Atmospheric River

An atmospheric river is a narrow corridor of concentrated water vapor in the atmosphere, also called a tropical plume, moisture plume, water vapor surge or cloud band, typically thousands of kilometres long but only a few hundred kilometres wide, often positioned along the frontal zones of extratropical cyclones over the ocean. A single atmospheric river can carry a greater flow of water than the largest river on Earth, and together they account for over 90 percent of north-south water vapor transport worldwide while covering less than 10 percent of any given latitude line, contributing roughly 22 percent of global runoff. They are the main cause of extreme precipitation and flooding along mid-latitude westerly coastlines such as the west coast of North America, Western Europe, North Africa, the Iberian Peninsula, Iran and New Zealand, and their absence has been linked to droughts in South Africa, Spain and Portugal.