How is the frost formed?

If someone has stayed in the countryside, or knows about rural life, they will understand what kind of phenomenon frost is. This is a relatively common agrometeorological disaster, which occurs in winter and spring, and is mostly a cold wave from the south. It usually happens at night when the weather turns from cloudy to sunny. So why does frost appear on a clear night? What are the characteristics of frostbite? Below, Baibai Safety Net will take you to know these little knowledge about natural disaster safety.

Frost often appears on sunny nights, mainly because there are few clouds on sunny nights, the atmospheric inverse radiation is weak, and the heat preservation effect is poor, so the temperature drops strongly and frost is prone to occur.

Frost is because the air near the ground is cooled by the radiation of the ground and cooled to the frost point.

That is, the surface temperature or ground temperature of ground objects in the gas layer drops below zero, and the supersaturated part of water vapor condenses into white ice crystals on some objects with poor heat transfer performance on the ground. Its structure is loose. Generally, it is formed in a period of time from night to early morning in cold season. When it is formed, it is mostly static wind. Frost sometimes appears in caves, glaciers and cracks in snow. ? In the mid-latitude areas with four distinct seasons in China, from late autumn to early spring of the following year, it is the time around beginning of winter, and the temperature can generally drop below 0℃ at night. On a clear night, because there is no cloud, the ground heat dissipates quickly. In the first half of the night, due to the large amount of heat stored on the ground during the day, the temperature is generally not easy to drop below 0℃. Especially in the middle of the night and before dawn, the ground emits a lot of heat, but the heat compensated by atmospheric radiation is very little, and the temperature drops rapidly. When the temperature drops below 0℃, the water vapor in the air near the ground adheres to the clods, stones, leaves, vegetation, low tiles and other objects on the ground and condenses into ice crystal frost.

Frost is mostly in the transition season of spring and autumn, with the temperature above zero degrees Celsius during the day and below zero for a short time at night. In agrometeorology, it refers to the phenomenon that the temperature on the soil surface or near the plant crown drops below zero, causing crops to suffer. When frost occurs, it is often accompanied by or without hoarfrost. Frost without hoarfrost is called "black frost" or "frost killing". On a clear and windless night, the frost formed by radiation cooling is called "radiation frost". Frost caused by cold air intrusion is called advection frost. The frost formed by these two processes is called advection radiation frost. No matter what kind of frost appears, it will bring more or less damage to crops.