What's the weather like in tornadoes?

Cyclone is a low-pressure weather system formed on the sea surface 3-5 latitudes away from the equator in tropical areas (such as the North and South Pacific, the North Atlantic and the Indian Ocean). Other movements are mainly influenced by large-scale weather systems such as Coriolis force, and eventually dissipate at sea, and then transform into extratropical cyclones or dissipate after landing. Tropical cyclones landing on land will cause serious property or casualties, which is a natural disaster caused by weather. However, tropical cyclones are also part of the atmospheric circulation, which can bring the thermal energy and angular momentum of the earth's rotation from the equatorial region to a higher latitude.

The biggest feature of tropical cyclones is that their energy comes from the latent heat released when water vapor cools and solidifies. Other weather systems, such as extratropical cyclones, are mainly caused by the temperature difference on the cold northern horizontal plane. Tropical cyclones will weaken and dissipate or become temperate cyclones after landing or moving to the surface of the ocean with lower temperature because of losing the energy provided by warm and humid air.

The airflow of tropical cyclone rotates around the center under the action of Coriolis force. Tropical cyclones rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

Different regions have different names for tropical cyclones. China, Taiwan Province Province, Japanese, Vietnamese, Philippine and other places along the western Pacific are used to calling local tropical cyclones typhoons. The Atlantic is used to calling local tropical cyclones hurricanes. Other places have different names for tropical cyclones. Meteorology, only tropical cyclones with a certain wind speed will be named "typhoon" and "hurricane".

Tropical cyclone is a low-pressure vortex that occurs on the surface of tropical or subtropical ocean, and it is a powerful and profound tropical weather system.

Climatic survey of tropical cyclones along the coast of China

Tropical cyclone is also one of the major disastrous weather systems affecting China. During its activities, it is accompanied by strong winds, heavy rains, huge waves and storm surges. Therefore, although tropical cyclones can alleviate the summer drought in the passing areas, they will also cause great losses to people's lives and property. China coastal areas from Liaoning in the north to Guangdong and Guangxi in the south are likely to be attacked by tropical cyclones every year, with the largest number of tropical cyclones landing in Guangdong, Fujian and Taiwan Province provinces.

Habitual address

Different regions have different names for tropical cyclones. Taiwan Province Province, China, South Korea, Japan, Vietnam and the Philippines along the Pacific Northwest are used to calling local tropical cyclones typhoons. The coastal areas of the Atlantic Ocean and the Northeast Pacific Ocean are used to calling local tropical cyclones tropical depression, tropical storm or hurricane according to their intensity. In the southern hemisphere and the northern Indian Ocean, the word "cyclone" is used as the abbreviation of "tropical cyclone". Meteorology, only tropical cyclones with a certain wind speed will be named "typhoon" or "hurricane".

structure

Structure of Tropical Cyclone A mature tropical cyclone has the following parts:

▲ Ground low pressure

The center of tropical cyclone near the ground or sea surface is a low pressure area. The lowest pressure (870 hectopascals) recorded on the earth's sea level is the strongest tropical cyclone recorded in the center of Taipei.

▲ Warm heart

The warm and humid air of tropical cyclone rotates and rises around the center. In this process, water vapor condenses and releases a lot of latent heat, and heat energy is distributed vertically near the center. The temperature inside the tropical cyclone is higher than that outside the cyclone at all heights (except near the sea surface).

▲ Central Miyun District

A dense cloud area around the center of a tropical cyclone, usually cirrus clouds produced by thunderstorms.

▲ Eye of the Wind

The circulation center of strong tropical cyclone is downdraft, which will form an eye. The weather in the eyes is usually calm, cloudless and even sunny in Wan Li (but the sea may still be rough). [4]。 The eye of the wind is usually round, ranging from 2 km to 370 km in diameter. [5][6] The eye of the weaker tropical cyclone may be covered by the central Miyun area, or even have no eye structure.

▲ Eye wall (or eye wall)

The eyes are surrounded by a barrel-shaped eye wall. Convection in the eye wall is very strong, the height of its cloud is usually the highest among tropical cyclones, and the intensity of precipitation and wind is also the largest among tropical cyclones. Strong tropical cyclones have an eye wall replacement cycle, which produces a new outer eye wall to replace the inner wall. [7] The reason is that the spiral rain belt around the eye wall of tropical cyclone gradually moves inward after recombination, stealing the water and energy from the eye wall. At this stage, tropical cyclones enter a weakening process. At the periphery, the new eye wall completely replaces the old eye wall, and if the environment permits, the tropical cyclone will strengthen again. [8] Through multi-frequency microwave scanning and radar, it can be clearly observed that tropical cyclones have binocular walls in the eye wall renewal cycle; [7] If the eye wall replacement process of tropical cyclone is obvious, it can be observed from visible light and infrared satellite cloud images.

▲ spiral rain belt

Spiral rainbands are rain clouds and thunderstorms that move around the center of tropical cyclones. In the northern hemisphere, the spiral rain belt moves counterclockwise around the center. Spiral rain belts will bring great wind and rain to the ground, but there will be calmness between each rain belt. Tornadoes will form in tropical cyclones and spiral rain belts near land. [4] Tropical cyclones with multiple spiral rain belts are generally strong and mature; But there are also some "wheel hurricanes", whose main feature is that there is no spiral rain belt.

▲ external circulation

All low-pressure systems need high-altitude divergence to continue to strengthen, and the divergence of tropical cyclones flows out from all directions. Due to the Coriolis force, the high altitude of tropical cyclone is an anticyclonic divergent circulation. The wind on the ground or sea surface rotates inward, weakens with the increase of height, and finally changes direction. This feature is related to the warm core structure in the center of tropical cyclone, so tropical cyclone needs weak vertical wind shear environment to maintain the warm core structure in order to continue divergence.