Simulating Southern Ocean Mixed Phased Aerosol-Cloud interactions and Ice Microphysics with the NCAR Community Atmosphere Model

The abundance of mixed phase clouds and dominance of marine aerosol over the Southern Ocean (SO) challenges the aerosol-cloud microphysical interactions that are currently represented in global climate models. These processes are important for correctly simulating cloud phase, precipitation, lifetime and thus cloud radiative forcing. Two limitations have challenged our ability to accurately simulate SO clouds: 1) poor numerical representations of the freezing processes occurring in SO clouds and 2) a severe lack of SO aerosol and cloud observations. Recent advances in cloud microphysical parameterizations used in the Community Earth System Model Version 2.0 (CESM) allow models to simulate supercooled liquid clouds, but biases remain. In this study, simulated aerosol and cloud phase are evaluated against remote sensing and in situ measurements of aerosol activation properties, cloud phase and structure from the 2018 Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES). Nudged simulations designed to investigate the role of primary ice nucleation, secondary ice production, and Wegener-Bergeron-Findeisen processes in SO cloud properties will also be presented.