Mapping of Jupiter's tropospheric NH 3 abundance using ground-based IRTF/TEXES observations at 5 µm
Mapping of Jupiter's tropospheric NH 3 abundance using ground-based IRTF/TEXES observations at 5 µm
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使用 5 µm 地面 IRTF/TEXES 观测绘制木星对流层 NH 3 丰度图
DOI：
10.1016/j.icarus.2018.06.002
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发表时间：
2018
期刊：
影响因子：
3.2
通讯作者：
Blain D
中科院分区：
文献类型：
--
作者：
Blain D
我们报告支持朱诺号任务的观测活动的结果。 2016 年初，我们使用安装在 NASA 红外望远镜设施 (IRTF) 上的 TEXES（德克萨斯梯队交叉色散阶梯光谱仪）获得了 1930-1943 cm−1 光谱范围（约 5 µm）的木星数据立方体，探测了 1-4 bar 区域的大气，光谱分辨率约为 0.15 cm−1，角度分辨率约为 1.4”。该数据集通过将逐行辐射传输模型与非线性最佳估计反演方法相结合的代码进行分析。反演检索了 NH 3 的垂直丰度剖面（这是这些波长的主要贡献者），最大灵敏度约为 1-3 bar，以及云透射率。该检索在我们的数据立方体的一千多个像素上执行，生成圆盘图，其中所有主要带都是可见的。我们展示了检索到的 NH 3 丰度图，可以将其与 Juno 的 MWR 观测到的 2 bar 区域的分布进行比较（Bolton 等人，2017 年；Li 等人，2017 年），并讨论它们对于理解木星大气动力学的重要性，我们能够显示重要的纬度变化，例如在北赤道带 (NEB)，观察到 NH 3 丰度下降至 60。在这些区域中，我们发现 NH 3 丰度随着深度的增加而增加，从 1 bar 时的 100±15 ppmv 到 3 bar 时的 500±30 ppmv。 2001），我们能够拟合这种关系，至少在 NEB 中，包括尺寸在 10 到 100 µm 之间的 NH 3-ice 或 NH 4 SH 颗粒。
We report on results of an observing campaign to support the Juno mission. At the beginning of 2016, using TEXES (Texas Echelon cross-dispersed Echelle Spectrograph), mounted on the NASA Infrared Telescope Facility (IRTF), we obtained data cubes of Jupiter in the 1930–1943 cm− 1 spectral ranges (around 5 µm), which probe the atmosphere in the 1–4 bar region, with a spectral resolution of≈ 0.15 cm− 1 and an angular resolution of≈ 1.4”. This dataset is analysed by a code that combines a line-by-line radiative transfer model with a non-linear optimal estimation inversion method. The inversion retrieves the vertical abundance profiles of NH 3—which is the main contributor at these wavelengths—with a maximum sensitivity at≈ 1–3 bar, as well as the cloud transmittance. This retrieval is performed on more than one thousand pixels of our data cubes, producing maps of the disk, where all the major belts are visible. We present our retrieved NH 3 abundance maps which can be compared with the distribution observed by Juno’s MWR (Bolton et al., 2017; Li et al., 2017) in the 2 bar region and discuss their significance for the understanding of Jupiter’s atmospheric dynamics. We are able to show important latitudinal variations—such as in the North Equatorial Belt (NEB), where the NH 3 abundance is observed to drop down to 60 ppmv at 2 bar—as well as longitudinal variability. In the zones, we find the NH 3 abundance to increase with depth, from 100±15 ppmv at 1 bar to 500±30 ppmv at 3 bar. We also display the cloud transmittance–NH 3 abundance relationship, and find different behaviour for the NEB, the other belts and the zones. Using a simple cloud model (Lacis and Hansen, 1974; Ackerman and Marley, 2001), we are able to fit this relationship, at least in the NEB, including either NH 3-ice or NH 4 SH particles with sizes between 10 and 100 µm.