Cause analysis of snowfall at home and abroad in 2008

Since the middle of 65438 10, there has been a rare large-scale rain and snow weather in China, and the number of precipitation days in the whole country and 12 provinces has exceeded the extreme value. The large-scale continuous low temperature, rain, snow and freezing weather has caused serious impacts and losses to China's roads, railways, aviation, power supply and people's lives. 65438+1On October 30th, China Meteorological Bureau held a news briefing, and analyzed the causes of this large-scale disaster. Relevant experts said that it was all caused by freezing rain.

Three snowfall and freezing weather processes

Causing extensive rain and snow disasters

At the news briefing, Jiao, spokesperson of China Meteorological Bureau and director of the Department of Forecasting and Disaster Reduction, introduced that since mid-October, due to the influence of cold and warm air, there have been three obvious rain and snow weather processes in China, including heavy snowstorms in Henan, Hubei, Anhui, Jiangsu, Hunan, northwestern Jiangxi and northern Zhejiang; Freezing rain or freezing weather occurred in Hunan, Guizhou, southern Anhui, Jiangxi and other places. The third process continues.

The first snowfall and freezing weather is June 65438+1October 10 to June 16. There are rain, sleet and snowfall in the south of Huanghuai and its south, and there are heavy snowstorms in central Shaanxi, southwestern Shanxi, central and northern Anhui, northern Jiangsu, Hubei, Hunan and northwestern Jiangxi. From 13 to 14, freezing rain occurred in central and southern Hunan, western and southern Guizhou. On 16, the snow depth in northern Shaanxi, southwestern Shanxi, southern and western Henan, central and southern Anhui, northern and eastern Hubei, southern Hunan and northwestern Jiangxi reached 3 ~ 10 cm.

The second snowfall and freezing weather was from June 5438 to1October 18 to 22, with heavy snowstorms in eastern Hubei, southern Henan, central and northern Anhui, northern Jiangsu and northern Hunan, and freezing rain in southern Anhui, most of Hunan, Guizhou and northeastern Guangxi. On the 22nd, the snow depth in north-central Shaanxi, Shanxi, Henan, Anhui, northwestern Jiangsu, northern and eastern Hubei, and Hunan reached 5 ~ 15cm, and the local area was 20cm.

The third snowfall and freezing weather is 65438+ years1October 25th-28th, which is also the strongest one. Blizzard appeared in southern Henan, eastern Hubei, Anhui, Jiangsu and northern Zhejiang, and the snow depth reached 20 ~ 45 cm on the 28th. At the same time, a large range of freezing rain occurred in Jiangxi Province, most of Guizhou and parts of Hunan Province were still freezing rain, and moderate to heavy rain occurred in southeastern Guangxi, Guangdong and parts of Fujian.

Wide range, high intensity, long time and heavy disaster.

Become the four characteristics of this disaster.

"Overall, the freezing rain and snow weather is rare since the founding of the People's Republic of China, with the characteristics of wide range, high intensity, long duration and heavy disasters." Jiao Meiyan introduced that the low-temperature rain, snow and freezing weather affected Guizhou, Hunan, Hubei, Jiangxi, Anhui, Henan, Guangxi, Jiangsu, Zhejiang, Shaanxi, Gansu, Qinghai, Sichuan, Tibet, Shanxi, Shanghai and other 16 provinces (autonomous regions and municipalities).

The precipitation in the whole country and six provinces of Henan, Sichuan, Shaanxi, Gansu, Qinghai and Ningxia has reached the maximum value in the same period since 195 1 year, and the precipitation in nine provinces (regions) of Gansu, Qinghai, Shaanxi, Sichuan, Tibet, Anhui, Shanxi, Jiangsu and Hubei has exceeded 20 years. The minimum temperature in the middle and lower reaches of the Yangtze River dropped to -6℃ ~ 0℃, and the daily maximum temperature was close to the minimum temperature. The average daily temperature in Wuhan and Changsha has been close to or below 0℃ for more than half a month. The temperature in Hubei, western Anhui, northwestern Jiangxi, Hunan, Guizhou and other places is 2℃ ~ 4℃ lower than normal. The average temperature in Hubei and Hunan is the lowest in the same period in history.

