What is a tornado?

A tornado is a strong, small-scale air vortex, which is generated by strong convective movement of air under extremely unstable weather. It is a funnel-shaped cloud (dragon) that extends from the bottom of the thunderstorm cloud to the ground. A strong cyclone produced by a hurricane, its wind force can reach level 12 or above, and the maximum can reach more than 100 meters per second. It is usually accompanied by thunderstorms and sometimes hail.

The air rotates rapidly around the axis of the tornado, and is attracted by the extremely reduced air pressure in the center of the tornado. In a thin layer of air tens of meters thick near the ground, the airflow is sucked into the bottom of the vortex from all directions. And then it turns into an upward vortex around the axis. The wind in a tornado is always cyclonic, and the air pressure in its center can be ten percent lower than the surrounding air pressure.

A tornado is a strong wind vortex accompanied by a high-speed rotating funnel-shaped cloud column. The wind speed near its center can reach 100m/s~200m/s, with a maximum of 300m/s. It is much faster than a typhoon (generated at sea). ) The maximum wind speed near the center is several times greater. The central air pressure is very low, generally as low as 400hPa, and as low as 200hPa. It has a great sucking effect and can suck the sea (lake) water away from the sea (lake) surface to form a water column, which is then connected with the clouds. It is commonly known as "dragon takes water". Because the air inside the tornado is extremely thin, the temperature drops sharply, prompting rapid condensation of water vapor, which is an important reason for the formation of funnel clouds. The diameter of the funnel cloud column is only about 250m on average. Tornadoes arise from strongly unstable cumulonimbus clouds. Its formation is related to the strong rise of warm and humid air, the southward movement of cold air, and topographic effects. Its life history is short, usually lasting from ten minutes to one or two hours, but its destructive power is astonishing. It can uproot large trees, blow down buildings, or roll parts of ground objects into the air.

Tornados are natural phenomena that are the product of thunderstorms in the clouds. Specifically, a tornado is a form in which a small part of the huge energy of a thunderstorm is concentrated and released in a small area. The formation of a tornado can be divided into four stages:

(1) The instability of the atmosphere produces a strong updraft, which is further strengthened due to the influence of the maximum passing airflow in the jet stream.

(2) Due to the interaction with the wind that has shear in both speed and direction in the vertical direction, the updraft begins to rotate in the middle of the troposphere, forming a mesoscale cyclone.

(3) As the mesoscale cyclone develops toward the surface and extends upward, it itself becomes thinner and intensifies. At the same time, a small area of ??enhanced coordination, that is, a nascent tornado is formed inside the cyclone. The same process that creates a cyclone forms the core of the tornado.

(4) The rotation in the core of a tornado is different from that in a cyclone. It is strong enough to make the tornado stretch all the way to the ground. When the developed vortex reaches the height of the ground, the surface air pressure drops sharply and the surface wind speed rises sharply, forming a tornado.

Tornadoes often occur during thunderstorms in summer, especially in the afternoon and evening. The attack range is small, and the diameter of a tornado is generally between ten meters and hundreds of meters. The survival time of a tornado is generally only a few minutes, and the longest is no more than a few hours. The wind is particularly strong, with wind speeds near the center reaching 100-200 meters/second. It is extremely destructive. Where a tornado passes, it often uproots trees, overturns vehicles, destroys buildings, etc. Sometimes it sucks people away, causing serious harm.

Dangers of tornadoes:

In 1995, a land tornado occurred in Ardmore, Oklahoma, USA. Heavy objects such as roofs were blown out several times. Ten miles away. Most debris falls on the left side of the landspout channel, often with well-defined landing zones based on weight. Lighter fragments may fly more than 300 kilometers before landing.

A tornado strikes suddenly and violently, producing the strongest winds on the ground. Tornadoes are second only to lightning in the number of deaths caused each year in the United States. It also causes serious and often devastating damage to buildings.

