Clouds appear light and fluffy, yet they are actually rather HEAVY
When flying above a blanket of clouds in an airplane, the pillars of white and gray appear soft, fluffy, and lighter than air. But don't be misled – those bouncy-looking clouds are much, much heavier than they appear.
So, how much weight does a cloud have? And how do you calculate the weight of a cloud? We asked the experts to find out.
Clouds are primarily composed of air and millions of tiny water droplets that form when water condenses around a "seed" particle. Seed particles can be anything from nitric acid to tree vapors, but they are typically very small.
There are several methods for calculating the weight of a cloud. The first step is to weigh the water vapor that makes up the cloud, which requires "you need to know something about the dimensions of the cloud," according to Armin Sorooshian(opens in new tab), a hydrologist at the University of Arizona. You must also understand how densely packed the droplets are.
Margaret LeMone(opens in new tab), an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colorado, wondered about the weight of water in a typical cumulus cloud several years ago. So she calculated. She began by measuring the size and height of a cloud's shadow, assuming a roughly cubic shape. Clouds aren't typically cube-shaped, but cumulus clouds are frequently about as tall as they are wide, so making this assumption simplified the volume calculation. She then estimated the density of water droplets at around 1/2 gram per cubic meter based on previous research. "I came up with around 550 tons [499 metric tons] of water," LeMone said.
That's the equivalent of 100 elephants hung over your head. "It's really impressive," said Soroohsian.
Of course, the weights of different types of clouds vary. "cirrus clouds are much lighter, because they have far less water per unit volume," LeMone said to Live Science. And cumulonimbus clouds (the black thunderheads seen shortly before a storm) are far heavier.
However, "the entire volume of the cloud is not just the droplets; there's air, too," Sorooshian added. If someone wanted to go a step further, they might consider the weight of the air between each droplet.
But, if the clouds are so heavy, why don't they collapse? For starters, "the droplets are so small that they don't fall very fast," according to LeMone. A cloud's typical water droplet is around one million times smaller than a raindrop - roughly the size ratio of Earth to the sun. Wind currents at high altitudes carry these small droplets along, keeping them in the air for considerably longer than if they were static.
Heat convection also assists in keeping the drops aloft. "A cloud is actually less dense than the air directly below it," Sorooshian said. As warm air (and warm water) rises, it becomes more buoyant than the cold air (and cold water) underneath it, like a layer of froth on top of a latte.
Clouds can, of course, "fall" in the form of rain. Cloud droplets grow as they cool and condense into one another, eventually becoming so heavy that they fall to Earth. Although a raindrop is substantially larger than a cloud droplet, according to the University Center for Atmospheric Research, each raindrop is just 0.08 inch (2 millimeters) in diameter (opens in new tab). Those small drops distribute the weight so that 550 tons of water does not fall on your head all at once.
So, the next time you see a cheerful little cloud pass overhead, remember: 100 elephants. And thank the stars for heat convection.
SOURCE
What do you think of this blog? Write down at the COMMENT section below.
No comments:
Post a Comment