Jiao said that the duration of this freezing rain, snow and freezing weather is rare in history. In Hunan and Hubei provinces, 1954 has the longest duration and the most serious impact since meteorological observation data were available; in Jiangxi, 1959 has the most serious impact since meteorological observation data were available; in 26 counties (cities) in Guizhou, the duration has broken the historical record; and in Anhui, the longest duration has occurred since meteorological observation data were available.

Freezing rain caused power failure and roads were frozen.

"In this disaster, the power supply was interrupted, the Hunan section of the Beijing-Guangzhou Railway was interrupted, and the Hunan section of the Beijing-Zhuhai Highway was interrupted. Low temperature and freezing rain are the main reasons. " Qiao Lin, chief forecaster of the Central Meteorological Observatory of China Meteorological Bureau, said that northerners don't know much about freezing rain. When falling from the sky, it is supercooled water droplets below 0℃. When it touches branches, wires, hay or other ground objects, it will freeze into a smooth, crystal clear ice shell on these objects.

"Freezing rain mostly occurs in winter and early spring. The area with more freezing rain in China is Guizhou Province, followed by Hunan, Jiangxi, Hubei, Henan, Anhui and other places. Among them, there are more mountains than plains and the most mountains. " Qiao Lin said that the freezing rain caused the wires in the power grid to freeze, and the wires were wrapped layer by layer. The most serious thing is that the diameter of the wire reached seven or eight centimeters, far exceeding the design load-bearing standard of the wire, which eventually led to a large area of damage to the whole power grid. The power grid interruption caused the electric locomotives in Hunan section of Beijing-Guangzhou Railway to be paralyzed, which caused power supply interruption in several cities. Freezing rain with wide range, high intensity and long time is the chief culprit of large-scale freezing rain and snow disaster in South China.

There will still be heavy snow in Hunan and other places

"In the next three days, there will be heavy rains in southern and western Jiangnan, heavy snow in central and northern Hunan, northwestern Jiangxi, northeastern Zhejiang and other places, heavy snow in some areas, and freezing rain in Hunan and other places will continue. 65438+1October 30th and 3 1 will be moved to Jiangnan and South China, and the rain and snow will have a serious impact. Starting from February 1, the rain area will move to the south of the Yangtze River. " Jiao said that in areas where freezing rain lasts for a long time, Guizhou and Hunan, including Jiangxi, will have freezing rain in the next three days, which should be a very noteworthy weather situation at present.

The Central Meteorological Observatory predicts that in the next 10 day, there will still be rainy and snowy weather in most parts of southwest China, Jiangnan and South China, and the temperature will continue to be low. The main precipitation process occurred on February 2 1 ~ 3 1 and February 4 ~ 5. In the coming week, the low temperature maintenance in the southern region, coupled with the disasters caused by the previous impact, can not be ignored. Especially in central and southern Guizhou, southern Hunan and northern Guangxi, freezing rain is still serious, which has a serious impact on the affected areas.

The direct cause is abnormal atmospheric circulation.

What is the main weather reason for this large-scale snowfall? Jiao said that the direct cause is the abnormal operation of atmospheric circulation. Since 65438+1October 10, the atmospheric circulation system has undergone a major adjustment, from sunny and warm weather in the previous period to low temperature and rainy weather now, which has a great impact on South China. In addition, the warm and humid air flow in the whole southwest is relatively strong, and there is also a continuous supply of warm and humid air flow in South China, which has caused continuous rainy weather.

Jiao said that in the longer term, the rain and snow weather process should be said to be a typical extreme weather and climate event, which was formed in a large climate background and related to the current abnormal atmospheric circulation, especially the current La Nina phenomenon. It is also a very strong stage. La Nina is relative to the El Ni? o phenomenon, which often causes low temperature and rainy weather in winter in China.

Extreme weather events should not be taken lightly.

"2007 is the year of global climate change. Especially at the Bali Conference in 2007, the heads of many countries and international organizations around the world studied the issue of climate change. The IPCC's Fourth Assessment Report also commented that extreme disastrous weather and climate events caused by climate change are increasing. This has been widely recognized by the global scientific community. " Jiao said that the top ten weather events in the world selected in 2007 were basically disastrous. In the context of climate warming, the impact of extreme weather and climate events has increased, which is more important for China. Facing the 2008 Beijing Olympic Games, the sandstorm in the spring of 2008 and the heavy precipitation in the summer, we should strengthen our defense.