The oldest "Jiujiu Song" is recorded in "A Brief Introduction to the Scenery of the Imperial Capital", saying: "March 27, the hedge blows? Hey. " ? Mountain is an ancient wind instrument, shaped like a trumpet, with reeds as its mouth and bamboo as its tube. Cold wind blows on the fence, like blowing? Obesity, whistling. The "Jiujiu Song" circulating in the northern region says that "March 9 and April 9 will walk on the ice", that is, "March 9" will freeze the earth and people will walk on the ice. The proverb says "March 9th is cold" and "March 9th is frozen with dogs". All these show that "March 9" is the coldest period. "March 9" is mostly from 65438+1October 9 to 17 (this year), while the slight cold season is all on March 9, which coincides with the beginning of April 9. The slight cold lasts *** 15 days, of which 12 days is in "Sanjiu and Sijiu", so the temperature is the lowest during the slight cold. Therefore, there is "349 slightly cold, and the north wind is cold."
Meteorologically speaking, the slight cold solar terms, the development of East Asia trough is the strongest and most stable, the Mongolian cold high and Aleutian low are also the strongest and most stable, and the ridge scale of the westerly trough is the largest, which matches the strongest westerly intensity. The cooling process of cold air is frequent in slight cold season. It can also be proved by meteorological proverbs in various places, such as "a slight cold freezes into a ball" and "a slight cold drops into ice". Liu Yong, a poet in the Song Dynasty, said in the poem "Looking at Mei": "In the slight cold season, the same clouds are miserable and the wind is blowing wildly."
In the long-term practice, people have found that slight cold weather has an impact on the future climate, and summed up many meteorological proverbs. Proverbs that predict the change of great cold according to slight cold, such as "slight cold is not cold but great cold" and "slight cold is hot, but great cold can't be said", mean that slight cold is not cold and great cold will be cold; Forecast the temperature changes after the Spring Festival, such as "slight cold and severe cold, warm spring in the coming year", "slight cold and warm shock", "slight cold and rainy, freezing seedlings by rain shock" and so on. Forecast the amount of rain and snow in the coming year, such as "mild cold and warm, beginning of spring snow" and "mild cold and not cold, clear the mire"; Predict the corresponding relationship between mild summer heat and severe summer heat. For example, "it doesn't snow in a slight cold, and the fields crack in a small summer" and "it doesn't rain in a slight cold, but it will dry in a small summer".
Why is a slight cold colder than a severe cold called "slight cold"? First of all, it conforms to the ancient philosophy of "step by step". The ancients thought: "cold air is cold for a long time, and the little one is not extreme." In the eyes of the ancients, cold is also a gradual accumulation of development process, which is gradual. There is a slight cold before the great cold, and the period when it does not reach the coldest is designated as a slight cold. "Twenty-four solar terms" records: "Slightly cold, December Festival. The cold was still small at the beginning of the month, so it was cloudy. It will be big in half a month. " Second, according to the ancient philosophical principle of "extremes meet", the "natural principle" of alternating cold and summer is that it will inevitably pick up after extreme cold. If you catch a cold first and then have a slight cold, you can't just find the feeling of "warming up" after the coldest. After the great cold, beginning of spring returned to the earth in spring, and the temperature began to rise, which was in line with the traditional thinking habits of the ancients. So the great cold should be put after the slight cold. Third, it corresponds to summer heat. The slight cold in winter corresponds to the slight heat in summer, so it is called "slight cold". Great cold, located after the slight cold solar term, is also a relatively cold season around April 9. There is a saying in the ancient "Jiujiu Song" that "four storehouses sleep like camping", and the great cold just corresponds to the great summer heat. So it is called "Great Cold".
Yuan Zhen, a poet in the Tang Dynasty, wrote "Twenty-four Poems": "A slight cold meets a big road, and a magpie builds a new nest. Picking up food to find a winding path, holding purple around the treetops. The frost eagle is near the north end. Pheasants gather in secret. Don't blame me for being strict, I will pay it in the first month at the turn of spring and summer. " In the twelve ancient laws of China, the "Yellow Law" corresponds to November and December respectively, so it is called "Han Xiao Law". The middle five sentences divide Xiaohan into three stages in ancient times: "First-class Yanbei Township, second-class magpies nest, and third-class pheasants nest". "Twenty-four solar terms" said: "Yanbei Township: the meaning of a guide. When the sun shines, geese will avoid the heat and return. Today, they will fly to the north and return to the early spring, and the birds will be angry first. Magpies began to build nests: magpies, magpies also; At the gate of the nest, every time it's too old, it starts to Tianyuan from the winter solstice, and the second sun has won the solar terms in the coming year. Magpies can make nests and know what to do. Start? : pheasant, civilized bird, sunny bird; ? The same voice of men and women is also felt in the sun, and then there is a sound. " It means that masculinity sprouts, geese start to move northward, magpies start to build nests, and pheasants start to sing. The last two sentences of the poem say that although it is winter, it is not far from the first month of spring. As Shelley, an English romantic poet, said in ode to the west wind, "If winter comes, can spring be far behind?"