An Atmospheric General Circulation Model for Pluto with Predictions for New Horizons
An Atmospheric General Circulation Model for Pluto with Predictions for New Horizons
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冥王星大气环流模型及新地平线预测
DOI：
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发表时间：
2015
期刊：
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通讯作者：
A. Zalucha
中科院分区：
文献类型：
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作者：
A. Zalucha
结果来自 3-D 冥王星大气环流模型，其中包括地下模型和挥发性循环。存在传导加热和冷却、2.3 和 3.3 微米甲烷非局部热力学平衡（非 LTE）加热、7.6 微米甲烷冷却非 LTE 冷却以及 LTE CO 旋转管线冷却。该冥王星模型很新颖，因为它具有详细的地下模型和大气模型组件。使用每次模拟固定的以下参数进行参数扫描：初始表面压力、甲烷浓度、表面反照率、发射率和电导率。假设最初的表面氮霜层很厚，足以充当大型散热器（与太阳能加热项相比），但又足够小，使得水冰地下特性也很重要。鉴于冥王星年的积分时间较短（30个地球年），表面压力和表面霜厚度可能尚未达到平衡。注意到夏季到冬季极地的小规模波动传输，但不足以显着改变表面压力。四种假设状态（其合理性得到了观测和先前建模工作的支持），为新视野号上的 Alice 和 REX 仪器以及地面恒星掩星观测提供了预测。通过该模型，可以区分 0.2 和 1.0 的甲烷浓度以及 8 和 24 微巴的表面压力。对于地基恒星掩星，不同甲烷浓度的光变曲线之间存在可检测到的差异，但对于不同的表面压力则不然。
Results are presented from a 3-D Pluto general circulation model that includes a subsurface model and volatile cycle. Conductive heating and cooling, non-local thermodynamic equilibrium (non-LTE) heating by methane at 2.3 and 3.3 microns, non-LTE cooling by cooliing by methane at 7.6 microns, and LTE CO rotational line cooling are present. This Pluto model is novel because it has both detailed subsurface and atmospheric model components. A parameter sweep was performed with the following parameters fixed for each simulation: initial surface pressure, methane concentration, and surface albedo, emissivity, and conductivity. An initially thick surface nitrogen frost layer was assumed such that it is large enough to act as a large heat sink (compared with the solar heating term) but small enough that the water ice subsurface properties are also significant. Given the short integration time (30 Earth years) with respect to a Pluto year, the surface pressure and surface frost thickness have probably not come into equilibrium. A small, summer-to-winter pole volatile transport was noted, but not enough to change the surface pressure significantly. Four hypothetical states (whose plausibility is supported by observations and previous modeling work), predictions are provided for the Alice and REX instruments on New Horizons and for ground-based stellar occultation observations. With this model it is possible to distinguish between 0.2 and 1.0 methane concentrations and 8 and 24 microbar surface pressures. For ground-based stellar occultations, a detectable difference exists between light curves with the different methane concentrations, but not for different surface pressures.