Formation Of Clouds

Background There are three basic types of clouds: cirrus, cumulus, and stratus. Cirrus clouds: located the highest in the atmosphere (6000 to 18000 metres). They are made of ice crystals. The word cirrus means “curl”. These wispy clouds look curly and travel very fast. They are often seen ahead of changes in the weather.

Cumulus clouds: look “puffy” like cotton balls Cumulus clouds: look “puffy” like cotton balls. They are found 1000 to 14000 metres above Earth. Cumulus means “pile”. When the lower sections of these clouds begin to darken, a storm is often near.

Stratus clouds: sometimes look like a blanket stretched across the sky Stratus clouds: sometimes look like a blanket stretched across the sky. They are usually located below 2500 metres. Stratus means “layer.” These clouds often bring rainy weather.

Activity One Where does rain fall from? What is a cloud? What are clouds made of? Are all clouds the same? How are clouds different? What can you tell from looking at clouds?

You are now going to create a cloud using four simple materials. Activity sheet A and Materials.

Follow these instructions: 1 Pour hot water into a glass jar to a depth of about 3cm. 2. Place a metal tray of ice cubes on top of the jar. 3. Turn the lights off in the room and close any curtains so the room is dark. 4. Shine a flashlight through the middle of the jar.

Record observations on activity sheet A. What did you notice when you shone the flashlight into the jar? Why do you think this happened? How can you compare this experiment to how real clouds are created? What do you think clouds are made of?

When air cools, water vapour condenses on dust particles in the air, forming tiny droplets of water. Millions of tiny droplets form a cloud (the cloud is made of water droplets of ice particles, depending on whether condensation occurred above or below the freezing point of water).

The cloud grows bigger if more condensation than evaporation occurs. The cloud becomes smaller if more evaporation than condensation occurs.

Activity Part two Observe the clouds for 7 days using activity sheet 4.4.2.