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Zidbits – Learn something new everyday! | October 26, 2014

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How Much Does A Cloud Weigh?

How Much Does A Cloud Weigh?

Lazily staring up at the sky, you may have once pondered… Since clouds are fluffy, they virtually lighter than air, and they contain mostly water vapor, they should weigh next to nothing, right? One reader wanted to know so we did a little research.

How Much Do Clouds Weigh?

Clouds can vary wildly in size, shape, and density. Because of this, there is no way to precisely or accurately gauge weight, but we can do a rough estimate. After a bit of research, we’ve discovered clouds are substantially heavier than we previously imagined.

The density of clouds can vary quite a bit, from about 1/10 gram per cubic meter to over 5 grams per cubic meter. This makes it quite hard to come up with an “average” cloud volume, as this varies even more widely than the actual water content.

CloudsTo get at least a rough order-of-magnitude estimate, we have to plug in some averages into our equation, making this far from scientifically accurate. If we model our cloud as a sphere of say, 1 kilometer radius, that gives a volume of about 4 billion cubic meters. Then if we use 1 gram per cubic meter as a ‘representative’ water content, we get an estimate for the mass of the cloud of 4 million kilograms, or 8,818,490 pounds. That’s 37 fully grown blue whales.

A good sized cumulonimbus cloud (also known as a thunderhead) might be ten kilometers tall, with a base ten kilometers in diameter. Estimating that, we come up with a volume of 785 billion cubic meters per cloud. This gives us a mass of roughly four billion kilograms per cloud. That’s 10,000 747 jets.

If one fell on us, it would … just get real foggy. Luckily, weight isn’t the same as mass. A cloud put on a scale wouldn’t weigh anything.

Eerie Looking Roll Clouds

A roll cloud (pictured at the top of this article) is a low, horizontal tube-shaped arcus cloud associated with a thunderstorm gust front, or sometimes a cold front. Cool air sinking air from a storm cloud’s downdraft spreads out across the surface with the leading edge called a gust front. This outflow undercuts warm air being drawn into the storm’s updraft.

As the cool air lifts the warm moist air water condenses creating cloud, which often rolls with the different winds above and below (wind shear).

References:
Glossary of Meteorology (June 2000). “Adiabatic Process”. American Meteorological Society.
Aerographer/Meteorology (2012). “Roll cloud formation on cumulonimbus
Pidwirny, M. (2006). “Cloud Formation Processes”, chapter 8 in Fundamentals of Physical Geography

Comments

  1. rosy

    If it weighs so much, then how does it flow?

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