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High levels of the hydroxyl radical in the winter urban troposphere
Author(s) -
Heard D. E.,
Carpenter L. J.,
Creasey D. J.,
Hopkins J. R.,
Lee J. D.,
Lewis A. C.,
Pilling M. J.,
Seakins P. W.,
Carslaw N.,
Emmerson K. M.
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl020544
Subject(s) - noon , ozone , troposphere , photodissociation , northern hemisphere , atmospheric sciences , environmental science , hydroxyl radical , latitude , high latitude , photochemistry , environmental chemistry , climatology , chemistry , radical , geology , organic chemistry , geodesy
Measurements of the OH radical during winter show that noon‐time concentrations at an urban site in Birmingham are only a factor of 2 less than during summer at the same site, despite a factor of 15 reduction in OH production from the photolysis of ozone. Noon‐time concentrations of HO 2 were similar for summer and winter. These high winter concentrations are quantitatively reproduced by a detailed box‐model, showing that the winter radical pool (OH, HO 2 , RO 2 ) is sustained by reactions of unsaturated hydrocarbons with ozone and by the photolysis of carbonyls. The high OH concentrations show there is significant chemical processing of volatile organic compounds (VOCs) in winter at mid‐to‐high latitudes in the northern hemisphere where emissions are high.