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One of the main goals of the feasibility study MOSE (MOdellig ESO Sites) is to evaluate the performances of a method conceived to forecast the optical turbulence above the ESO sites of the Very Large Telescope and the European-Extremely Large Telescope in Chile. The method implied the use of a dedicated code conceived for the optical turbulence (OT) called Astro-Meso-Nh. In this paper we present results we obtained at conclusion of this project concerning the performances of this method in forecasting the most relevant parameters related to the optical turbulence (CN2, seeing , isoplanatic angle theta_0 and wavefront coherence time tau_0). Numerical predictions related to a very rich statistical sample of nights uniformly distributed along a solar year and belonging to different years have been compared to observations and different statistical operators have been analyzed such as classical bias, RMSE and and more sophisticated statistical operators derived by the contingency tables that are able to quantify the score of success of a predictive method such as the percentage of correct detection (PC) and the probability to detect a parameter within a specific range of values (POD). The main conclusions of the study tell us that the Astro-Meso-Nh model provides performances that are already very good to definitely guarantee a not negligible positive impact on the Service Mode of top-class telescopes and ELTs. A demonstrator for an automatic and operational version of the Astro-Meso-Nh model will be soon implemented on the sites of VLT and E-ELT., Comment: This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. The version of record [doi: 10.1093/mnras/stw3111] is available online at: http://mnras.oxfordjournals.org/content/early/2016/11/30/mnras.stw3111.abstract?keytype=ref&ijkey=te4TKA10zzdydVK. 13 figures

This article aims at proving the feasibility of the forecast of all the most relevant classical atmospherical parameters for astronomical applications (wind speed and direction, temperature) above the ESO ground-base site of Cerro Paranal with a mesoscale atmospherical model called Meso-Nh. In a precedent paper we have preliminarily treated the model performances obtained in reconstructing some key atmospherical parameters in the surface layer 0-30~m studying the bias and the RMSE on a statistical sample of 20 nights. Results were very encouraging and it appeared therefore mandatory to confirm such a good result on a much richer statistical sample. In this paper, the study was extended to a total sample of 129 nights between 2007 and 2011 distributed in different parts of the solar year. This large sample made our analysis more robust and definitive in terms of the model performances and permitted us to confirm the excellent performances of the model. Besides, we present an independent analysis of the model performances using the method of the contingency tables. Such a method permitted us to provide complementary key informations with respect to the bias and the RMSE particularly useful for an operational implementation of a forecast system., Comment: 20 pages, 8 figures, 18 tables, published in MNRAS

The advent of a new generation of Adaptive Optics systems called Wide Field AO (WFAO) mark the beginning of a new era. By using multiple Guide Stars (GSs), either Laser Guide Stars (LGSs) or Natural Guide Stars (NGSs), WFAO significantly increases the field of view of the AO-corrected images, and the fraction of the sky that can benefit from such correction. Different typologies of WFAO have been studied over the past years. They all require multiple GSs to perform a tomographic analysis of the atmospheric turbulence. One of the fundamental aspects of the new WFAO systems is the knowledge of the spatio-temporal distribution of the turbulence above the telescope. One way to get to this information is to use the telemetry data provided by the WFAO system itself. Indeed, it has been demonstrated that WFAO systems allows one to derive the Cn2 and wind profile in the main turbulence layers (see e.g. Cortes et al. 2012). This method has the evident advantage to provide information on the turbulence stratification that effectively affects the AO system, property more difficultly respected by independently vertical profilers. In this paper, we compare the wind speeds profiles of GeMS with those predicted by a non-hydrostatical mesoscale atmospherical model (Meso-NH). It has been proved (Masciadri et al., 2013), indeed, that this model is able to provide reliable wind speed profiles on the whole troposphere and stratosphere (up to 20-25 km) above top-level astronomical sites. Correlation with measurements revealed to be very satisfactory when the model performances are analyzed from a statistical point of view as well on individual nights. Such a system appears therefore as an interesting reference to be used to quantify the GeMS wind speed profiles reliability., Comment: 10 pages, 5 figures - Proceedings of the SPIE, Adaptive Optics Systems IV, 9148-236

This article is the second of a series of articles aiming at proving the feasibility of the forecast of all the most relevant classical atmospherical parameters for astronomical applications (wind speed and direction, temperature, relative humidity) and the optical turbulence (Cn2 and the derived astro-climatic parameters like seeing, isoplanatic angle, wavefront coherence time...). This study is done in the framework of the MOSE project, and focused above the two ESO ground-bases sites of Cerro Paranal and Cerro Armazones. In this paper we present the results related to the Meso-Nh model ability in reconstructing the surface layer atmospherical parameters (wind speed intensity, wind direction and absolute temperature, [0-30] m a.g.l.). The model reconstruction of all the atmospherical parameters in the surface layer is very satisfactory. For the temperature, at all levels, the RMSE (Root Mean Square Error) is inferior to 1{\deg}C. For the wind speed, it is ~2 m/s, and for the wind direction, it is in the range [38-46{\deg}], at all levels, that corresponds to a RMSE_relative in a range [21-26{\deg}]. If a filter is applied for the wind direction (the winds inferior to 3 m/s are discarded from the computations), the wind direction RMSE is in the range [30-41{\deg}], i.e. a RMSE_relative in the range [17-23{\deg}]. The model operational forecast of the surface layer atmospherical parameters is suitable for different applications, among others: thermalization of the dome using the reconstructed temperature, hours in advance, of the beginning the night; knowing in advance the main direction which the strong winds will come from during the night could allow the astronomer to anticipate the occurrence of a good/bad seeing night, and plan the observations accordingly; preventing adaptive secondary mirrors shake generated by the wind speed., Comment: 25 pages, 17 figures, 14 tables, accepted for publication in MNRAS

