UK气象局GCM对热木星HD 209458 b应用了复杂的辐射方案
The UK Met Office GCM with a sophisticated radiation scheme applied to the hot Jupiter HD 209458b
摘要：
为了研究质量不断提高的观测结果所揭示的热木星大气层的复杂性，我们将英国气象局全球环流模型（GCM），统一模型（UM），适用于这些系外行星。UM解决了全三维纳维-斯托克斯方程与高度变化的重力，避免了目前应用于系外行星的大多数GCM中使用的简化。在这项工作中，我们提出了一个精确的辐射计划的基础上的双流近似和相关k方法与国家的最先进的不透明度ExoMol的UM动力学核心的耦合。我们第一次应用这个模型是专门研究热木星HD 209458b。我们已经推导出合成的发射光谱和相位曲线，并将它们与以前的两个模型进行比较，这些模型也是基于最先进的辐射转移和观测结果。我们发现观测值与我们的昼侧发射和热点偏移量之间有合理的一致性，但是，我们的夜侧发射太大。总的来说，我们的结果与Showman等人（2009年）用MITgcm发现的结果在定性上相似，但是，我们注意到几个定量差异：我们的模拟显示，大气中最热部分的位置随着压力的变化而显着变化，正如从简单的时间尺度参数所预期的那样，与Showman等人（2009年）发现的“垂直相干性”相反。我们还看到计算的合成观测值存在显著的定量差异。我们的比较加强了需要详细的相互比较的动力核心，辐射计划和后处理工具，以了解这些差异。为了根据大气环流模式的结果对这些大气作出可靠的结论，这项工作是必要的。
英文摘要：
To study the complexity of hot Jupiter atmospheres revealed by observations of increasing quality, we have adapted the UK Met Office global circulation model (GCM), the Unified Model (UM), to these exoplanets. The UM solves the full 3D Navier-Stokes equations with a height-varying gravity, avoiding the simplifications used in most GCMs currently applied to exoplanets. In this work we present the coupling of the UM dynamical core to an accurate radiation scheme based on the two-stream approximation and correlated-k method with state-of-the-art opacities from ExoMol. Our first application of this model is devoted to the extensively studied hot Jupiter HD 209458b. We have derived synthetic emission spectra and phase curves, and compare them to both previous models also based on state-of-the-art radiative transfer, and to observations. We find a reasonable a agreement between observations and both our day side emission and hot spot offset, however, our night side emission is too large. Overall our results are qualitatively similar to those found by Showman et al. (2009) with the SPARC/MITgcm, however, we note several quantitative differences: Our simulations show significant variation in the position of the hottest part of the atmosphere with pressure, as expected from simple timescale arguments, and in contrast to the "vertical coherency" found by Showman et al. (2009). We also see significant quantitative differences in calculated synthetic observations. Our comparisons strengthen the need for detailed intercomparisons of dynamical cores, radiation schemes and post-processing tools to understand these differences. This effort is necessary in order to make robust conclusions about these atmospheres based on GCM results.
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