Transport analysis and source attribution of seasonal and interannual variability of CO in the tropical upper troposphere and lower stratosphere
Transport analysis and source attribution of seasonal and interannual variability of CO in the tropical upper troposphere and lower stratosphere
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DOI：
10.5194/acp-13-129-2013
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发表时间：
2012-07
影响因子：
6.3
通讯作者：
Junhua Liu;J. Logan;L. Murray;H. Pumphrey;M. Schwartz;I. Megretskaia
中科院分区：
文献类型：
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作者：
Junhua Liu;J. Logan;L. Murray;H. Pumphrey;M. Schwartz;I. Megretskaia
抽象的。我们使用 GEOS-Chem 化学输运模型来研究表面排放和动力学过程对微波临边探测器 (MLS) 在对流层上层 (UT) 和平流层下层 (LS) 观测到的 CO 空间和时间模式的影响。由 GEOS-4 和 GEOS-5 同化场驱动的模型模拟呈现了对流层上层和平流层下层 CO 的季节性和年际变化的许多特征。模型模拟和 MLS 数据都显示了从 UT 的半年变化到 LS 的年度变化的转变。标记的CO模拟表明，UT中CO的半年变化主要是由不同大陆地表生物量燃烧的时间重叠以及深层对流的南北变化决定的。 GEOS-4 和 GEOS-5 在 4 月和 5 月都有最大的向上传输，在 7 月到 9 月有最小的向上传输。北半球 (NH) 火灾的 CO 峰值传播到 LS 的速度比南半球 (SH) 火灾的 CO 峰值传播得更快。因此，从半年周期到 80 hPa 左右的年周期的转变是由对流层顶的 CO 信号和布鲁尔-多布森环流的年周期的组合引起的。在 GEOS-5 中，由于向上传输不足，向年周期的转变发生在比 MLS CO 更低的高度。我们从 MLS CO 推导出垂直速度，并用它们来评估从存档的 GEOS 气象场导出的速度。我们发现GEOS-4的速度在215 hPa到125 hPa之间与MLS CO的速度相似，而GEOS-5的速度在春季和夏季太低。两个模型的平均热带垂直速度低于 100 hPa 以上从 MLS CO 推断的平均垂直速度，特别是在 GEOS-5 中，北半球夏季平均向下运动，而不是向上运动。因此，模型中 SH 燃烧产生的 CO 最大值的输送效率低于 147 hPa 以上的 MLS CO 输送效率，并且在 100 hPa 时几乎消失。 CO 记录的最强峰值出现在 2004 年末、2006 年和 2010 年，前两次是由印度尼西亚的重大火灾造成的，最后一次是由南美洲的严重燃烧造成的，所有这些都与严重干旱有关。
Abstract. We used the GEOS-Chem chemistry-transport model to investigate impacts of surface emissions and dynamical processes on the spatial and temporal patterns of CO observed by the Microwave Limb Sounder (MLS) in the upper troposphere (UT) and lower stratosphere (LS). Model simulations driven by GEOS-4 and GEOS-5 assimilated fields present many features of the seasonal and inter-annual variation of CO in the upper troposphere and lower stratosphere. Both model simulations and the MLS data show a transition from semi-annual variations in the UT to annual variations in the LS. Tagged CO simulations indicate that the semi-annual variation of CO in the UT is determined mainly by the temporal overlapping of surface biomass burning from different continents as well as the north-south shifts of deep convection. Both GEOS-4 and GEOS-5 have maximum upward transport in April and May with a minimum in July to September. The CO peaks from the Northern Hemisphere (NH) fires propagate faster to the LS than do those from the Southern Hemisphere (SH) fires. Thus the transition from a semi-annual to an annual cycle around 80 hPa is induced by a combination of the CO signal at the tropopause and the annual cycle of the Brewer-Dobson circulation. In GEOS-5, the shift to an annual cycle occurs at a lower altitude than in MLS CO, a result of inadequate upward transport. We deduce vertical velocities from MLS CO, and use them to evaluate the velocities derived from the archived GEOS meteorological fields. We find that GEOS-4 velocities are similar to those from MLS CO between 215 hPa and 125 hPa, while the velocities in GEOS-5 are too low in spring and summer. The mean tropical vertical velocities from both models are lower than those inferred from MLS CO above 100 hPa, particularly in GEOS-5, with mean downward, rather than upward motion in boreal summer. Thus the models' CO maxima from SH burning are transported less effectively than those in MLS CO above 147 hPa and almost disappear by 100 hPa. The strongest peaks in the CO tape-recorder are in late 2004, 2006, and 2010, with the first two resulting from major fires in Indonesia and the last from severe burning in South America, all associated with intense droughts.