There are signs of fog in winter.

The fog in winter indicates that it is sunny that day.

In autumn and winter, after the cold air in the north goes south, as the weather turns fine and sunny, the moisture content in the air gradually increases, which is easy to form radiation fog, so the fog in autumn and winter can often predict the good weather tomorrow. The temperature is higher during the day, so the air can hold more water vapor. But at night, the temperature drops and the capacity of water vapor in the air decreases, so some water vapor condenses into fog.

Especially in autumn and winter, due to the long nights, there are many opportunities for Feng Yun, and the ground heat dissipation is faster than that in summer, which leads to a sharp drop in ground temperature. In this way, the water vapor in the air near the ground can easily reach saturation in the middle of the night, condense into small water droplets and form fog. The morning temperature in autumn and winter is the lowest and the fog is the thickest.

Introduction of fog

Fog is a common weather phenomenon, which refers to water vapor condensate composed of water droplets or ice crystals suspended in the near-surface atmosphere. When the temperature reaches the dew point temperature (or near the dew point temperature), the water vapor in the air condenses to form fog. The difference between fog and clouds is that clouds are produced in the upper atmosphere, while fog is close to the surface.

There are several different types of fog according to the cause of condensation. When the temperature is above freezing point, water vapor condenses into water droplets. When the temperature is below freezing point, water vapor condenses directly into solid ice crystals, such as ice fog. Because dew point is only affected by air temperature and humidity, there are two main reasons for the formation of fog. First, the water vapor in the air increases greatly, which makes the dew point temperature rise, thus forming fog, such as steam fog and frontal fog. Second, when the temperature drops below the dew point, fog is generated, such as advection fog and radiation fog.