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Parikka J, Le Romancer M, Wauters N & Jacquet S. (2014). Insights into Virus-host relationships..
Abstract: EMBO Conference, Viruses of Microbes III, Zurich (Switzerland), 14-18 July.
Programme: 1077
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L. Testut and A.S Unnikrishnan. (2014). Overview of the Sea Level research activities in France, Indo-French collaboration : current status and perspective.
Abstract: 20 january 2014, INCOIS, Hyderabad (India).
Programme: 688
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Picard G, Royer A, Arnaud L, Fily M, . (2014). Influence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica
. TC, 8(3), 1105–1119.
Abstract: based on BIPOL and CALVA-snow
Programme: 1110
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Fréville H, Brun E, Picard G, Tatarinova N, Arnaud L, Lanconelli C, Reijmer C, van den Broeke M, . (2014). Using MODIS land surface temperatures and the Crocus snow model to understand the warm bias of ERA-Interim reanalyses at the surface in Antarctica
. TC, 8(4), 1361–1373.
Abstract: based on CALVA-snow activities
Programme: 1110
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Libois Quentin, Picard Ghislain, Dumont Marie, Arnaud Laurent, Sergent Claude, Pougatch Evelyne, Sudul Marcel, Vial David, . (2014). Experimental determination of the absorption enhancement parameter of snow
. Journal of Glaciology, 60(222), 714–724.
Abstract: In optical models snow is commonly treated as a disperse collection of particles. In this representation, the penetration depth of solar radiation is sensitive to the shape of the particles, in particular to the absorption enhancement parameter, B, that quantifies the lengthening
Keywords: SNOW, SNOW CHEMISTRY, SNOW PHYSICS, SNOW/ICE SURFACE PROCESSES,
Programme: 1110
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Roussel D., Marmillot V., Rouanet J.L., Monternier P.A. (2014). Mitochondrial phenotypic flexibility enhances energy savings during winter fast in king penguin chicks. 10ième journée scientifique du Comité National Français des Recherches Arctiques et Antarctiques (CNFRA), Rennes. (26-27 mai).
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Palerme C, Kay J E, Genthon C, L'Ecuyer T, Wood N B, Claud C, . (2014). How much snow falls on the Antarctic ice sheet?
. The Cryosphere, 8(4), 1577–1587.
Abstract: Abstract: Climate models predict Antarctic precipitation to increase during the 21st century, but their present day Antarctic precipitation differs. A model-independent climatology of the Antarctic precipitation characteristics, such as snowfall rates and frequency, is needed to assess the models, but was not available so far. Satellite observation of precipitation by active spaceborne sensors has been possible in the polar regions since the launch of CloudSat in 2006. Here we use two CloudSat products to build the first multi-year model-independent climatology of Antarctic precipitation. The first product is used to determine the frequency and the phase of precipitation, while the second product is used to assess the snowfall rate. The mean snowfall rate from August 2006 to April 2011 is 171 mm/year over the Antarctic ice sheet north of 82°S. While uncertainties on individual precipitation retrievals from CloudSat data are potentially large, the mean uncertainty should be much smaller but cannot be easily estimated. There are no in situ measurements of Antarctic precipitation to directly assess the new climatology. However distributions of both precipitation occurrences and rates generally agree with the ECMWF ERA-Interim dataset, the production of which is constrained by various in situ and satellite observations but did not use any data from CloudSat. The new dataset thus offers unprecedented capability to quantitatively assess Antarctic precipitation statistics and rates in climate models.
Programme: 1013
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Carmagnola C M, Morin S, Lafaysse M, Domine F, Lesaffre B, Lejeune Y, Picard G, Arnaud L, . (2014). Implementation and evaluation of prognostic representations of the optical diameter of snow in the SURFEX/ISBA-Crocus detailed snowpack model
. TC, 8(2), 417–437.
Abstract: In the SURFEX/ISBA-Crocus multi-layer snowpack model, the snow microstructure has up to now been characterised by the grain size and by semi-empirical shape variables which cannot be measured easily in the field or linked to other relevant snow properties. In this work we introduce a new formulation of snow metamorphism directly based on equations describing the rate of change of the optical diameter (dopt). This variable is considered here to be equal to the equivalent sphere optical diameter, which is inversely proportional to the specific surface area (SSA). dopt thus represents quantitatively some of the geometric characteristics of a porous medium. Different prognostic rate equations of dopt, including a re-formulation of the original Crocus scheme and the parameterisations from Taillandier et al. (2007) and Flanner and Zender (2006), were evaluated by comparing their predictions to field measurements carried out at Summit Camp (Greenland) in May and June 2011 and at Col de Porte (French Alps) during the 2009/10 and 2011/12 winter seasons. We focused especially on results in terms of SSA. In addition, we tested the impact of the different formulations on the simulated density profile, the total snow height, the snow water equivalent (SWE) and the surface albedo. Results indicate that all formulations perform well, with median values of the RMSD between measured and simulated SSA lower than 10 m2 kg-1. Incorporating the optical diameter as a fully fledged prognostic variable is an important step forward in the quantitative description of the snow microstructure within snowpack models, because it opens the way to data assimilation of various electromagnetic observations.
