What is the phenomenon of plum rain and summer drought?

In early summer, there are often long rainy days in the Jianghuai basin. At this time, the utensils are easy to be moldy, so it is also called "moldy rain" or "mildew" for short; It is also called "Plum Rain" or "Huang Meiyu" because plums in the south of the Yangtze River are yellow and ripe. It is recorded in China's historical records. For example, The Book of Beginners quoted the compilation of Emperor Liang Yuan in the Southern Dynasties, "Plum blossoms have plum rains when they are ripe". Liu Zongyuan's Plum Rain in the Tang Dynasty: "Shi Mei welcomes the rain, and it is worth the late spring." Wait a minute. It is recorded in China's almanac that there is mildew rain all day: it is called "mildew" at the beginning and "mildew" all day long. The first day after the awn is planted, it will be moldy, but it will not be moldy on the first day after the light summer. Mold always enters between June 6~ 15 and leaves between July 8~ 19. There is an obvious rainy season in the eastern part of China, with a long rainy period and relatively concentrated rainfall, which is caused by the displacement of the main rain belt from east to west to north, and is a unique phenomenon in the turn of atmospheric circulation in East Asia at the turn of spring and summer. After mid-June, the rain belt remained in the Jianghuai basin, which is Meiyu. The time that the rain belt stays is called "Meiyu season", the day when the rainy season begins is called "entering the plum blossom", and the day when it ends is called "emerging the plum blossom".

In addition, due to the high humidity in the air during this period, everything is easy to be damp and moldy, so people gave Meiyu an individual name, called "Moldy Rain". Xie Zaihang's Five Miscellaneous Torches in Ming Dynasty? "Tianbu No.1" describes: "Every year in March and April in the south of the Yangtze River, it rains bitterly, and everything is moldy, commonly known as Meiyu, and it is covered when it is green and yellow. From Xu Huai to the north, it is often dry in spring and summer. At the turn of June and July, it rained heavily and everything was moldy. " Li Shizhen, an outstanding medical scientist in Ming Dynasty, pointed out more clearly in Compendium of Materia Medica: "Plum rain or mildew rain, when it comes to clothes and things, will produce black mold." .

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The drought in dog days

The hottest midsummer season in China's old calendar is called "dog days". Generally from mid-July to mid-August. At this time, the stationary front of Meiyu moved to the middle and lower reaches of Yokogawa River and northeast China in early July, and the middle and lower reaches of the Yangtze River were controlled by the "subtropical high", forming an anticyclone weather, which was dominated by underflow air, with long sunshine, strong solar radiation, high temperature and strong evaporation. Crops grow fast, and farmland needs a lot of water. However, due to the single air mass, except for thunderstorms in some areas, there is no big rain area, and generally there is dry and hot summer weather, so it is called "summer drought". In this season, the afternoon temperature in the middle and lower reaches of the Yangtze River generally reaches 33 ~ 35℃, and the high temperature as high as 43 ~ 45℃ appears in some places.

Interviewee: Senior layman-No.1 scholar1Grade 4 7- 1 19:56

It refers to a period of continuous rainy weather from mid-June to early summer in mid-July, 28°-34° N east of Yichang in the middle and lower reaches of the Yangtze River in China, or from Jianghuai Valley to a narrow area in southern Japan. At this time, it is the season when plums in the south of the Yangtze River are yellow and ripe, so it is called "Meiyu". Meiyu weather is mainly characterized by rainy weather, short sunshine time, high relative humidity and abundant rainfall, often from heavy rain to heavy rain.

Meiyu is a large-scale precipitation weather process, which is caused by relatively stable atmospheric circulation. During the meiyu period, the blocking high pressure is often maintained at a higher latitude north of 50 north latitude, so that the cold air cannot go south on a large scale, but at a lower latitude. The ridge line of the western Pacific subtropical high is about 20-25 N, and the middle and lower reaches of the Yangtze River in China are just the intersection of the warm and humid airflow in the southwest and the cold air in the north transported by the western Pacific subtropical high. There are often shear lines and southwest vortex activities in this area, and there are quasi-static fronts and frontal cyclones on the ground, which cause long-term rainy weather and repeated heavy rains. On satellite images, the Meiyu front cloud belt is usually stable.

However, the "in" and "out" dates of Meiyu are different every year. There can be a difference of more than 40 days between morning and evening, sometimes there will be a phenomenon of "less plum" or "empty plum", and sometimes there will be a phenomenon of "abundant plum". For example, 1954 and 199 1 are both special years in the meiyu period, and the rainfall is particularly heavy, causing floods in the Jianghuai basin. However, in 1994, there was an abnormal drought in Shaomei and Jianghuai areas. This abnormal situation in meiyu period is often related to the abnormal change of global atmospheric circulation.

It refers to a period of continuous rainy weather from mid-June to early summer in mid-July, 28°-34° N east of Yichang in the middle and lower reaches of the Yangtze River in China, or from Jianghuai Valley to a narrow area in southern Japan. At this time, it is the season when plums in the south of the Yangtze River are yellow and ripe, so it is called "Meiyu". Meiyu weather is mainly characterized by rainy weather, short sunshine time, high relative humidity and abundant rainfall, often from heavy rain to heavy rain.

