Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere
Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere
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DOI：
10.5194/acp-15-13699-2015
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发表时间：
2015-12
影响因子：
6.3
通讯作者：
B. Vogel;G. Günther;R. Müller;J. Grooß;M. Riese
中科院分区：
文献类型：
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作者：
B. Vogel;G. Günther;R. Müller;J. Grooß;M. Riese
抽象的。考虑到2012年亚洲季风反气旋的季节内变化，通过使用人工排放示踪剂对平流层化学拉格朗日模式(CLAMS)进行模拟，分析了亚洲不同边界层源区对亚洲季风反气旋化学成分的影响。印度/中国地区模拟的CO、O_3和人工排放示踪剂的水平分布与Aura微波测深仪对O_3和CO的卫星测量结果吻合较好。此外，人工排放示踪与位涡的相关性表明，印度/中国的排放示踪可以很好地反映亚洲季风反气旋内痕量气体的空间分布。亚洲季风反气旋构成了排放示踪剂的水平输送障碍，其位置和形状变化很大。从6月底到8月初，反气旋北移，9月期间，印度/中国的排放示踪物向热带方向的空间分布有很强的展宽。除了反气旋位置的变化外，不同边界源区对对流层上层亚洲季风反气旋组成的贡献强烈地依赖于它的季节内变率，因此比迄今所认为的要复杂得多。位势温度为380K的印度北部和东南亚对反气旋气团的贡献最大。在2012年季风季的上旬(6月中旬至7月中旬)和下旬(9月)，东南亚的排放贡献最大；在其间(8月初)，印度北部的排放影响最大。结果表明，不同对流区贡献的时间变化印记在亚洲季风反气旋的化学成分中。起源于东南亚的气团在亚洲季风反气旋内外都有发现，这是因为这些气团除了在反气旋内输送外，还在反气旋东南侧和热带地区向上输送。随后，这些气团在380K左右发生等熵向极地输送，导致北半球温带外最低平流层在9月底被来自东南亚的气团淹没。即使在反气旋环流破裂后(9月底左右)，源自印度/中国的气团在亚洲上空对流层高层仍有显著贡献。我们的结果表明，印度、中国和东南亚的排放对北半球最低平流层的化学成分有显著影响，特别是在2012年9/10月季风季结束时。
Abstract. The impact of different boundary layer source regions in Asia on the chemical composition of the Asian monsoon anticyclone, considering its intraseasonal variability in 2012, is analysed by simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS) using artificial emission tracers. The horizontal distribution of simulated CO, O3, and artificial emission tracers for India/China are in good agreement with patterns found in satellite measurements of O3 and CO by the Aura Microwave Limb Sounder (MLS). Using in addition, correlations of artificial emission tracers with potential vorticity demonstrates that the emission tracer for India/China is a very good proxy for spatial distribution of trace gases within the Asian monsoon anticyclone. The Asian monsoon anticyclone constitutes a horizontal transport barrier for emission tracers and is highly variable in location and shape. From the end of June to early August, a northward movement of the anticyclone and, during September, a strong broadening of the spatial distribution of the emission tracer for India/China towards the tropics are found. In addition to the change of the location of the anticyclone, the contribution of different boundary source regions to the composition of the Asian monsoon anticyclone in the upper troposphere strongly depends on its intraseasonal variability and is therefore more complex than hitherto believed. The largest contributions to the composition of the air mass in the anticyclone are found from northern India and Southeast Asia at a potential temperature of 380 K. In the early (mid-June to mid-July) and late (September) period of the 2012 monsoon season, contributions of emissions from Southeast Asia are highest; in the intervening period (early August), emissions from northern India have the largest impact. Our findings show that the temporal variation of the contribution of different convective regions is imprinted in the chemical composition of the Asian monsoon anticyclone. Air masses originating in Southeast Asia are found both within and outside of the Asian monsoon anticyclone because these air masses experience, in addition to transport within the anticyclone, upward transport at the southeastern flank of the anticyclone and in the tropics. Subsequently, isentropic poleward transport of these air masses occurs at around 380 K with the result that the extratropical lowermost stratosphere in the Northern Hemisphere is flooded by the end of September with air masses originating in Southeast Asia. Even after the breakup of the anticyclonic circulation (around the end of September), significant contributions of air masses originating in India/China are still found in the upper troposphere over Asia. Our results demonstrate that emissions from India, China, and Southeast Asia have a significant impact on the chemical composition of the lowermost stratosphere of the Northern Hemisphere, in particular at the end of the monsoon season in September/October 2012.