A cloud weighs hundreds of tonnes
A modest fair-weather cumulus, about a kilometre on a side, holds on the order of a few hundred tonnes of liquid water.
Established2 min read
Cloud physicists measure liquid water content in grams per cubic metre. Half a gram is a typical value in a small cumulus. A cloud one kilometre by one kilometre by one kilometre is a billion cubic metres. Half a gram times a billion is 500 tonnes.
The droplets stay up because each one falls very slowly and the air is rising. The cloud is not a solid object you could put on a scale. It is a population, continuously condensing and evaporating, whose members happen to be heavy in total.
Caveats
- Real clouds are not perfect cubes, and water content varies. 'A few hundred tonnes' is the right order for a small cumulus, not a number for every cloud.
- A thunderstorm holds much more. The same arithmetic scales up.
Sources
- 1Rogers R. R., Yau M. K.. A Short Course in Cloud Physics. Pergamon Press, 1989.