If you look at the sky there is a good chance that a few clouds can be seen. They can have all kinds of shapes; from fluffy white tufts to a dense gray blanket. We know that clouds hang in the sky, but how high exactly do they hang?
Clouds are at different heights in the atmosphere. In meteorology we distinguish between low, medium and high clouds.
The low clouds, such as cumulus clouds, which usually have the shape of a cauliflower, can already arise at a few hundred meters. When these clouds grow, they can even reach heights above 10 kilometers. Fog is actually also a low cloud and you could say that this cloud is ‘on the streets’.
The middle clouds float at altitudes between 3 and 5 kilometers. These clouds are generally made up of droplets and very small ice crystals. When these clouds grow big, rain or snow can sometimes fall out.
The highest clouds float above 5 kilometers. These are the veil clouds that are often also called wind springs. No precipitation falls from these clouds. They are not thick enough for that. However, they consist entirely of ice crystals because at that height it is very cold.
Why do clouds float in the air and not fall down?
Clouds are made up of thousands of tiny droplets (high in the sky also called ice crystals). Due to the gravity of the earth, these droplets fall down. But why don’t we see that happen?
That’s because these droplets are very light. As a result of the friction with the air, the falling small droplets float on the air layer. As the small droplets get bigger and heavier they can overcome the frictional force of the air. The droplets then fall down and that is rain!
Then there is a second reason why clouds float. With a normal cloud (without rain) the bottom small droplets evaporate. They then become gas molecules (water vapor) and they are invisible, but they also float. Higher in the air it is colder, where the gas molecules become droplets again. We see this as a cloud.
Why do clouds darken when there is more rain in it?
Clouds are made up of many small water droplets. At high altitudes of 8 to 12 kilometers, that drop turns into ice crystals. That’s because it freezes so high in the air at about 50 to 60 degrees Celsius. Brrr!
Sunlight cannot penetrate these frozen drops. The drops reflect the light, as if it were a mirror. Just think of the sea: the sun shines on the water, but it is dark under water.
The more water droplets are in a cloud and the thicker the cloud, the less sunlight gets through. That light is all reflected by the water.
The thickness of those clouds is sometimes five to twelve kilometers, making it very dark underneath. Naturally, such a thick layer of drops means little light!
Then why are dark clouds rain clouds? That is because there is too much water in those clouds. The cloud becomes very heavy as a result of which the drops can no longer remain in the air. Then they fall down. It rains!