Atmospheric River Frequency-Category Characteristics Shape U.S. West Coast Runoff

Zhou, Yang, North, Joshua S., Rhoades, Alan M., Tao, Jing, Rudisill, William, Risser, Mark D. and Collins, William D. ORCID: https://orcid.org/0000-0002-4463-9848 (2025) Atmospheric River Frequency-Category Characteristics Shape U.S. West Coast Runoff. Journal of Geophysical Research: Atmospheres, 130 (2). ISSN 2169-897X

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Abstract

This study investigates the factors influencing runoff response to atmospheric rivers (ARs) over the U.S. West Coast. We focused on runoff time series variations impacted by AR characteristics (e.g., category and frequency) and land preconditions during Northern Hemisphere cool seasons in the period of 1940–2023. Results show that high-category ARs significantly increase local runoff with higher hourly precipitation rates leading to a greater incremental rate and peak runoff. Extreme runoff increases greatly with the AR category with an increase rate up to 12.5 times stronger than non-extreme runoff. Besides the AR category, land preconditions such as soil moisture and snowpack also play crucial roles in modulating runoff response. We found that runoff induced by weak-category ARs is more sensitive to land preconditions than high-category ARs, with high peak runoff occurring when soil is nearly saturated. Additionally, more than 50% of high-peak-runoff events in snow-covered grid cells are associated with rain-on-snow events particularly for the events associated with weaker ARs. Regression analysis reveals that AR precipitation and land preconditions jointly influence runoff, emphasizing the importance of including soil moisture and snowpack levels in AR impact assessments. The study also highlights the intensified runoff response to back-to-back ARs with short intervals, which may become more frequent with climate warming, posing increased flood risks via facilitating wet soil conditions. Our findings have significant implications for AR risk predictions and the development of prediction models for AR-induced runoff.

Item Type: Article
Additional Information: Data Availability Statement: The ERA5 hourly data can be retrieved from https://cds.climate.copernicus.eu/datasets/reanalysis‐era5‐pressure‐levels?tab=overview. The ERA5 cold content is calculated and archived in https://portal.nersc.gov/archive/home/a/arhoades/Shared/www/ERA5_Cold_Content.
Uncontrolled Keywords: antecedent soil moisture,atmospheric river,runoff,soil moisture,temporal clustering,geophysics,atmospheric science,space and planetary science,earth and planetary sciences (miscellaneous),sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/1900/1908
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 14 Aug 2026 15:22
Last Modified: 16 Aug 2026 06:24
URI: https://ueaeprints.uea.ac.uk/id/eprint/104156
DOI: 10.1029/2024JD041805

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