Why is it foggy in the morning and at night?

Why is it foggy in the morning and at night?

Fog and clouds are water vapor condensates composed of small water droplets or ice crystals floating in the air, but fog is generated in the near layer of the atmosphere, while clouds are generated in the higher layer of the atmosphere. Since fog is water vapor condensation, we should look for its reason from the conditions that cause water vapor condensation. There are two reasons for water vapor saturation in the atmosphere: first, evaporation increases water vapor in the atmosphere; The other is the cooling of the air itself. Cooling is more important for fog. When there are condensation nuclei in the air, if water vapor continues to increase or melt, condensation will occur in saturated air. Fog is formed when condensed water drops reduce the horizontal visibility to less than 1 km.

You know, because the temperature is low in the morning and the second condition is met, fog is formed.

Why is there fog? What caused it?

When the visibility in the atmosphere is lower than 1 km due to the condensation of suspended water vapor, meteorology calls this weather phenomenon fog.

Generally speaking, there is a lot of fog in autumn and winter mornings. Why? We know that when the water vapor contained in the air reaches the maximum, it reaches saturation. The higher the temperature, the more water vapor is contained in the air. 1 m3 air, the maximum water vapor capacity is 6.36g at 4℃; When the temperature is 20℃, the maximum water vapor content in 1 m3 air is17.30g. If there is more water vapor in the air than saturated water vapor at a certain temperature, the excess water vapor will condense out. When there is enough water, it will combine with tiny dust particles in the air, and at the same time, water molecules themselves will combine with each other and become small water droplets or ice crystals. The water vapor in the air exceeds saturation and condenses into water droplets, which is mainly caused by the temperature drop.

If the ground heat is lost, the temperature drops, and the air is quite humid, then when it cools to a certain extent, part of the water vapor in the air will condense out and become many small water droplets suspended in the air layer near the ground. This is fog. Both it and clouds are caused by temperature drop, and fog can actually be said to be a cloud near the ground.

The temperature is higher during the day, so the air can hold more water vapor. But at night, the temperature drops and the capacity of water vapor in the air decreases, so some water vapor condenses into fog. Especially in autumn and winter, due to the long nights, there are not many opportunities without Feng Yun, and the ground heat dissipation is faster than that in summer, which makes the ground temperature drop sharply, so that the water vapor in the air near the ground can easily reach saturation in the middle of the night, condense into small drops and form fog. The morning temperature in autumn and winter is the lowest and the fog is the thickest.

The conditions for fog formation are cooling and humidification to increase the water vapor content. This is caused by radiation cooling, which often occurs at night and early morning when the water vapor near the ground is abundant and stable or there is inversion, which is called radiation fog in meteorology; The other is the fog formed by the horizontal movement of warm and humid air and the gradual cooling after passing through the cold ground or water surface, which is called advection fog in meteorology; Sometimes the fog formed by two reasons is called mixed fog. It can be seen that it is late autumn and early winter that meet these conditions, especially in the morning of late autumn and early winter.

We can also see evaporation fog. That is, cold air flows through warm water. If there is a big difference between the air temperature and the water temperature, a lot of water vapor will evaporate from the water surface, and the cold air near the water surface will condense into fog. At this time, there is often an inversion layer on the fog layer, otherwise convection will make the fog dissipate. Therefore, the evaporation fog has a small range and weak intensity, and generally appears around the pond in the second half of the year.

The smog in the city is caused by another reason, and that is human activities. Morning and evening are the peak hours of heating boilers. Under the condition of low air pressure and low wind speed, a large number of pollutants, such as smoke, suspended solids and automobile exhaust, are difficult to diffuse, and it is easier to form smoke (fog) when combined with water vapor in the lower air, and this smoke (fog) often lasts for a long time.

The fog dissipates because, firstly, the fog drops evaporate due to the warming of the underlying surface; Second, the wind speed increases, blowing the fog away or rising into clouds; Then turbulent mixing, water vapor upload, heat transfer, and evaporation of droplets near the ground.

The duration of fog is mainly related to the humidity of the local climate: generally speaking, the short fog in arid areas dissipates within 1 hour, while the long fog in humid areas is the most common and lasts for about 6 hours.

What is fog?

If the air near the ground is cooled to a certain extent under the conditions of sufficient moisture, breeze and stable atmosphere, the moisture in the air will condense into tiny water droplets suspended in the air, which will reduce the visibility of the ground. This weather phenomenon is called fog. Fog is more common in spring from February to April.

Visibility is lower than 1000 where air is condensed by suspended water vapor.

