What is the phenomenon of frequent precipitation in continuous rainy weather?

In the early summer of each year, there is often a rainy weather with continuous heavy precipitation and frequent precipitation in the Jianghuai basin of China. This phenomenon is called (plum rain).

Meiyu refers to the weather and climate phenomenon that occurs in a certain area and a certain season. Meiyu is a unique weather and climate phenomenon in East Asia and the middle and lower reaches of the Yangtze River in China.

Meiyu refers to a period of continuous rainy weather from mid-June to early summer in mid-July, from the middle and lower reaches of the Yangtze River in China to 28°-34° N east of Yichang, or the Jianghuai Valley, to a narrow area in southern Japan.

Formation condition

1. There is blocking high pressure or stable high pressure ridge in the middle troposphere in high latitudes of Asia, and the atmospheric circulation is relatively stable with little change.

2. The westerly circulation in the mid-latitude area is gentle, and frequent short-wave activities provide cold air conditions for the Jianghuai area.

3. The western Pacific subtropical high has an obvious process of extending westward and jumping northward. The ridge line of the 500 HPA subtropical high is stable between 20 and 25 degrees north latitude, and the warm and humid air flow is transported from the edge of the subtropical high to the Jianghuai basin.

Under this circulation condition, Meiyu front lingers in the Jianghuai basin, often accompanied by southwest vortex and shear line, and the mesoscale system on Meiyu front is active. It not only maintains the continuous precipitation during the Meiyu period, but also provides abundant water for the rainstorm.