Large-Scale Controls and Latitudinal Dependence of North Pacific Atmospheric Rivers across a CESM2 Hierarchy

Atmospheric rivers (ARs), narrow plumes of copious horizontal water vapor transport, can have profound socioeconomic impacts through their ties to extreme precipitation. Model predictive skill and statistics of ARs, however, are challenged in part due to our insufficient understanding of the tropical and extratropical large-scale features that exert a strong influence on these storms. Moreover, the character of these precursor processes is highly dependent on the latitude of the landfalling AR. To explore these issues, we identify robust landfalling ARs within the northeast Pacific Ocean and examine the prominent large-scale features that lead to these events. We assess these systematic lagged relationships both in MERRA-2 reanalysis and across a CESM version 2 hierarchy spanning a range of ocean model complexity and including Earthlike and aquaplanet configurations. Results indicate that certain precursor features are common to AR landfalls both in the southwest and northwest United States, while others play a determining role in where northeast Pacific ARs make landfall. Such results have important implications for model AR predictability. An investigation of AR behavior in aquaplanets with incrementally increasing complexity is also reviewed in an effort to evaluate the fundamental processes that drive AR behavior.