What is the cause and harm of tornado, the fastest and fiercest strong wind on the earth?

The fastest and most violent strong wind on earth: tornado

The fastest and most violent strong wind on the earth-tornado

Tornado is a strong, small-scale air vortex, which is produced by strong convective movement of air in extremely unstable weather. It is a strong cyclone produced by funnel-shaped clouds (tornadoes) extending from the bottom of thunderstorm clouds to the ground. Its wind power can reach more than 12, and the maximum can reach more than 100 m/s, usually accompanied by thunderstorms and sometimes hail.

The air rotates rapidly around the axis of the tornado and is attracted by the extremely low air pressure in the center of the tornado. In the thin layer of air tens of meters thick near the ground, the airflow is sucked into the bottom of the vortex from all directions. Then it becomes a vortex around the axis. The wind in a tornado is always a cyclone, and the air pressure in its center can be 10% lower than that around it.

A tornado is a strong wind vortex accompanied by a funnel-shaped cloud column rotating at high speed. The wind speed near its center can reach 100 ~ 200m/s, with a maximum of 300m/s, which is several times higher than the maximum wind speed near the center of typhoon (generated at sea). The central air pressure is very low, generally as low as 400 hectopascals (hectopascals, barometric units) and as low as 200 hectopascals. It has a great sucking effect, which can suck the sea (lake) water away from the sea (lake) surface, form a water column, and then connect with the clouds, commonly known as "dragon water absorption". Because the air inside the tornado is extremely thin, the temperature drops sharply and the water vapor condenses rapidly, which is an important reason for the formation of funnel cloud column. The average diameter of the funnel cloud column is only about 250 meters. Tornadoes are produced in very unstable cumulonimbus clouds. Its formation is related to the strong rise of warm and humid air, the southward movement of cold air and topography. Its life history is short, usually lasting ten minutes to an hour or two, but its destructive power is amazing. It can uproot trees, blow down buildings, or roll some ground objects into the air. There are tornadoes in Jiangsu Province almost every year, but the location has no obvious regularity. It usually appears in June and July, sometimes in early or middle August.

How do tornadoes form?

Tornadoes are a natural phenomenon and 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 released in a small area. The formation of tornadoes 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 transit airflow in the rapids.

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

(3) With the development and upward extension of mesoscale cyclone to the ground, it becomes thinner and stronger. At the same time, a small area to strengthen cooperation, that is, the primary tornado is formed inside the cyclone, and the same process of producing the cyclone forms the tornado core.

(4) The rotation in the tornado core is different from that in the cyclone, and its intensity is enough to make the tornado extend to the ground. When the developing vortex reaches the ground, the ground air pressure drops sharply and the ground wind speed rises sharply, forming a tornado.

Tornadoes often occur in thunderstorm weather in summer, especially in the afternoon to evening. The attack range is small, and the diameter of tornadoes is generally between ten meters and several hundred meters. The survival time of tornadoes is generally only a few minutes, and the longest is no more than a few hours. The wind is particularly strong, and the wind speed near the center can reach 100 ~ 200m/s, which is extremely destructive. Where tornadoes pass, trees are often pulled up, vehicles are overturned, buildings are destroyed, and sometimes people are sucked away, which is very harmful.

Five-level tornadoes Tornadoes are divided into five levels (Fujita level /F? Scale, Fujita series), F 1, F2, F3, F4 and F5 respectively.

F 1 Tornado is small and weak enough to lift the roof and pull down the trailer. The wind speed at the vortex center is110 ~168km per hour. The F2 wind speed is between169 and 225 km, which is enough to overturn the van. F3 wind speed is as high as 390 kilometers per hour, which is enough to uproot trees. F4 is enough to roll up houses, trees and vehicles and fly hundreds of yards away. The most frightening thing is the unimaginable F5, which is enough to lift off solid houses, and reinforced concrete and other reinforced buildings will be torn to pieces. The tornado in Georgetown1May, 997, Texas, USA, belongs to this category, with a wind speed as high as 477 kilometers per hour. The diameter of this tornado exceeded 1 km, which caused hundreds of millions of dollars in losses to the United States.

After February 2007 1, the tornado in the United States was changed to improve the Fujita level.

The harm of tornado

1995 A tornado occurred in Admore, Oklahoma, USA, and heavy objects such as roofs were blown out dozens of kilometers away. Most of the debris falls on the left side of the tornado passage, and there are often obvious landing areas according to the weight. Lighter debris may fly more than 300 kilometers before landing.

