Qianjiang Evening News Hourly News Reporter Zheng Lin
According to the People's Network, from June 9, the cold air from the north will enter the middle and lower reaches of the Yangtze River in China, and the subtropical high pressure in the western Pacific Ocean will also be strengthened again, which means that the rainy season is coming again! At the same time, what does it mean to say "into the plum", "out of the plum", "empty plum", "pouring yellow plum"?
In this issue, we invited Hong Hanfang, a senior geography teacher at Zhuji Xuemian Middle School, to talk about the ins and outs of Meiyu.
Plums ripen plum rain comes
It usually lasts 20 days
Not only the plum rainy season in Jiangsu and Zhejiang, but also the middle and lower reaches of the Yangtze River in China, taiwan, as well as central and southern Japan and southern Korea will have plum rainy seasons.
Why is this period called the "rainy season"? "That's because this is the ripening period of Jiangnan plums, so the rain at this time is called 'plum rain'." Teacher Hong said.
A typical rainy season, usually in mid-to-late June "into the plum", in early July "out of the plum", lasted more than 20 days.
However, for specific years, there are great differences between the beginning and end of plum rain, the strength of plum rain, etc. Because, the summer monsoon is not very stable.
In some years, Mei Yufeng is particularly active, which is a year of abundant plums; in some years, Mei Yufeng is not obvious, and "empty plums" appear.
In some years, there will also be a phenomenon of the plum rain belt moving north and then returning to the Jianghuai River Basin, which is called "inverted yellow plum". For example, in late July 2009, there was a rainstorm in Jiangsu Province, which is the "pouring yellow plum" after "out of the plum".
The cold and warm air from the north to the south holds Jiangnan
Form a stable rainfall belt
Why is the rainy season formed? Teacher Hong wants to tell you about the geographical meteorological knowledge behind it.
First, learn about the monsoon. In summer, at the same latitude, the temperature on land will be significantly higher than that of the ocean. In this way, on land, the air expands and rises, forming a low air pressure. The air pressure on the ocean is higher than that on land, so the air will flow from the ocean to the mainland, forming a "wind". Since this wind changes with the seasons, it is called "monsoon".
China happens to be on the world's largest continent, Eurasia, and next door is the world's largest ocean, the Pacific Ocean. As a result, China's summer monsoon will be very significant, showing that in the summer, the southeast wind will blow, and the wind will become a "typhoon" when it is strong.
The warm and humid southeast wind will bring abundant precipitation to our country.
Every year from the spring onwards, the warm and humid air gradually strengthens, entering the mainland from the sea, first to South China in April and May, and then further northward, and from mid-to-late June to early July, it often extends to the middle and lower reaches of the Yangtze River, and sometimes to the Huai River and its north.
When the warm and moist air enters the Chinese mainland, it meets the cold air from the north to the south. At the junction of cold and warm air, a "front" is formed, and precipitation is generated near the front, which is the "front rain". Most of the precipitation in our country is frontal rain.
At this time, if the cold air force is relatively strong, the cloud rain area will move south with the cold air; if the warm air is stronger, the cloud rain area will move north with the warm air.
As in a tug-of-war, usually, cold and warm air wins and loses, so the area of rain will move north and south, and will not stagnate in one area.
However, in the early summer period, in the middle and lower reaches of the Yangtze River, on the one hand, warm and humid air has been quite active, on the other hand, the cold air from the north to the south still has a certain force, especially in the air layer close to the ground, there is often a small and a small strand of cold air going south.
In this way, cold and warm air cannot stand in this area, forming a stable rainfall belt. The rain belt is only 200 to 300 kilometers wide from north to south, but up to about 2,000 kilometers long from east to west, traversing the middle and lower reaches of the Yangtze River and extending east to Japan. This rain band is the scope of the "plum rainy season", so the plum rain in Japan is also obvious.
Proverbs associated with plum rain
In fact, it contains meteorological knowledge
In China, there are many proverbs related to plum rain. For example, "there is a lot of snow in the waxing moon, and the water is yellow plum" means that there is a positive correlation between the waxing moon snow and the plum rain. "Cold water dry, summer water dry" means that if there is less rain in winter, there is less plum rain. Because the weather continues to be dry, it is often caused by the relative stability of some kind of favorable weather situation in favor of drought. However, due to the fact that the atmosphere is in constant motion, the above relatively stable state is always destroyed and transformed to the opposite side under certain conditions.
"Exhausted peach blossom water, it must be dry yellow plum" is also used to predict plum rain in spring. "Peach blossom water" refers to precipitation during the Qingming Festival or during the opening of peach blossoms in April. "Dry yellow plum" refers to the lack of rain in the mandarin season or the start of plum rain late.
"If you have a spring wind, there will be summer rain" means that in years with more east winds in the spring, there will generally be more plum rain in summer. The "Sanjiu" in the sentence "Sanjiu owes the east wind, and the yellow plum has no heavy rain" refers to January 9-17 in the solar calendar, and "huangmei" refers to the mango seed festival (June 6-20). The meaning of this proverb is that if there is no east wind during the Three-Nine Period, or if there are few east winds, the amount of rainfall will be less.
Test you
Question: In some years in Zhejiang, the rainy season has increased significantly compared with the usual year, and in some years, there are few rainy days during the plum rain (this situation is commonly known as "empty plum"), please analyze the causes.
<b>Answer: The length of the plum rainy season is affected by the strength of the summer wind, the summer wind is strong, the rain belt is quickly pushed to the north, and the south will appear "empty plum"; the summer wind force is weak, the rain belt lingers in the south for a long time, and the plum rainy season in Shanghai is naturally longer than usual. </b>
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Source: Qianjiang Evening News Hourly News