Abstract Uncertainty was evaluated in four chemical mechanisms pertaining to O3 concentrations predicted over Japan by the Community Multiscale Air Quality Model (CMAQ) to investigate factors contributing to model overestimation of O3 concentration. The model setting and meteorological and emissions input data were obtained from a Japanese model inter-comparison project, Japan's Study for Reference Air Quality Modeling (J-STREAM). The compared gas-phase chemical mechanisms included the Carbon Bond Mechanism (CB05TUCL), Regional Atmospheric Chemical Mechanism (RACM2), and two mechanisms developed by the State Air Pollution Research Center (SAPRC), namely SAPRC07TC and SAPRC99. The O3 concentrations produced by CB05TUCL were low compared to those from SAPRC07TC. The RACM2 concentrations were similar to those from SAPRC07TC over inland Japan and lower over the sea. The concentrations from SAPRC99 were higher than those from SAPRC07TC in urban areas and lower in other areas. At most of the monitoring sites in Japan, the modeled O3 concentrations were higher than those from observations. Module overestimation can be ranked in the order of SAPRC99 > SAPRC07TC > RACM2 > CB05TUCL for urban sites and SAPRC07TC > SAPRC99 > RACM2 > CB05TUCL for rural sites. The concentration differences between the chemical mechanisms were within 10 ppb, whereas those between the observed and simulated O3 concentrations reached 40 ppb. Differences in O3 concentrations between the chemical mechanisms accounted for only a part of the model overestimation, while the rest remained unexplained. To investigate factors influencing the differences in O3 concentration between the chemical mechanisms, domain- and 10-vertical-layer-average hourly integrated process rates (IPRs) and integrated reaction rates (IRRs) were calculated using process analysis in CMAQ. The O3 chemical IPRs from SAPRC07TC were higher than those from CB05TUCL and RACM2. The SAPRC99 IPRs were higher than those from SAPRC07TC in urban areas and lower in other areas. The IRR differences in the chemical mechanisms showed that IRRs for the O3 and NO reactions were responsible for the differences in the O3 chemical IPR. The coefficients of determination between the O3 chemical process IPR and IRR differences in the chemical mechanisms were highest for the HO2-NO reaction in CB05TUCL and SAPRC99 and the RO2-NO reaction in RACM2. Differences in reaction rate constants and lumped volatile organic compounds may have caused some of the differences in O3 production between the chemical mechanisms.

中文翻译：

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CMAQ 在日本使用四种化学机制模拟的 O3 浓度的不确定性

摘要 在与社区多尺度空气质量模型 (CMAQ) 预测的日本 O3 浓度相关的四种化学机制中评估了不确定性，以研究导致模型高估 O3 浓度的因素。模型设置以及气象和排放输入数据来自日本模型比对项目，即日本参考空气质量模型研究 (J-STREAM)。比较的气相化学机理包括碳键机理（CB05TUCL）、区域大气化学机理（RACM2）和国家空气污染研究中心（SAPRC）开发的两种机理，即SAPRC07TC和SAPRC99。CB05TUCL 产生的 O3 浓度低于 SAPRC07TC。RACM2 浓度与 SAPRC07TC 在日本内陆和海上较低的浓度相似。SAPRC99 的浓度在城市地区高于 SAPRC07TC，在其他地区较低。在日本的大多数监测点，模拟的 O3 浓度高于观测值。对于城市站点，模块高估可以按照 SAPRC99 > SAPRC07TC > RACM2 > CB05TUCL 的顺序排列，对于农村站点可以按照 SAPRC07TC > SAPRC99 > RACM2 > CB05TUCL 的顺序排列。化学机制之间的浓度差异在 10 ppb 以内，而观察到的和模拟的 O3 浓度之间的差异达到 40 ppb。化学机制之间 O3 浓度的差异仅占模型高估的一部分，而其余部分仍然无法解释。为了研究影响化学机制之间 O3 浓度差异的因素，使用 CMAQ 中的过程分析计算了域和 10 层垂直层平均每小时综合过程速率 (IPR) 和综合反应速率 (IRR)。SAPRC07TC 的 O3 化学知识产权高于 CB05TUCL 和 RACM2。SAPRC99 的知识产权在城市地区高于 SAPRC07TC，在其他地区低于 SAPRC07TC。化学机制中的 IRR 差异表明 O3 和 NO 反应的 IRR 是造成 O3 化学 IPR 差异的原因。CB05TUCL和SAPRC99中的HO2-NO反应和RACM2中的RO2-NO反应在化学机理上的O3化学过程IPR和IRR差异之间的决定系数最高。