Mesoscale optical turbulence simulations at Dome C

In recent years, ground-based astronomy has been looking towards Antarctica, especially its summits and the internal continental plateau, where the optical turbulence appears to be confined in a shallow layer close to the icy surface. Preliminary measurements have so far indicated rather good values for the seeing above 30-35 m: around 0.3 arcsec at Dome C. Site-testing campaigns are however extremely expensive; instruments provide only local measurements and atmospheric modelling might represent a step ahead in the search and selection of astronomical sites, thanks to the possibility of reconstructing three-dimensional (3D) C(N)(2) maps over a surface of several km. The Antarctic Plateau therefore represents an important benchmark test to evaluate the possibility of discriminating between sites on the same plateau. Our group has proven that the analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) global model do not describe the Antarctic boundary and surface layers in the plateau with the required accuracy. A better description could be obtained with a mesoscale meteorological model. The mesoscale model Meso-NH has proven to be reliable in reproducing 3D maps of optical turbulence above mid-latitude astronomical sites. In this paper we study the ability of the Meso-NH model to reconstruct the meteorological parameters as well as the optical turbulence above Dome C with different model configurations (monomodel and grid-nesting). We concentrate our attention on the abilities of the model in reproducing the optical turbulence surface-layer thickness (h(s1)) and the integral of C(N)(2) in the free atmosphere and in the surface layer. It is worth highlighting that these are the first estimates ever made with a mesoscale model of the optical turbulence above the internal Antarctic Plateau.