Ground-based HCN submillimetre measurements in Titan's atmosphere: an intercomparison with Herschel observations
Ground-based HCN submillimetre measurements in Titan's atmosphere: an intercomparison with Herschel observations
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泰坦大气中的地面 HCN 亚毫米测量：与赫歇尔观测结果的对比
DOI：
10.1051/0004-6361/202141422
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发表时间：
2022
影响因子：
6.5
通讯作者：
Breitschwerdt D.
中科院分区：
文献类型：
--
作者：
Rengel M.;Shulyak D.;Hartogh P.;Sagawa H.;Moreno R.;Jarchow C.;Breitschwerdt D.
aimsThe本研究的目的是测量HCN的垂直分布在土卫六的平流层使用地基亚毫米观测获得准同时与thesherschelones。这使我们能够进行空间和地面观测之间的一致性检查，并建立一个参考平均HCN垂直剖面在泰坦的平流层MethodsUsing APEX和IRAM 30-m，我们得到的光谱发射HCN（4-3）和（3-2）线。使用GILDAS-CLASS减少了观察结果。我们采用逐线辐射传输程序计算HCN的合成光谱，并采用基于最优估计的反演算法反演温度和HCN的垂直分布。我们使用的标准偏差为基础的度量来量化的地面andHerschelHCN配置文件和平均one.ResultsOur派生HCN丰度配置文件之间的分散是一致的，从40 ppb在~100公里的4 ppm在~200公里，这是一个高度区域的HCN签名是敏感的。我们还表明，检索HCN分布的数据信息是敏感的，并限于土卫六的平流层。从APEX数据得到的HCN比IRAM数据的精度低，因为数据质量较差，并且覆盖的高度范围较窄。我们的结果和赫歇尔的值之间的比较显示相似的丰度分布，与2.5 ppm的最大差异范围内100和300公里的垂直范围。这些比较还使我们能够相互验证两个数据集，并表明可靠和一致的测量。推断的丰度也与以前的观测研究中的垂直分布一致，与阿尔马，卡西尼/CIRS和SMA（最新的低于230公里）的剖面一致。我们的HCN配置文件也是可比的光化学模型和低于230公里，并与250公里以上的一致。然而，在170公里、170公里和170公里以下以及400公里和400公里以上的估计数之间似乎有很大差异，尽管它们的形状相似。我们的结论是，这些特定的光化学模型需要改进。
AimsThe aim of this study is to measure the vertical distribution of HCN on Titan’s stratosphere using ground-based submillimetre observations acquired quasi-simultaneously with theHerschelones. This allows us to perform a consistency check between space and ground-based observations and to build a reference mean HCN vertical profile in Titan’s stratosphere.MethodsUsing APEX and IRAM 30-m, we obtained the spectral emission of HCN (4-3) and (3-2) lines. Observations were reduced with GILDAS-CLASS. We applied a line-by-line radiative transfer code to calculate the synthetic spectra of HCN, and a retrieval algorithm based on optimal estimation to retrieve the temperature and HCN vertical distributions. We used the standard deviation-based metric to quantify the dispersion between the ground-based andHerschelHCN profiles and the mean one.ResultsOur derived HCN abundance profiles are consistent with an increase from 40 ppb at ~100 km to 4 ppm at ~200 km, which is an altitude region where the HCN signatures are sensitive. We also demonstrate that the retrieved HCN distribution is sensitive to the data information and is restricted to Titan’s stratosphere. The HCN obtained from APEX data is less accurate than the one from IRAM data because of the poorer data quality, and covers a narrower altitude range. Comparisons between our results and the values fromHerschelshow similar abundance distributions, with maximum differences of 2.5 ppm ranging between 100 and 300 km in the vertical range. These comparisons also allow us to inter-validate both data sets and indicate reliable and consistent measurements. The inferred abundances are also consistent with the vertical distribution in previous observational studies, with the profiles from ALMA, Cassini/CIRS, and SMA (the latest ones below ~230 km). Our HCN profile is also comparable to photochemical models by and below 230 km and consistent with that of above 250 km. However, it appears to show large differences with respect to the estimates by , , and below 170 km, and by and above 400 km, although they are similar in shape. We conclude that these particular photochemical models need improvement.