Winter characteristics

Simplified as one of the 24 solar terms, the first solar term in first frost refers to the cold weather and the beginning of first frost. [/size][/size][size=9pt] Every year the solar calendar1starts when the sun reaches 2 10 degrees on the 23rd or 24th of October. [size= 10][size=3] At this time, the weather turned cold and began to frost. "Twenty-four solar terms" records: "In mid-September, the gas is cold and condensed, and the dew is like frost. [/size][size=9pt] During the first frost, southern China entered the busy season of autumn harvest and autumn planting, while the first frost generally appeared in the Yellow River basin. [/size][size = 10][/size][/size]

South of latitude [size= 10][size=3][font= ì], 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. From a scientific point of view, the saying that "dew becomes frost" is not accurate. The frozen dew formed by dew freezing is hard small ice beads. Frost refers to the phenomenon of crop freezing injury caused by the sudden drop of temperature, and its harmful temperature varies with crops, varieties and growth periods. To form frost, the temperature of the ground or ground objects must drop below 0℃, and the water vapor content in the air on the ground should reach a certain level. Therefore, there may not be frost in first frost, and there may not be frost in first frost. However, due to the low temperature during frost, if the temperature continues to drop, it will easily lead to frost. After the first frost, most areas in southern China began to collect and dig a large number of sweet potatoes. If the harvest is too early, the lump will not fully expand, which will affect the yield; But if the harvest is too late, it may be damaged by early frost, and the block will be frozen and deteriorated, so it is very important to dig it out in time. Su Shi, a great writer in the Northern Song Dynasty, said in a poem: "Thousands of trees are yellow, and only Furong is alone." The climate in the south is mild. In the first frost, the fields are lush, orange, yellow and green, autumn chrysanthemums are in full bloom, and hibiscus is in full bloom, which makes the rich "Tianfu" more gorgeous. [/font][/font]