Why are frosts prone to formation on clear nights in late autumn?

Daytime in the sun.

Under the irradiation, the surface of the earth continues to heat up, and the surface water evaporates. At night, there is no solar radiation, the surface dissipates heat, the temperature keeps dropping, and the moisture in the air is cold to form frost. In sunny weather, the atmospheric inverse radiation is weak, and the surface temperature rises rapidly during the day, and the surface heat dissipates quickly at night, and the temperature decreases rapidly.

On a clear night in late autumn, the temperature drops quickly, and the temperature is low enough to be a favorable condition for the formation of frost.

Atmospheric inverse radiation returns energy to the ground, which compensates for the heat lost by ground radiation to a certain extent, and plays a role in insulating the ground On a clear night, the atmospheric inverse radiation effect is weak, and the thermal insulation effect on the ground is weak, and it is easy to produce frost

The direction of atmospheric inverse radiation is opposite to that of ground radiation, and atmospheric inverse radiation returns energy to the ground, which compensates for the heat lost by ground radiation to a certain extent, and plays a role in insulating the ground Frost in late autumn mostly occurs in clear nights, and there are few clouds in the air, mainly because the atmospheric inverse radiation is weak at night, and the thermal insulation effect on the ground is weak

It is precisely because the autumn nights are very crisp and crisp, and there is a lot of moisture in the air, so it is easy to say, and the temperature at night drops a lot, and of course it is easy to form frost.

1.This is related to atmospheric inverse radiation, that is, the atmosphere has a thermal insulation effect, the thicker the clouds at night, the stronger the atmospheric inverse radiation, and the slower the heat loss; On the contrary, if the night is clear, the heat preservation effect is poor, and the temperature is low, and the frost phenomenon appears.

2.The fire in the field is equivalent to increasing the thickness of the atmosphere, and the atmospheric inverse radiation is enhanced, which plays a role in heat preservation, which reduces the frost and mainly protects the crops.

3.If both day and night are sunny, the temperature difference is greater than if both day and night are cloudy. Or the insulating and weakening effect of the atmosphere.

That's because in autumn, the sun has deviated from its orbit and has become very far away from the place where it shines very closely. Resulting in very cold air. Frost will be produced.

Because late autumn has arrived at the frost of the solar term, there is a frost.

Frost is a relatively common agrometeorological disaster, which refers to the sudden drop in air temperature, and the surface temperature suddenly drops below 0, causing damage to crops and even death. Frost mostly occurs in winter and spring, and is mostly caused by cold waves moving southward and the temperature dropping sharply in a short period of time. Or after being affected by the cold wave, the weather turns from cloudy to sunny on the night, due to the strong radiation cooling of the ground, which is often said to be "worse".

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Why do frosts occur on cold nights?

Let the small society tell you!

**。This is because there are few clouds at night, the atmospheric inverse radiation is weak, the thermal insulation effect is poor, and the ground heat is dissipated quickly, and the temperature is generally not easy to drop below 0 in the first half of the night due to the more heat stored during the day. But in the second half of the night and before dawn, the ground emits a lot of heat, and the heat that is compensated by atmospheric radiation is very small, and the temperature drops quickly, when the temperature drops below 0, the water vapor in the air near the ground adheres to the earth, stones, leaves, grass and trees, tiles of low houses and other objects, and condenses into the hoarfrost of ice crystals.

If you have lived in the countryside or know about rural life, you will understand what kind of frost is a phenomenon, which is a relatively common agrometeorological disaster that occurs in winter and spring, and is usually caused by cold waves moving south. It usually occurs on the night of the day when the weather changes from cloudy to sunny. So why do frosts appear on clear nights?

What are the characteristics of frost damage? The following Baibai safety network will take you to understand these natural disaster safety tips.

Frost mostly occurs at night on sunny days, mainly due to the lack of clouds at night, weak atmospheric reverse radiation, and poor thermal insulation effect, so it is strongly cooled and prone to frost.

Frost is due to the cooling of air close to the ground to the frost point due to the radiative cooling of the ground.

