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Extremely stable boundary layer on the Antarctic plateau

Extremely stable boundary layer on the Antarctic plateau C. genthon, M. Town, D. Six, V. Favier, LGGE, France L. Genoni, A. Pellegrini, ENEA, Italy C. Pouzenc, SIRENE, France genthon@lgge.obs.ujf-grenoble.fr. Climate Change 2007: Working Group I: The Physical Science Basis

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Extremely stable boundary layer on the Antarctic plateau

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  1. Extremely stable boundary layer on the Antarctic plateau C. genthon, M. Town, D. Six, V. Favier, LGGE, France L. Genoni, A. Pellegrini, ENEA, Italy C. Pouzenc, SIRENE, France genthon@lgge.obs.ujf-grenoble.fr Climate Change 2007: Working Group I: The Physical Science Basis Chapter 11: Regional Climate Projections Sub-chapter 11.8: The Polar Regions Excerpt: « ... Processes that are not particularly well represented in the models are clouds,planetary boundary layer processes and sea ice... » Predicted winter surface warming, 2090/2100 – 2000/2010 IPSLCM4 IPCC (°C)... .... and upper air Dome C, Antarctica Latitude 75°06.06S Longitude 123°20.74E Altitude 3300m A permanent station, Concordia, jointly operated by the French and Italian polar institutes (IPEV, PNRA) Dome C selected as a « hot spot » for CLMIP5 / IPCC AR5 A 45-m boundary layer profiling system was deployed in early 2008 The observations for the austral summer 2008, convective layer in the early afternoon, strong wind shear at night, are challenging for the ECMWF (and other) model (Genthon et al. 2010) OBS ECMWF Because of extremely cold temperatures and massive frost deposition, many instruments failed during the winter of 2008. They were subsequently improved and almost a full winter could finally be continuously sampled in 2009 Inversions of more than 0.7°C / m along the tower, more than 2°C / m locally, have been observed. This is only partially reproduced by the ECMWF model On the other hand, the chronological march of temperature is reproduced, including the occurrence and timing of warm events in winter during which surface temperature rises from -70°C to -30° within a day or so Other results (not shown): Relative humidity is consistently higher at the top of the tower, and in fact close to saturation, than at the (colder) surface: Moisture is brought to the lower atmosphere by subsidence from the free troposphere rather than by surface evaporation ; Strong wind shears are observed, that can only be sustained because of high static stability / strong stratification We acknowledge: IPEV and PNRA for support on the field, IPEV programs CONCORDIASI AND CALVA INSU and CNES for other support Reference: Genthon et al, 2010. Atmospheric boundary layer measurements and ECMWF analyses during summer at Dome C, Antarctica. J. Geophys. Res., 115, D05104, doi:10.1029/2009JD012741

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