How a lot do clouds weigh? – Torben, aged 10, London, UK
We see clouds typically: fluffy clouds on a pleasant summer season’s day, towering thunderstorms, wispy excessive clouds and even gray clouds that cowl the entire sky for days.
Clouds appear to be floating within the air, which could make you suppose that they don’t weigh very a lot in any respect – however you’ll be incorrect.
We are able to use our information of various kinds of cloud and what clouds are fabricated from, in addition to some maths, to work out how a lot they weigh.
Water and air
We first want to consider what clouds are fabricated from. Clouds are literally largely constituted of air, plus small water droplets (which may be frozen into small ice crystals). Once we take into consideration how a lot a cloud weighs, we have to measure each the load of the water and the load of the air.
The subsequent query is what sort of cloud we’re weighing. There are many various kinds of cloud, all with their very own names. The fluffy clouds that drift throughout the sky in summer season are known as cumulus clouds.
To start out with, we’ll take into consideration that fluffy summer season cloud, the cumulus cloud. A cumulus has roughly 1 / 4 of a gram of water for each cubic metre of cloud. 1 / 4 of a gram of water, all collectively, would make a drop of in regards to the measurement of a marble. However actually in our cubic metre there could be round 1 million drops, so they’re very tiny, too small to see.
The subsequent factor to think about is the scale of the cloud. You may see how large cumulus clouds actually are if you happen to take a look at their shadow on the bottom from a excessive view level on a sunny summer season day.
Summer season cumulus clouds differ in measurement, however a typical one could be about one kilometre throughout and about the identical tall. This implies we are able to take into account it to be a dice, with either side measuring 1km throughout. Meaning our cloud is 1,000 x 1,000 x 1,000 cubic metres in measurement – and this makes 1 billion cubic metres.
Our cloud had solely 1 / 4 of a gram of water per cubic metre, however that’s going to work out as relatively so much now there’s a billion of them. The load of the water within the cumulus cloud is 250,000,000 grams – 250 tonnes. That is about the identical as two grownup blue whales.
What in regards to the different cloud sorts? A thunderstorm cloud is larger, measuring about 10 km tall and the identical throughout. In addition they comprise way more water, which is why they rain so laborious: about two grams per cubic metre. Do the maths once more and we have now 2 million tonnes of water.
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Then there’s that gray sky cloud layer. This has about the identical quantity of water per cubic metre because the cumulus cloud, however they cowl the entire sky. They’re typically very shallow – maybe 200 metres thick – however they might simply be 500 km throughout. This makes them 50,000 occasions larger than the cumulus, in order that’s someplace round 10 million tonnes of water.
Lastly, we have to add the load of the water within the cloud to the load of the air. Allow us to return to our summer season cumulus cloud. The place these low clouds are, the air weighs round one kilogram for each cubic metre – 4,000 occasions greater than the water did.
Given the amount of our cumulus cloud, that’s 1 billion kg, or a million tonnes. That’s the reason the cloud can keep up within the air – the tiny water drops are held up by all that air.
If we do the identical maths for a thunderstorm cloud, we get one billion tonnes of air. For the gray sky cloud layer, it’s 50 billion tonnes.
If we add collectively the load of the water and the air in a cumulus cloud, then, it weighs a complete of 1,000,250 tonnes. You could possibly say, although, that perhaps the air doesn’t depend as a part of the cloud’s weight, as it will have been there anyway. Both means, clouds are heavier than you would possibly suppose.
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Rob Thompson receives funding from NERC.