Introduction Dome C, one of the summits of the Antarctic plateau (75°S, 123°E), was originally selected for the glaciological ice core programmes because glacier motions are minimal around a dome. Katabatic winds follow more or less the sFurface slopes, so that they are minimized near the domes, an a priori very favourable situation for astronomers. The local altitude is about 3260 m, but because of the low temperature, the surface pressure is equivalent to the surface pressure at an altitude of 3700 to 3800 m at more usual latitudes. Today, astronomy seems very likely to be among the major scientific activities to be intensely developed at Concordia in the future. At the Amundsen-Scott South Pole station, astronomy started a long time ago, and many site testing programs have been undertaken in optical and IR astronomy (see e.g. Pomerantz 1986). In 1991–92 Gillingham suggested that exceptionally good seeing could be expected above the high part of the Antarctic Polar Plateau. A preliminary site testing campaign was done at Dome C in 1996 (Marks et al. 1999). Then, during each summer campaign since 2000, with the construction of the permanent station, an astronomical site testing program has been implemented step by step, to be ready for operation during this first winter. It contains three DIMM (Differential Image Motion Monitor) telescopes (Aristidi et al. 2005a), one of them on top of a 5 m high platform, and the other two at the snow surface level, being operated together in the GSM (Grating Scale Monitor) mode (Ziad et al. 2000). Scintillation and isoplanatic angle measurements are also carried out. Temperature sensors have been installed on the 32 m high metallic mast for in situ measurements of the air turbulence in the ground based inversion layer. Meteorological balloons specially equipped with similar micro-thermal sensors are launched twice per week, for probing the turbulence up to the higher atmospheric layers (Azouit & Vernin 2005) The first seeing winter measurements was done in 2004 by the Automatic Astrophysical Site Testing International Observatory (AASTINO), installed at Dome C in 2003 by Australian team of University of New South Wales (Lawrence et al. 2004). From a combination of SODAR and MASS data, a mean seeing value of 0.27 arcsec was obtained during the autumn season (23 March–5 May), the measurements being sensitive to atmospheric layer above 30 m. In 2005, the first over-wintering team made it possible to run the site testing program during the whole winter. The DIMM instruments showed a regular deterioration of the ground based seeing quality with the decreasing winter temperature. On the other hand 30 radio-sounding during the dark time have shown a ground inversion layer that is very turbulent, with a thickness of 20–50 m (Agabi et al. 2006) During the four previous summers (mid-November to early February), 200 meteorological balloons equipped with standard meteo radiosondes were been launched (Aristidi et al. 2005b). They provide the following parameters: altitude, temperature, pressure, humidity, wind speed and direction, up to altitudes generally between 20 and 25 km, and sometimes slightly higher. One of the first astronomically interesting results of these summer radio- soundings has been the confirmation that wind speed above Antarctic Science 18 (3), 437–444 (2006) © Antarctic Science Ltd Printed in the UK DOI: 10.1017/S0954102006000484 437 On the atmosphere for astronomers above Dome C, Antarctica T. SADIBEKOVA 1,3 , E. FOSSAT 1 , C. GENTHON 2 , G. KRINNER 2 , E. ARISTIDI 1 , K. AGABI 1 and M. AZOUIT 1 1 Laboratoire Universitaire d’Astrophysique de Nice, Université de Nice Sophia Antipolis, UMR 6525 Parc Valrose 06108 Nice France 2 Laboratoire de Glaciologie et Géophysique de l’Environnement (Université Joseph Fourier, Grenoble I et CNRS) 54 Rue Moliere, DU BP 96 F-38402 Saint Martin d’Heres Cedex, France 3 ESO (European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany sadibeko@unice.fr Abstract: This paper describes a comparison between balloon radio-soundings made in summer at the Concordia station, Dome C, Antarctica and coincident model-based meteorological analyses. The comparison allows the assessment of the reliability of the analyses in summer. This allows the use of the winter analyses within an estimated range of uncertainty, while the first in situ measurements are just becoming available. The astronomical interest is to produce an estimate of atmospheric turbulence during the Antarctic winter at this very promising site. For this work the 6-hourly ECMWF operational analyses were used, concurrently with the data obtained in situ by the radio-sounding made at Concordia with standard meteorological balloons and sondes during four summer seasons (November–January), from December 2000 to the end of January 2004. Received 18 January 2006, accepted 18 April 2006 Key words: Antarctic plateau, ECMWF analyses, optical turbulence, radio-soundings, site testing, temperature gradient, wind gradient https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102006000484 Downloaded from https://www.cambridge.org/core. IP address: 78.245.229.30, on 13 Dec 2017 at 11:07:03, subject to the Cambridge Core terms of use, available at