Study previews how climate change may alter rain-making atmospheric rivers by 2100

The people, economy, and ecosystems of the Pacific coast states of California, Oregon and Washington are highly dependent on cool-season atmospheric rivers for their annual water supply. These long, narrow flows of saturated air can transport enormous amounts of water vapor - roughly equivalent to the flow at the mouth of the Mississippi River. They can unload heavy precipitation on the Cascade and Sierra Nevada ranges, but their annual yield regularly swings between boom and bust.

When atmospheric rivers, or ARs, fail to materialize, droughts often follow - especially in California, where they account for over 50% of the total annual precipitation. Anticipating future climate-induced changes to AR patterns is therefore exceedingly important. Global models, however, do a poor job of simulating precipitation over the complex terrain of coastal and inland mountain ranges. Now, a new NOAA study using data generated by regional climate models and published in the journal Climate Dynamics suggests climate change will likely alter atmospheric rivers in ways that will make managing water more difficult.

“These high-resolution climate simulations showed something we hadn't seen before, which was decreased future precipitation amounts across many mountainous regions of the western United States,” said lead author Mimi Hughes, a research scientist in NOAA’s Physical Sciences Laboratory.