Global Atmospheric Budget of Acetone: Air‐Sea Exchange and the Contribution to Hydroxyl Radicals
Global Atmospheric Budget of Acetone: Air‐Sea Exchange and the Contribution to Hydroxyl Radicals
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全球丙酮的大气收支：气海交换和对羟基自由基的贡献
DOI：
10.1029/2020jd032553
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发表时间：
2020
期刊：
影响因子：
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et al.
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文献类型：
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作者：
W. Siyuan;Apel E.;Schwantes R.;Bates K.;Jacob D.;Fischer E.;Hornbrook R.;Hills A.;Emmons L.;Pan L.;Honomichl S.;Tilmes S.;Lamarque J.‐F.;Yang M.;Marandino C.;Saltzman E.;Bruyn W.;Kameyama S.;Tanimoto H.;Omori Y.;et al.
丙酮是大气中最丰富的含氧挥发性有机化合物（VOC）之一。海洋对大气中的丙酮有很强的控制作用，但丙酮的海洋通量仍然受到很少的限制。在这项工作中，丙酮的全球预算使用两个全球模型进行评估：CAM-chem 和 GEOS-Chem。 CAM-chem 使用在线海气交换框架来计算双向海洋丙酮通量，该框架与面向数据的机器学习方法相结合。机器学习算法使用全球海水丙酮测量套件进行训练。 GEOS-Chem 使用固定的表面海水丙酮浓度来计算海洋通量。这两个模型模拟都与最近的全球规模、多季节活动——美国宇航局大气层析成像任务（ATom）的机载观测结果进行了比较。我们发现 CAM-chem 和 GEOS-Chem 都相当好地捕获了偏远大气中测得的丙酮垂直分布。综合观测和建模分析表明，(i) 海洋强烈调节丙酮的大气预算。热带和亚热带海洋主要是丙酮的净来源，而高纬度海洋是丙酮的净汇。 (ii) CMIP6 人为排放清单可能低估北半球的丙酮和/或其前体。 (iii) MEGAN 生物排放模型可能高估丙酮和/或其前体，和/或生物氧化机制可能高估丙酮产量。 (iv) 模型始终高估了南半球冬季南大洋上层对流层和平流层下层中的丙酮。 (v) 热带对流层上层/平流层下层羟自由基产生量中，丙酮贡献高达 30-40%。
Acetone is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere. The oceans impose a strong control on atmospheric acetone, yet the oceanic fluxes of acetone remain poorly constrained. In this work, the global budget of acetone is evaluated using two global models: CAM‐chem and GEOS‐Chem. CAM‐chem uses an online air‐sea exchange framework to calculate the bidirectional oceanic acetone fluxes, which is coupled to a data‐oriented machine‐learning approach. The machine‐learning algorithm is trained using a global suite of seawater acetone measurements. GEOS‐Chem uses a fixed surface seawater concentration of acetone to calculate the oceanic fluxes. Both model simulations are compared to airborne observations from a recent global‐scale, multiseasonal campaign, the NASA Atmospheric Tomography Mission (ATom). We find that both CAM‐chem and GEOS‐Chem capture the measured acetone vertical distributions in the remote atmosphere reasonably well. The combined observational and modeling analysis suggests that (i) the ocean strongly regulates the atmospheric budget of acetone. The tropical and subtropical oceans are mostly a net source of acetone, while the high‐latitude oceans are a net sink. (ii) CMIP6 anthropogenic emission inventory may underestimate acetone and/or its precursors in the Northern Hemisphere. (iii) The MEGAN biogenic emissions model may overestimate acetone and/or its precursors, and/or the biogenic oxidation mechanisms may overestimate the acetone yields. (iv) The models consistently overestimate acetone in the upper troposphere‐lower stratosphere over the Southern Ocean in austral winter. (v) Acetone contributes up to 30–40% of hydroxyl radical production in the tropical upper troposphere/lower stratosphere.