Appropriate knowledge of wind-speed distributions and optical turbulence at existing and potential astronomical observatories is crucial for siting ground-based telescopes and applying adaptive optics (AO) systems. In this paper, the wind-speed and optical-turbulence characteristics above Gaomeigu and the Tibetan Plateau are studied by employing the 20-yr (1999–2018) European Centre for Medium-Range Weather Forecasts’ fifth set of reanalysis data (ERA5). First, the meteorological parameters derived from ERA5 data are evaluated with coinciding radiosonde measurements. Results show that the meteorological parameters of ERA5 data in the free atmosphere have quite good reliability, with bias and root mean square error basically lower than 1.2 K in temperature and basically smaller than 2 m s⁻¹ for wind speed. Then, vertical distributions and seasonal behaviour of the wind speed at Gaomeigu and Lhasa station above the Tibetan Plateau are analysed. Thirdly, the Richardson number (R_i) in the free atmosphere is calculated to provides us with a map of relative probability of different periods and regions of optical turbulence being developed above the two sites. In general, the atmospheric stability of Gaomeigu is higher than that of Lhasa station. Particularly in June, for Gaomeigu, the atmospheric stability within 6–30 km a.s.l. is basically superior or equal to the stable condition found at two mid-latitude sites: Oukaimeden and La Palma. Moreover, Lhasa station has a relative higher stability during June–September than other months. Furthermore, we provide the |$( {C_n^2} )$| profiles using ERA5 data at Gaomeigu and Lhasa. The results indicate that the choice of an appropriate outer-scale model is crucial for revealing local turbulence characteristics.

中文翻译：

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利用ERA5数据分析高梅谷及青藏高原上的风速剖面和光学湍流

对现有和潜在天文台的风速分布和光学湍流的适当了解对于定位地面望远镜和应用自适应光学（AO）系统至关重要。本文采用20年（1999-2018年）欧洲中距离天气预报中心的第五组再分析数据（ERA5），对高梅谷和青藏高原上的风速和光学湍流特征进行了研究。首先，使用一致的探空仪测量值评估从ERA5数据得出的气象参数。结果表明，ERA5数据在自由大气中的气象参数具有很好的可靠性，其偏差和均方根误差在温度上基本小于1.2 K，基本小于2 ms ^-1风速 然后，分析了青藏高原高梅谷站和拉萨站风速的垂直分布和季节变化特征。第三，计算了自由大气中的理查森数（R _i），从而为我们提供了两个地点上方形成的不同周期和光学湍流区域的相对概率图。总体而言，高梅谷的大气稳定性高于拉萨站。特别是在6月，对于高梅谷来说，在6-30 km asl内的大气稳定性基本上优于或等于在两个中纬度站点：Oukaimeden和La Palma的稳定条件。此外，在6月至9月期间，拉萨站的稳定性相对较高。此外，我们提供| $（{C_n ^ 2}）$ | 使用高梅谷和拉萨的ERA5数据进行剖析。结果表明，选择合适的外部尺度模型对于揭示局部湍流特征至关重要。