What does plum blossom mean in the twenty-four solar terms?

Plum blossom, also called "broken plum blossom", refers to the date when the plum rain ends. Meiyu in Jianghuai area of China usually ends on July 8-12. In some years, the plum blossom period will be delayed, such as 1954 to August 2, and the plum rain period will last for 63 days.

Meteorologically, the beginning and ending time of plum rain are called "entering plum" (or "standing plum") and "leaving plum" (or "breaking plum") respectively. In the middle and lower reaches of the Yangtze River in China, plum blossoms in mid-June and in early July every year, lasting for more than 20 days. But for each specific year, the beginning and end of plum rains and the intensity of plum rains are very different. As a result, plum rains are obvious in some years, not obvious in some years, and even empty plums appear. For example, the rainy season in 1954 was particularly long and lasted for more than two months, which led to a rare waterlogging year in the middle and lower reaches of the Yangtze River. However, the rainy season of 1958 only lasted for two or three days, and there was a rare dry year in history.

(1) Normal Meiyu: Normal Meiyu in the middle and lower reaches of the Yangtze River begins in mid-June and ends in mid-July, which is in the two solar terms of "Miscanthus" and "Summer Solstice Day". The meiyu period is about 20-30 days, and the rainfall is between 200-400 mm. Before and after "Little Summer", the main rainfall belt moves northward to the Yellow River and Huaihe River basins, and then to Shandong and North China. The Yangtze River basin began to change from rainy and humid weather to sunny and hot summer. According to statistics, this normal plum rain accounts for about half of the total.

(2) Early Meiyu: In some years, Meiyu started very early and suddenly arrived at the end of May and the beginning of June. Meteorologically, the plum rain that began before "Mangzi" is generally called "early plum rain". The early plum rains will bring some abnormal phenomena. For example, since the cold air from north to south is still very frequent in the atmosphere near the ground at the beginning of the plum rain, the temperature is still relatively low and even a little chilly after the rainy day, which is the agricultural proverb: "You should freeze for three times after eating the Dragon Boat Festival brown". At the same time, there is no obvious damp phenomenon. Farmers in some areas in the middle and lower reaches of the Yangtze River call Huang Meiyu, where the temperature is relatively low, "cold water Huangmei". In the future, with the extension of rainy time and the strengthening of warm and humid air, the temperature will gradually increase, the humidity will continue to increase, and the inherent characteristics of Meiyu will become more and more obvious. The chance of early plum rain is roughly once in ten years. This kind of early plum rain often presents two situations. One is to start early and end late, even in late July. The rainy season lasts for forty or fifty days, and some years last for two months. The other is to start early and finish early. By the end of June, the middle and lower reaches of the Yangtze River entered midsummer. Due to the early arrival of midsummer, droughts of different degrees often occur in the middle and lower reaches of the Yangtze River.

(3) Late Meiyu: Contrary to early Meiyu, it is late Meiyu, which is usually called late Meiyu in meteorology. There are more opportunities for late meiyu than early meiyu. Because the solar term is already late, at the beginning of the late Meiyu, once the warm and humid air flows northward, its power is very strong, and the solar radiation is also relatively strong. When the air is heated, it is prone to strong convection, so there are often thunderstorms and showers in the later period of Meiyu. People also call this kind of Huang Meiyu "Huangmei". The duration of the late Meiyu is generally not long, with an average of only about half a month. However, the rainfall of this plum rain is sometimes quite concentrated.

