The Community Earth System Model 2 (CESM2) is the latest Earth System Model developed by the National Center for Atmospheric Research in collaboration with the university community and is significantly advanced in most components compared to its predecessor (CESM1). Here, CESM2's representation of the large‐scale atmospheric circulation and its variability is assessed. Further context is providedthrough comparison to the CESM1 large ensemble and other models from the Coupled Model Intercomparison Project (CMIP5 and CMIP6). This includes an assessment of the representation of jet streams and storm tracks, stationary waves, the global divergent circulation, the annular modes, the North Atlantic Oscillation, and blocking. Compared to CESM1, CESM2 is substantially improved in the representation of the storm tracks, Northern Hemisphere (NH) stationary waves, NH winter blocking and the global divergent circulation. It ranks within the top 10% of CMIP class models in many of these features. Some features of the Southern Hemisphere (SH) circulation have degraded, such as the SH jet strength, stationary waves, and blocking, although the SH jet stream is placed at approximately the correct location. This analysis also highlights systematic deficiencies in these features across the new CMIP6 archive, such as the continued tendency for the SH jet stream to be placed too far equatorward, the North Atlantic westerlies to be too strong over Europe, the storm tracks as measured by low‐level meridional wind variance to be too weak and a lack of blocking in the North Atlantic sector.

中文翻译：

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CESM2和其他CMIP模型中大尺度大气环流及其变化的评估

社区地球系统模型2（CESM2）是由美国国家大气研究中心与大学社区合作开发的最新地球系统模型，与之前的版本（CESM1）相比，它在大多数组件上都取得了显着进步。在这里，CESM2代表了大尺度大气环流及其变化。通过与CESM1大集合以及耦合模型比较项目（CMIP5和CMIP6）的其他模型的比较，提供了更多的上下文。这包括对急流和风暴轨迹，固定波，全球发散环流，环形模式，北大西洋涛动和阻塞的表示的评估。与CESM1相比，CESM2在暴风雨轨迹的表示上有了很大的改进，北半球（NH）驻波，NH冬季阻塞和全球发散环流。在许多这些功能中，它位列CMIP类模型的前10％。尽管SH射流大致位于正确的位置，但南半球（SH）环流的某些特征已经退化，例如SH射流强度，驻波和阻塞。该分析还突出显示了新CMIP6档案库在这些功能方面的系统缺陷，例如SH射流持续偏向赤道的持续趋势，北大西洋西风在欧洲范围内过于强大，风暴轨迹（以低气压衡量）级别子午风方差太小且在北大西洋地区缺乏阻塞。在许多这些功能中，它位列CMIP类模型的前10％。尽管SH射流大致位于正确的位置，但南半球（SH）环流的某些特征已经退化，例如SH射流强度，驻波和阻塞。该分析还突出显示了新CMIP6档案库在这些功能方面的系统缺陷，例如SH射流持续偏向赤道的持续趋势，北大西洋西风在欧洲范围内过于强大，风暴轨迹（以低气压衡量）级别子午风方差太小且在北大西洋地区缺乏阻塞。在许多这些功能中，它位列CMIP类模型的前10％。尽管SH射流大致位于正确的位置，但南半球（SH）环流的某些特征已经退化，例如SH射流强度，驻波和阻塞。该分析还突出显示了新CMIP6档案库在这些功能方面的系统缺陷，例如SH射流持续偏向赤道的持续趋势，北大西洋西风在欧洲范围内过于强大，风暴轨迹（以低气压衡量）级别子午风方差太小且在北大西洋地区缺乏阻塞。尽管SH射流位于大约正确的位置。该分析还突出显示了新CMIP6档案库在这些功能方面的系统缺陷，例如SH射流持续偏向赤道的持续趋势，北大西洋西风在欧洲范围内过于强大，风暴轨迹（以低气压衡量）级别子午风方差太小且在北大西洋地区缺乏阻塞。尽管SH射流位于大约正确的位置。该分析还突出显示了新CMIP6档案库在这些功能方面的系统缺陷，例如SH射流持续偏向赤道的持续趋势，北大西洋西风在欧洲范围内过于强大，风暴轨迹（以低气压衡量）级别子午风方差太小且在北大西洋地区缺乏阻塞。