Atmospheric River

weather · water cycle · climate · sky

Invisible floating rivers. Atmospheric rivers are narrow bands of concentrated water vapor in the atmosphere that move through the sky like actual rivers flow on the ground. They're sometimes hundreds of miles wide and thousands of miles long, carrying massive amounts of moisture from tropical regions toward the poles.

Extreme rainfall makers. When an atmospheric river collides with mountains or cooler air, all that moisture condenses and falls as rain or snow. A single atmospheric river can dump as much water in a few days as a region normally gets in several months.

Tropical to polar routes. These moisture corridors typically start over warm ocean waters near the tropics and travel toward higher latitudes, connecting tropical regions with polar areas. That's why they're sometimes called tropical plumes or tropical connections.

Both good and bad. While atmospheric rivers can cause dangerous flooding and mudslides, they also deliver essential water to dry regions and are a major part of Earth's water cycle. Without them, many areas would have very different weather patterns.

Recently discovered science. Scientists have been studying atmospheric rivers intensely only since the 1990s, using satellites and weather data to track and understand these powerful moisture systems better.