Why is it sunny even when the weather forecast is cloudy?

Fog is clouds on the ground, and clouds are fog in the sky. Because clouds and fog are both formed by the condensation of water vapor in the air after being cooled, they just appear in different locations. Clouds float in the sky and fog covers the ground.
What is the specific content of "many aspects"?
To accurately see the fog and know the sky, you must contact the weather before the fog. As the saying goes: "If it is clear for a long time, it will be foggy and rainy, if it is raining for a long time, it will be clear." Because it is clear for a long time, the air contains less moisture. Even if the temperature drops at night, there will generally not be heavy fog. If there is heavy fog, it is something else: The warm and humid air from the local area invades silently, forming advection fog, and the weather in the future will turn to rainy. On the contrary, there is plenty of moisture in the air after a rain. Because the clouds cover the earth like a quilt, the ground heat is not easy to dissipate. The temperature drops at night and the temperature difference is not large, so fog cannot form. If there is heavy fog, which is a typical radiation fog, it is a fog formed because the clouds in the sky break up at night, causing the ground to cool down strongly, and the weather is about to clear up.
To accurately see the fog in the sky, you must look at the density of the fog. Radiation fog is in the surface air. It is made of water vapor, so it is relatively light. You can see the blue sky through the fog; advection fog is caused by the cooling of a large area of ​​warm and humid air, and it looks relatively dense. The thickness of this fog has a lot to do with the weather. It is based on this relationship that people summed up their experience: "If the fog is small, the sky will be fine; if the fog is thick, there will be strong winds; if the fog is heavy, the rain will be fierce; if the fog is light, the sky will be sunny the next day." Depends on the color of the fog. Because radiation fog is relatively thin, it looks like a layer of milky white gauze; advection fog is relatively thick, and there are often clouds above it, which does not allow sunlight to pass through, making it look gray. "It's white and foggy, and it's gray and foggy" is exactly what it says.
To accurately understand the fog, you must also look at the duration of the fog. Radiation fog is caused by the condensation of water vapor due to cold weather. Therefore, as soon as the temperature rises during the day, it will disappear and the weather will be fine; otherwise, "if the fog persists, it will rain." If the fog does not dissipate during the day, it may be rainy the next day. Therefore, the folk proverb says: "The fog does not last until noon. After noon, you can hear the sound of rain."
Why is it the same fog, some indicate rain, and some What about the clear sign?
This needs to be explained from the knowledge of meteorology. As long as there is a large amount of water vapor in the lower air, the water vapor will condense into fog when the temperature drops sharply at night. Fog includes radiation fog, which is fog formed under relatively clear and stable conditions. As long as the sun comes out and the temperature rises, the fog will disappear naturally. In this regard, the folk saying is: "The fog is thick in the early morning, and the weather will be clear for a long time." "The sun is shining in the fog, and the sun is shining on the rocks." "The ground is covered with fog in the morning, so you can dry the rice." When people see radiation fog, they often say "ten fogs" Jiuqing". This leads to these statements.
In autumn and winter, after the cold air from the north moves southward, as the weather clears and the sun shines, the moisture content in the air gradually increases, easily forming radiation fog. Therefore, fog in autumn and winter can often pre dict good weather tomorrow. .
The fog in spring and summer is different. Most of it comes from the warm and moist air flow from the sea. When it hits the colder ground, the lower air also becomes colder, and the water vapor condenses into fog. This kind of fog is called advection fog. It is formed when warm and moist air from the sea invades the continent and suddenly encounters cold. When these warm and moist air currents meet the dry and cold air from the continent, it will naturally become cloudy and rainy. Therefore, fog in spring and summer indicates cloudy and rainy weather.
Fog is ever-changing and complex, but it is nothing more than radiation fog and advection fog. Although the phenomena are diverse, the essence is the same: water vapor condenses when it encounters cold. Sometimes the fog is forecast to be sunny, and sometimes the fog is forecast to be rainy, which seems confusing. However, as long as you master the characteristics of radiation fog and advection fog, observe from multiple parties, and analyze carefully, you can accurately grasp the laws of fog, clear skies, and falling rain. To pre dict the weather. This is useful for agriculture, transportation, aerospace, and navigation.
Fog is closely related to future weather changes. Since ancient times, the working people of our country have understood this truth, and it is reflected in many folk proverbs. For example: "There is fog in Huangmei, and you can row the boat without asking for directions." This means that the fog at the turn of spring and summer is the harbinger of rain, so there is also a folk saying of "summer fog and rain". Another example: "It's foggy and no one can be seen, so I dare to wash my clothes." This means that winter fog heralds sunny days, and so does autumn fog.