Aerosols of Different Sources on Marine Boundary Cloud Properties and Drizzle Formation

Marine Boundary Layer (MBL) clouds cover about 23% of the ocean surface, provide a strong cooling effect in the Earth system because of their high albedo, wide spread, and long lifetime. However, untangling how atmospheric aerosols modulate MBL clouds and drizzle remains challenging from both observation and modeling perspectives. By combining aircraft aerosol/CCN measurements during the field campaign and aerosol reanalysis data, we find even remote regions like the Eastern North Atlantic (ENA) site experience frequent transboundary aerosol intrusions. The plumes are mainly located in the free troposphere but can penetrate into the boundary. The long-range transported aerosols are typically composed of smoke, anthropogenic, and/or mineral dust. Our back-trajectory analysis showed that the smoke and man-made aerosols are mainly from continental US during the summer. We conduct a series of sensitivity simulations of aerosol effects using an aerosol-aware eddy-resolving WRF model equipped with a spectral bin cloud microphysics. we find distinct cloud responses to aerosols at different vertical levels, even though the signs of aerosol effect are the same. Even if an aerosol layer exists right above the cloud layer, it can still exert an influence following the turbulent mixing. More details in the process-level responses of MBL clouds to aerosol perturbation will be discussed in this presentation.