Why is the temperature difference between day and night large, and it is easy to produce foggy weather?

The large temperature difference between day and night is easy to cause dense fog;

When the water vapor contained in the air reaches the maximum, it reaches saturation. The higher the temperature, the more water vapor is contained in the air. 1 m3 air, the maximum water vapor capacity is 6.36g at 4℃; When the temperature is 20℃, the maximum water vapor content in 1 m3 air is17.30g. If there is more water vapor in the air than saturated water vapor at a certain temperature, the excess water vapor will condense out. When there is enough water, it will combine with tiny dust particles in the air, and at the same time, water molecules themselves will combine with each other and become small water droplets or ice crystals. The water vapor in the air exceeds saturation and condenses into water droplets, which is mainly caused by the temperature drop.

If the ground heat is lost, the temperature drops, and the air is quite humid, then when it cools to a certain extent, part of the water vapor in the air will condense out and become many small water droplets suspended in the air layer near the ground. This is fog. Both it and clouds are caused by temperature drop, and fog can actually be said to be a cloud near the ground.

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 not many opportunities without Feng Yun, and the ground heat dissipation is faster than that in summer, which makes the ground temperature drop sharply, so that the water vapor in the air near the ground can easily reach saturation in the middle of the night, condense into small drops and form fog. The morning temperature in autumn and winter is the lowest and the fog is the thickest.

Dense fog: In spring and autumn and rainy season, under the influence of high-pressure backflow before the front, large-scale and long-lasting dense fog often appears. Dense fog will hinder visibility. If the visibility is less than 200 meters, it will affect land or sea traffic. The Meteorological Bureau will issue a "special report on dense fog" in areas or sea areas where dense fog appears.