Under the attack of a strong tornado, the roof of the house will fly like a glider. Once the roof is swept away, the rest of the house will collapse. Therefore, if we can strengthen the stability of the roof when building houses, it will help to prevent the tornado from causing huge losses when crossing the border.

The tornado struck suddenly and violently, and the wind force produced was the strongest on the ground. In the United States, the number of deaths caused by tornadoes is second only to lightning every year. Its damage to buildings is also quite serious, often devastating.

Tornado in Texas, USA1On May 27th, 999, four counties in central Texas, including Austin, USA, were hit by tornadoes, killing at least 32 people and injuring dozens. It is reported that in the town of Jarrell, 40 kilometers north of Austin, more than 50 houses collapsed and more than 30 people were killed in the tornado. The damaged area is 1 km long and 200 yards wide. This is another tornado area in the United States after Miami was hit by a tornado on May 3, 65438.

Generally speaking, a tornado is a whirlwind. When it touches the ground, its diameter ranges from several meters to 1 km, with an average of several hundred meters. Tornadoes range from a few meters to dozens of kilometers, and robbed things are everywhere. The funnel-shaped center of tornado is composed of inhaled dust and condensed water vapor, which is a visible "dragon mouth". In the ocean, especially in the tropics, similar scenes are called sea tornadoes.

Most tornadoes rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, with some exceptions. The exact mechanism of tornado formation is still under study, and it is generally believed to be related to the violent activities of the atmosphere.

Since19th century, the accuracy of weather forecast has been greatly improved, and various disasters and storms such as tornadoes and hurricanes can be detected by weather radar.

Tornadoes are usually extremely fast, and it is not surprising that the wind speed of 100 m/s even exceeds 175 m/s, which is five or six times larger than that of typhoon 12. The range of wind is very small, generally the diameter is only 25 ~ 100 meters, and only in rare cases can the diameter reach more than 1 km; It takes only a few minutes from occurrence to disappearance, at most a few hours.

Tornadoes are also very powerful. On September 24th, 1956, a tornado appeared in Shanghai. It easily hoisted a large oil storage barrel weighing 1 10000 kg to an altitude of 15 meters, and then threw it away from 120 meters.

1879 at 4 pm on may 30th, two dark and thick clouds were merging over northern Kansas, USA. After 15 minutes, a vortex was generated at the lower end of the cloud. The vortex has grown rapidly and become a huge pillar of indomitable spirit. Within three hours, it ran wild all over the state like a dragon, and no one was spared wherever it went. However, the strangest thing happened at the beginning, when the tornado whirled across a small river and met a cliff. Obviously, it is impossible to surpass this obstacle, so the vortex turns to the west, and there happens to be a new 75-meter-long railway bridge over there. The tornado vortex actually pulled it down from the stone pier, twisted it a few times, and then threw it into the water.

About the detection of tornadoes

The tornado struck suddenly and violently, and the wind force produced was the strongest on the ground. Because of its suddenness and dispersion, it is difficult to observe it effectively.

What is the wind speed of a tornado? No one really knows, because the time from the occurrence to the dissipation of tornadoes is very short and the area of action is very small, so that the existing detection instruments are not sensitive enough to accurately observe tornadoes. Relatively speaking, Doppler radar is an effective and commonly used observation instrument. Doppler radar aims at the microwave beam emitted by the tornado, and the microwave signal is reflected by the debris and raindrops in the tornado and then received by the radar. If the tornado is far away from the radar, the frequency of the reflected microwave signal will move to the low frequency direction; On the contrary, if the tornado gets closer and closer to the radar, the reflected signal will move to the high frequency direction. This phenomenon is called Doppler frequency shift. After receiving the signal, the radar operator can calculate the speed and moving direction of the tornado by analyzing the frequency shift data.

Dragon absorbs water: another name for tornado. Tornado got its name because it is very similar to breaking the waves, the East China Sea Ceratosaurus in ancient mythology. In addition to "dragon absorbs water", it has many aliases, such as "dragon wags its tail" and "upside down dragon".

Precautions against Tornado (1) At home, be sure to stay away from doors, windows and external walls of houses, and hide in the wall or small room opposite the tornado. The safest place to avoid a tornado is the basement or semi-basement.

(2) In case of emergency such as pole collapse and house collapse, the power supply should be cut off in time to prevent electric shock or fire.

(3) When there is a tornado outside the venue, you should look for low-lying land nearby, but stay away from trees and telephone poles to avoid being smashed, crushed and electrocuted.

(4) When the car encounters a tornado when going out, don't drive to avoid it, let alone avoid it in the car, because the car has almost no defense against tornadoes. You should leave the car immediately and take refuge in low-lying areas.