While you’re flying in an airplane above a blanket of clouds, the pillars of white and grey look mushy, 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 thousands and thousands of tiny water droplets, which type when water condenses round a “seed” particle. Seed particles could be something from nitric acid to vapors launched by bushes, however they’re typically 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, “you might want to know one thing concerning the dimensions of the cloud,” Armin Sorooshian (opens in new tab), a hydrologist on the College of Arizona, instructed 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 Middle 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 scale of a cloud’s shadow and estimated its top, assuming a roughly cubic form. Clouds should not usually dice formed, however cumulus clouds are incessantly about as tall as they’re vast, 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 mentioned.
That is roughly the load of 100 elephants suspended above your head. “It is actually spectacular,” Soroohsian mentioned.
In fact, several types 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 instructed Stay Science. And cumulonimbus clouds (the darkish thunderheads you see simply earlier than a storm) are usually a lot heavier.
Nevertheless, “all the quantity of the cloud is not only the droplets; there’s air, too,” Sorooshian mentioned. 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 mentioned. The typical water droplet in a cloud is roughly 1 million instances smaller than a raindrop — concerning the measurement ratio of Earth to the solar. Excessive-altitude wind currents blow these tiny droplets alongside, maintaining 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 mentioned. 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 high of a latte.
In fact, clouds could be mentioned to “fall” within the type of rain. When cloud droplets cool and condense into each other, they develop, ultimately turning into so heavy that they plummet to Earth. Though a raindrop is way larger than a cloud droplet, every raindrop remains to be solely 0.08 inch (2 millimeters) in diameter, in keeping with the University Center for Atmospheric Research (opens in new tab). These small drops unfold out the load sufficient that 550 tons of water does not crash down in your head abruptly.
So, the subsequent time you see a cheerful little cloud passing overhead, simply keep in mind: 100 elephants. And thank your fortunate stars for warmth convection.