What are the four kinds of tropical cyclones?

Tropical cyclones are divided into four grades: tropical disturbance, tropical depression, tropical storm and hurricane.

1, tropical disturbance

Tropical disturbances generally refer to disturbances of various scales in the atmosphere of tropical areas, such as fluctuations in tropical convergence areas, tropical cyclones, monsoon depression, easterly waves, equatorial waves and typhoons. Some of them have no closed isobar on the surface weather map, and the instrument shows cyclone rotation or wind shear. It is an important weather system in tropical areas. In a narrow sense, it refers to a tropical cyclone with a wind force less than 7 near the center of the southern hemisphere ocean.

2. Tropical depression

Tropical depression, referred to as tropical depression, is a kind of tropical cyclone. The tropical depression refers to the tropical cyclone whose maximum wind speed is less than 17m/s in many countries. It belongs to the weakest level of tropical cyclone intensity (its maximum wind force is below 62 kilometers per hour). The tropical depression is composed of many upward strong convective clouds, which began with the so-called "tropical disturbance" formed by the clouds developing in the air unstable area on the tropical ocean.

3. Tropical storms

Tropical storm is a kind of tropical cyclone, which means that the maximum ground wind force near its center reaches 8-9 (17.2-24.4m/s). Tropical storm is the initial stage of Typhoon. For the convenience of application and external service, tropical storms, strong tropical storms, typhoons, strong typhoons and super typhoons are sometimes collectively referred to as "typhoons".

4. Hurricane

Hurricanes in the Atlantic Ocean and the East Pacific Ocean, strong and deep tropical cyclones (maximum wind speed 32.7m/s, wind 12 or more) are called hurricanes, and also refer to strong winds and any tropical cyclones and any strong winds with wind 12. There is an eye in the center of the hurricane. The smaller the eyes, the greater the destructive power.

positive impact

1, rain. The loss of life caused by tropical cyclones is immeasurable, but tropical cyclones will also bring important rainfall to arid areas. An important part of the annual rainfall in many areas comes from tropical cyclones. For example, tropical cyclones in the northeast Pacific bring rain to arid Mexico and the southwestern United States; Even nearly half of the annual rainfall in Japan comes from tropical cyclones.

2. Thermal balance. Tropical cyclones are also an important mechanism for maintaining global heat and momentum balance. Tropical cyclones project the sun into tropical areas and convert it into seawater heat energy, which is brought to the mid-latitude and polar regions. Tropical cyclone is also a strong vortex disturbance, which transports the easterly angular momentum accumulated at the equator to the westerly belt in the mid-latitude region.

The above contents refer to Baidu Encyclopedia-Tropical Storm Baidu Encyclopedia-Tropical Depression Baidu Encyclopedia-Tropical Disturbance.