Southern Ocean Solar Reflection Biases in CMIP6 Models Linked to Cloud Phase and Vertical Structure Representations

Over the Southern Ocean (SO, 40°S–70°S), climate models have consistently underestimated solar reflection. Here we evaluate relationship between cloud profiles, phase and radiation over SO in Coupled Model Intercomparison Project Phase 6 (CMIP6) against Clouds Earth's Radiant Energy System Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations. We find that lack of reflection is slightly improved CMIP6 compared to CMIP5's, attributable a better representation fraction phase. show clouds different vertical structure radiative effect south north where 0°C isotherm meets surface (∼55°S). Although capture greater extent 55°S, they fail reproduce observed increase reflection, which pinpoint biases. Increasing supercooled liquid opacity should help reduce their persistent shortwave