The simulated stratospheric dynamics have been improved compared to previous generations in many climate models taking part in the Coupled Model Intercomparison Project Phase 6 (CMIP6). This was achieved by going from low to high-top configurations, that is, increasing the atmospheric vertical resolution, raising the model lid height and including parameterization schemes, such as non-orographic gravity wave drag (GWD), to simulate small-scale processes. This also applies to the EC-Earth model, for which comprehensive analysis is now possible thanks to outputs archived within the Dynamics and Variability Model Intercomparison Project (DynVarMIP). Here we analyze atmosphere-only simulations and evaluate the stratospheric dynamics of low-top CMIP5 and high-top CMIP6 configurations of EC-Earth against the MERRA-2 and ERA5 reanalyses. This allows us to identify and interpret model biases in the atmospheric component and to highlight deficiencies needed to be addressed in future model versions. We find substantial improvements in the simulation of the stratosphere in the CMIP6 configuration, both in the tropical and extratropical regions. The zonal wind momentum budget in the tropical stratosphere is much improved in the high-top configuration. Seasonal variability of both models is qualitatively similar to the reanalysis, but for the low-top model this is likely due to compensating errors, as its intraseasonal variability is less realistic. The non-orographic GWD forcing is weak in the high-top model and this limits the realism of the tropical stratosphere variability. We point to persisting issues in the stratosphere of EC-Earth that should be tackled to improve hemispheric-scale circulation and variability.

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EC-地球模型模拟的平流层动力学从CMIP5到CMIP6的变化

参与耦合模型比对项目第六阶段（CMIP6）的许多气候模型中模拟的平流层动力学与前几代相比有所改进。这是通过从低顶配置到高顶配置来实现的，即增加大气垂直分辨率，提高模型盖高度并包括参数化方案，例如非地形重力波阻力（GWD），以模拟小规模过程。这也适用于 EC-Earth 模型，由于动力学和变异性模型比较项目 (DynVarMIP) 中存档的输出，现在可以对其进行全面分析。在这里，我们分析了仅大气模拟，并根据 MERRA-2 和 ERA5 重新分析评估了 EC-Earth 低顶 CMIP5 和高顶 CMIP6 配置的平流层动力学。这使我们能够识别和解释大气成分中的模型偏差，并强调未来模型版本中需要解决的缺陷。我们发现 CMIP6 配置中的平流层模拟在热带和温带地区都有显着改进。在高顶配置中，热带平流层的纬向风动量预算得到了很大改善。两个模型的季节性变化在质量上与重新分析相似，但对于低顶模型，这可能是由于补偿误差，因为其季节内变化不太现实。高顶模型中的非地形 GWD 强迫较弱，这限制了热带平流层变化的真实性。我们指出了 EC 地球平流层中持续存在的问题，应该解决这些问题，以改善半球尺度的环流和变化。