Why is there fog before sunrise?

Why is there fog before sunrise? In life, many people will find that getting up early in the morning is prone to fog, and sometimes there will be heavy fog, which will not only affect our vision, but also affect flights and high-speed rail. So why is there fog before sunrise?

Why is there fog before sunrise? 1 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. We know that because the sun shines on the ground during the day, a lot of water will evaporate, so that water vapor will enter the air and the ground will absorb a lot of heat.

In the evening, after the sun went down, the heat absorbed by the ground began to radiate to the sky, and the air temperature near the ground also decreased. The clearer the weather, the less clouds in the sky, the faster the ground heat radiation and the lower the temperature drop.

In the middle of the night and in the morning, the air temperature near the ground has dropped very low. At this time, even indoors, we will feel much cooler than the first half of the night. When the temperature near the ground drops, the water vapor in the air exceeds the saturation state, and the excess water condenses into tiny water droplets, which are distributed at low altitude to form fog. So when the sun comes out during the day, the ground temperature rises, the air temperature rises, and the capacity of water vapor in the air increases, and the fog will gradually dissipate.

Fog and clouds are caused by the drop of temperature, so fog can actually be said to be a cloud near the ground.

What is fog?

Scientifically speaking, "mass fog" is also fog in essence. Due to the influence of local microclimate environment, the fog appearing in the local range of tens to hundreds of meters in fog is more "thick" and the visibility is lower. If the line of sight is good outside the fog, it will be hazy inside. The prediction of large fog is difficult and regional, and it is easy to cause major traffic accidents. Compared with the urban areas, the suburbs and rural areas are more prone to fog, especially the relatively empty expressway section.

In autumn and winter, the temperature difference between day and night is large, there is no wind at night, or it is more prone to fog from 6: 00 to 8: 00 in the morning. The areas where it appears are generally low-lying and the air humidity is high.

Ten expressway that are prone to fog.

Shanghai-Kunming Expressway, Beijing-Hong Kong-Macao Expressway, Shanghai-Chongqing Expressway, Hangrui Expressway, Shenhai Expressway, Beijing-Kunming Expressway, Xiamen-Chengdu Expressway, Beijing-Taiwan-Macao Expressway, Yin Fu Expressway and Baomao Expressway.

Why is it foggy before the sun comes out? 2. The water in the air meets the fog formed by cold air condensation.

If the air near the ground is cooled to a certain degree, the water vapor in the air will condense into fine water droplets and be suspended in the air under the condition of sufficient water vapor, breeze and stable atmosphere.

In autumn and summer, there is much fog in the morning, the water vapor in the air exceeds saturation, and the temperature of condensed water is higher during the day, so the air can hold more water vapor. But at night, the temperature drops and the ability to hold water vapor in the air decreases. Therefore, some water vapor will condense into fog.

Especially in autumn and summer, due to the long nights, there are many opportunities for Feng Yun, and the ground heat dissipation is faster than that in summer, which leads to a sharp drop in ground temperature. In this way, the water vapor in the air near the ground can easily reach saturation from midnight to morning, condense into small water droplets and form 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.

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 summer, 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, making it easy for the water vapor in the air near the ground to reach saturation in the middle of the night, condense into small water droplets and form fog. In autumn and summer, the temperature is the lowest and the fog is the thickest in the morning. This is the reason for the fog in the morning.

Why is it foggy in the morning, and it must be sunny after clearing up?

The fog in the morning is the product of radiation and heat dissipation on the ground last night: due to the clear sky, the heat on the ground spreads smoothly all night, and the water vapor in the ground air becomes saturated and condenses into fog drops. You can see that the weather will clear up first, and then it will be foggy. Morning is the lowest temperature between day and night. Because the temperature is coldest, the fog is thickest at this time. In addition, as soon as the sun comes out, some oxygen in the air becomes ozone because ultraviolet rays shine on it.

This small amount of ozone will make a lot of dust (mostly combustion products, such as carbon dioxide, sulfur dioxide and so on) in the air. ) enhance your water absorption ability. So the fog curtain suddenly became thicker in the morning. But the sun rises, the heat intensifies, the ground becomes too hot, and the air in the lower layer will rise, so the fog drops will dissipate. In this way, the fog in the morning temporarily thickens, which is also the result of clear skies and sunny weather in Wan Li.

Why is it foggy before the sun comes out? Fog and clouds are caused by the drop of temperature. The water on the earth evaporates and flies into the air, and condenses and stores to form clouds. If the water vapor is cold at low altitude near the earth, it will freeze into small water droplets, and when it is stored together, it will become fog. So fog can actually be said to be a kind of cloud close to the earth.

People often see two kinds of fog: radiation fog and advection fog. Radiation fog mostly occurs in sunny mornings in summer, because the temperature is generally high during the day, but the temperature drops at night, and the water vapor that can be contained in the air decreases. If there was more water vapor in the air at that time, one side of the water vapor would freeze into fog.

Especially in summer, because the nights are long, the weather is clear and the wind is weak, the earth radiates heat faster than in summer, and the temperature near the ground drops sharply, which makes the water vapor in the air layer near the ground easily reach saturation and freeze into small water droplets from midnight to early morning, floating in the air near the ground, thus forming fog.

So it is often foggy in the early morning of summer. This fog is called radiation fog. "There is also a kind of advection fog, which mostly occurs in spring and summer. When warm air flows through the cold ocean or land, the temperature drops, the water vapor freezes, and fog forms in coastal areas.

Fog appears in the early morning of summer, when the sky is usually clear. This is because the sun shines on the earth during the day and the earth accumulates a lot of heat. Due to the evaporation of water, the air with higher temperature can also contain more water vapor than the water vapor in the air. After the sun goes down, the heat is first released into the air, and the air temperature near the earth is also low. The better the sky, the less clouds there are, and the heat of the earth is not hindered. The faster it is released, the lower the temperature.

By midnight and early morning, the temperature of the earth's air has dropped to a very low level. At this time, even indoors, we can easily feel much colder than last midnight. When the air temperature near the earth is low, the water vapor in the air exceeds the saturation state, and the excess water vapor freezes into fine water droplets and spreads at low altitude. This kind of fog is usually produced under high pressure.