Genesis of diamond dust, ice fog and thick cloud episodes observed and modelled above Dome C, Antarctica
Episodes of thick cloud and diamond dust/ice fog were observed during 15 March to 8 April 2011 and 4 to 5 March 2013 in the atmosphere above Dome 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 the processes that cause th...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/5221/2017/acp-17-5221-2017.pdf |
| Summary: | Episodes of thick cloud and diamond dust/ice fog were observed
during 15 March to 8 April 2011 and 4 to 5 March 2013 in the atmosphere above
Dome 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 the
processes that cause these episodes based on observations and to verify
whether operational models can evaluate them. The measurements were obtained
from the following instruments: (1) a ground-based microwave radiometer
(HAMSTRAD, H<sub>2</sub>O Antarctica Microwave Stratospheric and Tropospheric
Radiometers) installed at Dome C that provided vertical profiles of
tropospheric temperature and absolute humidity every 7 min; (2) daily
radiosoundings launched at 12:00 UTC at Dome C; (3) a tropospheric aerosol
lidar that provides aerosol depolarization ratio along the vertical at Dome
C; (4) down- and upward short- and long-wave radiations as provided by the
Baseline Surface Radiation Network (BSRN) facilities; (5) an ICE-CAMERA to
detect at an hourly rate the size of the ice crystal grains deposited at the
surface of the camera; and (6) space-borne aerosol depolarization ratio from the
Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar aboard the
Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)
platform along orbits close to the Dome C station. The time evolution of the
atmosphere has also been evaluated by considering the outputs from the
mesoscale AROME and the global-scale ARPEGE meteorological models. Thick
clouds are detected during the warm and wet periods (24–26 March 2011 and 4
March 2013) with high depolarization ratios (greater than 30 %) from the
surface to 5–7 km above the ground associated with precipitation of ice
particles and the presence of a supercooled liquid water (depolarization less
than 10 %) clouds. Diamond dust and/or ice fog are detected during the cold
and dry periods (5 April 2011 and 5 March 2013) with high depolarization
ratios (greater than 30 %) in the planetary boundary layer to a maximum
altitude of 100–300 m above the ground with little trace of precipitation.
Considering 5-day back trajectories, we show that the thick cloud episodes
are attributed to air masses with an oceanic origin whilst the diamond
dust/ice fog episodes are attributed to air masses with continental origins.
Although operational models can reproduce thick cloud episodes in the free
troposphere, they cannot evaluate the diamond dust/ice fog episodes in the
planetary boundary layer because they require to use more sophisticated cloud
and aerosol microphysics schemes. |
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| ISSN: | 1680-7316 1680-7324 |