What is frosting?

Frost phenomenon is that frost does not fall from the sky, but is formed in the air near the ground, which is a phenomenon of ground condensation.

Specific introduction 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.

In meteorology, the first frost in autumn is generally called "the first frost" or "the first frost", and the last frost in spring is called the last frost or the last 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 freezing point, while the temperature at which water vapor condenses into frost at frost point is lower than 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 white ice crystals formed by condensation of water vapor on the ground in cold weather; "Frost" refers to a common phenomenon of agrometeorological disasters.

Reasons for formation:

The meteorological conditions for dew and frost are sunny and breezy nights. Clear skies at night are conducive to the rapid radiation cooling of the ground or ground objects. Breeze can fully cool radiation in the thick gas layer, and can also replace the air close to the ground to ensure sufficient water vapor condensation.

When there is no wind, there is not much water vapor condensation. When the wind speed is too high, the turbulence is too strong, which makes the air close to the ground strongly mix with the warmer air in the upper layer, which leads to the slow cooling of the air close to the ground, which is not conducive to the formation of dew and frost. For frost, besides radiation cooling, it is beneficial to its formation after cold advection or when cold air gathers at low pressure.

This kind of frost is called advection frost or low pressure frost, and they are often strengthened by radiation cooling. Therefore, frost often occurs in depressions and valleys. Frost is not common in waterside plains and forest areas.