The sky is often abundant with clouds. We usually take little notice of them hovering above our heads, but sometimes we fear the weather they may bring. Continuously appearing and fading out of sight, what are these unique shapes that parade across the sky?
Clouds are created when rising air cools down enough to release the water vapour it contains, and the condensation produced in this process makes clouds visible. Cloud masses consist of tiny droplets of liquid, frozen crystals and other suspended particles, such as sea salt, dust and dirt. These particles are known as cloud condensation nuclei.
The volume, source and occurrence of clouds differ around the world according to the climate conditions. Near the equator, hot air rises at the most rapid rate, which results in heavy, tropical rainfall. In desert areas, meanwhile, the extreme lack of moisture means clouds are scarce. With no shade, temperatures soar in the day. But the desert also demonstrates the role clouds play in retaining heat: at night, deserts can become bitterly cold because there is no moisture in the air to hold onto heat.
The mountainous regions of Earth act to obstruct wind flow, which has a fascinating impact on resulting clouds. When air reaches these barriers, it is pushed drastically upwards, creating a unique form of clouds called lenticular clouds. In appearance, these are often compared to a stack of plates, and they are even mistakenly reported as UFOs from time to time.