Meiyu is a large-scale precipitation weather process, which is caused by relatively stable atmospheric circulation. During the meiyu period, the blocking high pressure is often maintained at a higher latitude north of 50 north latitude, so that the cold air cannot go south on a large scale, but at a lower latitude. The ridge line of the western Pacific subtropical high is about 20-25 N, and the middle and lower reaches of the Yangtze River in China are just the intersection of the southwest warm and humid airflow transported by the western Pacific subtropical high and the small cold air in the north. There are often shear lines and southwest vortices in this area, and there are quasi-static stops and fronts on the ground.

However, the "in" and "out" dates of Meiyu are different every year. There can be a difference of more than 40 days between morning and evening, sometimes there will be a phenomenon of "less plum" or "empty plum", and sometimes there will be a phenomenon of "abundant plum". For example, 1954 and 199 1 are both special years in the meiyu period, and the rainfall is particularly heavy, causing floods in the Jianghuai basin. However, in 1994, there was an abnormal drought in Shaomei and Jianghuai areas. This abnormal situation in meiyu period is often related to the abnormal change of global atmospheric circulation.

The hottest midsummer season in China's old calendar is called "dog days". Generally from mid-July to mid-August. At this time, the stationary front of Meiyu moved to the middle and lower reaches of Yokogawa River and northeast China in early July, and the middle and lower reaches of the Yangtze River were controlled by the "subtropical high", forming an anticyclone weather, which was dominated by underflow air, with long sunshine, strong solar radiation, high temperature and strong evaporation. Crops grow fast, and farmland needs a lot of water. However, due to the single air mass, except for thunderstorms in some areas, there is no big rain area, and generally there is dry and hot summer weather, so it is called "summer drought". In this season, the afternoon temperature in the middle and lower reaches of the Yangtze River generally reaches 33 ~ 35℃, and the high temperature as high as 43 ~ 45℃ appears in some places.

Responder: Look at the sword by the fence-Great Magician 13 level 7- 1 19:56.

Meiyu-A continuous rainy period from the Yangtze River valley in China to southern Japan in early summer. Because the plum is yellow and ripe, it is named.

Meiyu is produced in the front area of the western Pacific subtropical high edge (called Meiyu front), which is the product of the interaction between polar air mass and subtropical air mass. The location and stability of the Meiyu belt are closely related to the location and intensity of the subtropical high (the ridge line is generally stable between 20 and 25 north latitude), and also related to the circulation situation that the westerly belt is not conducive to the cold air moving south to the Yangtze River basin. At the beginning of June every year, when the atmospheric circulation situation is greatly adjusted, the ridge line of the western Pacific subtropical high jumps to the north of 20 north latitude, and people begin to blossom. When the ridge line of the western Pacific subtropical high jumps further northward and crosses 25 north latitude, the meiyu period ends and the Yangtze River basin enters the summer drought period.

Meiyu in Meiyu season

Meiyu refers to a period of continuous rainy weather from mid-June to mid-July and early summer. The middle and lower reaches of the Yangtze River in China refer to the range of 28-34 N east of Yichang, or the narrow area from Jianghuai Valley to southern Japan. During this period, due to the monsoon adjustment of atmospheric circulation, the warm and humid airflow from the ocean and the cold air from north to south continue to meet in the Jianghuai Basin, forming an east-west quasi-static front, commonly known as Meiyu Front, which makes the rain continuous and the rainstorm concentrated. It is called "Meiyu" or "Meiyu weather" because it is in the yellow ripening period of plums in the south of the Yangtze River. Because of the high temperature and humidity at this time, clothes are prone to mildew, also known as "mildew rain".

During the meiyu period, a stable and lasting rain belt was maintained from Jianghuai Valley to southern Japan. The distribution of rainstorm in rain belt is uneven, and there are often multiple rainstorm centers. The rainstorm intensity of Meiyu front is generally much smaller than that of typhoon, but the flood disaster area caused by Meiyu front is generally larger than that of typhoon because of its long duration and wide rainstorm range. For example, 199 1 and 1999, the rainy season in the Jianghuai basin lasted for two months, and heavy rains and serious floods occurred in the lower reaches of the Yangtze River, Taihu Lake and Huaihe River, which is rare in history. Taihu Lake, Lixia River, Chuhe River and Qinhuai River all have the highest water levels in history.

The atmospheric circulation conditions that form the Meiyu front rainstorm generally include:

(1) There are blocking high pressure or stable high pressure ridges in the middle troposphere at high latitudes in Asia, and the atmospheric circulation is relatively stable and rarely changes;

(2) The westerly circulation in the mid-latitude area is flat, 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 Jianghuai basin, often accompanied by southwest vortex and shear line. Mesoscale systems such as frontal cyclones are very active on the Meiyu front. This not only maintains the continuous precipitation during the Meiyu period, but also provides abundant water vapor for the rainstorm. Meiyu front rainstorm is a special weather in a specific area formed by the interaction of circulation systems of different scales.

