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Carbon and hydrogen isotopic ratios of atmospheric methane in the upper troposphere over the Western Pacific

机译：西太平洋对流层上层大气甲烷的碳氢同位素比

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We present the mixing ratio, δ13C and δD of atmospheric CH4 using commercial aircraft in the uppertroposphere (UT) over the Western Pacific for the period December2005–September 2010. The observed results were compared with those obtainedusing commercial container ships in the lower troposphere (LT) over the sameregion. In the Northern Hemisphere (NH), the UT CH4 mixing ratio showshigh values in the boreal summer–autumn, when the LT CH4 mixing ratioreaches a seasonal minimum. From tagged tracer experiments made using anatmospheric chemistry transport model, we found that such high CH4values are due to rapid transport of air masses influenced by CH4sources in South Asia and East Asia. The observed isotopic ratio data implythat these areas have CH4 sources with relatively low δ13C and δD signatures such as biogenic sources.Latitudinal distributions of the annual average UT and LT CH4 mixingratio intersect each other in the tropics; the mixing ratio value is lower inthe UT than in the LT in the NH and the situation is reversed in the SouthernHemisphere (SH), due mainly to the NH air intrusion into the SH through theUT. Such intersection of the latitudinal distributions is observable inδD but not in δ13C, implying anadditional contribution from reaction of CH4 with active chlorine in themarine boundary layer. δ13C and δDshow low values in the NH and high values in the SH both in the UT and in theLT. We also observed an increase in the CH4 mixing ratio and decreasesin δ13C and δ
机译：我们介绍了使用商用飞机在2005年12月至2010年9月期间在西太平洋上空对流层（UT）中大气CH 4 的混合比δ 13 C和δD。将观察到的结果与在同一区域低层对流层（LT）中使用商业集装箱船获得的结果进行了比较。在北半球，北半球夏季–秋季，UT CH 4 的混合比达到较高的值，而LT CH 4 的混合比达到季节的最小值。从使用大气化学迁移模型进行的标记示踪剂实验中，我们发现如此高的CH 4 值是由于南亚和太平洋地区受CH 4 源影响的空气质量的快速迁移所致。东亚。观察到的同位素比值数据表明这些地区的CH 4 来源具有较低的δ 13 C和δD签名（例如生物来源）。UT和LT CH年平均水平的纬度分布 4 混合比在热带彼此相交; NH中的混合比值比LT中的低，而南半球（SH）的情况则相反，这主要是因为NH空气通过UT进入SH。在δD中可观察到这种横向分布的交集，而在δ 13 C中则无法观察到，这意味着在海洋边界层中CH 4 与活性氯的反应产生了额外的贡献。 δ 13 C和δD在UT和LT中均显示出NH中的低值和SH中的高值。我们还观察到，在西太平洋的UT和LT，在2007–2008年期间，CH 4 的混合比增加，而δ 13 C和δ

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