Global tropospheric hydroxyl distribution, budget and reactivity
Global tropospheric hydroxyl distribution, budget and reactivity
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DOI：
10.5194/acp-16-12477-2016
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发表时间：
2016-10-05
影响因子：
6.3
通讯作者：
Taraborrelli, Domenico
中科院分区：
文献类型：
--
作者：
Lelieveld, Jos;Gromov, Sergey;Taraborrelli, Domenico
大气的自清洁或氧化能力主要由对流层中的羟基（OH）自由基控制。羟基有初级(P)和次级(S)来源，前者主要通过臭氧的光解作用产生，后者通过OH在自由基反应链中循环产生。我们使用最近的美因茨有机机制（MOM）来推进环流模型EMAC （ECHAM/凌乱大气化学）中的挥发性有机碳（VOC）化学，并表明S比之前假设的要大。通过包括大量的主要挥发性有机化合物的排放，并考虑到它们的完全分解和中间产物，MOM是质量守恒的，与以前的模型相比，它计算出的VOC氧化的OH反应活性要高得多。虽然先前发现P和S的大小相似，但目前的工作表明S可能是其两倍大，主要是由于自由对流层中的OH再循环。此外，我们发现夏季夜间OH的形成可能在受污染的副热带边界层中很重要。平均OH再循环概率约为67%，全球OH被缓冲，对自然或人为排放变化的扰动不敏感。大陆和海洋对流层原始环境和污染环境中互补的初级和次级OH形成机制，通过O3的远程输送连接起来，可以维持全球OH水平的稳定。
The self-cleaning or oxidation capacity of the atmosphere is principally controlled by hydroxyl (OH) radicals in the troposphere. Hydroxyl has primary (P) and secondary (S) sources, the former mainly through the photodissociation of ozone, the latter through OH recycling in radical reaction chains. We used the recent Mainz Organics Mechanism (MOM) to advance volatile organic carbon (VOC) chemistry in the general circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry) and show that S is larger than previously assumed. By including emissions of a large number of primary VOC, and accounting for their complete breakdown and intermediate products, MOM is mass-conserving and calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Whereas previously P and S were found to be of similar magnitude, the present work indicates that S may be twice as large, mostly due to OH recycling in the free troposphere. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. With a mean OH recycling probability of about 67 %, global OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary primary and secondary OH formation mechanisms in pristine and polluted environments in the continental and marine troposphere, connected through long-range transport of O3, can maintain stable global OH levels.