What is the symbol for fog?

In weather forecasts, "fog" is represented by three horizontal lines.

When the air holds the maximum amount of water vapor, it is saturated. The higher the temperature of the air, the more water vapor the air can hold. When the temperature is 4°C, 1 cubic meter of air can hold up to 6.36 grams of water vapor; when the temperature is 20°C, the maximum amount of water vapor that can be contained in 1 cubic meter of air is 17.30 grams.

If the air contains more water vapor than the saturated amount of water vapor at a certain temperature, the excess water vapor will condense out. When enough water molecules combine with the tiny dust particles in the air, At the same time, the water molecules themselves will stick to each other and become small water droplets or ice crystals. The water vapor in the air exceeds the saturation level and condenses into water droplets. This is mainly caused by the drop in temperature. This is also the reason why mornings in autumn and winter are foggy.

Extended information:

Types of fog:

1. Radiation fog is mostly formed at night when it rains or turns cloudy to clear. The main cause is that radiation cooling causes low-level The humidity increases and reaches saturation;

2. Advection radiation fog is mostly formed on the eve of sunny to cloudy days. The main causes are radiative cooling and advection humidification;

3. Advection radiation fog is formed on the eve of sunny to cloudy days. The main cause of rainy weather with high temperature and high humidity or the early stage of rainy weather is high advection humidity.