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Atmospheric Chemistry and Physics 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 (HOx ≡H+OH+peroxy radicals) and their reservoirs (HOy ≡HOx +peroxides) in the springtime Arctic atmosphere. We find that a standard gas-phase chemical mechanism overestimates the observed HO2 and H2 O2 concentrations. Computation of HOx and HOy 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 HO2 uptake by aerosols, favored by low temperatures and relatively high aerosol loadings, through a mechanism that does not produce H2 O2 . We implemented such an uptake of HO2 by aerosol in the model using a standard reactive uptake coefficient parameterization with γ(HO2 ) 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 HOx species and HOy reservoirs. HO2 uptake by aerosol is then a major HOx and HOy sink, decreasing mean OH and HO2 concentrations in the Arctic troposphere by 32% and 31% respectively. Better rate and product data for HO2 uptake by aerosol are needed to understand this role of aerosols in limiting the oxidizing power of the Arctic atmosphere.

Details

Title
Chemistry of hydrogen oxide radicals (HOx) in the Arctic troposphere in spring
Author
Mao, J.; Jacob, D. J.; Evans, M. J.; Olson, J. R.; Ren, X.; Brune, W. H.; Clair, J. M. St.; 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.; Sager, P. Le; Carouge, C.
First page
5823
Publication year
2010
Publication date
2010
Publisher
Copernicus GmbH
ISSN
16807316
e-ISSN
16807324
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
734797342
Copyright
Atmospheric Chemistry and Physics 2010