Due to the variability of atmospheric circulation, the "in" and "out" dates of Meiyu are different every year, and the difference between morning and evening can reach more than 40 days. In some years, the Meiyu front is particularly active, and heavy rains are frequent, causing floods. Sometimes the plum rain front is not obvious, and there will be a phenomenon of "less plum" or "empty plum". For example, in 1954, 199 1 year, and 1999, the meiyu period was particularly long, and there was a lot of precipitation, which caused floods in the Jianghuai basin. However, there were few plums in 1994, which made the Jianghuai area extremely dry. In other years, the Meiyu belt will move northward and then return to the Jianghuai basin to maintain relative stability, which is customarily called "inverted Huangmei". For example, Huangmei in August of 1980 has a great influence on agricultural production in various parts of Zhejiang. This abnormal situation in meiyu period is often related to the abnormal change of global atmospheric circulation.

Under normal circumstances, after the first ten days of July, the meiyu in Jianghuai Basin ended from south to north, the frontal rain belt moved to North China, and the Jianghuai Basin entered the summer drought weather with high temperature and little rain.

What is summer drought and how is it formed?

The drought that occurs in the dog days is called summer drought. It is characterized by strong solar radiation, high temperature, low humidity and large evaporation and transpiration. Under the control of the western Pacific subtropical high, the Yangtze River basin in China, especially in Hubei, Hunan, Jiangxi, Jiangsu, Anhui and other provinces, is sunny and hot, and the summer drought occurs frequently, reaching 50%. In other areas, there are droughts in some years. Summer is a period of vigorous crop growth, although summer drought is not as frequent as spring drought; However, the damage to crops is generally heavier than that in spring drought, so there is an agricultural proverb that "there is no drought in spring, and the drought in summer is halved". Summer drought is not only related to the growth of crops in that year, but also determines the reservoir capacity and the formation of soil moisture in that year, which has an important impact on the growth and yield of winter wheat and spring sowing crops in the coming year.

Respondent: qsmm- 12 ranked 7- 1 19:56.

People living in the middle and lower reaches of the Yangtze River often have such an experience: as soon as the sunny and rainy spring is over, early summer comes, but soon, the sky is overcast and rainy, and sometimes there will be bouts of heavy rain. This is what people often say, "Meiyu" is coming.

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

How did the name "Meiyu" come from? Initially, it originated from a meteorological term in China. In ancient times, Meiyu was usually called Huang Meiyu. As early as the Han Dynasty, there were many proverbs about Huang Meiyu. In the Jin Dynasty, there was already a record of "summer rain to the sun, named Huang Meiyu"; Since the Tang and Song Dynasties, there have been many interesting descriptions about Meiyu. Liu Zongyuan, a writer in the Tang Dynasty, once wrote a poem about Meiyu: "Shi Mei welcomes Meiyu, and it is already late spring. I am deeply worried about the night of the ape, and my dream has run out in the morning. The sea fog connects the South Pole, Jiang Yun dark Beijin, plain clothes today, not for the dust of the imperial city ". Among them, "Shi Mei welcomes the rain" means that when plums are ripe, they welcome the rain from summer to three o'clock in the future. At present, the meteorological plum rain refers to a rainy weather that transits from early summer to midsummer.

Zhu He was once called "He Meizi" in the Song Dynasty, which is said to be because he wrote such a famous sentence in the word "Jade Case": "One Sichuan tobacco, the city is full of wind, and plums are raining yellow." In Song Dynasty, Chen also wrote in Geng Shi Hua: "Plum blossoms are ripe in May in the south of the Yangtze River, and it rains for ten days, which is called it". In the Ming Dynasty, Xu wrote in Tang Yuzhi's Talk about Hui: "Plum blossoms stand after the awn, and plum blossoms are broken after the awn." In history, "Huang Meiyu" usually refers to the precipitation of "Mei" Festival. People in the middle and lower reaches of the Yangtze River are used to taking the solar term of "Mangzhong" as May Festival, which coincides with the mature season of plums, so it is also called "Huangmei".

In addition, due to the high humidity in the air during this period, everything is easy to be damp and moldy, so people gave Meiyu an individual name, called "Moldy Rain". Xie Zaihang's Five Miscellaneous Torches in Ming Dynasty? "Tianbu No.1" describes: "Every year in March and April in the south of the Yangtze River, it rains bitterly, and everything is moldy, commonly known as Meiyu, and it is covered when it is green and yellow. From Xu Huai to the north, it is often dry in spring and summer. At the turn of June and July, it rained heavily and everything was moldy. " Li Shizhen, an outstanding medical scientist in Ming Dynasty, pointed out more clearly in Compendium of Materia Medica: "Plum rain or mildew rain, when it comes to clothes and things, will produce black mold." .

It can be seen that the appellation of "plum rain" or "mildew rain" has a long history, and it began to spread in China, at least dating back to 1000 years ago.