Which of the following weather systems is a tropical cyclone? A: Tropical depression B: Typhoon C: Strong tropical storm D: Super typhoon.

According to the Notice of China Meteorological Bureau (GBT 1920 1-2006) [1]? Tropical cyclones are divided into six levels according to the maximum surface wind speed near the center:

Super typhoon: the maximum average wind speed near the bottom center is ≥ 5 1.0m/s, that is, 16 or more.

Strong typhoon (STY): The maximum average wind speed near the bottom center is 4 1.5-50.9 m/s, which is 14- 15.

Typhoon (TY): the maximum average wind speed near the center of the ground floor is 32.7-4 1.4m/s, which is 12- 13.

Severe tropical storm (STS): the maximum average wind speed near the bottom center is 24.5-32.6m/s, that is, wind10-1.

Tropical storm (TS): the maximum average wind speed near the center of the ground floor 17.2-24.4m/s, that is, the wind force is 8-9.

Tropical depression (TD): the maximum average wind speed near the bottom center 10.8- 17. 1 m/s, that is, the wind force is 6-7.