What is a typhoon and what is its structure?

Typhoons are all developed from the pre-existing tropical depression disturbance. According to China's statistics, the tropical cyclones in the western Pacific-South China Sea region come from four initial disturbances in intertropical convergence zone, accounting for 80% ~ 85%; East wind wave, accounting for about10%; The cut-off low pressure in the long wave trough at middle and high latitudes, or the cold vortex at high altitude, accounts for about 5%; Baroclinic disturbance accounts for less than 5%. ?

The temperature and humidity of the upper and lower atmosphere in tropical oceans are mainly determined by the sea surface water temperature. The higher the SST, the higher the temperature and humidity of the lower atmosphere, and the more obvious the potential instability.

Typhoons are formed on the warm ocean surface with SST ≥ 26 ~ 27℃. Generally speaking, the global tropical ocean surface meets this condition all year round, and only the SST in the equatorial southeast Pacific Ocean is ≤ 26.5℃ all year round, which is the main reason why there are no typhoons here.

Typhoon structure:

Typhoon is a deep low-pressure system, and its central air pressure is very low. There is an air flow converging towards the center at the lower level, and the air flow at the upper level mainly diverges outward. If the typhoon is cut horizontally, we can see that there are three obviously different areas, from the center to the outside: typhoon eye area, cloud wall area and spiral rain belt area. ?

Typhoon Eye Area: It's strange that the wind here is very light and the weather is sunny, with an average diameter of 40 kilometers. The sailors who participated in it humorously called Typhoon Eye "Xanadu".

Cloud wall area: the cloud wall area with a width of tens of kilometers and a height of more than ten kilometers around the typhoon eye, also called eye wall. The cloud wall is towering here, the wind is howling, the rain is pouring, the sea is churning, and the weather is the worst.