Climatic characteristics of vernal equinox

The climatic characteristics of vernal equinox are spring drought, dust, cold in late spring and low temperature and rainy weather.

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.

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 from high altitude, especially the air pollution caused by dust storms, have always been the focus of attention and become a hot topic for some time.

In early spring, the temperature rises quickly, and then it stays low for a while. This weather phenomenon is called late spring cold.

There has been a very serious late spring cold in the middle and lower reaches of the Yangtze River. 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. On that day, the average temperature was lower than 10 ~ 12℃ (different standards in different regions) for more than 5-7 days.

Because rice and cotton are both thermophilic crops, when the temperature is above 10 ~ 12, the minimum temperature is above 5℃. 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.

The historical origin of vernal equinox;

The "vernal equinox" means half, that is, it is divided into two parts, day and night are equally divided, and the cold and summer are balanced. In addition, the vernal equinox also means sharing spring equally. Traditionally, it is spring from beginning of spring to long summer, and the vernal equinox is in the middle of three months in spring. Therefore, the vernal equinox was also called "Japan-China", "Day and Night Equinox" and "Midspring Moon" in ancient times. At the vernal equinox, the sun shines directly at the equator of the earth, and the length of day and night is equal.

According to Yuan Wucheng's book "Twenty-four Solar Terms", "In mid-February, it is divided into 90 days and a half, so it is called division." "Li Mingshi Yi": "The dividing line, the point where Huangchi meets, the sun is here, and the day and night are equally divided." Another "Spring and Autumn Story" said: "The vernal equinox, Yin and Yang are also half-phase, so day and night are cold and summer." Lunar Book: "The bucket refers to the vernal equinox, which is about Sunday, and the northern and southern hemispheres are equally divided day and night (except the poles), which is also half of spring, so it is called the vernal equinox."

"Twenty-four solar terms" is the product of China's ancient farming civilization, which has a long history and is related to the time when officials raised gossip. In the process of cultural exchange and communication of historical development, four solar terms (vernal equinox, autumnal equinox, summer solstice, winter solstice) of China's "twenty-four solar terms" reflecting the return movement of the direct point of the sun spread throughout the pre-Qin period. The division of the four seasons in the west is based on the dichotomy, that is, spring is divided into beginning of spring.

The vernal equinox in the "vernal equinox" became the New Year in Uzbekistan, Turkey, Afghanistan, Iran and other countries, which lasted for more than 3,000 years. Twenty-four solar terms were introduced to Japan more than 1000 years ago, and some solar terms were also included in Japan's legal wishes. Vernal equinox is a public holiday in contemporary Japan.