References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-10-5823-2010

Chemistry of hydrogen oxide radicals (HOx) in the Arctic troposphere in spring

Mao

¹ Jacob

D. J.

¹ ² Evans

M. J.

³ Olson

J. R.

⁴ Ren

⁵ Brune

W. H.

⁶ Clair

J. M. St.

⁷ Crounse

J. D.

⁷ Spencer

K. M.

⁷ Beaver

M. R.

⁷ Wennberg

P. O.

⁸ ⁹ Cubison

M. J.

¹⁰ Jimenez

J. L.

¹⁰ Fried

¹¹ Weibring

¹¹ Walega

J. G.

¹¹ Hall

S. R.

¹² Weinheimer

A. J.

¹² Cohen

R. C.

¹³ Chen

⁴ Crawford

J. H.

⁴ McNaughton

¹⁴ Clarke

A. D.

¹⁴ Jaeglé

¹⁵ Fisher

J. A.

² Yantosca

R. M.

¹ Le Sager

¹ ¹⁶ Carouge

School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA

Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA

School of Earth and the Environment, University of Leeds, Leeds, LS2 9JT, UK

Science Directorate, NASA Langley Research Center, Hampton, VA, USA

Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA

Department of Meteorology, Pennsylvania State University, University Park, PA, USA

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA

Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA

Department of Chemistry and Biochemistry and Cooperative Institute for Research in the Environmental Sciences (CIRES),University of Colorado at Boulder, Boulder, CO, USA

Earth Observing Laboratory, National Center for Atmospheric Research, Boulder, CO, USA

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA

Department of Chemistry and Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA, USA

University of Hawaii at Manoa, Honolulu, Hawaii, USA

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

now at: KNMI, Chemistry and Climate Division, De Bilt, The Netherlands

01 07 2010

10 13 5823 5838

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/10/5823/2010/acp-10-5823-2010.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/5823/2010/acp-10-5823-2010.pdf

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 H2O2 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 H2O2. 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.

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