What is the relationship between cloud and water?

We are no strangers to clouds. White in sunny days and black in rainy days are called clouds. They make the sky unpredictable. People often see that the sky is sometimes blue and cloudless, sometimes white clouds are blooming, and sometimes dark clouds are gathering. Why sometimes there are clouds in the sky and sometimes there are no clouds? How are clouds formed? What is it made of?

Clouds floating in the sky are composed of many tiny water droplets or ice crystals, some of which are mixed together. Sometimes it also contains some big raindrops and ice particles. The bottom of the cloud does not touch the ground and has a certain thickness.

The formation of clouds is mainly caused by water vapor condensation.

More than ten kilometers from the ground, the closer to the ground, the higher the temperature and the denser the air; The higher the altitude, the lower the temperature and the thinner the air.

On the other hand, the water surface of rivers, lakes and seas, as well as the moisture of soil, animals and plants, evaporate into the air at any time and become water vapor. After water vapor enters the atmosphere, it turns into clouds to cause rainfall, or condenses into frost dew, and then returns to the ground, permeates the soil or flows into rivers, lakes and seas. Later it will evaporate (vaporize) and then condense (condense) and drop. It goes on and on.

After the water vapor enters the lower atmosphere from the evaporation surface, the temperature here is high and there is much water vapor. If the hot and humid air is lifted, the temperature will gradually decrease, and when it reaches a certain height, the water vapor in the air will reach saturation. If the air continues to be lifted, there will be excess water vapor. If the temperature there is higher than 0℃, the excess water vapor will condense into small water droplets; If the temperature is lower than 0℃, excess water vapor will condense into small ice crystals. When these small water droplets and small ice crystals gradually increase to a level that can be recognized by human eyes, it is a cloud.