Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean
Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean
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DOI：
10.1038/nature07035
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发表时间：
2008-06-26
期刊：
影响因子：
64.8
通讯作者：
Plane, John M. C.
中科院分区：
文献类型：
--
作者：
Read, Katie A.;Mahajan, Anoop S.;Plane, John M. C.
过去 150 年来对流层臭氧水平不断增加导致了严重的气候扰动(1)；对对流层臭氧未来趋势的预测需要充分了解其前体排放及其破坏过程。对流层臭氧损失的大部分发生在热带海洋边界层(2,3)，并且被认为主要是由高浓度水蒸气存在下的高臭氧光解率造成的。数值模型假设（4-7）可以通过公海海洋源排放的溴和碘进一步减少对流层臭氧负担，但迄今为止尚未得到观测证实。在这里，我们报告了佛得角天文台八个月的光谱测量结果，表明热带海洋边界层白天普遍存在一氧化溴和一氧化碘。与低空飞机观测相结合的同地原位地表痕量气体测量的全年数据集表明，平均每日观测到的臭氧损失比使用不包括卤素化学的经典光化学方案的全球化学模型模拟的损失高出 50%。我们进行的箱模型计算表明，观测到的卤素浓度会导致模型与观测结果相匹配所需的额外臭氧损失。我们的结果表明，卤素化学对热带大西洋边界层的光化学臭氧损失具有显着而广泛的影响。大气模型中卤素源及其化学成分的遗漏可能会导致历史和未来全球臭氧预算、对流层氧化能力和甲烷氧化速率的计算出现重大错误。
Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation(1); the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer(2,3) and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open- ocean marine sources has been postulated by numerical models(4-7), but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year- round data set of co- located in situ surface trace gas measurements made in conjunction with low- level aircraft observations shows that the mean daily observed ozone loss is similar to 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.