As a strong convective weather phenomenon, what are the causes and characteristics of a tornado? How will people defend?
Tornado is a strong, small-scale air vortex. Its scale is very small, generally around 100 meters. It is often caused by strong convection of air under extremely unstable weather conditions. The wind can reach 12 Above the level, the surface wind speed of the strongest tornado is between 110 m / s and 200 m / s. When the tornado is produced, there is always a funnel-shaped cloud column with a diameter ranging from tens of meters to several hundred meters spiraling down from the convective cloud. Some can reach the ground, the wind that causes disasters on the ground is called a tornado; some that are not on the ground or that do not produce a catastrophic wind on the ground are called air funnels; some reach the water surface and are called water dragons. .
Tornadoes are generally accompanied by thunderstorms, sometimes accompanied by hail. The difference between it and the general wind is that the path is smaller. The level of tornado is very small, ranging from a few meters to a few hundred meters in diameter, and the maximum is about 1 kilometer. The duration is usually only a few minutes, but the longest is only a few dozen minutes, but it can cause crops and trees to be destroyed instantly. The communication was interrupted, the house collapsed, and human and livestock casualties suffered major losses. In the United States, the number of deaths caused by tornadoes is second only to lightning, and the damage is very serious.
The occurrence of a tornado has certain geographical and seasonal characteristics. In China, it generally occurs in the plains of the middle and lower reaches of the Yangtze River. The plains are more than the mountains, and there are more in southern China. Due to the relationship between the underlying surfaces, tornadoes in large cities are rarely seen. Tornadoes occur mostly in the late spring and summer, and at the same time, the increase in humidity is also likely to cause tornadoes.
Regarding the early warning forecast of tornadoes, the main clues of the current forecast are medium- or higher-intensity cyclones. At the same time, it is necessary to pay close attention to the background conditions of the tornado, such as unstable weather background and vertical wind shear. Due to the short time from the occurrence of the tornado to the dissipation, the area of ​​impact is also small, and the existing detection instruments do not have sufficient sensitivity to accurately observe it. Relatively speaking, Doppler radar is a relatively effective and commonly used observation instrument. Because tornadoes often have a very strong convective matrix, it has a very obvious medium cyclone characteristic. This scale is generally between 2 km and 10 km. Doppler radar can clearly detect this, and radar operators can By analyzing the frequency shift data, the speed and direction of the tornado are calculated. Of course, in some cases, a tornado warning can be issued by identifying a medium or weak medium cyclone. The characteristics of a medium cyclone usually associated with a strong tornado may appear 20 minutes to 30 minutes before the tornado occurs.
In foreign countries, there are also reports of eyewitnesses to predict tornadoes. Many experienced or trained personnel report on tornadoes that have or may have occurred so that the government and the public can respond more fully.
In the tornado-prone areas, people need to understand some basic common sense and defensive measures about tornadoes, such as not staying in a building that is not strong and easy to collapse, and should hide in the basement in time. In the wild, you should stay away from the path of the tornado and fall to the ground when you encounter a tornado.
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