At about 9 a.m. on May 30, 1626 (the sixth day of May in the sixth year of Emperor Xizong’s reign in the Ming Dynasty), a strange disaster suddenly broke out around Wang Gong Factory in Beijing (today’s Xuanwumen area in Beijing) "Tianbiandichao", an official news and communication publication with important historical material value in the Ming Dynasty, has a detailed record of this disaster. The excerpt is as follows: "The east corner of Jizhou City collapsed and hundreds of houses were damaged. It was 180 years since the city left the capital. Ten miles away. On the tenth day of the lunar month, two people were dug out of the ground and they were still alive. They said, "Like a drunken dream." Another old man was dug up and he was still alive. "What kind of power was there in the strange disaster in Wang Gongchang? Can three people fly 180 miles from Beijing to Jizhou without dying? What kind of power can strip someone of their clothes so quickly and send them hundreds of miles away without hurting them? Why does the person being stripped not know how his clothes were removed? There must be some inevitable factor at play in this, but can this inevitable factor be recognized by humans in the future? Can this magical power be mastered, controlled and utilized by humans in the future? For details, see the extended reading blog post "The Strange "Strong Wind Blowing Man" Incident" below.

Precautionary measures against tornadoes

(1) When at home, be sure to stay away from doors, windows and the outer walls of the house, and hide in a wall or small room opposite to the direction of the tornado. Down. The safest place to hide from a tornado is in a basement or semi-basement.

(2) In the emergency situation where a power pole falls or a house collapses, the power supply should be cut off in time to prevent electric shock to the human body or fire.

(3) When encountering a tornado in the wild, you should find a nearby low-lying area and lie down on the ground, but stay away from big trees and electric poles to avoid being hit, crushed, and electrocuted.

(4) When a car encounters a tornado, you must not drive to avoid it, nor take shelter in a car, because cars have almost no defense against tornadoes. You should leave the car immediately and take shelter in a low-lying area.

On May 27, 1999, four counties in central Texas, including the capital Austin, were hit by a huge tornado, killing at least 32 people and injuring dozens more. According to reports, more than 50 houses collapsed and more than 30 people were killed in the tornado in the town of Jarrell, 40 miles north of Austin. The area of ??damage was a mile long and 200 yards wide. This is the second area in the United States to be hit by a tornado after the city of Miami was hit by a tornado on May 13.

Generally, a tornado is a type of cyclone. When it touches the ground, its diameter ranges from a few meters to 1 kilometer, with an average of several hundred meters. The impact range of tornadoes ranges from a few meters to tens or hundreds of kilometers, causing damage to everything wherever they go. The funnel-shaped center of the tornado consists of sucked dust and condensed water vapor forming a visible "dragon's mouth". Over the ocean, especially in the tropics, similar phenomena occur called maritime tornadoes.

Most tornadoes spin counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere, but there are exceptions. The exact mechanism of tornado formation is still under study, but it is generally believed to be related to the violent activity of the atmosphere.

Since the 19th century, the accuracy of weather forecasts has greatly improved, and weather radars can detect tornadoes, hurricanes and other disaster storms.

Tornadoes are usually extremely fast. It is not surprising that the wind speed is 100 meters per second, and even reaches more than 175 meters per second, which is five or six times greater than a Category 12 typhoon. The scope of the wind is very small, generally only 25 to 100 meters in diameter, and only in rare cases the diameter reaches more than one kilometer; the time from occurrence to disappearance only takes a few minutes, or at most a few hours.

A tornado is also very powerful. There was a tornado in Shanghai on September 24, 1956. It easily "lifted" a large oil storage barrel weighing 220,000 kilograms to an altitude of 15 meters, and then threw it 120 meters away.

