Ozone and organic nitrates over the eastern United States: Sensitivity to isoprene chemistry
Ozone and organic nitrates over the eastern United States: Sensitivity to isoprene chemistry
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DOI：
10.1002/jgrd.50817
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
J. Mao;F. Paulot;D. Jacob;R. Cohen;J. Crounse;P. Wennberg;C. Keller;R. Hudman;M. Barkley
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文献类型：
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作者：
J. Mao;F. Paulot;D. Jacob;R. Cohen;J. Crounse;P. Wennberg;C. Keller;R. Hudman;M. Barkley
我们在全球三维化学传输模型(GEOS-Chem)中实现了一个新的异戊二烯氧化机制。模型结果通过2004年夏季美国东部上空国际运输和转换飞机大气研究联盟的臭氧、异戊二烯氧化产物和相关物种的观测进行了评估。该模式实现了对边界层和自由对流层中臭氧的无偏模拟，反映了最近对异戊二烯化学、溴化学和气溶胶中HO2损失的模式更新的抵消效应。与以前版本的模型相比，臭氧-CO关联的模拟得到了改进，这归因于异戊二烯硝酸盐的可逆产率较低，提高了单位氮氧化物(NOx、≡、NO+NO2)的臭氧产生效率。该模型成功地再现了观测到的有机硝酸盐(∑和ANS)浓度及其与甲醛和臭氧的相关性。模型中的∑ANS主要由次生的异戊二烯硝酸盐组成，包括夜间异戊二烯氧化的主要贡献。然后，∑和ANS与甲醛和臭氧的相关性提供了异戊二烯化学的灵敏测试，特别是反对异戊二烯过氧基的快速异构化通道。∑ANS可以为从美国边界层输出NOx提供一个重要的蓄水池。我们发现，地面臭氧对异戊二烯排放的依赖是正的，即使NOx排放减少了4倍。以前的模型显示了负依赖关系，我们将其归因于异戊二烯错误滴定OH。
We implement a new isoprene oxidation mechanism in a global 3‐D chemical transport model (GEOS‐Chem). Model results are evaluated with observations for ozone, isoprene oxidation products, and related species from the International Consortium for Atmospheric Research on Transport and Transformation aircraft campaign over the eastern United States in summer 2004. The model achieves an unbiased simulation of ozone in the boundary layer and the free troposphere, reflecting canceling effects from recent model updates for isoprene chemistry, bromine chemistry, and HO2 loss to aerosols. Simulation of the ozone‐CO correlation is improved relative to previous versions of the model, and this is attributed to a lower and reversible yield of isoprene nitrates, increasing the ozone production efficiency per unit of nitrogen oxides (NOx ≡ NO + NO2). The model successfully reproduces the observed concentrations of organic nitrates (∑ANs) and their correlations with HCHO and ozone. ∑ANs in the model is principally composed of secondary isoprene nitrates, including a major contribution from nighttime isoprene oxidation. The correlations of ∑ANs with HCHO and ozone then provide sensitive tests of isoprene chemistry and argue in particular against a fast isomerization channel for isoprene peroxy radicals. ∑ANs can provide an important reservoir for exporting NOx from the U.S. boundary layer. We find that the dependence of surface ozone on isoprene emission is positive throughout the U.S., even if NOx emissions are reduced by a factor of 4. Previous models showed negative dependences that we attribute to erroneous titration of OH by isoprene.