What is plum weather?

Meiyu, as we usually call it, refers to a period of long-lasting rainy weather that often occurs in the middle and lower reaches of the Yangtze River from mid-June to early July every year. During this period, the sky was gloomy for days and precipitation continued. There is a popular proverb in the south, "The rain hits the yellow plum blossoms, and there is no sun for forty-five days", which refers to the plum rainy weather. Meiyu weather is a unique weather and climate phenomenon in East Asia. It only occurs in the areas from the middle and lower reaches of the Yangtze River in my country to the southern part of the Korean Peninsula (locally known as Changma) and southeastern Japan (locally known as Bai-yu). In the middle and lower reaches of the Yangtze River in my country, east of Yichang and between 29 and 33 degrees north latitude, around mid-June to early July every year, controlled by the air flow from the west of the subtropical high, a large amount of water vapor is transported from the warm and humid sea surface, bringing abundant The rainfall forms the unique plum rain weather in this area. Generally speaking, after the plum rains in the Jianghuai River Basin continue for a period of time, the rain belt moves to North China, and the Jianghuai River Basin begins to enter high temperature and less rain. The atypical characteristics of plum rain in recent years. In plum rain weather, the time when the rain belt stays is called the "ume rain season". The day at the beginning of the plum rain season is called "incoming plum rain" and the end day is called "out of plum rain season". The familiar characteristics of continuous rain during the Meiyu period in previous years have become less and less obvious since the 21st century. Since the standards for determining the start of the plum rain are different in various places, the time of the plum rain cannot be unified. The National Climate Center mainly uses observation data from five meteorological observation stations in Shanghai, Nanjing, Wuhu, Jiujiang and Wuhan in the middle and lower reaches of the Yangtze River to monitor and diagnose the onset, end and evolution of the Meiyu. Observations show that since 2000, the Meiyu weather in the middle and lower reaches of the Yangtze River has begun to show "atypical" characteristics. The so-called "atypical" characteristics are mainly manifested in the obviously shorter Meiyu period and less rainfall. This feature began in 2000, and there were even two empty plum rains in 2000 and 2002 (there was almost no obvious plum rain season). During the plum rain season, continuous rainy weather will put pressure on the flood control work in the middle and lower reaches of the Yangtze River in my country. Zhang Peiqun told reporters, "Judging from the current situation, the start time of the plum rainy season this year is obviously late." Statistics over the past 30 years show that the average time for the rainy season to begin is June 17, and as of now, it is difficult to determine the onset of the plum rain in the middle and lower reaches of the Yangtze River. The region has fully entered the rainy season. The Central Meteorological Observatory predicts that there will still be no obvious rainfall in the middle and lower reaches of the Yangtze River in the next two days, and the onset of the plum season will continue to be postponed. The Meiyu period starts sooner or later in each year, and the duration of the Meiyu period varies. In some years, the Meiyu weather is particularly active, with frequent heavy rains, causing floods. In some years, the Meiyu belt moves north and then returns to the Yangtze-Huaihe River Basin, and again The phenomenon that remains relatively stable is customarily called "inverted yellow plum rain"; there are also cases where the characteristics of plum rain are not obvious, with less precipitation in mid-to-late June, resulting in "empty plum rain", which will be followed by a latent drought in the middle and lower reaches of the Yangtze River. . The abnormal evolution of plum rains in the middle and lower reaches of the Yangtze River has a great impact on crops such as rice and cotton in this area. Although the Meiyu weather has become more and more "atypical" in recent years, the various weather changes that may occur in the middle and lower reaches of the Yangtze River from late June to early July still deserve the attention of meteorological departments at all levels.