What are the weather symbols of the three bars?

According to the weather forecast platform, three horizontal lines indicate fog. When the relative humidity reaches 100%, the water vapor in the air will condense into fine water droplets suspended in the air, which will reduce the visibility on the ground. This weather phenomenon is called fog. Most of them appear between February and April in spring. The forming conditions are cooling and humidification to increase the water vapor content. There are radiation fog, advection fog, mixed fog and evaporation fog. This weather phenomenon often brings disasters to aviation, navigation and road transportation.