What are the main conditions for the formation of fog, what are its types and causes, and analyze th

Conditions for the formation of fog.

One is cooling, the second is humidification, and the third is condensation nuclei to increase the water vapor content. A kind of fog is formed by radiative cooling, mostly in the night and early morning when it is clear, breezy, and the water vapor near the ground is relatively abundant and stable, or there is a temperature inversion, which is called radiant fog in meteorology; The other is the fog formed by the horizontal movement of warm and moist air, passing through the cold ground or water surface, and the water vapor in the air is gradually liquefied by cold, which is called advection fog in meteorology; Sometimes fog formed by both causes is called mixed fog. It can be seen that these conditions can be met in late autumn and early winter, especially in the morning of late autumn and early winter.

Smog in cities is caused by another cause, and that is human activity. Morning and evening are the peak period of heating boilers, and a large number of pollutants such as smoke and dust suspended solids and automobile exhaust are not easy to diffuse under the conditions of low air pressure and low wind, and combine with the water vapor in the low-level air, which is relatively easy to form smoke (fog), and this smoke (fog) often lasts for a long time. For example, London, which is known as the "fog capital" (Note:

London is no longer prone to severe smog).

The reasons for the dissipation of fog are, firstly, due to the heating of the underlying surface, the fog droplets evaporate; Second, the wind speed increases, blowing away the fog or lifting it into clouds; Then there is turbulent mixing, water vapor is transferred, heat is transferred downward, and near-surface droplets evaporate.

The duration of fog is mainly related to the dry and wet local climate: generally speaking, the fog is mostly short in arid areas, which mostly dissipates within 1 hour, while the long fog is most common in humid areas, which can last about 6 hours.

For a detailed explanation, see the encyclopedia.

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Fog can be divided into five categories according to the causes of formation: 1. Radiation fog: formed due to the supersaturation of radiative cooling on the ground, mainly occurring at night or in the morning when the ground is clear, breezy, near the ground, and water vapor is relatively abundant. 2 Advection Fog:

Advection fog is formed when warm, moist air flows through a cold sea or land surface, and the lower layers of the air are supersaturated by contact cooling. 3. Steam mist: If the water surface is warm and the air is cold, when they have a large temperature difference, the water vapor will continue to evaporate from the water surface, break into the cold air, and then condense from the cold air to become a vapor mist.

4 Uphill fog: Fog produced by moist air rising along the hillside and adiabatic cooling to supersaturate the air. This moist air must be stable and the slope of the hill must be small, otherwise convection will form and fog will be difficult to form.

5 Frontal fog: Frequently occurs near the front where cold and warm air meet. The conditions required for fog formation are cooling, humidification, and condensation nuclei to increase the water vapor content.

Fog is formed under the condition of cooling and humidification to increase the water vapor content, and the fog that occurs at night and early in the morning is called radiation fog; The fog formed by the horizontal movement of warm, moist air passing through the cold ground or water surface and gradually cooling is called advection fog; The fog that occurs at the same time for both causes is called mixed fog.

Vapor mist, advection fog, radiant fog, uphill fog, and evaporative fog. Water vapor, condensation nuclei, cold air, and atmospheric stability. When the air near the ground is cooled, the water vapor is easy to reach saturation, and the vertical temperature distribution of the cold and the warm at the bottom forms an inversion, and the fog is naturally generated.

Fog is a collection of tiny water droplets or ice crystals attached to a large number of suspended particles near the ground. The formation conditions are low temperature layer humidity and cooling conditions. According to fog, it can be divided into radiation fog, advection fog, mixed fog and comprehensive fog.

Preliminary analysis of the causes of fog.

In general, the types of fog are different, and the reasons for their formation are also significantly different. For example, radiation fog is mostly formed in rainy and cloudy nights, and the main cause is that the humidity of the lower layer increases and reaches saturation due to radiative cooling. Advection radiation fog is mostly formed on the eve of sunny to cloudy weather, and the main causes are radiative cooling and advection humidification. Advection fog is formed in the rainy weather with high temperature and high humidity or in the early stage of rainy weather, and the main cause is that the humidity of the advection is very high. The best meteorological elements associated with the formation of radiation fog and advection radiation fog are wind speed, cloud cover, humidity conditions, and especially wind speed.

In the case of similar weather conditions, if the humidity conditions and cloud cover conditions in the adjacent station area are similar, the main difference between fog and no fog is the difference in wind speed. The wind speed is too high, and there is often no radiation fog and advection radiation fog. The wind speed is related to the topography, in a large number of regional dense fog samples, in most cases, on the ground map at 14 o'clock in the afternoon of the same day, if northern or central Jiangxi are located in the front and bottom of the high pressure, and the ground south of the river is in the clear sky area with weak northerly winds, the radiation fog generated the next morning and advection-flow radiation fog have the characteristics of Poyang Lake area and the eastern part of Jiujiang area (except Lushan) due to the open and flat wind speed and less fog, and more fog on both sides of the lake area.

Sometimes there are more on the west side, sometimes there are more on the east side. The reason for more or less depends on the cloud cover of each site. The clear and cloudless and fog-free lake area has wind speeds of 3 m s more on both sides.

1. The conditions for the formation of fog are cooling, humidification, condensation nuclei, and increasing water vapor content; The main reason is that the heat loss on the ground, the temperature drops, and the air is quite humid, when it cools to a certain extent, a part of the water vapor in the air will condense and become many small water droplets, suspended in the air layer near the ground.

2. Experiments have proved that when white light shines on a transparent object, the light it transmits is mainly the light of the same color as the transparent object, and other colors are absorbed by the transparent body. If a transparent object can transmit light of all colors, then the transparent object is colorless, such as ice.

However, when the water turns into fog, many reflective surfaces are formed. At this time, the light cannot pass through, but is reflected, that is, the light of various colors is reflected, so the fog becomes white.