标题： 具有净反应的三维GCM微型化学方案I.：热化学动力学 显示英文标题

标题： A Mini-Chemical Scheme with Net Reactions for 3D GCMs I.: Thermochemical Kinetics

摘要： 越来越多的证据表明，全球组分分布在全球观测数据分析中扮演着不可或缺的角色。具有可靠化学和云处理的三维广义环流模型（GCMs）对于即将到来的观测尤为重要。在实现三维化学-气候建模的努力中，主要挑战在于需要昂贵的计算能力来处理大量的化学物种和反应。受对稳健且计算高效的化学方案的需求驱动，我们设计了一个最小物种和反应数量的微型化学网络，用于 H$_2$占主导的大气环境。我们采用了一种新颖的技术简化了从完整动力学模型 VULCAN 中的化学网络——用净反应取代了大量的中间反应。化学物种的数量从67减少到12，保留了热学和观测上重要的主要物种，包括 H$_2$O、CH$_4$、CO、CO$_2$、C$_2$H$_2$、NH$_3$和HCN。 总反应数从$\sim$ 800 减少到 20，大幅减少了反应规模。 通过验证四种系外行星大气（GJ 1214b、GJ 436b、HD 189733b 和 HD 209458b）中时间演化以及将其预测成分与 VULCAN 完整动力学进行基准对比，验证了最小化学方案的有效性。 对于主要物种在 1 巴至 0.1 毫巴压力范围内的化学时标和成分分布，它在各种金属丰度和碳氧比（C/O）条件下很好地再现了完整动力学的结果，误差在一个数量级以内。 最小化学方案的小规模使其使用简单且计算速度快，这非常适合在三维全球环流模型（GCM）或检索框架中实施。 本文重点研究净反应的热化学动力学，并在后续论文中讨论光化学。 显示英文摘要

摘要： Growing evidence has indicated that the global composition distribution plays an indisputable role in interpreting observational data. 3D general circulation models (GCMs) with a reliable treatment of chemistry and clouds are particularly crucial in preparing for the upcoming observations. In the effort of achieving 3D chemistry-climate modeling, the challenge mainly lies in the expensive computing power required for treating a large number of chemical species and reactions. Motivated by the need for a robust and computationally efficient chemical scheme, we devise a mini-chemical network with a minimal number of species and reactions for H$_2$-dominated atmospheres. We apply a novel technique to simplify the chemical network from a full kinetics model -- VULCAN by replacing a large number of intermediate reactions with net reactions. The number of chemical species is cut down from 67 to 12, with the major species of thermal and observational importance retained, including H$_2$O, CH$_4$, CO, CO$_2$, C$_2$H$_2$, NH$_3$, and HCN. The size of the total reactions is greatly reduced from $\sim$ 800 to 20. The mini-chemical scheme is validated by verifying the temporal evolution and benchmarking the predicted compositions in four exoplanet atmospheres (GJ 1214b, GJ 436b, HD 189733b, HD 209458b) against the full kinetics of VULCAN. It reproduces the chemical timescales and composition distributions of the full kinetics well within an order of magnitude for the major species in the pressure range of 1 bar -- 0.1 mbar across various metallicities and carbon-to-oxygen (C/O) ratios. The small scale of the mini-chemical scheme permits simple use and fast computation, which is optimal for implementation in a 3D GCM or a retrieval framework. We focus on the thermochemical kinetics of net reactions in this paper and address photochemistry in a follow-up paper.