The origin of autumnal equinox
The autumnal equinox is one of the twenty-four solar terms in Chinese traditional festivals and the sixteenth solar term in the twenty-four solar terms of the lunar calendar. Usually on September 22nd or 23rd every year. The climate in the south began to decline from this solar term. First, the sun reaches 180 degrees on this day, pointing directly at the equator of the earth, so a day is divided into 24 hours, each 12 hours; There is no extreme day and night phenomenon in the world. In ancient China, the autumnal equinox was divided into three periods: "When thunder comes, the sound will stop;" Second, wait for scorpion blank households; Wait for the water to dry. "After the autumnal equinox, the polar night range near the North Pole gradually expanded, and the polar day range near the South Pole also gradually expanded. Twenty-four solar terms say, "See you at the vernal equinox in mid-August" and "Those who divide are equal, so it is called division". "
In the autumn equinox, most parts of China have entered a cool autumn. The cold air from the south meets the gradually decaying warm and humid air, which causes repeated precipitation and the temperature drops again and again. As people often say, it's time for "an autumn rain and a cold", but the daily precipitation after the autumnal equinox will not be great. At this time, the field farming in the south and the north is different. In northern China, there is an agricultural proverb that says: "The white dew is early, the cold dew is late, and it is the right time to plant wheat in the autumn equinox." Proverbs clearly stipulate the sowing time of winter wheat in this area; And "White clouds come in autumn equinox, good songs and good rice seeds are everywhere" reflects the planting time of rice in Jiangnan area. In addition, the taboos of working people on the solar terms of the autumnal equinox are also summed up as proverbs, such as "the autumnal equinox is only afraid of lightning, and more meters are more expensive."
The rapid cooling in autumn makes the autumn harvest, autumn ploughing and autumn planting "Sanqiu" particularly nervous. According to research, the autumnal equinox has always been regarded as a symbol of farming in China. At the end of the Han Dynasty, Cui Mang wrote in the "Four-person Moon Order": "Where wheat is planted, the white deer can be in the thin field, the autumnal equinox in nakata, and the latter ten days in nakata." The autumnal equinox is a good time for harvest. Farmers' friends should grab the autumn harvest crops in time to avoid the harm of the first frost and continuous rain; It is also necessary to sow winter crops early in time to lay the foundation for high yield in the coming year.
Autumn Equinox: Sacrifice to the Moon
The autumnal equinox used to be the traditional "Festival of Sacrificing the Moon". For example, in ancient times, there was a saying that "the sun is sacrificed in spring and the moon is sacrificed in autumn". Now Mid-Autumn Festival comes from the traditional Mid-Autumn Festival. According to textual research, the original "Moon Festival" was set on the day of "Autumn Equinox", but there is not always a full moon because of the different days of August in the lunar calendar every year. And the moon without the moon is a big spoil the fun. Therefore, the Mid-Autumn Festival was later transferred from the Equinox to the Mid-Autumn Festival.
According to historical records, as early as the Zhou Dynasty, ancient emperors had the custom of offering sacrifices to the sun at the vernal equinox, to the earth at the summer solstice, to the moon at the autumnal equinox, and to heaven at the winter solstice. Its places of worship are called Ritan, Ditan, Yuetan and Tiantan. It is located in four directions: southeast and northwest. The Moon Altar in Beijing is the place where emperors of Ming and Qing Dynasties offered sacrifices to the moon. The Book of Rites says: "The son of heaven is sunny in spring and autumn is in the evening. The DPRK, the evening of the moon. " The moon here refers to offering sacrifices to the moon at night. This custom is not only pursued by the imperial court and the upper nobility, but also gradually affects the people with the development of society.
Autumnal equinox: temperature
According to the standard of climatology, in the "autumnal equinox" season, the average daily temperature in the Yangtze River basin and its northern area drops below 22℃, which is phenological autumn. At this time, the cold air mass from the north has had a certain impact. The rainy season has ended in most parts of the country, and words such as breezy breeze, blue sky and Wan Li, sunny weather, crisp autumn air, sweet osmanthus fragrance and yellow crab and fat chrysanthemum are all descriptions of this scene.
The autumnal equinox solar term is also an important solar term in agricultural production. After the autumnal equinox, the direct sunlight moved to the southern hemisphere, and the northern hemisphere got less and less solar radiation, but the ground lost more heat and the temperature dropped significantly. Agricultural proverbs say: "An autumn rain is a cold", "The white dew is divided into autumn nights, and one night is cold". "In August, the wild goose gate opens, and the foot of the wild goose is frosty." It is not surprising that the temperature in Northeast China drops early and frost appears at the autumnal equinox.
According to meteorologists, according to the lunar calendar, "beginning of autumn" is the beginning of autumn and ends with "the first frost". The "vernal equinox" is exactly half of the 90 days from beginning of autumn to the first frost. From the day of the autumnal equinox, the climate has three main characteristics: the position of direct sunlight continues to move from the equator to the southern hemisphere, and the phenomenon of short days and long nights in the northern hemisphere will become more and more obvious. The days will gradually shorten and the nights will gradually lengthen (until the winter solstice reaches the longest night and the shortest day); The temperature difference between day and night will gradually increase, and the amplitude will be higher than 10℃. The temperature drops day by day, getting colder every day, and gradually entering the late autumn season. The situation in the southern hemisphere is just the opposite.
The rapid cooling in autumn makes the autumn harvest, autumn ploughing and autumn planting "Sanqiu" particularly nervous. The autumnal equinox is a good time to harvest cotton and tobacco leaves from green to yellow. Winter wheat has been planted in North China, and the Yangtze River basin and vast areas in the south are busy harvesting late rice and ploughing the land to prepare for rape sowing. Drought and lack of rainfall or continuous rainfall in autumn equinox are the main unfavorable factors affecting the normal operation of Sanqiu, especially the continuous rainfall will make the upcoming crops lodging, mildewing or sprouting, resulting in serious losses. "Sanqiu" is a great help, and the word "early" is the key. Timely harvest of crops in autumn can avoid the harm of first frost and continuous rain, and timely sowing of crops in winter can make full use of heat resources before winter, cultivate strong seedlings to survive the winter safely, and lay the foundation for high yield in the coming year. The autumnal equinox doesn't appear, so cut it and feed it to the old cow. Heading and flowering of double-cropping late rice in South China is the key period for yield formation. The "autumnal equinox" weather formed in advance in low temperature and rainy weather is the main threat to the flowering and fruiting of double-cropping late rice, so we must do a good job in forecasting and defense.