Transport of trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates
Transport of trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates
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DOI：
10.5194/acp-18-11493-2018
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发表时间：
2018-08-15
影响因子：
6.3
通讯作者：
Krishnan, Raghavan
中科院分区：
文献类型：
--
作者：
Fadnavis, Suvarna;Roy, Chaitri;Krishnan, Raghavan
高度活跃的亚洲夏季风反气旋在亚洲对流层气团向温带对流层上层和平流层下层的有效输送中起着重要作用。本文利用MIPAS卫星观测资料、ERA中期再分析资料和ECHAM5-HAMMOZ全球化学气候模式，研究了亚洲痕量气体通过涡脱事件的远距离输送。模式模拟和观测一致地表明，亚洲边界层痕量气体在季风反气旋中被抬升到UTLS高度，并通过与反气旋分离的涡旋进一步水平向东和向西输送。我们描述了2003年7月1-8日的一次涡旋脱落事件，并讨论了1995-2016年的涡旋脱落事件的气候学。我们的分析表明，从反气旋分离出来的涡旋有助于亚洲微量气体从亚洲地区输送到西太平洋(北纬20-30度，东经120-150度)和西非(北纬20-30度，东经0-30度)。在过去20年中，估计西非发生涡旋脱落事件的频率类似于68%，而向西太平洋发生涡流事件的频率类似于25%。利用ECHAM5-HAMMOZ进行了考虑亚洲非甲烷挥发性有机化合物(NMVOCs)和氮氧化物(NOx)排放减少10%的模式敏感性试验，以了解亚洲排放对UTLS的影响。模式模拟结果表明，涡旋脱落引起的亚洲排放物输送对西非和西太平洋对流层高层(类似100-400百帕)和平流层低层(类似100-80百帕)的化学成分有显著影响。NMVOCs和NOx亚洲排放量减少10%，导致西非和西太平洋对流层高层的过氧乙酰硝酸盐(PAN)(200-80hPa2%-10%)、臭氧(1%-4.5%，150hPa附近)和臭氧加热率(0.001-0.004 Kd(-1))减少。
The highly vibrant Asian summer monsoon (ASM) anticyclone plays an important role in efficient transport of Asian tropospheric air masses to the extratropical upper troposphere and lower stratosphere (UTLS). In this paper, we demonstrate long-range transport of Asian trace gases via eddy-shedding events using MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) satellite observations, ERA-Interim reanalysis data and the ECHAM5-HAMMOZ global chemistry-climate model. Model simulations and observations consistently show that Asian boundary layer trace gases are lifted to UTLS altitudes in the monsoon anticyclone and are further transported horizontally eastward and westward by eddies detached from the anticyclone. We present an event of eddy shedding during 1-8 July 2003 and discuss a 1995-2016 climatology of eddy-shedding events. Our analysis indicates that eddies detached from the anticyclone contribute to the transport of Asian trace gases away from the Asian region to the western Pacific (20-30 degrees N, 120-150 degrees E) and western Africa (20-30 degrees N, 0-30 degrees E). Over the last two decades, the estimated frequency of occurrence of eddy-shedding events is similar to 68 % towards western Africa and similar to 25 % towards the western Pacific. Model sensitivity experiments considering a 10 % reduction in Asian emissions of non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOx) were performed with ECHAM5-HAMMOZ to understand the impact of Asian emissions on the UTLS. The model simulations show that transport of Asian emissions due to eddy shedding significantly affects the chemical composition of the upper troposphere (similar to 100-400 hPa) and lower stratosphere (similar to 100-80 hPa) over western Africa and the western Pacific. The 10 % reduction of NMVOCs and NOx Asian emissions leads to decreases in peroxyacetyl nitrate (PAN) (2 %10 % near 200-80 hPa), ozone (1 %-4.5 % near similar to 150 hPa) and ozone heating rates (0.001-0.004 K day(-1) near 300150 hPa) in the upper troposphere over western Africa and the western Pacific.