atmospheric river
noun
plural atmospheric rivers
: a concentrated band of water vapor that flows through the atmosphere and that is a significant part of the global hydrologic cycle and an important source of regional precipitation
Environment Canada is working on a new system to rank atmospheric rivers, a type of weather system that damaged highways, flooded farms and homes, and left at least four people dead in southern B.C. earlier this week.—Wendy Stueck
Atmospheric rivers are relatively long, narrow regions in the atmosphere—like rivers in the sky—that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.—National Oceanic and Atmospheric Administration
In a typical year, significant atmospheric river storms occur about 10 to 15 times in California. Ultimately, they account for up to 50% of the state's precipitation.—Paul Rogers
Cite this Entry
“Atmospheric river.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atmospheric%20river. Accessed 16 Sep. 2026.
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