covers the grassland, exceeding a certain depth. Some snow is not deep, but the density is high, or the snow is covered with ice to form an ice shell, which makes it difficult for livestock to open the snow layer to eat grass, causing hunger. Sometimes the ice shell is easy to cut the ankles of sheep and horses, causing frostbite, which often leads to emaciation of livestock, abortion of young livestock, low survival rate of old and weak young livestock and increased death. At the same time, it also seriously affects or even destroys lifeline projects such as transportation, communication and power transmission lines, posing a threat to the life safety and life of herders. Snow disasters mainly occur in stable snow-covered areas and unstable snow-covered mountainous areas, and occasionally appear in instantaneous snow-covered areas. Snow disasters in pastoral areas in China mainly occur in Inner Mongolia grassland, northwest China and parts of Qinghai-Tibet Plateau.

According to the formation conditions, distribution and manifestations of snow disasters in China, snow disasters can be divided into three types: avalanche, wind-blown snow disasters (snow disasters) and snow disasters in pastoral areas.

In addition, according to the stability of snow, snow can be divided into five types:

1. Permanent snow: the amount of snow above the snow balance line is greater than the melting amount in the current year, and the snow will not melt all the year round.

2. Stable snow (continuous snow): seasonal snow with continuous spatial distribution and snow accumulation time (more than 60 days); 3. Unstable snow (discontinuous snow): Although there is snow every year and the temperature is low, the snow is discontinuous in space and mostly distributed in points. In time, the number of snow days is 10~60 days, intermittent: Blizzard 4. Instant snow: it mainly occurs in South China and Southwest China where the average temperature is high, but in the year when the monsoon is particularly strong,

5. It doesn't snow: Except for some high-altitude mountainous areas, it doesn't snow all the year round.

Snow disasters mainly occur in stable snow-covered areas and unstable snow-covered mountainous areas, and occasionally appear in instantaneous snow-covered areas.

Snow can play an active defensive role in the wintering and heat preservation of pasture, and snowmelt in dry season can increase soil moisture and promote the regrowth of pasture. Snow is also the main water source of water-deficient or waterless grassland in winter and spring, which solves the problem of drinking water for people and animals. Too much snow, too deep snow and too long duration make it difficult for livestock to eat grass, or even unable to eat grass, leading to snowstorms.

Snowstorms can be divided into two types according to their climatic laws: sudden and persistent.

Sudden snowstorms will occur during or after snowstorm weather, and the thick snow lasting for several days will pose a threat to livestock. This kind of snowstorm is most common in late autumn and early spring with changeable climate, such as the rare snowstorm in late March to early April in 1982 and mid-October in 1985 in Qinghai Province, which is the most obvious example of this kind of snowstorm in recent years. Persistent snow disaster means that the thickness and density of snow that harms livestock gradually increase with snowfall, and the snow is stable for a long time. This type can last from late autumn to the following spring, such as the severe snowstorm in June 1974 to March 1975 in Qinghai Province, which lasted for five months, and the extreme minimum temperature dropped to MINUS 30-40 degrees.

Power transmission equipment crushed by snowstorm People usually regard the depth of grassland snow as the primary sign of snowstorm. Due to the different growth heights of grassland and pasture, the depth of snow forming snowstorm is also different. Based on the analysis of the observation and investigation data in Inner Mongolia and Xinjiang for many years, the relationship between snowfall and blizzard formation over the years is compared, and the blizzard indicators are as follows:

Light blizzard: the snowfall in winter and spring is equivalent to more than 120% of the snowfall in the same period of the year; Moderate snowstorm: the snowfall in winter and spring is equivalent to more than 140% of the snowfall in the same period of the year; Heavy snowstorm: the snowfall in winter and spring is equivalent to more than 160% of the snowfall in the same period of the year.

Snow disaster index can also be expressed by other physical quantities, such as snow depth, density and temperature. However, the biggest advantage of the above indicators is that they are easy to use and the data are easy to obtain.

According to the analysis of investigation materials, the snowstorm in grassland and pastoral areas in China has the law of once every ten years. As for the general snowstorm, its frequency is more frequent. According to statistics, pastoral areas in Tibet are about once every two to three years, and so are pastoral areas in Qinghai. In pastoral areas of Xinjiang, due to the great differences in climate and geography, the frequency of snowstorms varies greatly. The frequency of snow disasters in winter grassland and spring and autumn grassland in Altai Mountain, western Junggar, northern Xinjiang along Tianshan Mountain, western mountainous area of southern Xinjiang is 50%~70%, that is, snow disasters occur once every 5~7 years in 10. Other regions are below 30%. Snowstorm-prone areas are often serious, such as Altay, Fuyun and other places. The frequency of snowstorms is as high as 70%, and severe snowstorms are as high as 50%. On the contrary, areas with low frequency of snowstorms are often areas with light snowstorms. For example, the frequency of snowstorms in hot springs is only 5%, and it is a mild snowstorm. However, no matter which herder has a big snowstorm, it rarely happens year after year.

During a snowstorm, winter snow usually begins at 10, and Chun Xue usually ends in April. What is more harmful is generally the so-called "sitting in winter snow" formed by heavy snow in late autumn and early winter. Then there was a continuous snowfall, which made the grassland snow thicker and thicker, so that the snow that harmed livestock lasted all winter.

