Can we explain the observed methane variability after the Mount Pinatubo eruption?
Can we explain the observed methane variability after the Mount Pinatubo eruption?
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DOI：
10.5194/acp-16-195-2016
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发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Rockmann, T.
中科院分区：
文献类型：
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作者：
Banda, N.;Krol, M.;Rockmann, T.
1991年6月皮纳图博火山爆发后，大气中的甲烷增长率变化很大。据报告，在1992年期间，增长率下降了10 ppb/年以上，第二年有所恢复。虽然已经提出了几个原因来解释喷发后的CH 4的演变，他们的贡献所观察到的变化尚未解决。CH 4通过与对流层OH的反应从大气中去除，而对流层OH又通过紫外线辐射下的O-3光解产生。皮纳图博火山爆发后的CH 4去除可能受到对流层紫外线水平变化的影响，由于平流层SO2和硫酸盐气溶胶的存在，以及由于皮纳图博气溶胶的臭氧消耗增加。火山爆发后扰动的气候也改变了大气CH 4的源和汇。此外，甲烷浓度还受到这一时期自然变化的其他因素的影响，如厄尔尼诺-南方涛动和生物量燃烧事件。CO、NOX和非甲烷挥发性有机化合物（NMVOCs）的排放也通过影响对流层OH水平间接影响CH 4浓度。量化了1990 - 1995年期间每个驱动因素对全球CH 4变化的贡献。我们发现，减少810 ppb年（-1）CH 4是由上述过程的组合解释。然而，发现最低增长率的时间比观察到的要晚6-9个月。1990年至1995年期间CH 4增长率的长期下降被很好地捕捉到，可以归因于这一时期OH浓度的增加。我们模拟的CH 4增长率的潜在不确定性包括湿地的CH 4排放，生物质燃烧的CH 4和其他化合物的排放，生物NMVOC和OH NMVOC排放变化的敏感性。两个清单用于CH 4从湿地，ORCHIDEE和LPJ排放量，调查这些排放的不确定性的作用。虽然较高的气候敏感性的ORCHIDEE提高模拟的CH 4增长率变化后，皮纳图博，没有两个清单正确捕捉到观察到的CH 4在这一时期的变化。
The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr(-1) in the growth rate over the course of 1992 was reported, and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O-3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as El Nino-Southern Oscillation (ENSO) and biomass burning events. Emissions of CO, NOX and non-methane volatile organic compounds (NMVOCs) also affected CH4 concentrations indirectly by influencing tropospheric OH levels.Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 810 ppb yr(-1) CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6-9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.