What is the sign of frost?

The traces of frost are shown in the following figure:

When observing a certain weather phenomenon, meteorological observers should record the corresponding symbols in the "Weather Phenomenon" column of the observation record book of the day, except for a few phenomena, and also record the starting and ending time. Based on these symbols, combined with the intensity, coexistence and some characteristics of weather phenomena, a group of symbols that can be filled in weather maps are called cartographic symbols.

Extended data:

cause

"Frost" did not fall from the sky; It is formed by condensation of water vapor on the ground when it meets cold weather. Frost will appear in autumn, winter and spring. Frost is formed by the condensation of water vapor in the air close to the ground directly on or near the ground; The lower the temperature, the greater the air density and the greater the specific gravity.

With the flow of air, the coldest and heaviest air will flow to the lowest place, and after reaching the lowest place (depression), it will gradually accumulate and condense into frost. Therefore, depressions are usually more prone to frost than ordinary places, and plants in depressions are particularly prone to frost.