Atmospheric rivers and energy transport in a hierarchy of idealized models

Atmospheric rivers (ARs) play a major role in both global moisture and energy transport. There has been substantial research exploring the sources and pathways of moisture in these features, which often cooccur with extratropical cyclone systems and spatially overlap with the cyclone’s warm conveyor belt. However, how these features contribute to the convergence and transport of energy at a local and global scale is less well understood. Our new work uses Isca, an idealized modeling framework, to construct a hierarchy of models with varying complexity. By varying the radiation scheme from a simple, gray radiation scheme, to a scheme including water vapor feedbacks, to a full radiative transfer scheme, this model hierarchy allows us to use mechanism denial to better understand the physical processes that govern the AR size, frequency, and their role in energy convergence and transport. We examine how moisture and energy transport change throughout the AR lifecycle, and with varying levels of CO₂ forcing. We also present a new, threshold-free AR identification method that performs equally well across a variety of warming and cooling experiments, without arbitrary adjustments of thresholds, allowing us to accurately assess changes to AR frequency, size, and energy and moisture transport in a variety of climate states. This work provides new insight into the nature of ARs, their internal structure and lifecycles, and their role in the global energy budget.