When did the cold weather start? What are the rules?

"It's cold for nine, and it's cold in March.". "Sanjiu" usually appears in the winter from solstice to fright. "March 9th" refers to the third "nine days" after the winter solstice, that is, the 19th to 27th days after the winter solstice. "The third nine days after the winter solstice" refers to "March 99", which is also the day when March 99 and April 99 intersect, not "March 99", that is, "March 99" is nine days instead of one day.

The calculation method is from the solstice of winter (counting from the solstice of winter, which means the beginning of cold), every nine days are called a nine, the first nine days are called a nine, the second nine days are called a 29, and so on until the ninth nine days, when the number reaches 998 1 day.

During the winter solstice, the daytime is the shortest, the angle of direct sunlight on the ground is the smallest, and the sunshine intensity per unit area on the ground is also the smallest, so the ground gets the least solar heat every day, and the daily heat budget deficit on the ground has not reached the maximum. On the solstice after winter, although the day is growing day by day, the growth rate is very slow. From the winter solstice to the "March 9" period, the average daily growth is only about one minute. At the same time, the angle between the direct angle of the sun and the ground is slowly increasing.

The daily heat budget of the ground is still in deficit, so it continues to lose heat and the ground temperature continues to drop. The deficit of total heat balance on the ground only reaches the maximum in the season of March 9. Because the temperature is mainly affected by the ground temperature, this leads to the lowest temperature in the "March 9" season.

The earth absorbs heat from solar radiation during the day and releases heat at night. In summer, you absorb more heat during the day and emit less heat at night, so you can accumulate some heat every day. In winter, less heat is absorbed during the day and more heat is released at night. Not only can you not accumulate it every day, but you also need to use some of the heat accumulated in summer. During the winter solstice, less heat is absorbed during the day, but there is still some stored heat on the earth. After the winter solstice, less and less heat is stored. By March 9, the earth's heat storage is the least in a year, so it is the coldest.

There are many customs of "counting nine" to expand information, among which "ninety-nine poems" are the most extensive and have a long history. These songs skillfully use the phenological phenomena in nature and vividly reflect the laws of weather changes during the Ninth Five-Year Plan period. As far as most parts of China are concerned, the weather was not the coldest when the 29th passed, but "1929, I can't reach it." At the end of April 9, it was almost the "Great Cold" solar term, so we said "March 9, freezing cats and dogs".

After May 9, the earth gradually rejuvenated and the weather gradually warmed from cold, so "May 969, look at the willows by the river; 7989, walking alone. " By 1999, it was already a "shock pad" solar term, so "the thunder of 1999 made a lasting noise."

The custom of "painting nine" appeared in the Ming Dynasty. The so-called painting is actually a picture that calculates the warm date of spring after the winter solstice. In the Ming Dynasty, "A Brief Introduction to the Scenery of the Imperial Capital" contained: "From winter to the sun, draw a plum flower, one in eighty petals. Dye one petal a day, and 99 petals will come out, then the spring will be deep, saying that 99 will eliminate the cold. " In addition, there were "1999 Poems and Paintings for Eliminating Cold" in the Qing Dynasty.

There are four sentences in nine days and thirty-six sentences in the picture. The content ranges from "Huang San ruled the world in ancient times" to "the golden years of Qing Dynasty" in this dynasty, which is a beautiful historical "memorabilia".

After "painting nine", the custom of "writing nine" appeared in Qing Dynasty. "Writing Nine" has a strong cultural flavor, and often uses words such as "weeping willows in front of the pavilion and cherishing the spring breeze" or "sending fragrant flowers into the house in the spring vestibule" (traditional). Tick them into a picture first and fill them in from the ninth day (similar to "painting red" in calligraphy practice).

Black with a thick brush, nine strokes per word, one stroke per day, and it takes just 8 1 day to fill in these nine words. Interestingly, after filling in a stroke every day, you have to use a fine brush to record the weather of that day on the strokes. Therefore, a line of "writing nine" is also more detailed meteorological data in the past nine days.

Baidu Encyclopedia-Count Nine Cold Days