Once you’re flying in an airplane above a blanket of clouds, the pillars of white and grey look tender, fluffy and lighter than air. However do not be fooled — these bouncy-looking clouds are a lot, a lot heavier than they seem.
So simply how a lot does a cloud weigh? And the way do you weigh a cloud? We requested the consultants to search out out.
Clouds are composed primarily of air and hundreds of thousands of tiny water droplets, which type when water condenses round a “seed” particle. Seed particles will be something from nitric acid to vapors launched by timber, however they’re usually very tiny.
There are a few methods to measure the load of a cloud. The primary is to weigh the water vapor that composes it — and to try this, “it’s good to know one thing concerning the dimensions of the cloud,” Armin Sorooshian (opens in new tab), a hydrologist on the College of Arizona, advised Stay Science. You additionally should understand how densely packed the droplets are.
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A number of years in the past, Margaret LeMone (opens in new tab), an atmospheric scientist on the Nationwide Heart for Atmospheric Analysis in Boulder, Colorado, questioned concerning the weight of the water in a mean cumulus cloud. So she did the math. First, she measured the dimensions of a cloud’s shadow and estimated its top, assuming a roughly cubic form. Clouds should not sometimes dice formed, however cumulus clouds are steadily about as tall as they’re broad, so this assumption helped streamline the quantity calculation. Then, based mostly on prior analysis, she estimated the density of water droplets at round 1/2 gram per cubic meter. “I got here up with round 550 tons [499 metric tons] of water,” LeMone stated.
That is roughly the load of 100 elephants suspended above your head. “It is actually spectacular,” Soroohsian stated.
In fact, various kinds of clouds have totally different weights. For instance, “cirrus clouds are a lot lighter, as a result of they’ve far much less water per unit quantity,” LeMone advised Stay Science. And cumulonimbus clouds (the darkish thunderheads you see simply earlier than a storm) are typically a lot heavier.
Nevertheless, “the complete quantity of the cloud is not only the droplets; there’s air, too,” Sorooshian stated. If somebody needed to take LeMone’s calculations a step additional, they might issue within the weight of the air between every droplet.
But when clouds are so heavy, why do not they fall down? For one factor, “the droplets are so small that they do not fall very quick,” LeMone stated. The common water droplet in a cloud is roughly 1 million instances smaller than a raindrop — concerning the dimension ratio of Earth to the solar. Excessive-altitude wind currents blow these tiny droplets alongside, conserving them within the air for for much longer than in the event that they have been static.
Warmth convection additionally helps maintain the drops aloft. “A cloud is definitely much less dense than the air straight under it,” Sorooshian stated. As heat air (and heat water) rises, it turns into extra buoyant than the chilly air (and chilly water) beneath it, like a layer of froth on prime of a latte.
In fact, clouds will be stated to “fall” within the type of rain. When cloud droplets cool and condense into each other, they develop, finally turning into so heavy that they plummet to Earth. Though a raindrop is far larger than a cloud droplet, every raindrop continues to be solely 0.08 inch (2 millimeters) in diameter, in line with the College Heart for Atmospheric Analysis (opens in new tab). These small drops unfold out the load sufficient that 550 tons of water would not crash down in your head .
So, the following time you see a cheerful little cloud passing overhead, simply bear in mind: 100 elephants. And thank your fortunate stars for warmth convection.