What drives the observed variability of HCN in the troposphere and lower stratosphere?
What drives the observed variability of HCN in the troposphere and lower stratosphere?
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DOI：
10.5194/acp-9-8531-2009
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发表时间：
2009-01-01
影响因子：
6.3
通讯作者：
Mahieu, E.
中科院分区：
文献类型：
--
作者：
Li, Q.;Palmer, P. I.;Mahieu, E.
我们使用GEOS-Chem全球3-D化学传输模型来研究确定对流层和平流层下部氰化氢（HCN）观测变化的化学和物理过程的相对重要性。因此，我们调和地面的FTIR柱测量HCN，这表明每年和半年的变化，最近的空间测量HCN混合比在热带低平流层，这表明一个大的两年的变化。我们发现，所观察到的地面站的柱的变化是由几个区域燃烧源的HCN的叠加，与GEOS-Chem再现这些列数据的正偏差为5%。GEOS-Chem再现了微波临边探测器和大气化学实验卫星仪器观测到的HCN混合比，平均负偏差为20%，以及观测到的HCN变异性，平均负偏差为7%。我们表明，热带生物质燃烧排放解释了大部分观测到的HCN变化在对流层上部和平流层下部（UTLS），其余的是由于大气传输和HCN化学。在平流层中上层，大气动力学对HCN变化的影响越来越大。非洲和其他大陆燃烧季节之间的时间重叠程度是确定UTLS明显的两年周期的关键。对其他寿命较短的痕量气体进行的类似分析没有观察到UTLS中年度和两年周期之间的过渡，这可能是因为由于大气寿命较短，地面排放的年际变化信号在到达平流层低层之前就被稀释了。
We use the GEOS-Chem global 3-D chemistry transport model to investigate the relative importance of chemical and physical processes that determine observed variability of hydrogen cyanide (HCN) in the troposphere and lower stratosphere. Consequently, we reconcile ground-based FTIR column measurements of HCN, which show annual and semi-annual variations, with recent space-borne measurements of HCN mixing ratio in the tropical lower stratosphere, which show a large two-year variation. We find that the observed column variability over the ground-based stations is determined by a superposition of HCN from several regional burning sources, with GEOS-Chem reproducing these column data with a positive bias of 5%. GEOS-Chem reproduces the observed HCN mixing ratio from the Microwave Limb Sounder and the Atmospheric Chemistry Experiment satellite instruments with a mean negative bias of 20%, and the observed HCN variability with a mean negative bias of 7%. We show that tropical biomass burning emissions explain most of the observed HCN variations in the upper troposphere and lower stratosphere (UTLS), with the remainder due to atmospheric transport and HCN chemistry. In the mid and upper stratosphere, atmospheric dynamics progressively exerts more influence on HCN variations. The extent of temporal overlap between African and other continental burning seasons is key in establishing the apparent bienniel cycle in the UTLS. Similar analysis of other, shorter-lived trace gases have not observed the transition between annual and bienniel cycles in the UTLS probably because the signal of inter-annual variations from surface emission has been diluted before arriving at the lower stratosphere (LS), due to shorter atmospheric lifetimes.