Uncertainty in California Winter Precipitation Linked to Future Projections of North Pacific Large‐Scale Atmospheric Circulation
Accurate estimates of future changes in California winter precipitation are essential for informed water management in the region. In this study, we evaluate projected changes in winter precipitation and their uncertainties over California using the high‐resolution LOCA2‐HybridCA data set, downscaled from the Coupled Model Intercomparison Project 6 projections. Although this data set corrects model mean biases and realistically captures climatological orographic precipitation patterns, substantial inter‐model diversity remains in future projections. This diversity is closely related to the uncertainty in changes of the North Pacific Subtropical High (NPSH). Their relationship is strongest along the Central Coast, where 53% of the diversity in winter precipitation changes among models is explained by the diversity in NPSH latitude changes, which is largely linked to changes in extratropical North Pacific sea surface temperature. This result suggests that California winter precipitation changes in a warming climate are significantly influenced by North Pacific air–sea coupling. It highlights that accurately representing the North Pacific ocean and its interaction with the atmosphere is essential for reducing uncertainty in California's future hydroclimate.