October 1, 2018
Feature

Atmosphere Outpaces Ocean in Driving Extreme Winter Weather on U.S. West Coast

Researchers found that sea surface temperature, the more predictable element of the climate system, accounts for only 20 percent of extreme precipitation variability along the U.S. West Coast

Cloudy beach

Atmospheric dynamics account for 80 percent of variances in winter precipitation on the U.S. West Coast, while sea surface temperature contributes 20 percent.

The Science

Historical records show the U.S. West Coast exhibits a wide range of extreme precipitation during the winter. Understanding the large-scale environmental influences—or forcing—that contribute to this variability is important for improving predictions of regional climate. Scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory led a study to investigate the relative contributions of sea surface temperature (SST) and atmospheric dynamics to the year-to-year variability of extreme precipitation over the U.S. West Coast. They found that SST forcing accounted for only about 20 percent of the variances of winter extreme precipitation. The remaining 80 percent of extreme precipitation variations were associated with atmospheric dynamics, which are harder to predict than the slowly evolving SST.

The Impact

Extreme precipitation poses significant risks to human life and property, and challenges water management by causing flooding, landslides, and related hazards. Along the U.S. West Coast, extreme precipitation is marked by significant variability that is not fully understood or adequately simulated by models. This study ruled out SST forcing in favor of difficult-to-predict atmospheric variability as the primary influence on year-to-year winter extreme precipitation along the U.S. West Coast. Applied to the winter of 2016–17, the results suggest limited predictability for the multiple landfalling atmospheric rivers and the extreme precipitation that battered California.

 

Reference: L Dong, LR Leung, FF Song, and J Lu, 2018. "Roles of SST versus internal atmospheric variability in winter extreme precipitation along the U.S. West Coast." Journal of Climate 31, 8039-8058 (2018). [http://doi.org/10.1175/jcli-d-18-0062.1.]

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About PNNL

Pacific Northwest National Laboratory draws on its distinguishing strengths in chemistry, Earth sciences, biology and data science to advance scientific knowledge and address challenges in sustainable energy and national security. Founded in 1965, PNNL is operated by Battelle for the Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States. DOE’s Office of Science is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science. For more information on PNNL, visit PNNL's News Center. Follow us on Twitter, Facebook, LinkedIn and Instagram.

Published: October 1, 2018

Research Team

Lu Dong, Lai-yung Ruby Leung, Fengfei Song, and Jian Lu