At 4 pm on May 30, 1879, two dark and thick clouds merged together in the sky over northern Kansas. After 15 minutes, a vortex formed at the lower end of the clouds. The vortex grew rapidly and turned into a huge wind pillar that towered over the sky. Within three hours, it wreaked havoc across the entire state like an evil dragon, leaving no one safe wherever it went. However, the strangest thing happened at the beginning. The tornado vortex crossed a small river and encountered a cliff. Obviously, it could not surpass this obstacle. The vortex turned westward, where there happened to be a newly built 75 meter long railway bridge. The tornado vortex actually "plucked" it from the stone pier, twisted it a few times and threw it into the water.

Tornado Detection

Tornadoes have long been a mystery, and it is for this reason that it is necessary to understand them. A tornado strikes suddenly and violently, producing some of the strongest winds on the ground. Because its appearance and dispersion are very sudden, it is difficult to effectively observe it.

How fast is the wind speed of a tornado? No one really knows because the time it takes for a tornado to dissipate is short and its area of ??effect is so small that existing detection instruments are not sensitive enough to accurately observe tornadoes. Relatively speaking, Doppler radar is a more effective and commonly used observation instrument. The Doppler radar is aimed at the microwave beam emitted by the tornado. The microwave signal is reflected by the debris and raindrops in the tornado and is then received by the radar. If the tornado moves away from the radar, the frequency of the reflected microwave signal will move toward low frequency; conversely, if the tornado gets closer and closer to the radar, the reflected signal will move toward higher frequency. This phenomenon is called Doppler shift. Once the signal is received, radar operators can calculate the speed and direction of movement of the tornado by analyzing the frequency shift data.

Dragon absorbs water: Another name for tornado. Tornado is named because it resembles the East China Sea dragon that sprang out of the waves and soared into the mist in ancient mythology. It also has many aliases, such as "dragon sucking water", "dragon swinging its tail", "upside down dragon", etc. wait.

Characteristics of tornadoes

A tornado is the strongest vortex phenomenon in the atmosphere. Although its impact range is small, it is extremely destructive. It often destroys crops and tens of thousands of fruit trees in an instant, disrupts transportation, collapses houses, and causes loss of human and animal life. The horizontal range of tornadoes is very small, ranging from a few meters to hundreds of meters in diameter, with an average of about 250 meters and a maximum of about 1 kilometers. The diameter in the air can be several kilometers, with a maximum diameter of 10 kilometers. The maximum wind speed can reach 150 kilometers per hour to 450 kilometers per hour. The duration of a tornado is generally only a few minutes, and the longest is only tens of minutes, but the disaster caused is very serious.

Tornadoes often occur during thunderstorms in summer, especially in the afternoon and evening. The attack range is small, and the diameter of a tornado is generally between ten meters and hundreds of meters. The survival time of a tornado is generally only a few minutes, and the longest is no more than a few hours. The wind was extremely strong. It is extremely destructive. Where a tornado passes, it often uproots trees, overturns vehicles, destroys buildings, etc. Sometimes it sucks people away, causing serious harm.

Levels of tornadoes

There are five levels of tornadoes (Fujita scale/F-Scale), namely F1, F2, F3, and F4 level and F5 level. F1 tornadoes are smaller and have weaker winds, enough to lift roofs and pull down mobile homes. The wind speed in the center of the vortex is between 73 and 112 miles per hour. The car overturned. F3 wind speeds were as high as 260 miles, which was enough to uproot trees. F4 winds were strong enough to roll up houses, trees and vehicles. Soaring hundreds of yards away, the most terrifying thing is the unimaginable F5. It is enough to lift up solid houses, and reinforced buildings such as reinforced concrete will also be torn into pieces. The tornado in Cholo County, Texas in May 1997 It falls into this category, with wind speeds as high as 318 miles; the tornado was more than one kilometer in diameter and caused hundreds of millions of dollars in damage to the United States. Tip: If the British unit "1 mile" is converted into kilometers per hour, multiply it by 1.6. For example, the wind speed is 112 miles, which is converted into kilometers. When 112 miles is multiplied by 1.6, the speed can reach 180 kilometers per hour.