What are the main reasons for the late flood season in South China?

What are the main reasons for the late flood season in South China? It is mainly caused by tropical cyclone precipitation.

The pre-flood season in South China refers to the rainy period in South China from April to June, and the post-flood season in South China refers to the rainy period in South China from July to September.

Differences between pre-flood season and post-flood season in South China

The pre-flood season in South China refers to the rainy period in South China from April to June, and the post-flood season in South China refers to the rainy period in South China from July to September. What's the difference between them except time?

South China, located at the southernmost tip of China, is a tropical-subtropical region with high temperature, rainy weather and evergreen seasons. The annual precipitation in most places here is between 1400-2000mm, but from a perennial point of view, there are two precipitation peaks in South China, one in April-June, that is, the pre-flood season in South China, and the other in July-September, that is, the post-flood season in South China.

The precipitation in the first flood season in South China mainly occurs in the westerly belt on the north side of the subtropical high, which is caused by the convergence of cold and warm air currents, and the characteristics of frontal precipitation can often be seen. Late May to early June is the peak of the first flood season in South China, which coincides with the Dragon Boat Festival, so it is also called "Dragon Boat Water".

There are about 20 rainstorms every year in the first flood season in South China, which is persistent in time, extensive in region and fierce in degree. It is easy to cause secondary disasters such as waterlogging and mountain torrents, but sometimes it can alleviate the persistent drought since autumn and winter.

The late flood season in South China is mainly caused by tropical weather systems such as easterly waves, especially the rainfall brought by typhoons, which directly affects the amount and regional distribution of rainfall in the late flood season in South China. The intensity of precipitation in the latter flood season in South China is strong, causing local disasters, but the overall rainfall is less than that in the first flood season in South China.