Impact of model resolution on chemical ozone formation in Mexico City; application of the WRF-Chem model
Impact of model resolution on chemical ozone formation in Mexico City; application of the WRF-Chem model
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DOI：
10.5194/acp-10-8983-2010
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发表时间：
2010-09
影响因子：
6.3
通讯作者：
X. Tie;G. Brasseur;Zhuming Ying
中科院分区：
文献类型：
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作者：
X. Tie;G. Brasseur;Zhuming Ying
抽象的。区域化学/动力模式的分辨率对城市大气污染物分布的计算有重要影响。在这项研究中，不同的模式分辨率的空气污染物和光化学臭氧生产的敏感性进行了评估，通过应用区域化学/动力学模型（第3版的天气研究和预报化学模型-WRF-Chemv 3）的情况下，墨西哥城。与3，6，12和24公里的分辨率的模型结果进行比较，当地的表面测量的CO，NOx和O3。研究表明，3和6公里的模式分辨率提供合理的模拟表面CO，NOx和O3浓度和日变化。当分辨率降低到12 km或更低时，模式往往会低估测量值，在24 km分辨率下计算的地表CO、NOx和O3浓度明显低于测量值。本研究认为，城市规模与阈值分辨率之比为6：1，此比值可作为其他城市地区模型分辨率设置的检验值。模式分辨率对O_3和O_3前体物计算的影响主要有三个因素：（1）计算的气象条件;（2）臭氧前体物排放的空间分布;（3）光化学臭氧产生的非线性。模型研究表明，对于O3和O3前体物的计算，空间分辨率（由不同的气象条件和运输过程产生）的影响大于与排放清单相关的分辨率的影响。结果表明，在排放清单分辨率较低（24 km）、气象条件分辨率较高（6 km）的情况下，CO和O3的计算结果比在排放清单和气象条件分辨率较低（24 km）的情况下得到的结果有了较大的改善。表面辐射的分辨率对计算的浓度场有重要影响，但其影响比模式分辨率的影响要小。这项研究还表明，模式分辨率对O3前体物的影响导致臭氧的光化学形成的重要影响。这直接来自O3形成和O3前体浓度之间的非线性关系。最后，这项研究表明，考虑到模型性能和当前计算机所需计算时间之间的平衡，6公里分辨率是计算墨西哥城等城市地区臭氧及其前体的最佳分辨率。
Abstract. The resolution of regional chemical/dynamical models has important effects on the calculation of the distributions of air pollutants in urban areas. In this study, the sensitivity of air pollutants and photochemical ozone production to different model resolutions is assessed by applying a regional chemical/dynamical model (version 3 of Weather Research and Forecasting Chemical model – WRF-Chemv3) to the case of Mexico City. The model results with 3, 6, 12, and 24 km resolutions are compared to local surface measurements of CO, NOx, and O3. The study shows that the model resolutions of 3 and 6 km provide reasonable simulations of surface CO, NOx, and O3 concentrations and of diurnal variations. The model tends to underestimate the measurements when the resolution is reduced to 12 km or less. The calculated surface CO, NOx, and O3 concentrations at 24 km resolution are significantly lower than measured values. This study suggests that the ratio of the city size to the threshold resolution is 6 to 1, and that this ratio can be considered as a test value in other urban areas for model resolution setting. There are three major factors related to the effects of model resolution on the calculations of O3 and O3 precursors, including; (1) the calculated meteorological conditions, (2) the spatial distribution for the emissions of ozone precursors, and (3) the non-linearity in the photochemical ozone production. Model studies suggest that, for the calculations of O3 and O3 precursors, spatial resolutions (resulting from different meteorological condition and transport processes) have larger impacts than the effect of the resolution associated with emission inventories. The model shows that, with coarse resolution of emission inventory (24 km) and high resolution for meteorological conditions (6 km), the calculated CO and O3 are considerably improved compared to the results obtained with coarse resolution for both emission inventory and meteorological conditions (24 km). The resolution of the surface emissions has important effects on the calculated concentration fields, but the effects are smaller than those resulting from the model resolution. This study also suggests that the effect of model resolution on O3 precursors leads to important impacts on the photochemical formation of ozone. This results directly from the non-linear relationship between O3 formation and O3 precursor concentrations. Finally, this study suggests that, considering the balance between model performance and required computation time on current computers, the 6 km resolution is an optimal resolution for the calculation of ozone and its precursors in urban areas like Mexico City.