Abstract The European Directive (2008/50/EC) encourages the use of models in the assessment and forecasting of air quality, and assigns them a supporting or replacing role with respect to fixed ground-based measurements. A thorough knowledge of performance of the modeling tools over urban areas is therefore required. In this study, we analyze sensitivity tests with the WRF-CHIMERE modeling system in order to investigate the effect of (1) the horizontal model grid size, (2) the resolution of the anthropogenic emission inventory, and (3) the introduction of urban canopy models. The work focuses on L'Aquila and Milan, two Italian cities widely differing for the number of inhabitants, the extension and the geographical location. We found a clear advantage in increasing the model resolution up to ∼4 km, but a further increase at ∼1 km resolution does not seem to be justified. Moreover, we found that the ozone simulation is generally degraded at higher resolution. The introduction of a more detailed treatment of the urban canopy and of the anthropogenic emissions suggests the potential for further improvement, but this requires a fine tuning on the area of application. For example, the Building Environment Parameterization corrects the surface wind speed daily cycle, but it also increases the planetary boundary layer height, resulting in excessive dilution of primary pollutants. The anthropogenic emissions should be refined proportionally to the increase in dynamic model resolution, possibly through new bottom-up inventories, rather than through a downscaling of a coarser inventory. We suggest that future work should primarily focus on intensive campaign periods, where a comprehensive observational characterization of the three dimensional structure and evolution of the planetary boundary layer is available.

中文翻译：

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高分辨率空气质量建模：使用 WRF-CHIMERE 对水平分辨率和城市冠层进行敏感性测试

摘要 欧洲指令 (2008/50/EC) 鼓励在空气质量评估和预测中使用模型，并指定它们在固定地面测量方面的支持或替代作用。因此，需要全面了解城市地区建模工具的性能。在本研究中，我们使用 WRF-CHIMERE 建模系统分析敏感性测试，以研究 (1) 水平模型网格大小、(2) 人为排放清单的分辨率和 (3) 引入城市天篷模型。作品的重点是拉奎拉和米兰，这两个意大利城市在居民数量、范围和地理位置上都有很大差异。我们发现将模型分辨率提高到约 4 公里有明显的优势，但进一步增加约 1 公里的分辨率似乎是不合理的。此外，我们发现臭氧模拟通常在高分辨率下会降低。对城市冠层和人为排放进行更详细的处理表明有进一步改进的潜力，但这需要对应用领域进行微调。例如，建筑环境参数化修正了地表风速日循环，但同时也增加了行星边界层高度，导致一次污染物被过度稀释。人为排放应与动态模型分辨率的增加成比例地细化，可能通过新的自下而上清单，而不是通过缩小粗略清单。