Why is there no typhoon at the equator?

The geostrophic deflection is very small (that is, close to the equator), and the relative vorticity of typhoon is also very small at the beginning. Although there is a certain convergence field, the vorticity is difficult to produce or cannot be produced quickly. Can't reach the typhoon circulation. Therefore, it is impossible for a typhoon to form at and near the equator. Only in areas beyond a certain latitude from the equator, usually five latitudes from the equator, can typhoons occur.

The influence of geostrophic parameters is beneficial to the formation of cyclonic vortex. For a given convergence value, the change of vorticity with time is proportional to the absolute vorticity. At the equator, f=0, if the relative vorticity of the disturbance is also zero, then the vorticity of the disturbance will not increase no matter how much radiation.

In the f≠0 region far from the equator, convergence can cause vorticity to increase. For the same convergence, the farther away from the equator, the higher the vorticity generation rate.

Therefore, typhoons are all generated in the tropical ocean five latitudes away from the equator, and only a few typhoons in the northwest Pacific are generated near 3° n, while typhoons are rarely found within three latitudes near the equator.

Extended data

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.

1, typhoon eye area: It is very strange that the wind here is very light and the weather is sunny, with an average diameter of 40 kilometers. The sailors involved humorously called Typhoon Eye "Xanadu".

2. 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 known as the 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.

3. Spiral rain belt area: there are spiral rain belts outside the cloud wall, and several rain (cloud) belts gather spirally around the eye wall. The bandwidth of rain is tens to hundreds of kilometers, and it is several meters long in Qian Qian. There will be showers and windy weather where the rain belt passes.

Baidu Encyclopedia-Typhoon