The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Water at the Earth's surface evaporates into water vapor which rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation.
Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human interference.
• Water Science School HOME • The Water Cycle •
Water cycle components » Atmosphere · Condensation · Evaporation · Evapotranspiration · Freshwater lakes and rivers · Groundwater flow · Groundwater storage · Ice and snow · Infiltration · Oceans · Precipitation · Snowmelt · Springs · Streamflow · Sublimation · Surface runoff
The atmosphere is full of water
The water cycle is all about storing water and moving water on, in, and above the Earth. Although the atmosphere may not be a great storehouse of water, it is the superhighway used to move water around the globe. Evaporation and transpiration change liquid water into vapor, which ascends into the atmosphere due to rising air currents. Cooler temperatures aloft allow the vapor to condense into clouds and strong winds move the clouds around the world until the water falls as precipitation to replenish the earthbound parts of the water cycle. About 90 percent of water in the atmosphere is produced by evaporation from water bodies, while the other 10 percent comes from transpiration from plants.
Atmosphere • Condensation • Evaporation • Evapotranspiration • Groundwater flow • Groundwater storage • Ice and snow • Infiltration • Lakes and freshwater • Oceans • Precipitation • Snowmelt • Springs • Streamflow • Sublimation • Surface runoff
There is always water in the atmosphere. Clouds are, of course, the most visible manifestation of atmospheric water, but even clear air contains water — water in particles that are too small to be seen. One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles (mi3) or 12,900 cubic kilometers (km3). That may sound like a lot, but it is only about 0.001 percent of the total Earth's water volume of about 332,500,000 mi3 (1,385,000,000 km3), as shown in the table below. If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch.
How much does a cloud weigh?
Do you think clouds have any weight? How can they, if they are floating in the air like a balloon filled with helium? If you tie a helium balloon to a kitchen scale it won't register any weight, so why should a cloud? To answer this question, let me ask if you think air has any weight—that is really the important question. If you know what air pressure and a barometer are, then you know that air does have weight. At sea level, the weight (pressure) of air is about 14 ½ pounds per square inch (1 kilogram per square centimeter).
Since air has weight it must also have density, which is the weight for a chosen volume, such as a cubic inch or cubic meter. If clouds are made up of particles, then they must have weight and density. The key to why clouds float is that the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air in clouds is less dense than dry air.
We still need to answer the question of how much a cloud weighs. To confuse things more, the weight depends on how you define it:
- The weight of the water droplets in the cloud
- The weight of the water droplets plus the weight of the air (mostly above the cloud, pressing down)
We're only going to look at the weight of the actual cloud particles. One estimate of cumulus cloud density is given at https://www.sciencealert.com/this-is-how-much-a-cloud-weighs, as a density of about 0.5 gram per cubic meter. A 1 km3 cloud contains 1 billion cubic meters.
Doing the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud. That is about 500,000 kilograms or 1.1 million pounds (about 551 tons). But, that "heavy" cloud is floating over your head because the air below it is even heavier— the lesser density of the cloud allows it to float on the dryer and more-dense air.
Global distribution of atmospheric water
| Water source | Water volume, in cubic miles | Water volume, in cubic kilometers | Percent of total freshwater | Percent of total water |
|---|---|---|---|---|
| Atmosphere | 3,094 | 12,900 | 0.04% | 0.001% |
| Total global fresh water | 8,404,000 | 35,030,000 | 100% | 2.5% |
| Total global water | 332,500,000 | 1,386,000,000 | -- | 100% |
Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp. 817-823.
The little cloud that could—but why?
Why is this tiny cloud the only one in the sky?
Sources and more information
- How much does a cloud weigh? - National Oceanic and Atmospheric Administration
- Overview
The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Water at the Earth's surface evaporates into water vapor which rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation.
Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human interference.
