Microphysical Properties of Mixed-phase and Ice Clouds over the Southern Ocean and Antarctica and Comparison with NCAR CAM model

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Description

Mixed-phase and ice clouds play very important roles in regulating atmospheric radiation over the Southern Ocean and Antarctica. Previously, ground-based and in-situ observations over this remote region are very limited, and there is a scarcity of observational-based studies that evaluated global climate model simulations in the southern high latitudes. In this work, we will use the DOE ARM ground-based observations at Antarctica and two NSF flight campaigns over the Southern Ocean, to examine cloud macrophysical and microphysical properties from the microscale to mesoscale. Three datasets to be used in this work are: DOE ARM West Antarctic Radiation Experiment (AWARE) campaign based at the McMurdo station at Antarctica (2016 – 2017), the NSF O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) Study campaign based at Punta Arenas, Chile (2016), and the NSF Southern Ocean, Clouds, Radiation, Aerosol, Transport Experimental Study (SOCRATES) campaign based at Hobart, Australia (2018). Simulations from the NCAR Community Atmosphere Model Version 5 and Version 6 (CAM5 and CAM6) will be compared with observations. One of the highlights of our analyses is that we conducted a scale-aware comparison by averaging in-situ observations over horizontal lengths from ~100 meters to 50 kilometers (D’Alessandro et al. 2019). Various scales of observations will be used to show the impacts of horizontal scales on the model-observation comparisons. Cloud characteristics to be examined include the occurrence frequency of cloud thermodynamic phases, mass partition of liquid and ice at various temperatures, liquid/ice water content, liquid/ice number concentrations, relative humidity and ice supersaturation conditions. Reference D’Alessandro, J. J., M. Diao, C. Wu, X. Liu, J. B. Jensen, and B. Stephens, 2019: Cloud phase and relative humidity distributions over the Southern Ocean in austral summer based on in situ observations and CAM5 simulations. Accepted, doi:10.1175/JCLI-D-18-0232.1.