Why do clouds stay in the sky?

In Physics by Mystifact

Did you know that the average cumulus cloud has the same weight as 100 elephants? This is a whopping 1.1 million pounds and there are hundreds of them floating above our heads in the sky, throughout the day. We see clouds all the time, but why do they stay up there, in the sky?

Let’s lay down some interesting fundamentals.

How do clouds form?

As water evaporates and this warm air rises, it expands and cools, as a result, it condenses into very small liquid droplets; forming a cloud [1].

How do clouds take a specific shape?

The cloud shape is determined by the way this water vapour rises, which is why clouds have so many names [2]. For example if the wind pushes this vapour up a mountain, you could get Lenticular clouds. Some air-planes leave a trail behind them which is also a type of cloud; it is called a Wispy Cirrus cloud. The most common cloud is the one you most likely will see if you look out your window; Cumulus clouds. This still does not answer our main question of why they don’t come crashing down on us if they weigh as much as a huge pack of elephants!

Why do clouds stay in the sky?

Warm air is less dense so it rises. This is why you tend to find clouds above any source of a warm up-draft, such as above somewhere where there is grass on a sunny day. When hot water vapour rises, it cools as it gets higher up in the atmosphere, which causes its molecules to slow down. As a result, some of them join and stick together to form very small water droplets. This warm up-draft from the ground below cushions the newly formed cloud, thus stopping it from falling.

Do all clouds rest on a warm up-draft? Not in all cases. If it is a windy day, the clouds are blown away from this up-draft, therefore, how does the cloud maintain this buoyancy and stay in the sky?

Condensation is the answer. Let’s make an analogy. The human body sweats in order to cool itself down; when we sweat, it evaporates which carries away heat, hence why you feel cooler when relaxing after having sweat a lot. With clouds, the opposite happens. When the warm air condenses in the cloud; it releases heat which ends up heating the cloud itself from the inside. This keeps the cloud in the air just like a hot air balloon, thus maintaining its buoyancy.

If you have any questions, leave them below and until next time, take care.

~ Mystifact

[1]: http://www.weatherquestions.com/How_do_clouds_form.htm
[2]: https://www.thenakedscientists.com/forum/index.php?topic=25639.0
[3]: https://www.scientificamerican.com/article/why-do-clouds-float-when/

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