How did this freezing rain form?

Freezing rain is a weather phenomenon seen in early winter or late winter and early spring. When the strong cold air meets the southbound warm and humid airflow, the cold air is inserted under the warm air like a wedge, and the near-surface temperature drops below zero, and the humid warm air is lifted to form clouds, causing rainfall. When raindrops fall from the air, because the temperature near the ground is very low, a layer of crystal clear thin ice will form on the surface of telephone poles, trees, vegetation and roads, which is called "freezing rain" in meteorology. In some areas of southern China, freezing rain is also called "ice falling", while in northern China, it is called "gutter oil". Rain that freezes immediately after raindrops collide with the ground, ground objects, airplanes and other objects is called freezing rain. This kind of rain is supercooled water drops below 0℃ falling from the sky. When it comes into contact with branches, wires, hay or other ground objects, it will freeze into a smooth, crystal-clear ice shell on these objects, and sometimes it will freeze like an icicle. This kind of ice layer is also called "rime" or ice in meteorology. Freezing rain is a transparent or translucent ice layer formed by supercooled raindrops or Mao Mao rain whose temperature is lower than freezing point, and the water drops quickly freeze on the ground and objects. This kind of ice layer can form a magnificent scene of "thousands of cliffs in the ice and thousands of peaks in the crystal". If it rains in Mao Mao, particles will appear with rough surface and clear particle structure. In case of heavy rain or heavy rainfall intensity, clear ice mounds often form. The surface of the ice clearing mound is smooth, transparent and dense, and it often freezes when flowing on wires, branches or ships, forming long ice hangings. Freezing rain mostly occurs in winter and early spring. In China, Guizhou Province is the region with more freezing rain, followed by Hunan, Jiangxi, Hubei, Henan, Anhui, Jiangsu, Shandong, Hebei, Shaanxi, Gansu and southern Liaoning. Among them, there are more mountains than plains, and the mountains are the highest. Can rain fall from the sky and turn into ice? Yes, this kind of ice accumulation to a certain extent is not only harmful, but also harmful.

cause

In winter, rain falls on trees, tall buildings, rocks, telephone poles and other objects and immediately becomes ice. People used to call it "dripping into ice". This kind of rain is called "freezing rain" in meteorology (its condensate is called "Song Yu"); It is a kind of supercooled water drop (the temperature is lower than 0℃), which is different from the common water drop that people often say. In the cloud, it should be condensed into ice particles or snowflakes, but the necessary freezing nucleus can not be found when freezing, so it becomes supercooled water droplets that can be frozen when touching objects.

"Freezing rain" falls on wires, branches and the ground, and then forms a thin layer of smooth ice. The ice is getting thicker and thicker, and it freezes while flowing in the process of condensation. As a result, a series of stalactite-like icicles and ice spines (commonly known as "ice hanging") were produced. They are crystal clear, and when they meet the sun, they give off colorful light, which is really beautiful! Unfortunately, when its weight exceeds the carrying capacity of the object, tragedy happens. To form "freezing rain", it is often inseparable from specific weather conditions to make supercooled water droplets land on the ground smoothly: the temperature of the air layer about 2000 meters near the ground is slightly lower than 0℃; The temperature of the air layer from 2000 meters to 4000 meters is higher than 0℃, which is warmer; The upper layer is lower than 0℃, so the supercooled water droplets, ice crystals and snowflakes on the upper layer of the cloud fall into the warmer gas layer and become liquid water droplets. Then it falls and enters the frozen layer which is not too thick. When they fall with the wind and are ready to freeze, they have already touched the cold objects in the form of supercooling, and suddenly formed a solid "freezing rain"!

Freezing rain is composed of supercooled water droplets, which collide with objects with a temperature below 0℃ and freeze immediately. Raindrops below 0℃ can remain supercooled in air with a temperature slightly lower than 0℃, and their appearance is the same as that of ordinary raindrops. When they fall on an object with a temperature below 0℃, they will immediately freeze into a smooth and transparent ice layer, which is called snowball. Severe snowstorms will crush trees and telephone poles, stop communication and power supply, hinder road and railway traffic, and threaten the flight safety of aircraft. When freezing rain occurs, the ground is often not too cold (0℃ ~ 3℃), the sky is unstable and there is a warm layer with a temperature higher than 0℃. Precipitation is a raindrop in the warm layer. When it falls into the atmosphere near the ground, it becomes supercooled and freezing rain, which often causes some harm.

