Aircraft-Based Observations of Ozone-Depleting Substances in the Upper Troposphere and Lower Stratosphere in and Above the Asian Summer Monsoon
Aircraft-Based Observations of Ozone-Depleting Substances in the Upper Troposphere and Lower Stratosphere in and Above the Asian Summer Monsoon
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DOI：
10.1029/2020jd033137
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发表时间：
2021-01-16
影响因子：
4.4
通讯作者：
Laube, Johannes C.
中科院分区：
文献类型：
--
作者：
Adcock, Karina E.;Fraser, Paul J.;Laube, Johannes C.
最近的研究表明，亚洲夏季风反气旋(ASMA)将亚洲快速工业化国家的排放输送到热带对流层上层。在这里，我们提供了一套独特的测量方法，对2016年和2017年夏天在地中海、尼泊尔和印度北部上空多次飞行的M55GePhysica高空科考机收集的100多个空气样本进行了测量，这是欧盟StratoClim项目的一部分。对这些空气样本测量了27种臭氧消耗物质，其中许多高于预期水平，包括氯化的极短寿命物质、二氯甲烷(CH2Cl2)、1，2-二氯乙烷(CH2ClCH2Cl)和氯仿(CHCl3)。对流层顶区域的CH2Cl2混合比为65-136 ppt，而2013-2014年热带对流层顶层的混合比估计为30-44 ppt。用化学运输模型CLAM的轨迹模块计算并由ERA5再分析驱动的反向轨迹表明，CH2Cl2可能来自南亚。我们推导了总当量氯(ECL)和当量平流层有效氯(EESC)，发现这些量大大高于文献中以前的估计。根据2016年的测量，平均空龄为3年的EESC为1,861-1,872ppt，而之前估计的EESC为1,646 ppt。我们的研究结果表明，ASMA向对流层上层和平流层下部输送的长寿命和极短寿命OD的混合比大于预期，可能导致对平流层臭氧层的影响。
Recent studies show that the Asian summer monsoon anticyclone (ASMA) transports emissions from the rapidly industrializing nations in Asia into the tropical upper troposphere. Here, we present a unique set of measurements on over 100 air samples collected on multiple flights of the M55 Geophysica high altitude research aircraft over the Mediterranean, Nepal, and Northern India during the summers of 2016 and 2017 as part of the European Union project StratoClim. These air samples were measured for 27 ozone-depleting substances (ODSs), many of which were enhanced above expected levels, including the chlorinated very short-lived substances, dichloromethane (CH2Cl2), 1,2-dichloroethane (CH2ClCH2Cl), and chloroform (CHCl3). CH2Cl2 mixing ratios in the tropopause region were 65-136 parts per trillion (ppt) in comparison to previous estimates of mixing ratios in the tropical tropopause layer of 30-44 ppt in 2013-2014. Backward trajectories, calculated with the trajectory module of the chemistry-transport model CLaMS and driven by the ERA5 reanalysis, indicate possible source regions of CH2Cl2 in South Asia. We derived total equivalent chlorine (ECl), and equivalent effective stratospheric chlorine (EESC) and found that these quantities were substantially higher than previous estimates in the literature. EESC at mean age-of-air of 3 years based on the 2016 measurements was 1,861-1,872 ppt in comparison to a previously estimated EESC of 1,646 ppt. Our findings show that the ASMA transports larger than expected mixing ratios of long-lived and very short-lived ODSs into the upper troposphere and lower stratosphere, likely leading to an impact on the stratospheric ozone layer.