The Science Behind the Weather: How clouds form
Meteorologist/Science Writer
Wednesday, April 22, 2015, 10:49 PM - The clouds above our heads can have a mass of up a million kilograms or more, but they float nonetheless. This great video explains why.
The concept behind how clouds form isn't horribly complicated, but it is complex, as there are a lot of factors going on all at the same time. Simply relying on a written or spoken explanation can be difficult to capture everything, and while adding images certainly helps, this video from Minute Earth lays it all out perfectly.
One interesting thing that the video points out is that clouds don't form from only water vapour. The water molecules need something to cling onto - tiny particles, called cloud condensation nuclei - which can be dust, pollen, smoke particles, salt crystals ... even meteoroid dust (for the highest and rarest clouds). Still, given how tiny the nuclei are compared to the droplets, the cloud is still at least 99 per cent water.
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Without the cloud condensation nuclei, it is possible for clouds to form, but you need very specific conditions - supercooled water held in that state for several hours, or there has to be so much water saturating the air that you'd likely only find those conditions in a controlled environment, such as a laboratory.
Sources: Minute Earth | NWS
