Long-Range Transported Aerosols Modulate Clouds, Radiation, and Precipitation over the Greenland Ice Sheet

Atmospheric rivers (ARs) originating in the mid-latitudes can trigger extreme precipitation and melt events across the Greenland Ice Sheet (GrIS) by transporting heat and moisture. Additionally, ARs reaching Greenland can serve as pathways for episodic aerosol intrusions. Because Greenland has a limited local supply of aerosols, aerosol intrusions from the mid-latitudes could affect its cloud properties, radiative transfer, and precipitation. Yet, the impacts of aerosols transported by ARs on the GrIS remain poorly constrained. To address this knowledge gap, we analyzed an event involving long-range moisture and aerosol transport associated with the AR in April 2019 using the polar-optimized WRF-Chem. Compared with observations, the full-aerosol baseline simulation reasonably reproduced the aerosol optical depth, surface radiation balance, snow accumulation, and vertical cloud structure. Comparisons between sensitivity experiments with different aerosol boundary conditions but identical meteorological initial and boundary conditions yield two major findings. First, long-range-transported aerosols induced a GrIS-averaged net radiative warming of 2 W/m 2 (16% change), with warming reaching up to 22 W/m 2 over the ice-sheet interior. Second, the aerosol intrusion increased total precipitation over the GrIS by 6.3% and shifted precipitation from valleys (7.3% decrease) to ridges (7.9% increase) in southeastern Greenland. Both orographic forcing and cloud microphysical processes play important roles in precipitation redistribution. Furthermore, aerosol-cloud interactions, rather than direct aerosol-radiation interactions, dominate the changes in surface radiation and precipitation. Overall, these results demonstrate that aerosols can modulate the surface radiation balance and precipitation across the GrIS, with potential implications for its surface mass balance.