Introduction | How Does Water Get In and Out of the Atmosphere?
Who Needs the Atmosphere? | Create a Portable Cloud!

How does the water get into the atmosphere?
Only a tiny fraction of Earth’s water is in the atmosphere at any one time. It doesn’t stay up there for long and there are several different ways that it can get up there!

  • Heat from the Sun causes water to evaporate from the surface of lakes and oceans. This turns the liquid water into water vapor in the atmosphere.
  • Plants, too, help water get into the atmosphere through a process called transpiration! After absorbing water from the ground, plants “sweat” water vapor through their leaves to stay cool.
  • Water can also get into the atmosphere from snow and ice. Instead of melting, some frozen water changes into water vapor gas and goes into the atmosphere through a process called sublimation.

How long does water spend in the atmosphere?
On average, water spends about eight days in the atmosphere before it falls back to Earth. It travels in the wind over oceans and over land. That sounds like quite an exciting trip!

How does it get out of the atmosphere?
When the water vapor comes out of the air, it often causes precipitation like rain and snow. First, when water vapor is cooled it transforms into tiny droplets of liquid water or ice crystals that grab onto particles of dust in the atmosphere. Tons of these little droplets or ice crystals make clouds. When you look at clouds from the ground, the tiny droplets and ice are too far away to see, but many of them together look like a cloud. If the droplets or ice crystals get large enough, they fall from the sky as rain or snow.