A model intercomparison of Titan's climate and low-latitude environment
A model intercomparison of Titan's climate and low-latitude environment
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DOI：
10.1016/j.icarus.2019.05.031
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发表时间：
2019-11
期刊：
影响因子：
3.2
通讯作者：
J. Lora;T. Tokano;J. Vatant d'Ollone;S. Lebonnois;R. Lorenz
中科院分区：
文献类型：
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作者：
J. Lora;T. Tokano;J. Vatant d'Ollone;S. Lebonnois;R. Lorenz
卡西尼-惠更斯提供了丰富的数据来约束土卫六的数值模型。在过去的十年里，这种模式已经被用于研究土卫六大气和气候的各个方面，现在已经出现了几个高度逼真地模拟土卫六的三维大气环流模式(GCM)。然而，大量的不确定性依然存在，同时没有专门的相互比较来评估这些模型彼此或观察结果的一致程度。为了弥补这一差距，并受到拟议的蜻蜓Titan着陆器任务的激励，我们直接比较了三个Titan GCM彼此之间的差异，并对Titan GCM进行了态势观测，还提供了对北方初冬季节低纬度环境的多模型预期。在全球范围内，这些模型在表示大气结构和环流方面定性一致，尽管有一个模型严重低估了经向温度梯度和纬向风。我们发现，在低纬地区，模拟的大气温度和观测的大气温度在所有情况下都非常接近，而边界层以上的测量风速只有一个模型在定量上匹配。然而，这些模型模拟了类似的近地表风，所有这些都表明这些风很弱。同样，低纬地区的温度和甲烷含量在不同的模型之间也是相似的，但也存在一些差异，这在很大程度上要归因于模型假设。所有模型都预测了与惠更斯探测器遇到的环境非常相似的环境，包括北部冬季低纬度地区很少或根本没有降水。最显著的差异与甲烷循环有关，尽管这些模型在这一领域的可比性最差，仍然存在很大的不确定性。我们认为，虽然土卫六上这个季节的整体低纬环境现在受到了很好的限制，但未来的现场测量和监测将改变我们对区域和时间变异性、大气-地表耦合、土卫六甲烷循环及其模型的理解。
Cassini-Huygens provided a wealth of data with which to constrain numerical models of Titan. Such models have been employed over the last decade to investigate various aspects of Titan's atmosphere and climate, and several three-dimensional general circulation models (GCMs) now exist that simulate Titan with a high degree of fidelity. However, substantial uncertainties persist, and at the same time no dedicated intercomparisons have assessed the degree to which these models agree with each other or the observations. To address this gap, and motivated by the proposed Dragonfly Titan lander mission, we directly compare three Titan GCMs to each other and toin situobservations, and also provide multi-model expectations for the low-latitude environment during the early northern winter season. Globally, the models qualitatively agree in their representation of the atmospheric structure and circulation, though one model severely underestimates meridional temperature gradients and zonal winds. We find that, at low latitudes, simulated and observed atmospheric temperatures closely agree in all cases, while the measured winds above the boundary layer are only quantitatively matched by one model. Nevertheless, the models simulate similar near-surface winds, and all indicate these are weak. Likewise, temperatures and methane content at low latitudes are similar between models, with some differences that are largely attributable to modeling assumptions. All models predict environments that closely resemble that encountered by the Huygens probe, including little or no precipitation at low latitudes during northern winter. The most significant differences concern the methane cycle, though the models are least comparable in this area and substantial uncertainties remain. We suggest that, while the overall low-latitude environment on Titan at this season is now fairly well constrained, futurein situmeasurements and monitoring will transform our understanding of regional and temporal variability, atmosphere-surface coupling, Titan's methane cycle, and modeling thereof.