What is the relationship between freezing rain and global climate?

Overview Freezing rain is a weather phenomenon seen in early winter or late winter and early spring. When strong cold air moves southward and encounters warm and humid air, the cold air is inserted below the warm air like a wedge. The temperature near the ground drops sharply below zero, and the moist warm air is lifted up and turns into clouds and rain. When raindrops fall from the sky, due to the low temperature near the ground, a thin layer of crystal clear ice will freeze on the surfaces of telephone poles, trees, vegetation and roads. This weather phenomenon is called "freezing rain" in meteorology. In some areas of southern my country, freezing rain is also called "Xiabingling", while in northern areas it is called "diyouzi". Rain that freezes immediately when raindrops collide with the ground, ground features, aircraft, etc. is called freezing rain. When this kind of rain falls from the sky, it is supercooled water droplets below 0°C. When it hits branches, wires, dead grass or other ground objects, it will freeze on these objects to form a smooth, crystal-clear ice shell. Sometimes it freezes and drips, like icicles. This kind of ice is also called "rain" or ice in meteorology. Freezing rain is supercooled raindrops or drizzle falling on the ground with a temperature below freezing point. The water droplets quickly freeze on the ground and objects to form a transparent or translucent ice layer. This ice layer can form the "Thousand Cliffs of Ice Jade, Ten Thousand Peaks of Crystal" 'A magnificent scene. If it encounters drizzle, grains will appear. The surface of the grains is rough and the granular structure is clearly discernible. If it encounters larger raindrops or the rainfall intensity is high, clear ice will often form. The surface of the grains will be smooth. Transparent and dense, it often freezes while flowing on wires, branches or ships, forming long ice hangings. The areas with more freezing rain in my country are Guizhou Province, followed by Hunan, Jiangxi, and China. Hubei, Henan, Anhui, Jiangsu and Shandong, Hebei, Shaanxi, Gansu, Liaoning and other places have more mountainous areas than plains, and the highest number of mountains. Rain falls from the sky and freezes. Can this kind of ice cause harm? When accumulated to a certain extent, it is not only harmful, but also harmful.

Causes

In winter, rain falls on trees, tall buildings, rocks, electric poles and other objects, and it forms immediately. When it freezes, people are accustomed to calling it "dropping water to form ice". This kind of rain is called "freezing rain" in meteorology (its condensation is called "rainy rain"); it is different from the ordinary water droplets that people often say, but is a kind of super-cooled water droplet. (temperature below 0°C), it should condense into ice particles or snowflakes in the cloud, but the necessary freezing nuclei for freezing cannot be found, so it becomes supercooled water droplets that freeze when they hit objects.

"Freezing rain" falls on wires, branches, and the ground, and then forms a thin layer of ice with a smooth surface. The ice becomes thicker and thicker. During the agglomeration process, it flows and freezes, resulting in a Strings of stalactite-like icicles and ice spikes (commonly known as "ice hangings") are crystal clear and emit colorful light when exposed to sunlight. It's a pity that when its weight exceeds the carrying capacity of the object! , the tragedy happened. To form "freezing rain", for supercooled water droplets to fall to the ground smoothly, it is often inseparable from specific weather conditions: the temperature of the air layer about 2000 meters near the ground is slightly lower than 0℃; between 2000 meters and 4000 meters The temperature of the air layer is higher than 0℃, which is warmer; the temperature of the layer above is lower than 0℃. This structure of the atmosphere causes the supercooled water droplets, ice crystals and snowflakes in the upper clouds to fall into the warmer air. layer, all turn into liquid water droplets. Then they fall down and enter the not-so-thick frozen layer. When they fall with the wind and are about to freeze, they have already been supercooled and contacted the cold object, and in an instant they form a solid layer. "Freezing rain"!

Freezing rain is composed of supercooled water droplets that freeze immediately when they collide with objects with a temperature below 0℃. Raindrops below 0℃ can freeze in air with a temperature slightly below 0℃. Remaining in a supercooled state, its appearance is the same as that of ordinary raindrops. When it falls on an object with a temperature below 0°C, it immediately freezes into a smooth and transparent ice layer, which is called raindrops. Severe raindrops can break trees. , telephone poles, interrupting communications and power supply, hindering highway and railway transportation, and threatening the flight safety of aircraft. When freezing rain occurs, the ground is often not very cold (0?-3℃), and the upper sky is inversely stable, with a layer of temperature higher than 0℃. warm layer. Precipitation occurs as raindrops in the warm layer, and when it falls into the atmosphere near the ground, it becomes supercooled freezing rain, which often causes some harm.

