Stable water isotopes are data‐rich tracers of the hydrological cycle, and, recently, the advent of isotope‐enabled climate models has allowed for investigations into the utility of water isotopes for tracking changes in the large‐scale atmospheric circulation. Among the suite of published isotope‐enabled climate models, those with intermediate complexity offer the benefits of efficiency, allowing for long ensemble runs. However, the ability of these models to simulate the response to global warming with the same fidelity as state‐of‐the‐art models is questionable. Here we evaluate an intermediate complexity model, SPEEDY‐IER, in a high‐CO₂ scenario and compare its performance to an Intergovernmental Panel on Climate Change (IPCC)‐class model, iCAM5. SPEEDY‐IER can generally simulate changes in tropical circulation, the weakening of the Walker circulation, and the narrowing of the deep tropics. A deeper investigation of water isotope fields indicates SPEEDY‐IER simulates qualitative trends in precipitation and vapor isotopes with fidelity, but it does not simulate amplitudes or spatial patterns of water isotope changes shown in iCAM5. This bias in SPEEDY‐IER is mainly due to its coarse resolution and simplified convection scheme. We then modify the model by introducing condensation and detrainment in intermediate convection levels; this modification successfully improves SPEEDY‐IER's simulation of water isotope fields, though the response of the Walker circulation to climate change is weakened. We demonstrate that evaluating water isotope fields reveals hidden biases in a climate model and guides improvements to the model's performance. Thus, the examination of water isotope fields and validation against available observations likely provides more stringent constraints for model physics.

中文翻译：

---

启用同位素的GCM复杂性在模拟高CO2情景中的热带环流变化中的作用

稳定的水同位素是水文循环的丰富数据示踪剂，最近，启用同位素的气候模型使人们能够研究水同位素在跟踪大规模大气环流变化中的效用。在已发布的支持同位素的气候模型套件中，具有中等复杂性的模型具有效率优势，可以长期集成。但是，这些模型以与最新模型相同的保真度来模拟对全球变暖的响应的能力值得怀疑。在这里，我们评估了高CO _2中的中间复杂度模型SPEEDY‐IER情景，并将其表现与政府间气候变化专门委员会（IPCC）级模型iCAM5进行比较。SPEEDY‐IER通常可以模拟热带环流的变化，Walker环流的减弱和热带深层的缩小。对水同位素场的更深入研究表明，SPEEDY‐IER可以真实地模拟降水和蒸气同位素的定性趋势，但不能模拟iCAM5中显示的水同位素变化的幅度或空间模式。SPEEDY‐IER中的这种偏差主要是由于其较粗的分辨率和简化的对流方案。然后，我们通过在中间对流水平引入凝结和减量来修改模型。这种修改成功地改善了SPEEDY‐IER对水同位素场的模拟，尽管沃克环流对气候变化的反应减弱了。我们证明，评估水同位素场揭示了气候模型中隐藏的偏差，并指导了模型性能的改进。因此，对水同位素场的检查和对现有观测资料的验证可能会为模型物理提供更严格的约束。