Exploration of the circulation and cloud structure of the atmospheres of the Giant Planets with ground- and space-based telescopes

旅行者2号在1986年和1989年飞越天王星和海王星，为我们提供了这些冰巨人世界的唯一特写镜头。现在，超过四分之一个世纪后，冰巨人被认为是未来行星任务的关键目的地，也是我们银河系中最常见的行星类的最接近的例子。旅行者号的飞越揭示了动态的世界，其大气层与木星和土星上常见的带状云结构完全不同，但这些遭遇的短暂性阻止了详细的审查。天王星被证明是相当缓慢的，而海王星的特点是动态的云活动和漩涡。这种差异从来没有得到令人满意的解释，随后的地面观测表明，这两颗行星上的活动随着时间的推移而变化很大。该项目旨在构建对冰巨大气的三维理解，以将对流层天气层（对流云形成并被剪切分离的地方）的活动与中层大气（平流层，主要是波动活动和光化学）联系起来。候选人将试图将云活动的变化和VLT/MUSE和VLT/SINFONI等仪器测量的反射率光谱（波长< 3 μ m）的变化与热红外光谱（波长> 5 μ m，例如，VLT/VISIR，斯皮策），以揭示这些冰巨星大气的潜在动力学和环流。这项工作将用于确定温度和云活动的空间变化、垂直分布和时间演变，并更好地了解在这些寒冷大气中起作用的凝结过程。这项工作将用于计划和执行进一步的观测，并为计划于2021年发射的美国宇航局詹姆斯韦伯太空望远镜（JWST）进行的计划观测做好准备。

Voyager 2 flew past Uranus and Neptune in 1986 and 1989, and provided our only close-up views of these ice giant worlds. Now, more than a quarter of a century later, the ice giants are recognised as key destinations for future planetary missions and as our closest examples of a planetary class that appears commonplace throughout our galaxy. The Voyager flybys revealed dynamic worlds with atmospheres quite unlike the familiar banded cloud structures seen on Jupiter and Saturn, but the brevity of these encounters prevented detailed scrutiny. Uranus was shown to be rather sluggish, whereas Neptune featured dynamic cloud activity and vortices. This difference has never been satisfactorily explained and subsequent ground-based observations have since suggested that the activity on both of these planets varies hugely with time. This project aims to construct a three-dimensional understanding of ice giant atmospheres to connect activity in the tropospheric weather layer (where convective clouds form and are sheared apart) to the middle atmosphere (the stratosphere, dominated by wave activity and photochemistry). The candidate would attempt to link changes in cloud activity and albedo in reflectivity spectra (wavelengths < 3 um) measured by instruments such as VLT/MUSE and VLT/SINFONI, with the temperature and composition of the ice giants as measured in thermal-infrared spectra (wavelengths> 5 um, e.g., VLT/VISIR, Spitzer) to reveal the underlying dynamics and circulations of these ice giant atmospheres. This work will be used to determine the spatial variation, vertical distribution and temporal evolution of temperature and cloud activity and better understand the condensation processes at work in these frigid atmospheres. This work will be used to plan and execute further observations and also prepare for the reduction of planned observations made with NASA's James Webb Space Telescope (JWST), scheduled for launch in 2021.The key result of this project will be a self-consistent picture of the circulation and cloud-forming processes at work on the ice giants, paving the way for future atmospheric studies by visiting spacecraft.