How are clouds formed?

Clouds are the tangible result of the huge water cycle on the earth. The sun shines on the surface of the earth, and water evaporates to form water vapor. Once the water vapor is supersaturated, water molecules will gather around the dust (condensation nucleus) in the air, and the generated water droplets or ice crystals will scatter sunlight in all directions, thus generating clouds.

Clouds absorb heat from the ground and reflect it back, which helps to keep the earth warm. However, clouds also reflect sunlight directly back into space, which has a cooling effect. Which effect is dominant depends on the shape and location of the cloud.

In the atmosphere more than ten kilometers from the ground, the closer to the ground, the higher the temperature and the richer 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, evaporates into the air and becomes 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.

Extended data

Long-term observation and practice show that the generation and dissipation of clouds, as well as the evolution and transformation between various clouds, are carried out under certain water vapor conditions and atmospheric movement conditions. People can't see water vapor or atmospheric movement, but we can see every move of water vapor and atmospheric movement from the evolution of clouds, and water vapor and atmospheric movement play an extremely important role in weather phenomena such as rain, snow, freezing hail.

For thousands of years, the working people in our country have summed up the rich experience of "knowing the sky by observing the clouds" according to the changes in the shape, direction, moving speed, thickness and color of clouds in production practice, and compiled these experiences into proverbs.

1, "Hook cloud is hanging in the sky and raining on the ground": Hook cloud refers to a hooked cirrus cloud. Behind this cloud, there are often fronts (especially warm fronts), low pressure or low pressure troughs moving, which indicates that rain is coming;

2. "Battery cloud, rain": Battery cloud refers to fort-shaped altocumulus cloud or fort-shaped stratocumulus cloud, which appears in front of the trough with low pressure, indicating that the air is unstable, and thunderstorms usually come every 8- 10 hours.

3. "Clouds pass through clouds, and it's raining": Clouds pass through clouds, which means that the moving directions of upper and lower clouds are inconsistent, that is to say, the height and wind direction of clouds are inconsistent, which often occurs near the front or low pressure, so it indicates rain, and sometimes the wind direction of clouds is opposite to the ground, so there is a saying that "if you go against the wind, the sky will change".

Baidu Encyclopedia-Cloud