Why is the rainy season called rainy season? The Origin and Formation of Meiyu Season

1. Every year from mid-June to early July, it is the rainy season. During this period, the sky was cloudy for several days, with constant precipitation, sometimes big and sometimes small. At this time, the temperature is high, the humidity is high, the wind speed is low, the light is scarce, and the utensils are prone to mildew, so it is also called "mildew rain". Meiyu season usually appears in June-July. Meiyu is a long-lasting rainy weather, which often occurs in the Jianghuai Valley in early summer.

2. The reason for the formation of Meiyu is that from late May to early June every year, cold air from the north and warm air from the south meet in South China, forming a quasi-static front in South China. By the end of June, the influence of warm air was strengthened, and the quasi-static front moved northward to Jianghuai area, becoming the quasi-static front of Jianghuai (also known as Meiyu front).

Because the warm air from the south carries a lot of water vapor, when it meets the cold air mass, it will produce a lot of convection activities. Because of the equal influence of cold and warm air during this period, the front stays in Jianghuai area. At present, the meteorological plum rain refers to a rainy weather that transits from early summer to midsummer.