Episodes of thick cloud and diamond dust/ice fog were observedduring 15 March to 8 April 2011 and 4 to 5 March 2013 in the atmosphere aboveDome C (Concordia station, Antarctica; 75°06′ S, 123°21′ E; 3233 m a.m.s.l.). The objectives of the paper are mainly to investigate theprocesses that cause these episodes based on observations and to verifywhether operational models can evaluate them. The measurements were obtainedfrom the following instruments: (1) a ground-based microwave radiometer(HAMSTRAD, HO Antarctica Microwave Stratospheric and TroposphericRadiometers) installed at Dome C that provided vertical profiles oftropospheric temperature and absolute humidity every 7 min; (2) dailyradiosoundings launched at 12:00 UTC at Dome C; (3) a tropospheric aerosollidar that provides aerosol depolarization ratio along the vertical at DomeC; (4) down- and upward short- and long-wave radiations as provided by theBaseline Surface Radiation Network (BSRN) facilities; (5) an ICE-CAMERA todetect at an hourly rate the size of the ice crystal grains deposited at thesurface of the camera; and (6) space-borne aerosol depolarization ratio from theCloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar aboard theCloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)platform along orbits close to the Dome C station. The time evolution of theatmosphere has also been evaluated by considering the outputs from themesoscale AROME and the global-scale ARPEGE meteorological models. Thickclouds are detected during the warm and wet periods (24–26 March 2011 and 4March 2013) with high depolarization ratios (greater than 30 %) from thesurface to 5–7 km above the ground associated with precipitation of iceparticles and the presence of a supercooled liquid water (depolarization lessthan 10 %) clouds. Diamond dust and/or ice fog are detected during the coldand dry periods (5 April 2011 and 5 March 2013) with high depolarizationratios (greater than 30 %) in the planetary boundary layer to a maximumaltitude of 100–300 m above the ground with little trace of precipitation.Considering 5-day back trajectories, we show that the thick cloud episodesare attributed to air masses with an oceanic origin whilst the diamonddust/ice fog episodes are attributed to air masses with continental origins.Although operational models can reproduce thick cloud episodes in the freetroposphere, they cannot evaluate the diamond dust/ice fog episodes in theplanetary boundary layer because they require to use more sophisticated cloudand aerosol microphysics schemes.
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