Why does the rainy season appear as soon as Guangdong arrives in Tomb-Sweeping Day?

The middle and lower reaches of the Yangtze River in China are usually rainy from mid-June to early July every year. In the past few days, the sky has been gloomy and the precipitation has been constant, sometimes big and sometimes small. Therefore, there is a popular proverb in southern China: "Rain hits plum blossoms, and there is no sun for forty-five days". Continuous rain, high temperature and high humidity are the main characteristics of plum rain.

Very different from the climate in the same latitude area, Meiyu refers to the weather and climate phenomenon that occurs in a certain area and a certain season. It is found that Eurasia is between 20 N and 40 N, which is alternately controlled by subtropical high and westerly belt. The west coast of the mainland is controlled by the downdraft on the east side of the subtropical south pressure in summer, with sunny weather, partly cloudy and dry climate; In winter, under the influence of westerlies, warm and humid air is brought from the Atlantic Ocean, resulting in more precipitation and a mild and rainy climate. That is, the subtropical Mediterranean climate is dry in summer and humid in winter.

The east coast of the mainland is controlled by the west side of subtropical high in summer, and the downward flow is dry, but it absorbs a lot of water vapor from the warm and humid sea surface, bringing abundant precipitation and producing a subtropical humid climate. Due to the strong contrast between land and sea, a unique monsoon climate has formed here, which is characterized by rainy summer and dry winter, with rainfall concentrated in summer, which is just the opposite of the Mediterranean climate.

If compared with the east coast of Britain at the same latitude, it is also very different. There will be no rainy weather for a long time before and after the summer monsoon in the mid-latitude zone of the east coast of the United States, and people do not feel the feeling of sultry weather for a long time, so it is difficult to appear moldy. It can be seen that the precipitation season at the same latitude varies greatly. So there are only Huangmei in the middle and lower reaches of the Yangtze River in China, starting from the area east of Yichang and 29-33 degrees north latitude, as well as the southeast of Japan and the southernmost tip of the Korean Peninsula. In other words, Meiyu is a unique weather and climate phenomenon in East Asia and the middle and lower reaches of the Yangtze River in China.