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Astron. Astrophys. Suppl. Ser. 137, 185-202

3D mapping of optical turbulence using an atmospheric numerical model

I. A useful tool for the ground-based astronomy

E. Masciadri1 - J. Vernin1 - P. Bougeault2

Send offprint request: E. Masciadri

1 - U.M.R. 6525 Astrophysique, Université de Nice-Sophia Antipolis, Centre National de la Recherche Scientifique, Parc Valrose, 06108 Nice Cedex 2, France
2 - Centre National de Recherches Météorologiques Météo France, 42 Av. G. Coriolis, 31057 Toulouse, France

Received June 4, 1998; accepted February 4, 1999


These last years have seen the development of many devices to measure and monitor some atmospheric parameters characterizing the image degradation at the telescope focus. Many uncertainties about the possibility to forecast such parameters are real although this skill is fundamental for site testing, flexible scheduling and optimization of the performance of both interferometry and adaptive optics. We present our atmospheric numerical model, conceived to provide 3D maps of the classic meteorological parameters P, T and $\vec{V}$, and also 3D maps of the $C_{\rm N}^2 $ optical turbulent profiles. Knowing the wind $\vec{V}$ and the $C_{\rm N}^2 $ profiles, the following integrated parameters are coded: seeing $\varepsilon $, coherence wavefront time $\tau_{\rm AO} $, isoplanatic angle $\theta_{\rm AO} $, scintillation rate $\sigma ^{2}_{\rm I} $ and spatial coherence outer scale ${\cal L}_0 $.

The ability of the model to produce a 3D map of optical turbulence in the vicinity of a telescope and the effects of horizontal grid size are discussed. We demonstrate, for the same night, the global coherence of the different simulation outputs. Here we consider the use that this model could have in ground-based astronomy and we describe how it could be used to give a real forecast of the optical turbulence.

Key words: atmospheric effects, turbulence, site testing

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