Traditional Culture Encyclopedia - Weather inquiry - What does the first frost mean?
What does the first frost mean?
The significance of the first frost
Every year, in the middle and late period of 10, the first frost comes in the traditional 24 solar terms. The first frost is also the last solar term in autumn, which is an alternate solar term in autumn and winter. At this time, the temperature difference between morning and evening is very large, sometimes the temperature has reached below 0 degrees at night, and the ice needles directly condensed on the ground or plants are faintly visible, which proves that the first frost in the 24 solar terms indicates that the weather is getting colder.
After the first frost, the plants are lifeless, which shows the ruthlessness and cruelty of the frost. Of course, most of the first frost can only be reflected in the north, even in the solar terms of the first frost, there is no first frost in the south.
Although the wind has cooled down and the temperature has gradually cooled down after the first frost, there is still a difference between the first frost and the frost. When crops encounter frost, the harm will be great, while when crops encounter first frost, the harm will be much less. Because the frost condensed by steam covers the leaves of crops, it can not only harm crops, but also release a lot of heat energy when steam melts.
First frost and crops
Frost. "Twenty-four solar terms": "In mid-September, the essence is cold and condensed, and dew cream". At this time, frost has appeared in the Yellow River Basin of China, and a silver ice crystal shines in the fields thousands of miles away. At this time, the leaves turned yellow and fell. The ancient book "Twenty-four solar terms" says: "When the frost comes, the yin begins to coagulate."
It can be seen that "first frost" means that the weather is getting colder and it begins to frost. Meteorologically, the first frost in autumn is generally called "first frost" or "first frost", and the last frost in spring is called "late frost" or "final frost". The interval from the last frost to the first frost is a frost-free period.
Frost is formed by condensation of water vapor. How can water vapor condense into frost? Lv Benzhong, a poet in the Southern Song Dynasty, wrote in Luzi IV in the Southern Song Dynasty: "The moon invades the post, and the bridge spends the night frost." Lu You wrote in Frost Moon that "the withered grass is frosty and gray, and the cold window is full of new shadows." It shows that frost appears on a clear moonlit night in autumn.
There are no clouds in the autumn night, and the ground is like a quilt, which radiates a lot. When the temperature suddenly drops below 0℃, the water vapor on the ground will condense on streams, bridges, leaves and soil, forming tiny ice needles, and some will become hexagonal frost flowers. Frost can only form on sunny days. People say that "the thick frost is fierce" is the reason.
Climatic characteristics of the first frost
Because there is frost when it is frozen (sometimes no frost is called black frost), autumn frost and spring frost are collectively called frost. The solar term of the first frost means that the weather is getting colder and first frost begins. To the south of latitude, the average temperature is around 16℃, and there are three solar terms before the first frost day. In the southern valley of South China, frost can only be seen in the dead of winter.
Of course, even at the same latitude, the temperature and humidity of the air close to the stratum are different due to the difference of altitude and topography, and the first frost period and frost day are also different. In the first frost season, the cool autumn wind blew to Guangzhou, the flower city. The average temperature in northeast China, eastern Inner Mongolia and most parts of northwest China has been below 0℃.
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