If raindrops continue to fall on the surface of these frozen objects, they will slowly form icicles. After the sun comes out, the icicles sparkle under the sunlight and are particularly enchanting. The freezing rain adds to the beautiful and moving scenery. But the harm it causes is also very serious. For example, if ice forms on the wires, it will increase in weight and shrink when exposed to cold, causing the wires to break, leading to interruptions in communications and power transmission. Crops will suffer frostbite and freeze to death after encountering freezing rain. If ice forms on the ground, traffic accidents will increase dramatically. . Therefore, if freezing rain occurs for several days, the damage caused will still be great.

Hazards The scenery of freezing rain is worth watching, but it is a kind of disastrous weather after all, and the harm it causes cannot be ignored. After the wires freeze, they shrink when exposed to cold, and under the influence of the weight of freezing rain, they will break. At times, rows of power poles were pulled down, disrupting telecommunications and power transmission. Road traffic has been hampered by icy ground and traffic accidents have increased. Freeze in the field will freeze the winter wheat that has returned to green, or freeze to death the crop seedlings sown in early spring. In addition, freezing rain can destroy young forests and frostbite fruit trees in large areas.

At the end of February 1972, a large-scale freezing rain occurred in my country. Telecommunications from Guangzhou, Changsha, Nanjing, Kunming, Chongqing, Chengdu, Guiyang and other places to Beijing were temporarily interrupted, causing extremely serious economic losses.

In 1955, hundreds of electric poles were destroyed due to "freezing rain" in the Zhejiang-Jiangxi region, and railway transportation in Nanxun and Zhejiang-Jiangxi was temporarily interrupted; in November 1987 and December 1989, Zhengzhou City had two When "freezing rain" occurs, more than 200 people are injured; in the southwestern region of the former Soviet Union, a "freezing rain" destroyed or overturned nearly 10,000 electric poles, causing widespread telecommunications outages. In late mid-January 1984, affected by strong cold air, freezing rain occurred in many areas of Guizhou, Hunan, Jiangxi, Hubei and other provinces, causing power lines to be broken and poles toppled. All wired telephone calls in Guizhou Province were interrupted, seriously affecting communication work. The thickness of ice on transmission lines in Hunan is more than 20 mm, and some high-voltage lines melt ice 5-6 times a day. Due to the freezing weather, 803 long-distance buses were suspended at Guiyang Bus Station, and 418 rural buses were suspended intermittently. Several counties near Changsha, Hunan, suspended 339 shuttle buses; Linwu and Zixing counties alone had nearly 5 million broken bamboo and wood roots. In Guizhou, 10% of early-bolted rapeseeds were damaged by freezing.

Prevention The thickness of freezing rain generally reaches 10 to 20 mm, with the thickest being 30 to 40 mm. When freezing rain occurs, the wind is often stronger, so freezing rain has a greater impact on transportation, especially communications and transmission lines. According to the analysis of meteorological experts, freezing rain is a precipitation phenomenon produced under a specific weather background. During this period, the northwest airflow and southwest airflow over the Jianghuai River Basin are very strong, cold air invades from the ground, and warm air flows northward from 1500 to 3000 meters above. The vertical structure of the atmosphere is cold at the top and warm at the middle, from top to bottom. They are ice crystal layer, warm layer and cold layer. That is, the atmospheric temperature at altitudes above 3,000 meters is often below -10°C. At an altitude of around 2,000 meters, the atmospheric temperature is generally around 0°C, while the temperature below 2,000 meters is lower than 0°C. Freezing rain mostly occurs within more than a month from early January to early or mid-February. The starting date is early in the north and late in the south, early in the mountainous areas and late in the plains, and the end date is opposite. In mountainous areas with higher terrain, freezing rain starts early and ends late, and the freezing rain period is slightly longer. For example, at Guangmingding in Huangshan Mountain in southern Anhui, freezing rain usually starts in early November and ends in early April of the following year, lasting up to 5 months. According to statistics, freezing rain weather in the Yangtze-Huaihe River Basin occurs once every 2 to 3 years along the northern 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 mountaintops. Some valleys in mountainous areas have almost no freezing rain, while freezing rain occurs almost every year in higher mountains. Freezing rain is a kind of disastrous weather. When it freezes and accumulates in large quantities, it can break down electric wires and telephone lines. Severe freezing rain can collapse houses. When an airplane flies in clouds with supercooled water droplets, water will accumulate on the wings and propellers. , affecting the aerodynamic performance of the aircraft and causing a crash. The main ways to eliminate freezing rain disasters are to mobilize residents along the transmission lines to continuously scrape the raindrops off the power lines when freezing rain occurs; to install de-icing equipment on aircraft or simply to avoid freezing rain areas.