Exploring Titan's dynamic atmosphere using spacecraft remote sensing observations from Cassini and James Webb Space Telescope

项目背景土卫六是土星最大的卫星，也是太阳系中唯一拥有大气层的卫星，大气层由氮、甲烷和大量微量有机物组成。在许多方面，土卫六是地球的缩小版，但在更冷的条件下，具有异国情调的大气成分。许多发生在地球上的大气过程与土卫六上的类似，包括极地涡旋、大尺度大气环流、光化学、极夜辐射冷却、云的形成和暴雨。例如，土卫六的平流层有机烟雾和微量气体与地球臭氧层的作用相似。研究土卫六的大气层本身就很吸引人，但也为探索基本的大气化学和动力学过程提供了一个天然的实验室。这些过程对于了解地球大气层和太阳系内外许多其他行星的大气层也很重要。项目目的和方法本项目将研究土卫六平流层和中间层的动力学和化学过程。特别是极端行星尺度的风（喷流）和极地和中纬度气团之间的混合过程。这些过程控制着土卫六上发生的大部分大规模季节变化，是了解其气候的基础。将利用轨道航天器（卡西尼号）、空间望远镜（詹姆斯·韦伯）和地面观测站（阿尔马）的红外光谱观测研究大气特征。也将有机会在博士期间提出额外的新望远镜观测。光谱将使用辐射传输方法和逆理论技术进行分析，以恢复最适合观测和现有限制的大气特性。由此得出的物理和化学大气状态，然后可以用来开发大气环流，光化学和季节演变的解释。微量有机化学物质特别令人感兴趣，因为它们可以作为大气环流的示踪剂，并可用于探测风和空气混合。学生将有机会指导项目方向，特别是在数据分析和解释或提出新的观测结果时。航天器数据分析将包括项目的大部分内容，由主要主管（Teanby博士）领导。为了帮助解释观测到的大气特征，结果将与理论预测和根据地球大气研究改编的数值行星气候模型进行比较，这些模型目前正在由监督小组成员（Seviour博士和Mitchell博士）开发。这些观测-理论-模型的比较将使我们能够更全面地了解土卫六的大气层，并有可能反馈到我们对基本气候物理学的理解中。研究结果还将为下一代太空任务提供信息，例如飞往泰坦的蜻蜓核动力无人机使命。

Project BackgroundTitan is the largest moon of Saturn and is the only moon in our solar system with a substantial atmosphere, composed of nitrogen, methane and a host of trace organic species. In many ways Titan is a miniature version of Earth, but under much colder conditions and with an exotic atmospheric composition. Many atmospheric processes occurring on Earth have analogues on Titan, including polar vortices, large-scale atmospheric circulation, photochemistry, polar night radiative cooling, cloud formation, and rainstorms. For example, Titan's stratospheric organic hazes and trace gases play a similar role to Earth's ozone layer. Studying Titan's atmosphere is fascinating in its own right, but also provides a natural laboratory for probing fundamental atmospheric chemical and dynamical processes. These processes are also important for understanding Earth's atmosphere and those of many other planets in the Solar System and beyond.Project Aims and MethodsThis project will study dynamical and chemical processes in Titan stratosphere and mesosphere. In particular, extreme planetary-scale winds (jets) and mixing processes between polar and mid-latitude air masses. These processes control much of the large-scale seasonal changes occurring on Titan and are fundamental to understanding its climate. Atmospheric features will be studied using infra-red spectroscopic observations from orbiting spacecraft (Cassini), space telescopes (James Webb), and ground-based observatories (ALMA). There will also be opportunities to propose additional new telescope observations during the PhD. Spectra will be analysed using radiative transfer methods and inverse theory techniques to recover atmospheric properties that best fit observations and existing constraints. The derived physical and chemical atmospheric state can then be used to develop interpretations of atmospheric circulation, photochemistry, and seasonal evolution. Minor organic chemical species are particularly interesting as they act as tracers of atmospheric circulation and can be used to probe winds and air mixing. There will be opportunities for the student to guide the project direction, in particular during data analysis and interpretation or in proposing new observations.Spacecraft data analysis will comprise the bulk of the project, led by the main supervisor (Dr Teanby). To help interpret observed atmospheric features, results will be compared to theoretical predictions and numerical planetary climate models adapted from studies of the Earth's atmosphere, which are currently under development by members of the supervisory team (Dr Seviour and Dr Mitchell). These observation-theory-model comparisons will allow more complete understanding of Titan's atmosphere and will potentially feed back into our understanding of fundamental climate physics. Results will also inform the next generation of space missions such at the Dragonfly nuclear-powered drone mission to Titan.