The area where the snowstorm occurs is closely related to the distribution of precipitation. For example, in pastoral areas of Inner Mongolia, snowstorms mainly occur in Bameng, Wumeng, Xilin Gol League, Zhao Meng and northern Zhemeng in central Inner Mongolia, with the frequency of more than 30%, of which the snowstorms in Yinshan area are the heaviest and most frequent; Due to the unusually dry winter in the west, there are almost no snowstorms. In pastoral areas of Xinjiang, snow disasters are mainly concentrated in mountain pastures around Junggar Basin in northern Xinjiang. Snow disasters rarely occur in southern Xinjiang except in the western mountainous areas. In Qinghai pastoral areas, snowstorms are mainly concentrated in Hainan, Guoluo, Yushu, Huangnan and Haixi, which have more precipitation in winter in the south. In the pastoral areas of Tibet, snow disasters are mainly concentrated in Naqu area near Tanggula in northern Tibet and Xigaze area in southern Tibet.

According to "Zi Jian" and other books, the earliest snowstorm in China occurred more than 2,000 years ago, that is, in 37 BC, in the second year of the Western Han Dynasty, a heavy snow with a depth of 5 feet fell in Chu (including Changsha, Hunan). It was not until the Five Dynasties and Ten Kingdoms period (950) after the Tang Empire that the history books clearly marked the heavy snow in Changsha for the first time, that is, "the heavy snow in Tanzhou was four feet." Tanzhou ruled Changsha today.

In the first year of the apocalypse in Xi, Ming Taizu (162 1), snow and ice appeared in Changsha, Hua Shan, Yiyang and Liuyang, and Liuzhai, Datun Bridge in Hua Shan (now south of Changsha) "froze six people to death overnight"; During the Kangxi period, Xiangjiang ice was "feasible"; In the fifth year of Jiaqing in Qing Dynasty (1800), there was a heavy snow in September in Changsha, Hua Shan, Pingjiang, Xiangxiang and Huangzhou Guilds.

The "big freeze" of 1954 began on1954 65438+February 26th. That evening, "the cold current began to harass Dongting Lake for the second time, and all the dams in Dongting Lake were quickly covered with snow and ice. The trees on the bank were bent by the snow and ice, and dozens of wires were broken by the ice. The temperature dropped sharply from 20℃ to -8℃, and the snowstorm lasted 1 1 day. The old man by the lake said: This is the freezing cold that Dongting Lake has not seen for more than 20 years.

196 1 year, the Chronology of Natural Disasters in Hunan compiled by Hunan Provincial Institute of History and Archaeology records that before the founding of New China, Hunan was frozen for 40 days (Pingjiang) and for 3 months. In the days of snow and ice disasters, there is often heavy snow or continuous rainfall in the freezing of Hunan, with the snowfall reaching more than 40 days (Yongzhou), and the snowfall from Xiaotian to February of the following year (Anhua), with the snow depth reaching four or five feet (Xiangxiang, Xiangyin, Pingjiang and Shaoyang). It not only damages trees, fruits and vegetables, kills people and animals with ice, but also hinders traffic.

On June 65438+ 10/0, 2008, a snowstorm broke out in the south. The severely affected areas are Hunan, Guizhou, Hubei, Jiangxi, northwestern Guangxi, northern Guangdong, western Zhejiang, southern Anhui and southern Henan. As of February, 2008, 12, 2 1 provinces (autonomous regions, municipalities and corps) in China were affected by freezing rain, snow and ice disasters to varying degrees, resulting in 107 deaths, 8 missing, and 15 12000 emergency. The affected area of crops was 65.438+0.77 billion mu, and the harvest was 2530 mu. The damaged forest area is nearly 260 million mu; 354,000 houses collapsed; Causing direct economic losses of RMB111100 million yuan.

The main cause of this snowstorm is the abnormal atmospheric circulation, especially the abnormal air flow in the Eurasian balloon.

As we all know, the atmospheric circulation has its own operating rules, and it maintains a stable circulation state for a certain period of time. There is a low-value system in the southwest of Qinghai-Tibet Plateau, while Siberia maintains a relatively high-value system, namely, meteorological low-pressure system and high-pressure system. These two systems have existed in these two areas for a long time, and the low-pressure system has brought abundant precipitation to the southern part of China, mainly in the southern sea and the Indian Ocean. Cold high pressure from Siberia pushes cold air to the south. Obviously, in general, the main control in winter is the cold air from Siberia, which makes most parts of China dry and cold.

On June 5438+ 10, 2008, the warm and humid air flow in the southwest affected most parts of China, while the high-pressure system in the north was stable, and the cold air was continuously transported from Siberia to the south, so the cold and warm air met in the middle and lower reaches of the Yangtze River and the south. The density of cold air is relatively high, and warm air will slide upward along the cold air layer, so the rich water vapor carried by warm and humid airflow will condense, forming rain and snow weather. Due to the unusually long-term intersection of cold and warm air in this area, the rainy and snowy weather in southern China lasts for a long time.

In fact, the three rain and snow weather processes in the south are mainly the three strengthening of the warm and humid airflow in the southwest, and three relatively large rain and snow weather processes have appeared accordingly.

Among them, the third large-scale continuous rain and snow weather process on June 5438+1October 26-28, 2008 was strong, and the impact of the previous two times caused the most serious losses.