Clouds are a collection of tiny droplets of water and ice that have been evaporated from the surface of the earth. Clouds come in many different shapes and sizes and exist at different levels in the earth’s troposphere. There are three main types of cloud; they are stratus cloud, cirrus cloud and cumulus cloud. There are other scientific terms for specific clouds that are a combination of these names. Clouds appear darker when they are heavy with water or very dense. This is why you often see dark clouds before a storm.
The Formation of Clouds
The air all around us contains water vapor (water in a gas form). For a cloud to form three things must happen, lifting (evaporation), cooling and condensing. When the sun warms the earth it causes water to be evaporated from the surface. This becomes water vapor in the air around us. As the sun heats the earth it also heats the layers of air closest to the ground. This hot air rises and becomes cooler as it ascends. Cool air is unable to hold as much water as warm air does, so as the warm air rises the water vapor condenses (turns back into a liquid rather than a gas) onto tiny pieces of atmospheric dust (similar to what happens in the side of a glass). These tiny water droplets clump together and form visible clouds. The collection of water droplets reflects the light of the sun and we see them as white formations in the sky. If the cloud becomes thick enough or it is high enough in the atmosphere it appears gray because it blocks the light from the sun.