• Water Science School HOME • The Water Cycle •
Water cycle components » Atmosphere · Condensation · Evaporation · Evapotranspiration · Freshwater lakes and rivers · Groundwater flow · Groundwater storage · Ice and snow · Infiltration · Oceans · Precipitation · Snowmelt · Springs · Streamflow · Sublimation · Surface runoff
The atmosphere is full of water
The water cycle is all about storing water and moving water on, in, and above the Earth. Although the atmosphere may not be a great storehouse of water, it is the superhighway used to move water around the globe. Evaporation and transpiration change liquid water into vapor, which ascends into the atmosphere due to rising air currents. Cooler temperatures aloft allow the vapor to condense into clouds and strong winds move the clouds around the world until the water falls as precipitation to replenish the earthbound parts of the water cycle. About 90 percent of water in the atmosphere is produced by evaporation from water bodies, while the other 10 percent comes from transpiration from plants.
Sources/Usage: Public Domain.Clouds in the atmosphere - The water cycleThis picture shows a lenticular cloud over the Tararua Range mountains, North Island, New Zealand. What's happening above those mountains? Several clouds are stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance.In this picture, the sun is probably low in the sky off to the right side., with the sunlight coming upward and hitting the bottom of the clouds. The clouds are made of trillions of tiny water droplets that are clear but still reflect light (as a prism). The way in which light is reflected from an object determines what color you see. White light, as from the sun, is actually made up of light waves that produce all colors, but mixed together, look white.The mountains look green because when sunlight hits the plants and trees, they reflect more of the green portion of the sunlight to your eyes. So, because of the way water drops reflect light, at the moment this picture was taken, the drops were reflecting the parts of sunlight that look golden to you. The main thing is to enjoy your sunrises and sunsets even if you don't understand how they work.Components of the water cycle:
Atmosphere • Condensation • Evaporation • Evapotranspiration • Groundwater flow • Groundwater storage • Ice and snow • Infiltration • Lakes and freshwater • Oceans • Precipitation • Snowmelt • Springs • Streamflow • Sublimation • Surface runoffThere is always water in the atmosphere. Clouds are, of course, the most visible manifestation of atmospheric water, but even clear air contains water — water in particles that are too small to be seen. One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles (mi3) or 12,900 cubic kilometers (km3). That may sound like a lot, but it is only about 0.001 percent of the total Earth's water volume of about 332,500,000 mi3 (1,385,000,000 km3), as shown in the table below. If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch.
How much does a cloud weigh?
Sources/Usage: Public Domain.Credit: Wikimedia, Creative Commons Do you think clouds have any weight? How can they, if they are floating in the air like a balloon filled with helium? If you tie a helium balloon to a kitchen scale it won't register any weight, so why should a cloud? To answer this question, let me ask if you think air has any weight—that is really the important question. If you know what air pressure and a barometer are, then you know that air does have weight. At sea level, the weight (pressure) of air is about 14 ½ pounds per square inch (1 kilogram per square centimeter).
Since air has weight it must also have density, which is the weight for a chosen volume, such as a cubic inch or cubic meter. If clouds are made up of particles, then they must have weight and density. The key to why clouds float is that the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air in clouds is less dense than dry air.
We still need to answer the question of how much a cloud weighs. To confuse things more, the weight depends on how you define it:
- The weight of the water droplets in the cloud
- The weight of the water droplets plus the weight of the air (mostly above the cloud, pressing down)
We're only going to look at the weight of the actual cloud particles. One estimate of cumulus cloud density is given at https://www.sciencealert.com/this-is-how-much-a-cloud-weighs, as a density of about 0.5 gram per cubic meter. A 1 km3 cloud contains 1 billion cubic meters.
Doing the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud. That is about 500,000 kilograms or 1.1 million pounds (about 551 tons). But, that "heavy" cloud is floating over your head because the air below it is even heavier— the lesser density of the cloud allows it to float on the dryer and more-dense air.
Global distribution of atmospheric water
One estimate of global water distribution
Water source Water volume, in cubic miles Water volume, in cubic kilometers Percent of total freshwater Percent of total water Atmosphere 3,094 12,900 0.04% 0.001% Total global fresh water 8,404,000 35,030,000 100% 2.5% Total global water 332,500,000 1,386,000,000 -- 100% Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp. 817-823.
Sources/Usage: Some content may have restrictions. Visit Media to see details.The little cloud that could—but why?
Why is this tiny cloud the only one in the sky?Sources and more information
- How much does a cloud weigh? - National Oceanic and Atmospheric Administration