When rice is wet, meteorology calls this weather phenomenon fog.

Conditions for fog formation:

One is cooling, and the other is humidifying to increase the water vapor content.

Types of fog:

1. Radiation fog: It mostly appears at night and early morning when the sun is shining, the breeze is blowing gently, and the water vapor near the ground is rich and stable or the temperature is reversed.

2. advection fog: Warm and humid air moves horizontally, passes through the cold ground or water surface, and gradually cools to form fog, which is called advection fog in meteorology.

3. Mixed fog: Sometimes the fog formed by two reasons is called mixed fog.

4. Evaporation fog: that is, cold air flows through warm water. If there is a big difference between the air temperature and the water temperature, a large amount of water vapor will evaporate on the water surface, and the cold air near the water surface will condense into fog. ......

Why is it foggy in the morning?

There is a limit to the water vapor that can be contained in the air. When it reaches the maximum limit, it is called water vapor saturation. The higher the temperature, the more water vapor is contained in the air. For example, in the air of 1 m3, the maximum water vapor that can be accommodated is 6.36g at 4℃; At the temperature of 20℃, 1 m3 of air can contain at most17.3g of water vapor. If the air contains more water vapor than water vapor at a certain temperature, the excess water vapor will condense out and become small water droplets or ice crystals.

If there is 7.36 grams of water vapor in 1 m3 air at 4℃, the excess 1 gram of water vapor will condense into water droplets. So if the water vapor in the air exceeds saturation, it will condense into water droplets, which is mainly caused by the temperature drop.

The loss of ground heat will reduce the ground temperature, and at the same time, it will affect the air layer near the ground, so that the air temperature will also decrease. If the air layer near the ground is quite humid, then when it is cold to a certain extent, some water vapor in the air will condense out and become many small water droplets suspended in the air layer near the ground. If there are too many small water droplets in the air layer near the ground, which hinders people's sight, fog will form.

The temperature is generally higher during the day, and more water vapor can be contained in the air. But at night, when the temperature drops, the amount of water vapor that can be contained in the air decreases. If there was more water vapor in the air at that time, some water vapor would condense into fog. Especially in winter, due to the long nights, sunny days and low winds, the heat dissipation on the ground is faster than that in summer, and the temperature near the ground drops sharply, so that the water vapor in the air layer near the ground can easily reach saturation, supersaturation and condense into small water droplets from midnight to morning, and float in the air near the ground to form fog. Therefore, it is often foggy in sunny mornings in winter. This fog meteorology is called "radiation fog".

Why is there fog after rain?

