Mesoscale optical turbulence simulations at Dome C: refinements

In a recent paper, the authors presented an extended study aimed at simulating the classical meteorological parameters and optical turbulence at Dome C during the winter with the atmospheric mesoscale model Meso-NH. The goal of that paper was to validate the model above Dome C with the support of measurements and to use it afterwards above the Internal Antarctic Plateau to discriminate between the qualities of different potential astronomical sites on the plateau. A statistical analysis has been presented and the conclusions of that paper were very promising. Wind speed and temperature fields (important for the computations of the optical turbulence parameters) were revealed to be reconstructed very well by the Meso-NH model, with better performances than achieved with the European Centre for Medium-Range Weather Forecasts (ECMWF) global model, especially near the surface. All results were revealed to be resolution-dependent and it has been proved that a grid-nesting configuration (three domains) with a high horizontal resolution (Delta X = 1 km) for the innermost domain is necessary to reconstruct all the optical turbulence features with a good correlation to measurements. High-resolution simulations provided an averaged surface-layer thickness just similar to 14m higher than estimated by measurements, and the seeing in the free atmosphere showed a dispersion from the observed one of just a few hundredths of an arcsec (Delta epsilon similar to 0.05 arcsec). The unique limitation of the previous study was that the optical turbulence in the surface layer appeared to be overestimated by the model in both low- and high-resolution modes. In this study we present the results obtained with an improved numerical configuration. The same 15 nights have been simulated, and we show that the model results now match the observations almost perfectly in all their features: the surface thickness, the seeing in the free atmosphere and in the surface layer. This result now permits us to investigate other Antarctic sites using a robust numerical model well adapted to the extreme polar conditions (Meso-NH).