How do Clouds form?

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Artist depiction of formation of clounds

A Cloud is a visible mass of water droplets of frozen ice crystals suspended in the Earth’s atmosphere above the surface of the Earth or other planetary body. Clouds in atmosphere are studied in the nephrology or cloud physics branch of meteorology. Two processes, possibly acting together, can lead to air becoming saturated with moisture: cooling the air and / or adding water vapor to the air. Whether or not a cloud is low, middle or high level depends on how far above the ground its base forms. Some cloud types, especially those with significant vertical extent, can form in the low or middle ranges depending on the moisture content of the air. Clouds have been observed on other planets and moons within the Solar system, but due to their different temperature characteristic, they are composed of other substances such as methane, ammonia or sulfuric acid.


Why are clouds white?

Clouds are white because they reflect the light of the sun. Light is made up of colors of the rainbow and when added together it gives white. The sun appears a yellow color because it sends out more yellow light than any other color. Clouds reflect all the colors the exact same amount so they look white.


How exactly does a cloud form?

Clouds require key atmospheric components to form. They are:

  • Water: Water molecules must have a surface on which to collect. The air is constantly full of water. When we look into the sky and see a cloud, it is actually moisture we are seeing. Most of the time water vapor in the air cannot be seen unless it collects and condenses to form a cloud.
  •  Dust particles: Clean air (without any dust or particles) will not produce clouds without super saturation (or relative humidity above 100%). Small particles in the air become surfaces on which water vapor can condense and forms cloud droplets which are known as cloud condensation nuclei. Sources of cloud condensation nuclei can be from nature and human-caused. The dust needed for the formation of clouds comes from the sources such as volcanoes, cars, sea spray from the ocean and fires. Other particles in the atmosphere, including bacteria can also play a major role in serving as condensation nuclei.
  •  Temperature or pressure changes: When temperatures and pressures decrease, the air cannot hold as much as water. The lower the temperature, the greater the condensation of gaseous water to liquid water.

So, once the stage is set, cloud formation happens as water joins together.


Why do clouds float?

A cloud is made up of liquid water droplets. A cloud forms when air is heated by the sun. As it rises, it slowly cools and reaches the saturation point and water condenses, forming a cloud. As long as the cloud and the air that it’s made of are warmer than the outside air around it, it floats.

How do clouds move?

Clouds move with the wind. The most common high clouds, the cirrus clouds are pushed along by the jet stream, sometimes travelling at more than 100 miles per hour. When clouds are part of a thunderstorm they usually travel at 30 – 40 mph.


What are the different types of clouds?

  •  Cirrus clouds: they are the most common high clouds. They are composed of ice and are thin, wispy clouds blown in high winds into long streamers. Cirrus clouds are usually white and predict fair to pleasant weather. They are above 18,000 feet.
  •  Alto clouds: Alto clouds are gray or blue gray midlevel clouds composed of ice crystals and water droplets. These clouds cover the entire sky. They are 6,500-18,000 feet.
  •  Stratus clouds: they are uniform grayish clouds that often cover the entire sky. They resemble fog that does not reach the ground. Light mist or drizzle sometimes falls out of these clouds. They are up to 6,500 feet.
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