Atmos. Chem. Phys. Discuss., 10, 12827-12858, 2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
NO2 photolysis frequencies in street canyons
P. Koepke1, M. Garhammer1, M. Hess1, and E.-P. Roeth2
1L-M University Munich, Meteorological Institute, Theresienstr. 37, 80333 Muenchen, Germany
2Research Centre Juelich GmbH, ICG1-Stratosphaere, Leo Brandt Strasse, 52425 Juelich, Germany

Abstract. Photolysis frequencies for NO2 are modeled for the conditions in urban streets, which are taken into account as canyons with variable height and width. The effect of a street canyon is presented with absolute values and as a ratio RJ of the photolysis frequency within the street against those with free horizon, which allows further use of the existing photolysis parameterizations. Values are presented for variable solar elevation and azimuth angles, varying atmospheric conditions and different street properties. The NO2 photolysis frequency in the street, averaged over atmospheric conditions and street orientation, is reduced to less than 20% for narrow streets, to about 40% for typical urban streets, and only to about 80% for garden streets, each with about ±5% uncertainty. A parameterization of RJ with the global solar irradiance is given for values that are averaged over the meteorological conditions and the street orientation.

Citation: Koepke, P., Garhammer, M., Hess, M., and Roeth, E.-P.: NO2 photolysis frequencies in street canyons, Atmos. Chem. Phys. Discuss., 10, 12827-12858, doi:10.5194/acpd-10-12827-2010, 2010.
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