Chemistry of Hydrogen Oxide Radicals \((HO_x)\) in the Arctic Troposphere in Spring
Author
Evans, M. J.
Olson, J. R.
Ren, X.
Brune, W. H.
St. Clair, J. M.
Crounse, J. D.
Spencer, K. M.
Beaver, M. R.
Wennberg, P. O.
Cubison, M. J.
Jimenez, J. L.
Fried, A.
Weibring, P.
Walega, J. G.
Hall, S. R.
Weinheimer, A. J.
Cohen, R. C.
Chen, G.
Crawford, J. H.
McNaughton, C.
Clarke, A. D.
Jaeglé, L.
Fisher, J. A.
Yantosca, R. M.
Carouge, C.
Note: Order does not necessarily reflect citation order of authors.
Published Version
https://doi.org/10.5194/acp-10-5823-2010Metadata
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Mao, Jialin, Daniel J. Jacob, M. J. Evans, J. R. Olson, X. Ren, W. H. Brune, J. M. St. Clair, et al. 2010. “Chemistry of Hydrogen Oxide Radicals \((HO_x)\) in the Arctic Troposphere in Spring.” Atmospheric Chemistry and Physics 10 (13) (July 1): 5823–5838. doi:10.5194/acp-10-5823-2010. http://dx.doi.org/10.5194/acp-10-5823-2010.Abstract
We use observations from the April 2008 NASA ARCTAS aircraft campaign to the North American Arctic, interpreted with a global 3-D chemical transport model (GEOS-Chem), to better understand the sources and cycling of hydrogen oxide radicals \((HO_x≡H+OH+\)peroxy radicals) and their reservoirs \((HO_y≡HO_x+\)peroxides) in the springtime Arctic atmosphere. We find that a standard gas-phase chemical mechanism overestimates the observed \(HO_2\) and \(H_2O_2\) concentrations. Computation of \(HO_x\) and \(HO_y\) gas-phase chemical budgets on the basis of the aircraft observations also indicates a large missing sink for both. We hypothesize that this could reflect \(HO_2\) uptake by aerosols, favored by low temperatures and relatively high aerosol loadings, through a mechanism that does not produce H2O2. We implemented such an uptake of \(HO_2\) by aerosol in the model using a standard reactive uptake coefficient parameterization with \(\gamma(HO_2)\) values ranging from 0.02 at 275 K to 0.5 at 220 K. This successfully reproduces the concentrations and vertical distributions of the different \(HO_x\) species and \(HO_y\) reservoirs. \(HO_2\) uptake by aerosol is then a major \(HO_x\) and \(HO_y\) sink, decreasing mean OH and \(HO_2\) concentrations in the Arctic troposphere by 32% and 31% respectively. Better rate and product data for \(HO_2\) uptake by aerosol are needed to understand this role of aerosols in limiting the oxidizing power of the Arctic atmosphere.Terms of Use
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