Atmospheric Rivers


What is an atmospheric river?

You’ve probably heard the media refer to the recent winter storms we’ve experienced as part of an atmospheric river (AR), but what is it?

Atmospheric rivers are relatively narrow regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics.

They come in many shapes, sizes, and strengths. Those that contain the largest amounts of water vapor, the strongest winds, and capability to stall over watersheds vulnerable to flooding, can create extreme rainfall and floods.

Warning and Water Supply.

These events can disrupt travel, induce mud slides, and cause catastrophic damage to life and property. However, not all ARs cause damage – most are weak, and simply provide beneficial rain or snow that is crucial to water supply.

They are a primary feature in the entire global water cycle, and are tied closely to both water supply and flood risks, particularly in the Western U.S. On average, about 30-50% of annual precipitation in the west coast states occurs in just a few AR events, thus contributing to water supply.

From Drought to Deluge.

While we may be experiencing an atmospheric river now, please know that one wet year is not a drought buster. The wet beginning to 2017 is a welcome relief from the past five dry years…but the rains did not wash away California’s major water challenges.