How did the fire whirlwind form?

Tornado is a kind of vortex: the air rotates rapidly around the axis of tornado and is attracted by the extremely low air pressure in the center of 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 cyclonic, and the air pressure in its center can be 10% lower than that around it.

Tornado formation

Tornadoes 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 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.

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 things are robbed everywhere. The funnel-shaped center of tornado is composed of inhaled dust and condensed water vapor, which is a visible "dragon mouth". On 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.

1995 In a tornado in Admore, Oklahoma, USA, heavy objects such as roofs were blown dozens of miles 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.

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.

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.

Tornadoes are usually extremely fast. It is not surprising that the wind speed is 100 m per second, even reaching more than 175 m per second, which is five or six times larger than the 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 one kilometer; 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 lifted a large oil storage barrel weighing 220,000 Jin to the altitude of15m, and then threw it away from120m.

Tornadoes, also known as cyclones in America, are common natural phenomena. Cyclones are often more destructive than earthquakes.

1879 at 4 pm on may 30, two dark and thick clouds were merging over northern Kansas. 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 newly built 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.

Tornado detection

Tornadoes have long been a mystery, and it is for this reason that it is necessary to understand them. 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.

The danger of tornadoes.

1995 In a tornado in Admore, Oklahoma, USA, heavy objects such as roofs were blown dozens of miles 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.

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.

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.

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

Characteristics of tornadoes

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.