If raindrops keep hitting the surface of these frozen objects, they will gradually form icicles. After the sun came out, the icicles in the sun shone, enchanting and charming, and the freezing rain added beautiful and moving scenery to people. But the harm it causes is also very serious. If the weight of the conductor increases after icing, it will shrink when it is cold, which will lead to the fracture of the conductor and the interruption of communication and transmission; Crops are frostbitten and frozen to death after freezing rain; If the ground freezes, traffic accidents will increase sharply. Therefore, the freezing rain for several days in a row has caused great disasters.

harm

The scenery of freezing rain is worth seeing, but after all, it is disastrous weather, and the harm caused cannot be ignored. After the wire freezes, it will shrink when it is cold, and it will break under the influence of the weight of freezing rain. Sometimes, rows of telephone poles are knocked down, resulting in interruption of telecommunications and transmission. Highway traffic is blocked by ground icing, and traffic accidents increase accordingly. If the ground freezes, it will freeze the green winter wheat or the crops planted in early spring. In addition, freezing rain will also destroy young forests and frostbitten fruit trees in a large area. The thickness of freezing rain can generally reach 10 ~ 20mm, and the thickest is 30 ~ 40 mm. When freezing rain happens, the wind is often strong, so freezing rain has a great influence on transportation, especially communication and transmission lines. According to meteorologists, freezing rain is a precipitation phenomenon under a specific weather background. During this period, the northwest airflow and southwest airflow over the Jianghuai Basin are very strong, cold air invades the ground, and warm air flows northward over1500-3000m. The vertical structure of the atmosphere is cold from top to bottom and warm in the middle, with ice crystal layer, warm layer and cold layer from top to bottom. That is to say, the atmospheric temperature above 3000 meters is often below-10℃, at an altitude of about 2000 meters, the atmospheric temperature is generally around 0℃, while the temperature below 2000 meters is below 0℃. Freezing rain mostly occurs from the first ten days of 1 month to the first ten days of February, and lasts for more than 1 month, with the characteristics of early in the north and late in the south, early in the mountains and late in the plains, but the end is the opposite. In mountainous areas with higher terrain, freezing rain starts early and ends late, and the freezing rain period is slightly longer. For example, in Guangmingding of Huangshan Mountain in southern Anhui, freezing rain generally starts from the first ten days of 165438+ 10 and ends in the first ten days of April of the following year, lasting for five months. According to statistics, the freezing rain weather in the Jianghuai basin occurs once every 2-3 years along the Huaihe River and once every 7-8 years south of the Huaihe River. However, in mountainous areas, there is a big difference between valleys and mountain tops. There is almost no freezing rain in some valleys in mountainous areas, while there is freezing rain in higher mountainous areas almost every year. Freezing rain is a disastrous weather, and a large amount of freezing will break power lines and telephone lines. Severe freezing rain will cause houses to collapse. When an airplane flies in a cloud with supercooled water droplets, the wings and propellers will accumulate water, which will affect the aerodynamic performance of the airplane and cause a crash.

1955, hundreds of poles were destroyed in Zhejiang and Jiangxi due to freezing rain, and the transportation in Nanxun and zhejiang-jiangxi railway was once interrupted; 1987, 1 1, 1989, there were two "freezing rains" in Zhengzhou, and more than 200 people were injured. In the southwest of the former Soviet Union, a "freezing rain" destroyed and overturned nearly 10,000 telephone poles, causing a large-scale telecommunication interruption. 1at the end of February, 972, there was a large-scale freezing rain in China, and the telecommunications from Guangzhou, Changsha, Nanjing, Kunming, Chongqing, Chengdu and Guiyang to Beijing were once interrupted, causing extremely serious economic losses. 19841in the middle and late October, due to the influence of strong cold air, freezing rain occurred in many areas of Guizhou, Hunan, Jiangxi, Hubei and other provinces, resulting in broken wires and inverted poles. All the wired telephones in Guizhou province were interrupted, which seriously affected the communication work. The icing thickness of transmission lines in Hunan is more than 20 mm, and some high-voltage lines melt ice 5-6 times a day. Affected by freezing weather, 803 long-distance buses in Guiyang bus station stopped working, and 4 18 buses in rural areas stopped working intermittently. Several counties near Changsha, Hunan stopped 339 buses; Nearly 5 million bamboo trees were broken in Linwu and Zixing counties alone. In Guizhou, 10% of early bolting rape was damaged by freezing.

On June 5438+ 10, 2008, Nanchang, Jiangxi Province was blacked out for three hours due to freezing rain, and the train could not start to enter Nanchang Railway Station due to rail freezing, resulting in tens of thousands of people being congested at the railway station.