Atmospheric Rivers Impacting Northern California Exhibit a Quasi‐Decadal Frequency. Issue 15 (10th August 2021)

• Record Type: Journal Article
• Authors: Stuivenvolt‐Allen, Jacob; Wang, Shih‐Yu Simon; Johnson, Zachary; Chikamoto, Yoshimitsu
• Is Part Of: Journal of geophysical research. Volume 126:Issue 15(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-10
• Subjects: atmospheric rivers -- quasi‐decadal variability -- water availability -- Northern California; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD034196
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Periods of water surplus and deficit in Northern California follow a pronounced quasi‐decadal cycle. This cycle is largely driven by the frequency of atmospheric rivers (ARs), affecting the region's wet and dry periods. Our analyses demonstrate that the quasi‐decadal cycle of AR frequency relies on moisture transport associated with the position and intensity of the Aleutian Low. In observations, the Aleutian Low is shown to covary with tropical Pacific sea surface temperature anomalies. A modeling experiment, which incorporates ocean observations from the equatorial Pacific into the fully coupled climate model, provides support that the quasi‐decadal cycle of the Aleutian Low is forced by the tropical Pacific. Subsequently, the tropical Pacific modulates the wet season moisture transport toward California on decadal time scales, affecting AR frequency. These results provide metrics for improving interannual‐to‐decadal prediction of AR activity, which drives hydrological cycles in Northern California. Plain Language Summary: In Northern California, much of the precipitation and surface water comes from atmospheric rivers–corridors of moisture transport from the tropics. The frequency of atmospheric rivers is cyclical, with periods of water surplus and deficit in the region that repeat every 10–17 years. While many social and political factors influence water resource distribution, understanding the climate factors that regulate water availability is important for managing water in the future. Using data from observations and modeling experiments, the pronounced wet/dry cycle in this area of the Western United States is mainly attributed to regular fluctuations in sea surface temperatures in the tropical Pacific Ocean. This analysis provides a potential source of predictability for atmospheric river frequency, and thus water availability, years before a winter season. Key Points: The frequency of atmospheric rivers over Northern California exhibits a pronounced quasi‐decadal cycle Cyclical variability in the tropical Pacific accentuates or weakens the Aleutian Low–impacting atmospheric river frequency This analysis provides metrics for improving decadal prediction of atmospheric rivers and regional surface hydrology