In the context of the MOSE project, in this contribution we present a detailed analysis of the Meso-NH mesoscale model performances and their dependency on the model and orography horizontal resolutions in proximity of the ground. The investigated sites are Cerro Paranal (site of the ESO Very Large Telescope - VLT) and Cerro Armazones (site of the ESO European Extremely Large Telescope - E-ELT), in Chile. At both sites, data from a rich statistical sample of different nights are available - from AWS (Automated Weather Stations) and masts - giving access to wind speed, wind direction and temperature at different levels near the ground (from 2 m to 30 m above the ground). In this study we discuss the use of a very high horizontal resolution (dX=0.1 km) numerical configuration that overcomes some specific limitations put in evidence with a standard configuration with dX=0.5 km. In both sites results are very promising. The study is co-funded by ESO and INAF., Comment: SPIE 2012 Conference - 12 pages - 8 figures

We present in this study a mapping of the optical turbulence (OT) above different astronomical sites. The mesoscale model Meso-NH was used together with the Astro-Meso-Nh package and a set of diagnostic tools allowing for a full 3D investigation of the Cn2. The diagnostics implemented in the Astro-Meso-Nh, allowing for a full 3D investigation of the OT structure in a volumetric space above different sites, are presented. To illustrate the different diagnostics and their potentialities, we investigated one night and looked at instantaneous fields of meteorologic and astroclimatic parameters. To show the potentialities of this tool for applications in an Observatory we ran the model above sites with very different OT distributions: the antarctic plateau (Dome C, Dome A, South Pole) and a mid-latitude site (Mt. Graham, Arizona). We put particular emphasis on the 2D maps of integrated astroclimatic parameters (seeing, isoplanatic angles) calculated in different slices at different heights in the troposhere. This is an useful tool of prediction and investigation of the turbulence structure. It can support the optimization of the AO, GLAO and MCAO systems running at the focus of the ground-based telescopes.From this studies it emerges that the astronomical sites clearly present different OT behaviors. Besides, our tool allowed us for discriminating these sites., Comment: 7 pages, 5 figures, SPIE 2010 conference

In two recent papers the mesoscale model Meso-NH, joint with the Astro-Meso-NH package, has been validated at Dome C, Antarctica, for the characterization of the optical turbulence. It has been shown that the meteorological parameters (temperature and wind speed, from which the optical turbulence depends on) as well as the Cn2 profiles above Dome C were correctly statistically reproduced. The three most important derived parameters that characterize the optical turbulence above the internal antarctic plateau: the surface layer thickness, the seeing in the free-atmosphere and in the total atmosphere showed to be in a very good agreement with observations. Validation of Cn2 has been performed using all the measurements of the optical turbulence vertical distribution obtained in winter so far. In this paper, in order to investigate the ability of the model to discriminate between different turbulence conditions for site testing, we extend the study to two other potential astronomical sites in Antarctica: Dome A and South Pole, which we expect to be characterized by different turbulence conditions. The optical turbulence has been calculated above these two sites for the same 15 nights studied for Dome C and a comparison between the three sites has been performed., Comment: 13 pages, 5 figures, 9 tables, accepted in MNRAS

In a recent paper the authors presented an extended study aiming at simulating the classical meteorological parameters and the optical turbulence at Dome C during the winter with the atmospherical mesoscale model Meso-NH. A statistical analysis has been presented and the conclusions of that paper have been very promising. Wind speed and temperature fields revealed to be very well reconstructed by the Meso-NH model with better performances than what has been achieved with the European Centre for Medium-Range Weather Forecast (ECMWF) global model, especially near the surface. All results revealed to be resolution-dependent and it has been proved that a grid-nesting configuration (3 domains) with a high horizontal resolution (1km) 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 ~14 m higher than what is estimated by measurements, the seeing in the free atmosphere showed a dispersion from the observed one of just a few hundredths of an arcsecond (~0.05"). The unique limitation of the previous study was that the optical turbulence in the surface layer appeared 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 almost perfectly the observations in all their features: the surface thickness, the seeing in the free atmosphere as well as in the surface layer. This result permits us to investigate now other antarctic sites using a robust numerical model well adapted to the extreme polar conditions (Meso-NH)., Comment: 5 pages, 4 figures, accepted for publication in MNRAS

Mesoscale model such as Meso-Nh have proven to be highly reliable in reproducing 3D maps of optical turbulence (see Refs. 1, 2, 3, 4) above mid-latitude astronomical sites. These last 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 pretty good value for the seeing above 30-35 m: 0.36" (see Ref. 5) and 0.27" (see Refs. 6, 7) at Dome C. Site testing campaigns are however extremely expensive, instruments provide only local measurements and atmospheric modelling might represent a step ahead towards the search and selection of astronomical sites thanks to the possibility to reconstruct 3D Cn2 maps over a surface of several kilometers. The Antarctic Plateau represents therefore an important benchmark test to evaluate the possibility to discriminate sites on the same plateau. Our group8 has proven that the analyses from the ECMWF global model do not describe with the required accuracy the antarctic boundary and surface layer in the plateau. A better description could be obtained with a mesoscale meteorological model. In this contribution we present the progress status report of numerical simulations (including the optical turbulence - Cn2) obtained with Meso-Nh above the internal Antarctic Plateau. Among the topic attacked: the influence of different configurations of the model (low and high horizontal resolution), use of the grid-nesting interactive technique, forecasting of the optical turbulence during some winter nights., Comment: 12 pages, 4 figures, SPIE 2008 conference