Atmospheric Rivers

Atmospheric rivers (AR) are long and narrow bands of moist air in the lower troposphere. They are typically more than 2000 km long and less than 1000 km wide, located at levels below 700 hPa. ARs are characterized by strong low-level winds, which run in parallel to the river itself. ARs carry out the majority of global water transport from the tropics to the north, like rivers in the sky. They are primarily found over the oceans on the warm side of the polar front, often in the warm sector of extratropical cyclones near the leading edge of a cold front. When making landfall, ARs are responsible for episodes of heavy precipitation.