What weather do the three horizontal lines represent?

In the weather forecast, the icon of three wavy lines is dense fog.

Fog is a natural phenomenon, which is common in autumn and winter. The formation principle of fog is to condense water vapor in the air into fine water droplets suspended in the air, which reduces the horizontal visibility of the ground. To form fog, it is necessary to reduce temperature, humidify and increase water vapor content.

There are many kinds of fog, radiation fog and advection fog. The straight line is generally because there is an obvious front (the cold and warm peaks are obvious), while the curve is that the cold and warm peaks are not obvious.

Extended data:

1. When observing a certain weather phenomenon, meteorological observers should record the corresponding symbols in the "Weather Phenomenon" column of the observation record book of the day, and record the start and end time at the same time. Based on these symbols, combined with the intensity, coexistence and some characteristics of weather phenomena, a group of symbols that can be filled in weather maps are called cartographic symbols.

2. Weather symbols are a set of graphic images representing weather phenomena, which are easy for the public to understand and identify, and are used by TV or other public media.