How big are clouds? Like, how much geographical space could they cover? A town? A city?
In: Physics
Pilot here.
There is no theoretical limit to how big clouds can get in the horizontal plane (There is a limit in the vertical, to about 50’000 feet because air pressure drops away. No air pressure = no cloud). If the environmental conditions and earth surface allow for it, they can be huge, in both the vertical and horizontal planes. However a large cloud that exists for many miles in the horizontal plane tends to actually be made of lots of smaller clouds that clump together. Aviators generally only consider clouds to be “Big” when they are big in the vertical plane.
As pilots, the cloud we fear is a type called “Cumulonimbus”. In terms of size these things can be monsters, stretching as high as 40’000 feet in altitude, and they have been sighted higher (Unusually). They are the type of cloud that brings rain, thunderstorms and the only cloud that can form hail.
We have a nickname for them…”Charlie Bangers”…from their short weather code of “Cb”. For pilots, they are the universal “Go around or go back” sign and no matter what you fly, you do not enter them. Period.
There are three main ways a cloud can form but the typical one is when formed by moisture in the air that “Clumps” together when the air is rising and begins to cool and the pressure drops. Because warm air carries more moisture than cold air, the air holding the water vapour has to be at a certain temperature first and as it gets higher and cools it meets something called the “Dew point” which is where the temperature drops to a sufficient level the air can no longer hold it.
Clouds form a lot easier when there is pollution, dust or some kind of particulate in the air for the water molecules to cling to.
Oh and a fun fact. Fog is actually cloud. It’s just the temperature and pressure is just right for the dewpoint to be close to the ground.
If you want a real world example of how big cloud can be, I once took off from Berlin and did not see a break in the cloud till the coast of France.
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