Moisture Transport by Extratropical Cyclones and Fronts in High-Resolution Climate Change Simulations

Extratropical cyclones (ETCs) play a pivotal role in hydrological processes of the atmosphere, such as evaporation, moisture transport and precipitation. Long-term changes in the hydrological contribution of ETCs will therefore have important impacts on shifts in precipitation patterns, droughts, and extreme events. ETCs are projected to decrease in frequency and increase in intensity under global warming—maintaining a near balance in their net contribution to moisture fluxes. However, hydrological cycle changes associated with cyclonic fronts may exhibit stronger signals and are more uncertain, because these frontal systems are often under-resolved in coarse grid simulations.

In this study, we investigate how higher resolution modeling affects the impacts that ETCs will have on atmospheric moisture fluxes under global warming, while also accounting for the contribution of cyclonic fronts. We analyze long-term MESACLIP historical and future simulations at varying resolutions (up to ~25 km). Using cyclone and front tracking algorithms, we quantify long-term changes in ETC-induced freshwater fluxes and compare results across model resolutions. Because small-scale processes are crucial for cyclogenesis and associated fluxes, we expect stronger air–sea coupling and enhanced vertical motions along cyclonic fronts in higher-resolution models, potentially amplifying the overall imprint of ETCs on important hydrological processes of the atmosphere. Our work highlights the need to adequately account for frontal processes when assessing future changes in atmospheric moisture fluxes.