When you look up high in the sky and see those white, wispy forms floating through the air, you notice that they can look like all sorts of things. What are we talking about? Clouds, of course!
Have you ever stopped to WONDER exactly what clouds are? How do they get there? Are they made of smoke that floats up high into the atmosphere? Could they be placed there by magical creatures who like to paint the sky?
Don't get too excited about the thought of magical creatures painting cloud pictures in the sky for you. When it comes to clouds, they can be explained easily by science!
Look around right now. Can you see the air around you? Of course not, right? It's invisible! But did you realize that the air around you is full of water and other particles? It's true. Water in its gaseous form, called water vapor, is present in the air around you.
The air is also full of other tiny particles, including dust, dirt, and salt. Scientists call these particles aerosols. People who study the weather, called meteorologists, also call these particles cloud condensation nuclei or cloud seeds.
Clouds form when tiny droplets of water vapor condense from a gas back into a liquid. This process, called condensation, occurs when the air becomes saturated, which means it cannot hold any more water vapor.
This usually happens when the air is cooled to its dew point. As air rises into the atmosphere, it expands and cools. When it reaches the dew point, condensation occurs and tiny droplets of water vapor turn to liquid water and attach themselves to cloud seeds floating in the air.
Once attached to aerosols, these tiny droplets of liquid water (or solid ice if they're high enough up in the atmosphere) group together to form the clouds we see. There are many factors that affect how and where clouds form. For example, when the Sun heats large bodies of water, water vapor from evaporation rises into the air and eventually cools into clouds.
Other weather factors, such as fronts of warm and cold air colliding, the movement of the jet stream, and variances in winds, can also affect cloud formation. Topographical features of Earth's surface, such as mountain ranges, can also influence the flow of air and thus the creation of clouds.
Because of all of these factors, the atmosphere is constantly changing. This means that condensation and evaporation occur continuously, even after a cloud forms. If evaporation increases, a cloud will dissipate. If condensation increases, the cloud will grow. This explains why clouds change shape as we watch them in the sky.