Xiao Shuang means face to face at night.

First, the basic definition of frost

Frost refers to white ice crystals that condense on the ground or objects when the air near the ground is cooled below the frost point (dew point is below 0) due to the radiation cooling of the ground. Frost is a weather phenomenon, which belongs to ground meteorological observation in China. "Frost" usually appears from autumn to spring. Meteorology generally refers to the first frost in autumn as "first frost" or "first frost";

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. Scientifically speaking, frost is made up of ice crystals, similar to dew. When the relative humidity in the air reaches 100%, water is separated from the air. The only difference between them is that the dew point (the temperature at which water vapor liquefies into dew) is higher than the freezing point, while the frost point (the temperature at which water vapor condenses into frost) is lower than the freezing point.

Therefore, only when the near-surface temperature is lower than 0℃ will frost. Frost, frost and first frost are not the same thing, but three different concepts. "Frost" refers to a kind of white ice crystal condensed by water vapor on the ground in cold weather; "Frost" refers to a common agricultural meteorological disaster phenomenon; The "first frost" solar term refers to the season that reflects the sudden drop of temperature, while the "first frost" does not mean "frosting", but refers to the cold weather.

2. In which season does frost appear?

Frost usually appears in autumn, winter and spring. The solar terms "first frost", "first frost" and "First Frost" are not the same thing, but three different concepts. "Frost" refers to a kind of white ice crystal condensed by water vapor on the ground in cold weather; "Frost" refers to a common agricultural meteorological disaster phenomenon; The "first frost" solar term refers to the season that reflects the sudden drop of temperature.

The first frost is the eighteenth of the twenty-four solar terms, the last solar term in autumn and the transitional solar term from autumn to winter. Every year on the 23rd or 24th day of Gregorian calendar 10 year 10, the first frost solar term is when the sun moves to 2 10 degrees of the longitude of the Yellow River. The temperature is low at this time, so get up in the morning and open the window. On the roof, flowers are white. This is Frost.