Programme: 1042
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Legrand M, Preunkert S, Frey M, Bartels-Rausch T, Kukui A, King M D, Savarino J, Kerbrat M, Jourdain B, . (2014). Large mixing ratios of atmospheric nitrous acid (HONO) at Concordia (East Antarctic plateau) in summer: a strong source from surface snow?
. Atmos. Chem. Phys. Discuss., 14(8), 11749–11785.
Abstract: During the austral summer 2011/2012 atmospheric nitrous acid was investigated for the second time at the Concordia site (75060 S, 123330 E) located on the East Antarctic plateau by deploying a long path absorption photometer (LOPAP). Hourly mixing ratios of HONO measured in December 2011/January 2012 (35±5.0 pptv) were similar to those measured in December 2010/January 2011 (30.4±3.5 pptv). The large value of the HONO mixing ratio at the remote Concordia site suggests a local source of HONO in addition to weak production from oxidation of NO by the OH radical. Laboratory experiments demonstrate that surface snow removed from Concordia can produce gas phase HONO at mixing ratios half that of NOx mixing ratio produced in the same experiment at typical temperatures encountered at Concordia in summer. Using these lab data and the emission flux of NOx from snow estimated from the vertical gradient of atmospheric concentrations measured during the campaign, a mean diurnal HONO snow emission ranging between 0.5 and 0.8×109 moleculescm-2 s-1 is calculated. Model calculations indicate that, in addition to around 1.2 pptv of HONO produced by the NO oxidation, these HONO snow emissions can only explain 6.5 to 10.5 pptv of HONO in the atmosphere at Concordia. To explain the difference between observed and simulated HONO mixing ratios, tests were done both in the field and at lab to explore the possibility that the presence of HNO4 had biased the measurements of HONO.
Programme: 903
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Kukui A, Legrand M, Preunkert S, Frey M M, Loisil R, Gil Roca J, Jourdain B, King M D, France J L, Ancellet G, . (2014). Measurements of OH and RO2 radicals at Dome C, East Antarctica
. Atmos. Chem. Phys. Discuss., 14(10), 14999–15044.
Abstract: Concentrations of OH radicals and the sum of peroxy radicals, RO2, were measured in the boundary layer for the first time on the East Antarctic Plateau at the Concordia Station (Dome C, 75.10 S, 123.31 E) during the austral summer 2011/2012. The median concentrations of OH and RO2 radicals were 3.1×106 molecule cm-3 and 9.9×107 molecule cm-3, respectively. These values are comparable to those observed at the South Pole, confirming that the elevated oxidative capacity of the Antarctic atmospheric boundary layer found at the South Pole is not restricted to the South Pole but common over the high Antarctic plateau. At Concordia, the concentration of radicals showed distinct diurnal profiles with the median maximum of 5.2×106 molecule cm-3 at 11:00 and the median minimum of 1.1×106 molecule cm-3 at 01:00 for OH radicals and 1.7×108 molecule cm-3 and 2.5×107 molecule cm-3 for RO2 radicals at 13:00 and 23:00, respectively (all times are local times). Concurrent measurements of O3, HONO, NO, NO2, HCHO and H2O2 demonstrated that the major primary source of OH and RO2 radicals at Dome C was the photolysis of HONO, HCHO and H2O2, with the photolysis of HONO contributing _ 75% of total primary radical production. However, photochemical modelling with accounting for all these radical sources overestimates the concentrations of OH and RO2 radicals by a factor of 2 compared to field observations. Neglecting the OH production from HONO in the photochemical modelling results in an underestimation of the concentrations of OH and RO2 radicals by a factor of 2. To explain the observations of radicals in this case an additional source of OH equivalent to about 25% of measured photolysis of HONO is required. Even with a factor of 4 reduction in the concentrations of HONO, the photolysis of HONO represents the major primary radical source at Dome C. Another major factor leading to the large concentration of OH radicals measured at Dome C was large concentrations of NO molecules and fast recycling of peroxy radicals to OH radicals.
Programme: 903
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