What kind of climatic conditions fog is easy to form

Water vapor condenses when cold air passes, and fog tends to form in the morning. Due to the increase in air pressure, it must be a sunny day.

Only three conditions are required for the formation of fog: a light breeze, sufficient water vapor, and near-surface air to form a stable layer that is cold at the bottom and warm at the top.

The meteorological conditions for the formation of fog are light breezes and sufficient water vapor, that is, the water vapor content in the atmosphere reaches more than 90% to 100%, and is accompanied by condensation, producing fog droplets. Third, the near-surface air forms a stable layer that is cold at the bottom and warm at the top, or an inversion layer, with poor air fluidity.

Fog generally occurs at night and early in the morning when it is clear, breezy and relatively abundant and stable near the ground, that is, it has the meteorological conditions to form fog. There are fogs formed by various meteorological conditions, such as radiative fog formed by radiative cooling; the other is advection fog formed by the horizontal movement of warm and moist air, passing through the cold ground or water surface, and gradually cooling; Sometimes fog formed by both causes is called mixed fog. There are also frontal fog, slope fog, etc.

Pay attention to safety when traveling on foggy days.

1. The speed and visual distance of the vehicle should not be underestimated. Visibility is low in foggy weather, so slow down, strictly follow the traffic rules, and don't drive fast. The shorter the viewing distance, the lower the speed must be.

2. Reasonable use of front and rear headlights and fog lights, when the fog is very thick, you can turn on the double flashing lights to move forward. But don't turn on the high beams, the high beams are easy to cover the fog lights and enter the driver's line of sight, causing other drivers to obstruct their vision, forming a white expanse in front of the car, and nothing can be seen when driving.

3. Honk the horn frequently to indicate your position. Visibility is low in foggy days, the horn penetrates the air strongly, and the propagation of sound indicates that there is a car ahead. You can also alert pedestrians on the road that a car is coming, and pay attention to evasion.

4. On foggy days when you can't distinguish the distance between cars, don't slam on the brakes. Rear-end collisions are very likely to occur on foggy days. If you have to brake suddenly, try applying the brakes gently and gradually.

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.

Fog forms when these three conditions occur at the same time, one is cooling, the other is humidification, and the third is condensation nuclei, which increases the water vapor content. Fog occurs at night and early in the morning when it is clear, breezy, and has abundant and stable near-surface water vapor, or there is a temperature inversion, and this fog is also known as radiation fog.

There are also several types of fog, including radiant fog produced at night or early in the morning when it is sunny and water vapor is abundant, and there is also a large amount of vehicle exhaust in the city, and the smoke and smoke produced by the combination of industrial dust pollution and water vapor in the air.

The cause of fog formation is that when the air holds the maximum amount of water vapor, it reaches saturation. And the higher the temperature of the air, the more moisture can be contained in the air. If the air contains more water vapour than the amount of saturated water vapour at a certain temperature, the excess water vapour will condense and when enough water molecules combine with the tiny dust particles in the air, they will become small water droplets or ice crystals, also known as fog.

The conditions required for fog formation are cooling, humidification, and 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.