Comparing large-eddy simulations of marine cold-air outbreaks in the Arctic under contrasting aerosol and ice nucleating particle concentrations and origins.

Marine cold-air outbreaks (MCAOs) in the Arctic lead to the formation of mixed-phase clouds that downwind from the sea ice edge transition from stratocumulus clouds organized as convective rolls to open convective cells. Results from modelling studies of MCAOs suggest that increases in ice nucleating particles (INP), ice crystal number concentrations (Ni) and frozen hydrometeors in general, cause a decrease in cloud water, which can accelerate the cloud transition. In this study, we make use of observations conducted during MCAOs characterized by both high INP concentrations, potentially linked to long-range transport, and low INP concentrations, most likely associated with local sources. We perform quasi-Lagrangian large-eddy simulations of two MCAOs in the Arctic with distinctly different meteorological conditions and investigate the impact of differences in the aerosol and INP concentrations and origin. We examine how perturbations in aerosols, INPs and the predicted cloud ice in the model affect the evolution of the mixed-phased clouds, aerosol processing, and the cloud radiative feedback during these cold air outbreaks.