Ice and Mixed-Phase Cloud Characteristics over McMurdo, Antarctica and the Southern Ocean

Ice and mixed phase clouds over the Southern Ocean and Antarctica have large impacts on global cloud radiative effects. Previously, most evaluation studies of global climate models (GCM) relied on spaceborne remote sensing observations due to the remoteness of these locations and the lack of in-situ or ground-based observations. In this work, we will use ground-based observations at McMurdo, Antarctica as well as in-situ aircraft observations over the Southern Ocean to evaluate three climate models, i.e., NCAR Community Earth System Model version 2 / Community Atmosphere Model version 6 (CESM2/CAM6), NCAR CESM1/CAM5, and DOE Energy Exascale Earth System Model (E3SM).

A series of instrumental measurements are used, including the DOE ARM Ka-Band ARM Zenith Radar (KAZR), High-Spectral Resolution Lidar (HSRL), and radiosonde data in the DOE ARM West Antarctic Radiation Experiment (AWARE) campaign, as well as in-situ observations of clouds, water vapor and aerosols onboard the NSF/NCAR Gulfstream-V research aircraft during the NSF Southern Ocean Clouds, Radiation, Aerosol, Transport Experimental Study (SOCRATES) campaign. Occurrence frequencies of three cloud thermodynamic phases have been evaluated, including ice, liquid, and mixed phases. While CAM6 shows more similar results for cloud phase occurrence frequency compared with in-situ observations over the Southern Ocean, other model biases were also found. Quantifications of various model biases will be presented, including cloud fraction, cloud phase, cloud microphysical properties (i.e., ice water content, liquid water content, ice crystal and liquid droplet number concentration), and aerosol indirect effects.