Bringing the Universe to America's Classrooms
Mountains and Rain Shadows

It Starts with Evaporation and Moisture in the Air

To understand how a mountain range affects the climate nearby, first think about where the moisture in the atmosphere comes from.

When wind blows over the ocean or other source of water, the air picks up water vapor as water evaporates from the surface of the body of water. 

In this way, the wind carries off moisture as it moves away from the body of water.
An illustration showing water moving from the ocean to the air. Arrows show molecules of water evaporating from the ocean surface and moving upward to become moisture in the atmosphere.

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To understand how a mountain range affects the climate nearby, first think about where the moisture in the atmosphere comes from.

Play the video to see what happens when water from the ocean evaporates into the atmosphere, a process that can be observed by satellite.
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