This study evaluates the performance of 36 historical CMIP6 GCM trajectories (1979-2005) in reproducing atmospheric circulation over the Iberian Peninsula in the summer months (June-September) using the Lamb Weather Type (WT) classification scheme. Using ERA5 reanalysis as the observational reference, we introduce a methodological framework-applicable to any region worldwide-to evaluate GCM performance. This approach extends traditional daily frequency analysis by evaluating both the daily frequency distribution of WTs and their 24-hour dynamic evolution (i.e., transition probabilities and persistence). Model performance is quantified using the Overlap coefficient. A filtering process is applied where only trajectories that successfully reproduce both daily and conditional distributions with a minimum Overlap threshold $t_{sim}$ across a set number of grid points are retained. The findings show that while several models can adequately reproduce daily WT frequencies (16 out of 36), some struggle to capture day-to-day atmospheric transitions. This leads to a final selection of 12 trajectories over the Iberian Peninsula. Model performance across the region is then evaluated using integrated metrics assessing daily reproduction, conditional reproduction, and transition dynamics. Overall, models from the ec earth3 family-specifically the ec earth3 aerchem trajectory-exhibit the best and most consistent performance across the region. Additionally, the results highlight a geographical performance gap: while models generally represent circulation well in the northwest, they face significant challenges in the central and southern Mediterranean regions of the Peninsula. Ultimately, this study establishes that assessing WT persistence and transitions provides a far more discriminative, objective tool for GCM selection than evaluating daily distributions alone.

翻译：本研究利用Lamb天气类型（WT）分类方案，评估了36个历史时期（1979-2005年）的CMIP6 GCM轨迹在夏季月份（6-9月）再现伊比利亚半岛大气环流的表现。以ERA5再分析资料作为观测参考，我们提出了一种适用于全球任何地区的方法框架，用以评估GCM性能。该方法在传统日频率分析基础上进行了扩展，既评估WT的日频率分布，也评估其24小时动态演化（即过渡概率和持续性）。模型性能通过重叠系数进行量化。采用过滤过程，仅保留那些在设定数量的格点上同时以最小重叠阈值 $t_{sim}$ 成功再现日频率分布和条件分布的轨迹。结果表明，虽然有多个模型能够充分再现日WT频率（36个中有16个），但部分模型难以捕捉逐日的大气过渡过程。这导致最终在伊比利亚半岛上筛选出12条轨迹。随后，使用集成指标（评估日频率再现、条件再现和过渡动态）对该区域内的模型性能进行了评估。总体而言，来自ec earth3系列——特别是ec earth3 aerchem轨迹——的模型在该区域表现出最佳且最一致的性能。此外，结果还揭示了地理性能差异：模型普遍能较好代表西北部的环流，但在半岛中部和南部地中海区域面临显著挑战。最终，本研究证实，评估WT的持续性和过渡为GCM选择提供了比单独评估日分布更具区分度的客观工具。