The vernal equinox of 20 10 is 12 hours 10 minute, regardless of day and night. Why?
Spring Equinox
The vernal equinox, also known as "Japan-China", "Day and Night Equinox" and "Midspring Moon" in ancient times, is celebrated around March 21(20th-22nd) every year, and the lunar calendar date is not fixed, and the sun reaches 0 o'clock. According to the "Twenty-four solar terms": "In mid-February, it is divided into half, which is half of ninety days, so it is called minutes." Another article, Spring and Autumn Stories, Yin and Yang in and out, said: "At the vernal equinox, Yin and Yang are also half-phase, so day and night are cold and summer." There is a "Li Mingshi Yi" cloud: "The dividing line, the point where Huangchi intersects, the sun is here, and the day and night are equally divided." Therefore, the significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Second, in ancient times, it was spring from beginning of spring to long summer, and the vernal equinox happened to be in the three months of spring, and spring was equally divided.
In ancient China, the vernal equinox was divided into three periods: "First, waiting for the arrival of birds; Second, wait for Lei Nai to make a sound; Third, wait for electricity. " In other words, after the vernal equinox, swallows will fly from the south, and when it rains, the sky will thunder and lightning. The vernal equinox is recorded in the ancient calendar of China: "Three days before the vernal equinox, the sun entered the equator."
On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. Then the direct sunlight position gradually moved northward, and the days were long and the nights were short.
The farther the earth is from the equator, the smaller the noonday angle of the sun, and the less sunlight and heat it gets. Generally, March, April and May are spring in the northern hemisphere and autumn in the southern hemisphere.
During the spring equinox and solar terms, the East Asian trough is obviously weakened, and the trough ridge activity in the westerly belt is obviously enhanced. From Mongolia to the northeast, there are often low-pressure activities and cyclone development. Low-pressure movement causes cold air to go south, and it is windy and windy in the north. When the long wave trough moves eastward, there will be continuous rainy and cold weather due to the intersection of cold and warm air masses.
During the vernal equinox, the daily average temperature in all parts of China rose steadily to above 0℃ except the alpine mountain area and the area north of 45 north latitude. The severe cold has passed, and the temperature rises rapidly, especially in North China and Huanghuai Plain. The daily average temperature rises to above 10℃ almost at the same time as the rainy areas along the Yangtze River and the south of the Yangtze River, entering a bright spring. On the vast land, the willows are green on the shore, the grass is growing in Fei Ying, the wheat is jointing, the rape is fragrant, the peach blossom is red, Li Bai is welcoming the spring, and the yellow is yellow. South China is a scene of late spring. According to the climate law, the precipitation in Jiangnan increased rapidly at this time, and it entered the period of "peach blossom flooding" in spring; In the northeast, north and northwest regions where "spring rain is as expensive as oil", precipitation is still very little, so resisting the threat of spring drought is the main problem of agricultural production.
"Wheat rises at the vernal equinox, and every moment is worth 1000 yuan." In the northern areas with little rain in spring, we should pay close attention to spring irrigation, water saving and jointing fertilization, and pay attention to preventing late frost and freezing injury. South China still needs to continue to do a good job in drainage and flood prevention. Early rice seedling raising in Jiangnan and Jianghuai areas has started, and the weather changes frequently in early spring. Attention should be paid to soaking seeds to accelerate germination when cold air comes, and sowing in sunny days when cold air ends. The experience of the masses says, "A cold tail warms the head, so there is no need to worry about seedlings." According to the weather conditions, strive for 3-5 sunny days after sowing to ensure that all seedlings are sown at one time. Spring tea has begun to sprout, so it is necessary to apply quick-acting fertilizer to control pests and diseases in time and strive for high yield and high quality tea.
"February is the vernal equinox, and planting trees and fertilizing farmland is deep." The vernal equinox is also a good opportunity to plant trees. In ancient poems, there is a saying that "Niu Jiao girls started planting trees in the middle of the night, and it was the vernal equinox in the Ming Dynasty". In the hot busy farming season, we should continue to use our hands to green the mountains and rivers of the motherland and beautify our environment.
The vernal equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, beginning of spring, Changxia, beginning of autumn and beginning of winter were used to indicate the beginning of the four seasons. The vernal equinox, summer solstice, autumn equinox and winter solstice are in the middle of each season. On the vernal equinox, the sun shines directly on the equator, and the time between day and night is equal all over the earth. Therefore, the ancient vernal equinox and autumnal equinox are also called "equinox", and there is a folk proverb that "vernal equinox and autumnal equinox are equally divided day and night".
After the vernal equinox, the overwintering crops in most parts of southern China entered the spring growth stage. In central China, there is an agricultural proverb, "Wheat starts at the vernal equinox, and every moment is worth a thousand dollars". The temperature in most parts of the south continues to rise, but generally it doesn't rain as fast as the vernal equinox. In late March, the average temperature in northern South China is mostly 13℃ to 15℃, and in southern South China it is mostly 15℃ to 16℃. Most of the plateau has been melted by snow, and the ten-day average temperature is about 5℃ to 10℃. Most areas in South China, such as river valleys, have the highest temperature, with an average of 18℃ to 20℃. In the south, except for the marginal mountainous areas, the average daily temperature rose steadily to above 12℃ in 1978, which is beneficial to planting crops such as rice and corn, and is also very suitable for afforestation. However, before and after the vernal equinox, there is often a strong cold air intrusion in South China, and the temperature drops obviously, as low as 5℃. Sometimes a small stream of cold air comes one after another, forming a low temperature and rainy weather that lasts for several days, which is not good for agricultural production. According to this feature, we should make full use of the weather forecast, grasp the cold tail and warm head, and sow in time.
On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. The difference is that it is spring in the northern hemisphere and autumn in the southern hemisphere. Then the direct sunlight position gradually moved northward, the solar radiation in the northern hemisphere gradually increased, and the weather became warmer day by day. At the same time, the days get longer and the nights get shorter. The spring equinox solar terms are affected by the intersection of cold and warm air masses, and the rain will also increase.
As the saying goes, "The spring equinox begins with wheat, and the fat and water should follow". A spring rain was warm. After the spring rain, I was busy plowing. The busy farming season in spring is about to begin, and spring management, spring ploughing and spring planting are about to enter a busy stage. After the vernal equinox, overwintering crops enter the growth period, so field management should be strengthened. As the temperature rises rapidly and the water demand is relatively large, farmers should strengthen water storage and moisture conservation.
Calculation of vernal equinox date [Y*D+C]-L
Interpretation of the formula: the last two digits of the number of years are multiplied by 0.2422 plus 20.646, and the integer is subtracted from the number of leap years. C value 2 1 century vernal equinox =20.646.
For example, the date of 1992 vernal equinox = [92× .0.2422+20.646]-[92/4] = 42-23 = 19, and March19 is the vernal equinox.
Exception: calculation result in 2084 plus 1 day.