Mesoscale optical turbulence simulations at Dome C

Abstract

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 2 N 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 sl ) and the integral of C 2 N 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.

Optical turbulence vertical distribution with standard and high resolution at Mt Graham

“…The atmospheric models have been used for the first time to reconstruct and characterize the C 2 N profiles by Masciadri, Vernin & Bougeault (1999a,b). Since then, much progress has been achieved by our group: the model has been applied to different astronomical sites in a simple monomodel configuration (Masciadri, Vernin & Bougeault 2001; Masciadri & Garfias 2001) and more recently in a grid‐nesting configuration (Lascaux et al 2009), a new calibration technique has been proposed (Masciadri & Jabouille 2001) and statistically validated (Masciadri, Avila & Sanchez 2004) and the first application of the Meso‐Nh model as a tool of turbulence characterization has been presented (Masciadri & Egner 2006). However, so far we could always access GS measurements concentrated in a well‐defined period of time.…”

One Year of Surface-Based Temperature Inversions at Dome C, Antarctica

“…Studying the performance of the Antarctic Mesoscale Prediction System (described by Powers et al 2003) in retrieving surface temperature, Bromwich et al (2005) have shown that over the Antarctic plateau this model gives a positive bias of about 1 • C during the summer. Lascaux et al (2009), when comparing 47 radiosoundings temperature profiles collected at Dome C in the winter of 2005 with the results of a mesoscale model simulation, found substantial differences between experimental and model profiles in the first 200 m above the surface. Gallée and Gorodetskaya (2010) validated a limited area model over Dome C during the cold season.…”

“…For this reason, in recent years, the optical turbulence over the Antarctic plateau has been the subject of studies by astronomers (e.g. Aristidi et al 2005a,b;Geissler and Masciadri 2006;Hagelin et al 2008;Trinquet et al 2008;Lascaux et al 2009). As shown by e.g.…”

Optical turbulence: site selection above the internal Antarctic plateau with a mesoscale model

“…2006). More recently, it has been statistically validated above Dome C by Lascaux et al (2009Lascaux et al ( , 2010. The most important results obtained in these last papers are summarized in Table 1.…”

“…4 For this study, therefore, the RAMP Digital Elevation Model has been used. The orography of each area of interest in this study (Dome C, Dome A, South Pole) is displayed on Fig.…”