Definition

Atmospheric rivers are long, relatively narrow (on average 400-600 km wide) regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics. These flowing columns of condensed vapor move with the weather and are present somewhere on the Earth at any given time.

Description

When the atmospheric rivers make landfall, the water vapor rises and cools and is often released in the form of rain or snow.

 A strong atmospheric river can transport an amount of water vapor roughly equivalent to 7.5 to 15-times the average flow at the mouth of the Mississippi River in the United States, which is the 15th largest river in the world as measured by discharge volume. The Mississippi discharges nearly 16,800 cubic meters of water per second into the Gulf of Mexico.

The atmospheric rivers that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding. Not all atmospheric rivers cause damage; most are weak systems that often provide beneficial rain or snow that is crucial to the water supply.

Related Articles

• Atmosphere
• Weather

Further Reading

• "What are atmospheric rivers?," National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce, December 2015.
• Atmospheric River Portal, Physical Sciences Laboratory, NOAA, website.
• "Rivers in the Sky: 6 Facts You Should Know About Atmospheric Rivers," U.S. Geological Survey (USGS), U.S. Department of the Interior, 14 Dec. 2021.