The atmospheres of synchronously rotating exoplanets are intrinsically 3D, and fast vertical and horizontal winds are expected to mix the atmosphere, driving the chemical composition out of equilibrium. Due to the longer computation times associated with multidimensional forward models, horizontal mixing has only been investigated for a few case studies. In this paper, we aim to generalize the impact of horizontal and vertical mixing on the chemistry of exoplanet atmospheres over a large parameter space. We do this by applying a sequence of post-processed forward models for a large grid of synchronously rotating gaseous exoplanets, where we vary the effective temperature (between 400 and 2600 K), surface gravity, and rotation rate. We find that there is a dichotomy in the horizontal homogeneity of the chemical abundances. Planets with effective temperatures below 1400 K tend to have horizontally homogeneous, vertically quenched chemical compositions, while planets hotter than 1400 K exhibit large compositional day-night differences for molecules such as CH4. Furthermore, we find that the planet’s rotation rate impacts the planetary climate, and thus also the molecular abundances and transmission spectrum. By employing a hierarchical modelling approach, we assess the relative importance of disequilibrium chemistry on the exoplanet transmission spectrum, and conclude that the temperature has the most profound impact. Temperature differences are also the main cause of limb asymmetries, which we estimate could be observable with the James Webb Space Telescope. This work highlights the value of applying a consistent modelling setup to a broad parameter space in exploratory theoretical research.

中文翻译：

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潮汐锁定系外行星的伪二维化学模型网格 – I. 垂直和水平混合的作用

同步旋转的系外行星的大气本质上是 3D 的，预计快速的垂直和水平风会混合大气，使化学成分失去平衡。由于与多维前向模型相关的计算时间较长，因此仅针对少数案例研究对水平混合进行了研究。在本文中，我们旨在概括水平和垂直混合对大参数空间内系外行星大气化学的影响。我们通过对同步旋转的气态系外行星的大型网格应用一系列后处理正向模型来做到这一点，其中我们改变了有效温度（在 400 到 2600 K 之间）、表面重力和旋转速率。我们发现化学丰度的水平同质性存在二分法。有效温度低于 1400 K 的行星往往具有水平均匀、垂直淬火的化学成分，而温度高于 1400 K 的行星则表现出 CH4 等分子的巨大组成昼夜差异。此外，我们发现行星的自转速度会影响行星气候，从而影响分子丰度和透射光谱。通过采用分层建模方法，我们评估了不平衡化学对系外行星透射光谱的相对重要性，并得出结论认为温度具有最深远的影响。温度差异也是肢体不对称的主要原因，我们估计可以通过詹姆斯韦伯太空望远镜观察到。