Fog is the condensation phenomenon of water vapor in the air near the ground. There are two basic conditions for the formation of fog. One is that the air near the ground is rich in water vapor, and the other is that the ground temperature is low. There is a lot of water on the ground after the rain, which is evaporated, and the temperature is still low after the rain, so it constitutes a condition. The following are the classification and formation reasons of various fogs: the most common fog on land is radiation fog: this kind of fog is formed because the air is supersaturated by radiation cooling, which mainly appears in sunny, breezy, near the ground and in the morning with abundant water vapor. At this time, there is no cloud cover in the sky, the ground heat radiates rapidly, and the temperature near the ground layer drops rapidly. If there is too much water vapor in the air, it will soon reach supersaturation and condense into fog. In addition, the wind speed also has a certain influence on the formation of radiation fog. If there is no wind, there will be no exchange between the upper and lower air, and the radiation cooling effect only occurs in the air layer near the ground, which can only produce thin shallow fog. If the wind is too strong, the upper and lower air exchange is fast and the flow is large, and the temperature is not easy to drop a lot, it is difficult to achieve supersaturation. Only when there is a breeze of L-3m/s, communication with appropriate intensity can not only extend the cooling effect to a certain height, but also not affect the full cooling of the lower air, so it is most conducive to the formation of radiation fog. Radiation fog appears on a clear and cloudless night or morning. As soon as the sun rises, the air will return to unsaturated state with the increase of ground temperature, and the fog drops will evaporate and dissipate immediately. Therefore, the appearance of radiation fog in the morning often indicates a sunny day. "Morning fog covers the ground, although it dries rice" and "ten fogs and nine sunny days" refer to this kind of radiation fog. The second kind of fog is advection fog: when warm and humid air flows through the cold ocean or land, the fog condensed in the lower layer of the air due to contact cooling is advection fog. As long as there is a suitable wind direction and speed, once the fog is formed, it often lasts for a long time. If there is no wind, or the wind direction changes, the source of warm and humid air flow is interrupted, and the fog will dissipate immediately. The third kind of fog is steam fog: if the water surface is warm and the air is cold, when the temperature difference between them is large, the water vapor will continuously evaporate from the water surface, break into the cold air, and then condense out of the cold air to become steam fog. Generally, the warm ocean currents in the south enter the polar regions, and the cold air in the polar regions will cover the warm water surface and form steam fog. For example, there is a strong Gulf Stream warm ocean current in the North Atlantic Ocean, which often rushes into the Arctic Ocean, causing a large area of steam fog on the surface of the Arctic Ocean. Sometimes, the cold air in the Arctic stays on the ice, where the ice cracks, the warmer water under the ice is exposed, forming a regional steam fog, which mostly appears in the high latitude Arctic region, so people often call it "Arctic smoke". In addition to the polar regions, cold air often covers warm water in inland lakeside areas. At night, the lake is warmer than the land surface. When the land breeze blows to the warm lake at night, relatively shallow steam fog will form on the lake. In autumn and winter, whenever the cold air goes south, in the clear Wan Li and windy morning, when the warm water surface has not had time to cool down, this steam fog will diffuse. The fourth kind of fog is uphill fog: this is the fog produced by humid air rising along the hillside and adiabatic cooling to supersaturate the air. This humid air must be stable and the slope of the hillside must be small, otherwise convection will form and it is difficult to form fog. The fifth kind of fog is frontal fog: it often occurs near the front where cold and warm air meet. Before and after, but mostly near the warm front. The fog in front of the front is formed because the raindrops in the warm air cloud above the front fall into the ground cold air and evaporate, which makes the air supersaturated and condensed. The fog behind the front is formed by warm and humid air moving to the area originally occupied by cold air before the warm front and cooling to supersaturation. Because the fog near the front often moves with the front, the army often uses this frontal fog to cover the troops and make sudden attacks on the enemy. Other Fogs: With the development of modern industry, many new fogs have been added. For example: photochemical smog formed by industrial waste gas, black smog emitted by boilers, kilns and small coal stoves.

Why is there fog?

When water vapor is cold, it liquefies into small water droplets and adheres to the surface of objects.

Why is it foggy in summer?

When the visibility in the atmosphere is lower than 1 km due to the condensation of suspended water vapor, meteorology calls this weather phenomenon fog.

The air contains more water vapor than saturated water vapor at a certain temperature, and the excess water vapor will condense out. When enough water is combined with tiny dust particles in the air, water molecules themselves will also combine with each other and become small water droplets or ice crystals. The water vapor in the air exceeds saturation and condenses into water droplets, which is mainly caused by the temperature drop.

If the ground heat is lost, the temperature drops, and the air is quite humid, then when it cools to a certain extent, part of the water vapor in the air will condense out and become many small water droplets suspended in the air layer near the ground. This is fog.

Fog is closely related to the temperature and humidity of the sky and the ground. Generally speaking, there is a lot of fog in autumn and winter morning, but it will also fog in summer with large temperature difference.

Why does the mirror fog?

In winter, when people enter the house from the outside, the temperature of the mirror is low, while the temperature of indoor water vapor H2O is high, so the water vapor around the mirror will condense into small water droplets and adhere to the mirror, so the mirror will fog.

I hope I can help you. If you feel good, please adopt it!

Why is it sometimes foggy on rainy days? What is the reason for the fog?

There are many water molecules in the air on rainy days. When there are many tiny dust in the air, these dust will mix with water molecules and then form what you call fog.

Why is there fog?

Fog is formed in the atmosphere near the ground. It is sunny and windy during the day, the ground is radiated by the sun, the temperature is high, and the water vapor on the ground evaporates, so it is difficult to reach saturation of water vapor in the atmosphere. At night, it was calm and the ground temperature gradually decreased. Because the air near the ground is cooled to the dew point temperature by the radiation of the ground, if the humidity in the atmosphere near the ground is high, the water vapor will be saturated, and the remaining large amount of water vapor will condense into many small water droplets or ice crystals, suspended in the low altitude near the ground. These little drops of water are swimming around at low altitude. When the visibility is around 1000 meters, it is called "fog". This fog formed by ground radiation is called "radiation fog" in meteorology. Fog can be divided into light fog, ordinary fog, dense fog and dense fog. Generally speaking, the visibility of light fog is above1000m, and that of ordinary fog is within1000m. When the visibility decreases to 50 ~ 100 meters, it is called fog, and when the visual distance is less than 50 meters, it is called fog.