Methyl chloride in the upper troposphere observed by the CARIBIC passenger aircraft observatory: Large‐scale distributions and Asian summer monsoon outflow
Methyl chloride in the upper troposphere observed by the CARIBIC passenger aircraft observatory: Large‐scale distributions and Asian summer monsoon outflow
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加勒比客机观测站观测到的对流层上层甲基氯：大范围分布和亚洲夏季风流出
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发表时间：
2014
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通讯作者：
C. Brenninkmeijer
中科院分区：
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作者：
T. Umezawa;A. Baker;D. Oram;C. Sauvage;D. O’Sullivan;A. Rauthe;S. Montzka;A. Zahn;C. Brenninkmeijer
我们提供了 2005-2011 年主要通过基于仪器集装箱的民用飞机定期大气调查 (CARIBIC) 客机观测到的对流层上层 (UT) 中甲基氯 (CH3Cl) 的时空变化。欧洲UT上空的CH3Cl混合比全年高于欧洲地面基线站观测到的混合比，表明北半球中纬度地区存在持续的正垂直梯度。非洲和南亚上空的一系列飞行表明，CH3Cl 混合比向热带纬度方向增加，并且在这两个地区和大西洋上空观测到的 UT CH3Cl 水平高于在偏远地表站点测得的水平。热带地区 CH3Cl 的强烈排放以及通过 UT 的经向空气运输可以解释这种垂直和纬度梯度。与一氧化碳 (CO) 数据的比较表明，热带地区的非燃烧源主要有助于形成 UT 中 CH3Cl 的纬度梯度。我们还观察到南美洲和非洲受生物质燃烧影响，空气中 CH3Cl 和 CO 的混合比例升高，这些地区的 CH3Cl 与 CO 的增强比例与之前的观察结果一致。相比之下，相关性表明亚洲夏季季风反气旋中 CH3Cl 与 CO 的比率高达 2.9 ±0.5 ppt ppb−1，推测南亚的国内生物燃料排放是造成这种情况的原因。我们估计南亚的 CH3Cl 排放量为 134 ± 23 Gg Cl yr−1，由于本研究中观察到的 CH3Cl 与 CO 比率较高，因此高于之前的估计。
We present spatial and temporal variations of methyl chloride (CH3Cl) in the upper troposphere (UT) observed mainly by the Civil Aircraft for Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) passenger aircraft for the years 2005–2011. The CH3Cl mixing ratio in the UT over Europe was higher than that observed at a European surface baseline station throughout the year, indicative of a persistent positive vertical gradient at Northern Hemisphere midlatitudes. A series of flights over Africa and South Asia show that CH3Cl mixing ratios increase toward tropical latitudes, and the observed UT CH3Cl level over these two regions and the Atlantic was higher than that measured at remote surface sites. Strong emissions of CH3Cl in the tropics combined with meridional air transport through the UT may explain such vertical and latitudinal gradients. Comparisons with carbon monoxide (CO) data indicate that noncombustion sources in the tropics dominantly contribute to forming the latitudinal gradient of CH3Cl in the UT. We also observed elevated mixing ratios of CH3Cl and CO in air influenced by biomass burning in South America and Africa, and the enhancement ratios derived for CH3Cl to CO in those regions agree with previous observations. In contrast, correlations indicate a high CH3Cl to CO ratio of 2.9 ± 0.5 ppt ppb−1 in the Asian summer monsoon anticyclone and domestic biofuel emissions in South Asia are inferred to be responsible. We estimated the CH3Cl emission in South Asia to be 134 ± 23 Gg Cl yr−1, which is higher than a previous estimate due to the higher CH3Cl to CO ratio observed in this study.