At least three people have been killed by falling trees as a powerful storm drenches California (USA) bringing flooding, mudslides and power outages.
- The storm is due to an “atmospheric river” effect, a phenomenon in which water evaporates into the air and is carried along by the wind, forming long currents that flow in the sky like rivers flow on land.
- Atmospheric rivers are narrow bands of concentrated water vapor in the atmosphere, typically extending from the tropics to mid- and high latitudes.
- These intense atmospheric moisture bands are invisible to the naked eye, but satellite instruments can help us see these “rivers in the sky” by using infrared sensors, which is how scientists visualize them.
- Atmospheric rivers are responsible for transporting large amounts of water vapor across the globe, particularly from the tropics to the poles.
- Atmospheric rivers are often associated with strong low-level wind ahead of the cold front of an extratropical cyclone, particularly during the winter.
- A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.
