Weather before and after typhoon

The typhoon center is low pressure. Because the air pressure in the center is very low, the air flow will always blow to the center, and the air in the center will be lifted by the surrounding air flow. So the airflow in the eyes will always flow from the bottom up, and the rising airflow will spread around and finally flow around, forming a cycle. Tropical cyclone is a cyclonic circulation occurring on the sea surface in tropical and subtropical areas, and it is one of the most destructive weather systems in geophysical environment. Strong tropical cyclones not only form strong winds and huge waves, but also are often accompanied by heavy rains and storm surges, causing serious disasters.

Typhoon pressure field and pressure distribution in typhoon area. The basic characteristics of its horizontal distribution are that the central air pressure is very low, the isobar is approximately circular, and the air pressure gradient around the typhoon eye is the largest. Because the typhoon temperature field is a warm center structure, the typhoon vortex weakens with the increase of height. That is, in the lower troposphere, the central pressure is much lower than that around, and the pressure gradient is the largest, while in the upper troposphere, the pressure gradient decreases rapidly and the low pressure center tends to disappear gradually. Therefore, in meteorology, the ground center pressure value of typhoon is often used as the index of typhoon intensity.

Typhoon temperature field, because the typhoon temperature field is a warm center structure, the typhoon vortex weakens with the increase of height. That is, in the lower troposphere, the central pressure is much lower than that around, and the pressure gradient is the largest, while in the upper troposphere, the pressure gradient decreases rapidly and the low pressure center tends to disappear gradually. Therefore, there is no wind within dozens of kilometers of the typhoon center, and the temperature is higher than other normal places due to the phenomenon of air sinking and heating up, which leads to clouds and rain falling and becomes the eye of the typhoon.

When the updraft in the cloud wall reaches high altitude, due to the weakening of the pressure gradient, a large amount of air is forcibly thrown out, forming an outer layer, while a small amount of air flows inward into the typhoon center and sinks, resulting in a clear typhoon center, namely the typhoon eye area. The radius of typhoon eye is about 10 ~ 70km, with an average of about 25km. The release and warming of latent heat in the cloud wall area and the sinking and warming of the typhoon eye area make the typhoon a warm-hearted low-pressure system.