How is a typhoon formed?

Causes of typhoon formation: Typhoon originated from tropical sea surface, where the temperature is high and a large amount of seawater is evaporated into the air, forming a low pressure center. With the change of air pressure and the movement of the earth itself, the inflow of air also rotates, forming a counterclockwise air vortex, which is a tropical cyclone. As long as the temperature does not drop, this tropical cyclone will get stronger and stronger, and finally a typhoon will form.

Extension:

1 typhoon

Typhoon refers to a tropical cyclone formed on the vast sea surface above 26℃ in tropical or subtropical areas.

According to the definition of the World Meteorological Organization, tropical cyclones with sustained central wind speed of 12 to 13 (i.e. 32.7~4 1.4m/s) are typhoons or hurricanes.

Definition of Japan Meteorological Agency: central sustained wind speed118 ~156km/h (32.8 ~ 43.3m/s)? Call it a typhoon.

The western part of the North Pacific (north of the equator, west of international date line, east of east longitude 100 degrees) is usually called a typhoon, while the North Atlantic and the East Pacific are generally called hurricanes. Every summer and autumn, there are many violent storms called typhoons in the Pacific Northwest adjacent to China. Some dissipate at sea, while others land on land, bringing storms, which is a natural disaster.

2. Typhoon source

Typhoon source refers to the sea areas where typhoons often occur, and global typhoons mainly occur in 8 sea areas. In the northern hemisphere, there are five sea areas: the western and eastern North Pacific, the western North Atlantic, the Bay of Bengal and the Arabian Sea, while in the southern hemisphere, there are three sea areas: the western South Pacific, the western and eastern South Indian Ocean. It can be seen from the regional distribution map of the number of typhoons each year and their percentage in the total number of typhoons in the world that there are 62 typhoons every year on average, and there are many more typhoons in the western ocean than in the eastern ocean. Among them, the northwest Pacific is the most (accounting for more than 36%), while typhoons have not been found in the South Atlantic and Southeast Pacific. Typhoon sources in the northwest Pacific are divided into three relatively concentrated areas: the ocean east of the Philippines, the ocean near Guam and the central South China Sea. The typhoon formed in the South China Sea has a great influence on the south of China.

Most typhoons occur at 5 ~ 20 latitudes, especially at 10 ~ 20, accounting for 65% of the total. However, only 65,438+03% typhoons occur at higher latitudes outside 20, and there are few typhoons within 5 near the equator, but there are occasional typhoons. For example, Fujian Meteorological Observatory found that there were three typhoons in the northwest Pacific Ocean south of 5° n in recent two years. According to the analysis of satellite data in recent ten years, the disturbed clouds that developed into typhoons can be found a few days ago, so the initial position of the disturbance is actually eastward than the previously found position. For example, in the North Atlantic, it used to be thought that most of the initial disturbances that developed into typhoons originated in the middle of the ocean, while some people thought that two-thirds of typhoon disturbances originated from the African continent every year according to cloud image analysis. These disturbances usually appear in the form of inverted V-shaped or vortex clouds. They moved westward along the easterly airflow and developed into typhoons when they reached the central North Atlantic and the Caribbean. The initial disturbance position of typhoons in the northwest Pacific and South China Sea is also eastward than that previously found.

3. Typhoon classification

In the past, China used to call the tropical cyclone formed on the tropical ocean surface above 26℃ a typhoon. According to its intensity, it is divided into six grades: tropical depression, tropical storm, strong tropical storm, typhoon, strong typhoon and super typhoon. Since 1989, China has adopted the international tropical cyclone name and classification standard.

According to international practice, the maximum wind force near its center is divided into:

Tropical depression with maximum wind speed of 6-7, (10.8- 17. 1 m/s); ?

Tropical storm with maximum wind speed of 8-9 (17.2-24.4m/s);

Strong tropical storm, maximum wind speed 10 ~ 1 1, (24.5 ~ 32.6m/s);

Typhoon (ty-typhoon), maximum wind speed 12 ~ 13, (32.7m/s ~ 41.4m/s);

Strong typhoon with maximum wind speed14 ~15 (41.5m/s ~ 50.9m/s);

Super typhoon with maximum wind speed ≥ 16 (≥5 1.0m/s).