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The Global Budget of Atmospheric Methanol: New Constraints on Secondary, Oceanic, and Terrestrial Sources
Journal of Geophysical Research: Atmospheres ( IF 4.4 ) Pub Date : 2021-02-03 , DOI: 10.1029/2020jd033439
Kelvin H. Bates 1 , Daniel J. Jacob 1 , Siyuan Wang 2 , Rebecca S. Hornbrook 2 , Eric C. Apel 2 , Michelle J. Kim 3, 4 , Dylan B. Millet 5 , Kelley C. Wells 5 , Xin Chen 5 , Jared F. Brewer 1 , Eric A. Ray 6, 7 , Róisín Commane 8 , Glenn S. Diskin 9 , Steven C. Wofsy 10
Affiliation  

Methanol is the second‐most abundant organic gas in the remote atmosphere after methane, but its sources are poorly understood. Here, we report a global budget of methanol constrained by observations from the ATom aircraft campaign as implemented in the GEOS‐Chem global atmospheric chemistry model. ATom observations under background marine conditions can be fit in the model with a surface ocean methanol concentration of 61 nM and a methanol yield of 13% from the newly implemented CH3O2 + OH reaction. While terrestrial biogenic emissions dominate the global atmospheric methanol budget, secondary production from CH3O2 + OH and CH3O2 + CH3O2 accounts for 29% of the total methanol source, and makes up the majority of methanol in the background marine atmosphere sampled by ATom. Net emission from the ocean is comparatively minor, particularly because of rapid deposition from the marine boundary layer. Aged anthropogenic and pyrogenic plumes sampled in ATom featured large methanol enhancements to constrain the corresponding sources. Methanol enhancements in pyrogenic plumes did not decay with age, implying in‐plume secondary production. The atmospheric lifetime of methanol is only 5.3 days, reflecting losses of comparable magnitude from photooxidation and deposition. GEOS‐Chem model results indicate that methanol photochemistry contributes 5%, 4%, and 1.5% of the tropospheric burdens of formaldehyde, CO, and ozone, respectively, with particularly pronounced effects in the tropical upper troposphere. The CH3O2 + OH reaction has substantial impacts on radical budgets throughout the troposphere and should be included in global atmospheric chemistry models.

中文翻译:

全球大气甲醇预算:次级,海洋和陆地来源的新限制

甲醇是遥远大气中仅次于甲烷的第二大有机气体,但其来源知之甚少。在这里,我们报告了全球甲醇预算,该预算受制于GEOS-Chem全球大气化学模型中ATom飞机战役的观测结果所限制。可以将背景海洋条件下的ATom观测值拟合到模型中,该模型的表面海洋甲醇浓度为61 nM,新实施的CH 3 O 2  + OH反应的甲醇产率为13%。尽管陆地生物成因排放量占全球大气甲醇预算的主导,但CH 3 O 2  + OH和CH 3 O 2  + CH 3 O 2的二次生产占甲醇总来源的29%,并构成了ATom采样的背景海洋大气中的大部分甲醇。海洋的净排放量相对较小,特别是由于海洋边界层的快速沉积。在ATom中取样的老化的人为和热原烟羽具有大量甲醇增强的特性,从而限制了相应的来源。甲醇在热烟羽中的增强不会随年龄而衰减,这意味着在管内进行二次生产。甲醇的大气寿命仅为5.3天,反映出光氧化和沉积造成的损失程度相当。GEOS-Chem模型结果表明,甲醇光化学分别占对流层甲醛,CO和臭氧负荷的5%,4%和1.5%,在热带对流层上的影响尤为明显。CH3 O 2  + OH反应对整个对流层的自由基预算有重大影响,应纳入全球大气化学模型中。
更新日期:2021-02-22
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