Sulfur‐water chemistry plays an important role in the middle atmosphere of Venus. Ground‐based observations have found that simultaneously observed SO₂ and H₂O at ~64 km vary with time and are temporally anticorrelated. To understand these observations, we explore the sulfur‐water chemical system using a one‐dimensional chemistry‐diffusion model. We find that SO₂ and H₂O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the middle cloud top (58 km). The behavior of sulfur‐water chemical system can be classified into three regimes, but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO₂ self‐shielding effect causes H₂O above the clouds to respond to the middle cloud top in a nonmonotonic fashion. Through comparison with observations, we find that mixing ratio variations at the middle cloud top can explain the observed variability of SO₂ and H₂O. The sulfur‐water chemistry in the middle atmosphere is responsible for the H₂O‐SO₂ anticorrelation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the middle atmosphere are significantly influenced by the lower atmospheric processes. Continued ground‐based measurements of the coevolution of SO₂ and H₂O above the clouds and new spacecraft missions will be crucial for uncovering the complicated processes underlying the interaction among the lower atmosphere, the clouds, and the middle atmosphere of Venus.

中文翻译：

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再次探讨金星中层大气中的硫水化学系统

硫水化学在金星的中层大气中起着重要作用。地面观测发现，在〜64 km处同时观测到的SO ₂和H ₂ O随时间变化，并且在时间上是反相关的。为了理解这些观察，我们使用一维化学扩散模型探索了硫水化学系统。我们发现云层上方的SO ₂和H ₂ O混合比高度依赖于中云层顶部（58 km）处两种物种的混合比。硫水化学系统的行为可以分为三种状态，但是这些状态之间没有突然过渡。特别地，不存在如先前要求保护的分叉行为。我们还发现SO ₂自屏蔽效应使云层上方的H ₂ O以非单调的方式响应中间云层。通过与观测值的比较，我们发现中云顶的混合比变化可以解释观察到的SO ₂和H ₂ O的变化。中层大气中的硫水化学作用是造成H ₂ O-SO ₂反相关的原因。 64公里 涡流的变化本身不能解释两个物种的变化。这些结果表明，中层大气中物种丰度的变化受到较低大气过程​​的显着影响。对SO ₂和H ₂的协同演化进行持续的地面测量云层之上的O和新的航天器任务对于揭示低空大气层，云层和金星中层大气之间相互作用的复杂过程至关重要。