Conditions for frost formation
The conditions for frost formation are as follows:
"Frost" does not fall from the sky, but is condensed by water vapor on the ground when it meets cold weather. Frost will appear in autumn, winter and spring. Frost is formed by condensation of water vapor in the air close to the formation directly on the ground 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, it is usually easier to form frost in depressions than in ordinary places, and plants in depressions are particularly vulnerable to frost. ?
The meteorological conditions for dew and frost formation are clear and breezy nights. Clear at night is conducive to rapid radiation cooling of the ground or ground objects. The breeze can make the radiation cooling fully carried out in the thick gas layer, and can also make the air close to the ground be replaced to ensure that there is enough water vapor for condensation. When there is no wind, there is not much water vapor for condensation. When the wind speed is too high, the turbulence is too strong, which makes the air close to the ground mix strongly 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, except radiation cooling, it is beneficial to its formation after cold advection or when cold air is gathered in depression. This kind of frost is called advection frost or depression frost, and they are often strengthened by radiation cooling. Therefore, in depressions and valleys, frost occurs frequently. Frost is produced less frequently in the waterside plains and forest areas. ?
Ground condensation is an important part of weather phenomena. It is a phenomenon that water vapor condenses from the air and condenses on objects or the ground (China Meteorological Bureau, 23). Common ground condensation phenomena include dew and frost. "Frost" and "Frost" and "first frost" solar terms are not the same thing, they are three different concepts.
"frost" refers to a kind of white ice crystal formed by condensation of water vapor on the ground in cold weather; "Frost" refers to a common phenomenon of agrometeorological disasters; 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 rather cold weather. From a scientific point of view, it is not accurate to say that "dew forms frost".
The frozen dew formed by freezing dew drops is hard small ice beads. Frost refers to the phenomenon of crop freezing injury caused by the sudden drop of temperature, and its damage temperature varies with crops, varieties and growth periods. To form frost, the temperature of the ground or ground objects must drop below ℃, and the water vapor content in the air in the ground should reach a certain standard.
therefore, frost does not necessarily occur when frost occurs, and frost does not necessarily occur when frost occurs. However, because the temperature at the time of frost is already relatively low, if it continues to cool, it will easily lead to frost.