(4) Extra-long Meiyu: 1954, a once-in-a-century flood occurred in the Jianghuai Valley of China, which was caused by extra-long Meiyu. This year, there were many spring rains in the middle and lower reaches of the Yangtze River in the second half of May before the beginning of Meiyu. Meiyu came very early and began in early June. The weather has been rainy and rainy, with heavy rain and heavy rain from time to time, which lasted for a long time until the beginning of August. When the rainy weather ended and turned to midsummer weather, it was near "beginning of autumn". This year, the whole meiyu period lasted for two months, and with the spring rain in May, it reached more than two and a half months. After entering the "light summer heat" and "great summer heat", the middle and lower reaches of the Yangtze River should have been sunny and hot, but it has been gloomy and difficult to see the sun. From time to time, pouring rain poured down to the ground, floods rolled in, and "cold" hit people in many areas. In this year, the rainfall in the middle and lower reaches of the Yangtze River from May to July is generally 800- 1000 mm, which is close to the annual rainfall in normal years in this area. The rainfall in some areas is as high as 1500-2000mm, which is equivalent to the rainfall in the same area for one and a half years, leading to flooding. China has a vast territory, and local floods often occur. Some may be caused by typhoon rainstorm, and some may be caused by several consecutive rainstorms brought by other weather systems, but their duration is not long, the flood recedes quickly, and the influence range is relatively small. It is extremely rare that the rainfall time like 1954 reaches more than two months, resulting in a basin-wide flood in the Yangtze River basin. This rare flood is usually associated with abnormal plum rains. Like the flood in 1998, it was also caused by the extremely long plum rain.

(5) "Short plum" and "empty plum": Contrary to Foreign Minister Geiger's plum rain, in some years, plum rain is very inconspicuous. Like a passer-by in a hurry. After ten days in the middle and lower reaches of the Yangtze River, it hurried north. Moreover, there is not much rain during this period, and it is rare to have one or two heavy rains. This situation is called' short plum'. What's more, in some years, since early summer, there has been no continuous rainy weather in the Yangtze River basin. Most days are sunny, warm as spring, and cool in the morning and evening, so the weather of "Huangmei season is dry and loose" appears. Moldy clothes, which often happens in rainy season, almost never happen. As soon as the cool weather is over. Then it became midsummer. This year is called "empty plum". The probability of "short regret" and "empty plum" appears, with an average of l-2 times in ten years. In the years of "short plum" and "empty plum", summer drought often occurs, and some years can also cause serious drought.

(6) Huangmei: In some years, the days of Huangmei in the middle and lower reaches of the Yangtze River seem to have passed, the weather turned fine and the temperature rose, showing the characteristics of midsummer. However, a few days later, hot and humid thunderstorms and showers reappeared and remained for quite some time. This situation is like Huangmeitian retrogression, returning to the middle and lower reaches of the Yangtze River, so it is called "Huangmeitian". There is thunder in summer, and Huangmei is upside down. This is a weather proverb widely circulated in the middle and lower reaches of the Yangtze River. It means that after the meiyu has passed, if there is thunder in the "light summer heat", the meiyu will be reversed. There is some truth in this statement. Because after the meiyu, the weather in the middle and lower reaches of the Yangtze River is usually more and more stable, and thunderstorm is a symbol of weather instability. Besides, in the "little summer", cold air usually no longer affects the Yangtze River basin, and the occurrence of thunderstorms is often related to the southward movement of a small cold air in the north, which is conducive to the re-establishment of rain belts in the middle and lower reaches of the Yangtze River. Of course, "pour Huangmei" does not necessarily appear after the thunder in summer. Generally speaking, the duration of "pouring Huangmei" is very short, ranging from about one week to ten days and a half months. However, during the "Huangmei" period, due to many thunderstorms and showers, the rainfall is often quite concentrated, which needs attention. Because "inverted yellow plum" is a kind of plum rain, it usually turns into sunny and hot weather after it ends.

From the various plum rains described above, we can see that Huang Meiyu, which is usually considered to be similar, is actually diverse, and the differences between them are sometimes quite large. In terms of "entering Mei", the earliest is May 26th, and the latest is July 9th. The earliest date of "plum blossom" is June 16, and the latest date is August 2, with a difference of one and a half months. The longest year of plum rains lasts for more than two months, which can cause rare floods, while the short year has only a few days, and some even have "empty plums", which brings serious drought. It can be seen that plum rain is a complex weather and climate phenomenon, which is far from being as simple as "entering the plum blossom" and "leaving the plum blossom" as stipulated in the lunar calendar. Compared with normal plum rain, early plum, late plum, extra-long plum rain, empty plum and severe yellow plum all belong to abnormal plum rain.