Vernal equinox in the twenty-four solar terms

Vernal equinox in the twenty-four solar terms

Do you know what the vernal equinox is in the 24 solar terms? According to the needs of agricultural production, people in ancient China divided a year into 24 solar terms, and the vernal equinox was the fourth of the 24 solar terms. A friend wants to know the information about the vernal equinox in the 24 solar terms. Please look at my collection.

The vernal equinox of the 24 solar terms 1 What is the vernal equinox?

The vernal equinox is one of the 24 solar terms, also known as "Japan-China", "Day and Night Equinox" and "Mid-spring Moon" in ancient times. It is celebrated around March 2 1(20-22) every year, and the lunar calendar date is not fixed. At this time, the sun reaches 0 on the meridian.

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".

Climatic characteristics of vernal equinox

The vernal equinox is the fourth of the twenty-four solar terms and the fourth of the six solar terms in spring. The vernal equinox begins on March 20th (or 2 1) and ends on April 4th (or 5th) every year. At the vernal equinox, the barrel refers to the position (due east). Every year on March 20th or at 2 1 day of Gregorian calendar, the sun starts when it reaches 0 degrees of the yellow meridian (vernal equinox). The length of day and night is average, just half of the 90th day of spring, so it is called "vernal equinox". In ancient times, it was also called "Japan-China", "Day and Night" and "Mid-spring Moon". 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. 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 vernal equinox is an important solar term, which not only has astronomical significance: the northern and southern hemispheres are equally divided day and night; Climatically, there are also obvious characteristics. During the spring equinox, China has entered a beautiful spring scenery except the Qinghai-Tibet Plateau, Northeast China, Northwest China and North China. On the vast land, willows are green, Fei Ying grass grows, wheat jointing and rape blossoms are fragrant.

The vernal equinox is a period in which yin and yang are balanced, day and night are equal, and cold and summer are equally divided. The so-called "vernal equinox, yin and yang are also half, so it is cold and summer day and night." The common people say that "the vernal equinox, the vernal equinox, and the day and night are equally divided" is the truth.

At the vernal equinox, the temperature in the north and south of China rises above zero, and everything enters the stage of spring warming in bloom. It is "spring flies when peaches and apricots bloom, butterflies and bees come" that makes the countryside busy and the wheat has entered the stage of turning green.

Climatic characteristics of vernal equinox in 24 solar terms

aeolian sand

During the vernal equinox, the northwest, the northern part of North China and most of the northeast are still in the transitional stage from winter to spring, with sunny and windy days, and it is warm and cold at first sight. According to the statistics of dusty weather in recent years, April is the most frequent, followed by March, and the vernal equinox is 15 days, that is, from the end of March to the beginning of April. In these areas, dust blown by strong winds and floating dust at high altitude, especially the air pollution caused by dust storms, have always been concerned by everyone and become a hot topic for some time.

Low temperature and humid weather

At the vernal equinox, cold air constantly invades the south of China, and there will be cold weather in spring with low temperature. At this time, the continuous rain will have a great impact on crops.

Low temperature and humid weather

If the average temperature is lower than 10 ~ 12℃ for more than 5-7 days, it may cause serious rice seedling rot. Because rice and cotton are both thermophilic crops, when the temperature is above 10 ~ 12 and the minimum temperature in sunny days is above 5℃, it is beneficial to all seedlings. Conversely, if there is low temperature and rainy weather, you can imagine.

First frost is the product of cold wave and strong cold air in spring. In the case of warmer climate, cold waves are relatively rare, but we should not be careless.

Abnormal cold weather in early spring

In early spring, the temperature rises quickly, and then it stays low for a while. This weather phenomenon is called late spring cold. In the south, the main influence of late spring cold is the rotten seedlings of early rice. In the north, it will affect the growth of peanuts, vegetables and cotton, and seriously cause the phenomenon of wheat seedling death. A very serious late spring cold occurred in the middle and lower reaches of the Yangtze River, just at the vernal equinox, that is, from late March to early April of 1976. The loss of grain seeds in Hunan, Jiangxi and Hubei provinces alone reached 700-800 million Jin.

spring drought

In the north, especially in the northwest and north China, there is a saying that "spring drought lasts for ten years and nine months" and "spring rain is as expensive as oil". When there is little rain and snow in winter, winter wheat is in the wintering period and is not very sensitive to water shortage. After March, the soil thawed and the wheat turned green; In spring, crops are sown from south to north. If the precipitation continues to be less at this time, the drought will be clearly reflected, and the situation of seedlings can be imagined.

Pre-flood season in southern China

There are two rainfall concentration periods in South China, one is the first flood season from April to June, and the other is the second flood season formed by typhoon rainfall from July to September. The first flood season begins in early April and reaches its peak in mid-May, with an average of 20 rainstorms per year, with the most in June, accounting for more than half of the total rainstorms. It lasts for a long time and the rain is fierce. Because the "vernal equinox" only touches the beginning of the flood season, I won't go into details here.