That is, the surface temperature of the ground object or the ground temperature in the gas layer drops below zero, and the supersaturated part of the water vapor contained in it condenses on some objects with poor heat transfer performance on the ground to form white ice crystals. Its structure is loose. It is generally formed during the period of night to early morning in the cold season.

When formed, it is mostly a calm wind. Frost can sometimes occur in caves, in crevices in glaciers, and on snow surfaces. In the middle latitudes of China, where the four seasons are distinct, the late autumn to the second year of the early spring festival is the time before and after the beginning and end of winter, and the temperature at night can generally be reduced below 0.

In the clear night, because of the noisy clouds, the ground heat is dissipated quickly, and in the first half of the night, because the ground stores more heat during the day, the temperature is generally not easy to drop below 0. Especially in the second half of the night and before dawn, the ground emits a lot of heat, and the heat that obtains atmospheric radiation compensation is very little, the temperature drops very quickly, when the temperature drops below 0, the water vapor in the air near the ground adheres to the earth's clods, stones, leaves, grass and trees, tiles and other objects of the low house, and condenses into the hoarfrost of ice crystals.

Frost is mostly in the transition season between spring and autumn, and the temperature during the day is higher than zero degrees Celsius, and the temperature at night drops below zero for a short time. In agrometeorology, it refers to the phenomenon that the temperature on the soil surface or near the canopy of plants drops below zero degrees Celsius and causes damage to crops. When frost occurs, it is often accompanied by hoarfrost or without hoarfrost, and frost without hoarfrost is called "black frost" or "killing frost".

On a clear and windless night, the frost formed by radiative cooling is called "radiant frost". The frost deficiency formed by the invasion of cold air is called "advection frost". The frost formed by the combined action of the two processes is called "advection radiation frost".

No matter what kind of frost appears, it will bring more or less damage to the crop.

On a clear and windless night, the ground is low due to the strong radiation and heat dissipation, which is called "clear frost" or "quiet frost" by the masses, and meteorologically called radiation frost.

First of all, due to the invasion of strong cold air in the north, the temperature drops sharply, the night is clear after the wind stops, the radiation heat dissipation is strong, and the temperature drops again, causing frost, which is called mixed frost or Pingxiao quiet flow radiation frost, which is also the most common kind of frost.

Once this kind of frost occurs, the temperature is often drastic, the air is dry and cold, and it is easy for crops and garden plants to wither and die. Therefore, this kind of frost should be paid special attention to avoid serious economic losses.

Because when frost is formed, the requirements for ambient temperature are relatively high, and this kind of ambient temperature must reach a relatively low time before frost can really form. So if it is in a clear night, there is no white clouds at this time, and the ground stores enough heat during the day, then when there is no sun at night, the heat on the ground will be dissipated very quickly, and there is no cloud obstruction, and the heat on the ground will be dissipated very quickly. However, if there are clouds, then the weather will be in a relatively cloudy state, and the heat on the ground cannot be quickly lost through the clouds, so the temperature of the ground will be in a relatively high state, and it is difficult to freeze.

The existence of these hoarfrost is generally due to the low heat at night and the noise is at 0 degrees, or when it is around 0 degrees, if it is higher than such a temperature, even if there is more water vapor on the ground, it will not let them easily solidify into hoarfrost. But if the temperature reaches such a level, but there is not enough moisture, there is no way to successfully condense into hoarfrost. However, in the respiration of plants, water is formed.

In this state at night, plants can only respire, but cannot photosynthesize, so there is no way for this water to be fully converted into other energy, and the excess water will be emitted with the respiration of plants.

Although the moisture they emit is relatively lacking, if this moisture is placed in front of nature, this moisture can be said to be a relatively large existence, and it is very easy for people to use this moisture to condense frost. But keep it clear, because this will allow the night temperature to drop to a suitable condensation temperature.

Therefore, this is the reason why frosts in our country mostly occur in clear nights, and there is no way to have frost in the general cloudy nights.