Understanding the Role of Air–Sea Interaction on Extreme Rainfall in Aquaplanet and Earth-like CESM

Extreme precipitation events are associated with anomalous, latitudinally dependent dynamical and convective weather systems. For example, plumes of excessive poleward water vapor transport and topographical effects drive extreme precipitation events in the midlatitudes, while intense tropical precipitation is associated with organized convective systems. In both cases, air-sea fluxes have the potential to contribute significantly to the moisture budget of these storms, but the roles of surface fluxes and upper-ocean processes and their impact on precipitation extremes have yet to be explored in sufficient detail. To examine such mechanisms, we implement a climate model hierarchy that encompasses a spectrum of ocean models, from prescribed-SST to fully dynamic, as well as both aquaplanet and Earth-like lower boundary types within the Community Earth System Model (CESM). Using the CESM hierarchy and comparing to observations, we identify key moisture processes and related air-sea interactions that drive extreme precipitation events across different latitudes in Earth-like models and then generalize the analyses in aquaplanet configurations to highlight the most salient features. The analyses are applied to both present-day and global warming conditions to investigate how these fundamental mechanisms might change extreme precipitation events in the future climate.