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Ever seen a cloud form out of clear air, or burn away to nothing?
The thing is, all the water that makes a cloud visible is still in the air even when you can’t see it—it’s a combination of temperature and pressure changes that cause invisible water vapor to condense into visible water droplets. So you could be looking at a clear sky on a warm day that actually holds a greater mass of water than a sky full of clouds on a cold day.
That's true. I'm ok with either option though, the mass of the condensed water, or the total mass of water in the volume of the cloud.
I think you'd be better served to ask about the average volume of a cloud (if that makes sense, given how diverse they come). Because the mass is pretty much exactly volume multiplied with density. And the average density of clouds is pretty much exactly that of the surrounding air at the given altitude (because otherwise the cloud would not float, but either rise up or sink down). And the density of air at any given altitude is given by the Barometric formula. If you take a kubik kilometer of cloud (honestly, I have no idea how big clouds are), it would have a mass of approximately 364 thousand tons at 11 km above sea level, 88 thousand tons at 20 kilometers above sea level, 860 tons at 51 km above sea level and ca. 64 tons at 71km above sea level. But "regular" clouds only go up to ca. 20km, and 95% of the clouds you see are probably below 8km. Unfortunately the quoted wikipedia page has no entry for the barometric pressure at that altitude and I am too lazy to try and calculate it right now ;)
At sea level air is about 1.25 kg/m³, so for one cubic kilometer cloud that is :
1 250 000 tons.
I put your result into table ~~to show a problem at 51 km and above... since density decreases monotically with altitude.~~
| mass (tons) | altitude (km) |
|---|---|
| 1 250 000 | 0 |
| 364 000 | 11 |
| 88 000 | 20 |
| 860 | 51 |
| 64 | 71 |
Clouds can be easily 10 cubic km.
I'm mostly interested in how much water is in a cloud. The mass of air is also interesting, but it isn't what I was originally thinking when I asked
I’m mostly interested in how much water is in a cloud.
Should've started with that, that's a very different question :)
The question is a work in progress 😉 You don't always know what you really want to ask until you start a discussion.
Fair enough, that's a good take on asking questions / learning :)
https://www.iflscience.com/how-much-does-a-cloud-weigh-67107
Researchers at the US National Centre for Atmospheric Research calculated the density of a cumulus cloud to be around 0.5 grams (0.018 ounces) of water per cubic meter, so a 1 cubic kilometer (0.24 cubic mile) wide cloud would contain 1 billion cubic meters (35 million cubic feet). If you calculate the number of cubic meters times by the density, 1,000,000,000 x 0.5, you’ll be left with the total weight of a cumulus cloud of that size – 500,000 kilograms (1.1 million pounds).
I think the term "weight" - while useful at sea level - can easily confuse people when it comes to clouds, as the density of the water in a cloud doesn't have much to do with the weight of the cloud - see my elaborated edited response (unless I mis-guesstimated) - the mass of a cloud changes so drastically with altitude that the relative or even the absolute weight of water (vapor) therein is going to give people the wrong idea.
According to Randall Munroe (the author behind xkcd.com) in his book 'what if? 2' a house sized cumulus cloud, which would be very small for a cloud, contains roughly one litre of water, which in turn weighs 1 kilogramm.
If you want to look it up and somehow find a version of the book online, this information is in the chapter about the largest thing you could theoretically eat in one sitting (it's the cloud).
Should the mass of the air within the cloud be considered as well?
Oh shit good question. I'm gonna say no because I was really trying to ask about how much ice/water/dust is involved, but I'm also curious about the air.
