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arXiv 1105.2667astro-ph.IMphysics.ao-ph
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使用Meso-NH模式在Mt Graham进行的光学turbulence模拟

Optical turbulence simulations at Mt Graham using the Meso-NH mode

S. Hagelin, E. Masciadri, F. Lascaux

摘要:

本文用中尺度模式Meso-NH模拟了美国亚利桑那州格雷厄姆山的光学湍流。从41个夜晚的广义scidar获得的CN 2-配置文件的测量用于校准和量化模型的能力,以重建光学湍流。测量值分布在一年中的不同时期,使我们能够研究模型在不同季节的性能。对模拟的所有最重要的天体气候参数进行了统计分析:CN 2廓线、视宁度ε、等晕角θ0和波前相干时间τ0。该模型在重建光学湍流的形态(CN2的垂直分布的形状)以及所有综合的天文气候参数的强度方面表现出了良好的能力。41个夜晚的全大气视宁度平均值的相对误差(相对于测量值)在9.0%以内。逐夜的相对误差的中值为18.7%,因此模型仍然保持很好的性能。在部分垂直板(自由大气和边界层)和不同季节(夏季和冬季)观察到的百分比相当。我们证明,目前最迫切的问题是提高模式重建高层大气中很弱和很强湍流条件的能力。这主要影响模式对等晕角预报的性能,其逐夜的相对误差的中值为35.1%。其他天体气候参数没有发现大的问题。测试了标准校准方法的变体,但我们发现它不能提供更好的结果,证实了标准方法的坚实基础。

英文摘要:

The mesoscale model Meso-NH is used to simulate the optical turbulence at Mt Graham (Arizona, USA), site of the Large Binocular Telescope. Measurements of the CN2-profiles obtained with a generalized scidar from 41 nights are used to calibrate and quantify the model's ability to reconstruct the optical turbulence. The measurements are distributed over different periods of the year, permitting us to study the model's performance in different seasons. A statistical analysis of the simulations is performed for all the most important astroclimatic parameters: the CN2-profiles, the seeing ε, the isoplanatic angle θ0 and the wavefront coherence time τ0. The model shows a general good ability in reconstructing the morphology of the optical turbulence (the shape of the vertical distribution of CN2) as well as the strength of all the integrated astroclimatic parameters. The relative error (with respect to measurements) of the averaged seeing on the whole atmosphere for the whole sample of 41 nights is within 9.0 %. The median value of the relative error night by night is equal to 18.7 %, so that the model still maintains very good performances. Comparable percentages are observed in partial vertical slabs (free atmosphere and boundary layer) and in different seasons (summer and winter). We prove that the most urgent problem, at present, is to increase the ability of the model in reconstructing very weak and very strong turbulence conditions in the high atmosphere. This mainly affects the model's performances for the isoplanatic angle predictions, for which the median value of the relative error night by night is equal to 35.1 %. No major problems are observed for the other astroclimatic parameters. A variant to the standard calibration method is tested but we find that it does not provide better results, confirming the solid base of the standard method.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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