Have you ever wondered how much a cloud weighs? Obviously, the answer depends on the size and type of cloud. An average cumulus cloud weighs about 1.1 million pounds or 500,000 kilograms. So, while a cloud may appear fluffy, it’s certainly not light! Here’s a look at how to calculate the weight of a cloud and an explanation for why clouds don’t fall even though they are very heavy.
How to Find the Weight of a Cloud
You can’t just place a cloud on a scale and weigh it. Its mass and weight are calculated from its volume and density. Volume is the cloud’s three-dimensional size. Density is the mass of a cloud per unit of volume. To find the mass or weight of a cloud, the two values are combined:
Density = mass / volume
solving for mass:
Mass = density x volume
Different types of clouds have different density values. Rain-bearing cumulonimbus clouds are more dense than lacy cirrus clouds. A cumulus cloud is a good starting point for a density calculation because this type of cloud has a fairly regular size and shape. Scientists have measured the average density of a cumulus cloud as about 0.5 grams per cubic meter. Meteorologists use laser Doppler velocimetry to get this value.
One way to measure the size of a cloud is to drive at a fixed rate of speed across its shadow when the sun is directly over head. If you know the speed and how long it took to cross the shadow, you can find the length of the shadow, which is the same as the length of the cloud at noon:
Distance = speed x time
Using this method, a typical cumulus cloud is about 1 kilometer or 1000 meters across. While clouds aren’t perfect cubes, the width and height of a cumulus cloud are about the same as its length, so the volume is:
Volume = length x width x height
Volume = 1000 meters x 1000 meters x 1000 meters
Volume = 1,000,000,000 cubic meters
Clouds are gigantic! Next, plug in the density and volume values to find a cloud’s mass, which is also its weight on Earth.
Mass = density x volume
Mass = (0.5 grams/cubic meter) x (1,000,000,000 cubic meters)
Mass = 500,000,000 grams or 500,000 kilograms
Converting this value to pounds, the weight of a cloud is 1.1 million pounds.
Cirrus clouds are smaller and less dense, so they weigh less than cumulus clouds. Cumulonimbus clouds are much larger and denser than cumulus clouds, so they weigh much more. A cumulonimbus cloud can weigh 1 million tonnes.
What Weighs as Much as a Cloud
It’s hard to visualize what 1 million pounds looks like. To put it into perspective, the weight of a cloud is about the same as:
- 3 blue whales (375,000 pounds each)
- 100 elephants
- 40 school buses
- about $20,000,000 in US quarters
- Airbus A380 passenger jet (1.1 million pounds)
- Union Pacific Big Boy steam locomotive (1.2 million pounds)
- Antonov An-225 Mriya cargo aircraft (1.28 million pounds)
- Power station transformer (1.28 million pounds)
Why Clouds Don’t Fall
If clouds are so massive, why don’t they fall from the sky? The answer is that they would, if there wasn’t anything between them and the ground. But, clouds rest on a layer of air that is dense enough to support them. You can think of clouds as ships that sail on a sea of air. The reason the air is more dense than the cloud is because the air and cloud aren’t the same temperature. Also, clouds are dynamic. Evaporation and condensation of water occur within the cloud. These changes of state of matter absorb and release energy, changing the temperature within a cloud. Sometimes the air around a cloud becomes warm enough that it can absorb a cloud. The cloud becomes water vapor dispersed in the air and shrinks or disappears. Other times, clouds do become too heavy to remain aloft. They may sink toward the ground or release precipitation in the form of rain or snow.
References
- Freud, E.; Rosenfeld, D. (2012). “Linear relation between convective cloud drop number concentration and depth for rain initiation”. Journal of Geophysical Research. 117 (D2). doi:10.1029/2011JD016457
- Grenci; Lee M.; Nese, Jon M. (2001). A World of Weather: Fundamentals of Meteorology: A Text / Laboratory Manual (3rd ed.). Kendall/Hunt Publishing Company. ISBN 978-0-7872-7716-1.
- Jaramillo, A.; Mesa, O. (June 19, 2017). “On the relative density of clouds.” Quarterly Journal of the Royal Meterological Society. Vol. 144; Iss. 707, pp. 2650-2653. doi:10.1002/qj.3099