All About Clouds for Middle School Science

Feb 20

3 min read

Clouds are an important part of the water cycle. Clouds are how liquid water moves through the atmosphere. This blog post will teach you all about how clouds form, the different types of clouds, and how clouds affect the Earth.

If you would like a copy of the picture book, you can get it along with the reading passage, flashcards, and comprehension activities at Teachers Pay Teachers.

Clouds

Clouds are collections of water droplets and ice crystals floating in the sky. The water droplets in the atmosphere come from water that evaporated from the surface of the Earth. Around 80% of the evaporating water comes from oceans.

Liquid water evaporates and becomes water vapor, a colorless gas. Rising warm air carries the water vapor higher in the atmosphere. Warm air can hold more water vapor than cold air, and as the warm air rises, it cools. As a result, some of the water vapor in the air condenses back into liquid water.

Tiny drops of liquid water evaporate easily, so they are unlikely to form clouds. However, when water vapor condenses onto a piece of dust, it gathers with other drops of water and will not quickly evaporate. Scientists call the tiny particles of dirt, salt, or smoke in the atmosphere condensation nuclei because they are the key to making clouds. All of the water droplets that condensed around the particles join together to form a cloud.

While clouds float in the air, they are extremely heavy. The average cumulus cloud can hold over one million pounds of water. These massive clouds float because they have a large amount of surface area, and the rising warm air pushes them up.

Most clouds are white because the water droplets and ice crystals scatter the seven wavelengths that make up visible light, including red, orange, yellow, green, blue, indigo, and violet. The scattering of all seven wavelengths results in white light. Some clouds look gray because they are so thick that light can't pass through them.

Meteorologists name clouds based on their shape and their height in the atmosphere. Most clouds form in the troposphere, which reaches 65,000 feet above the ground, but occasionally clouds are spotted in the stratosphere the mesosphere, which begins 50 miles up.

Heights of clouds are organized into three groups: high, middle, and low. High clouds form 20,000 feet or higher above sea level. They are usually made up of ice crystals because the air is so cold high in the atmosphere. The clouds of the high altitudes often have a cirro- prefix because they are often wispy.

Middle clouds form between 6,500 and 20,000 feet above sea level. The warmer temperatures mean they are made up of both ice crystals and water droplets. These clouds usually have the prefix alto- in their names to show that they form in the middle altitudes.

Low clouds form within 6,500 feet of the surface of the Earth. Because these are the warmest clouds, they are mostly full of water droplets. They often have the prefix strato- in their names because they are usually flat or layered.

Meteorologists combine words to name clouds based on how they look. For example, cirrostratus clouds are high clouds that are thin, wispy, and cover the entire sky. Cirro means wispy, and stratus means flat or layered. Cumulonimbus clouds are clouds that start at a low level and can extend to a high level. They are huge, puffy towers. Cumulo means puffy, and nimbus means full of rain.

There are irregular types of clouds too. For example, fog is a cloud at the surface of the Earth. Lenticular clouds look like flying saucers, and they form because of the way wind flows down a mountain. Fractus clouds are the small, ragged cloud fragments that can appear and disappear throughout the sky on a mostly clear day. Contrails form when the hot exhaust from airplanes meets the cold air high in the troposphere.

Earth isn't the only planet with clouds. All planets with atmospheres have clouds, but they are different from our clouds. For example, sulfuric acid clouds surround Venus, and on Jupiter and Saturn, the clouds rain diamonds.

Luckily for us, the clouds on Earth are made up of water. They play an essential role in the water cycle that cleans and moves water throughout the world. Clouds can also deflect the Sun's heat during the day and act like a blanket, keeping the Earth warm at night. We couldn't live without clouds.