title: Modelling segregation effects of heterogeneous emissions on ozone levels in idealised urban street canyons: using photochemical box models.
abstract: Air quality models include representations of pollutant emissions, which necessarily entail spatial averaging to reflect the model grid size; such averaging may result in significant uncertainties and/or systematic biases in the model output. This study investigates such uncertainties, considering ozone concentrations in idealised street canyons within the urban canopy. A photochemical model with grid-averaged emissions of street canyons is compared with a multiple-box model considering each canyon independently. The results reveal that the averaged, 'one-box' model may significantly underestimate true (independent canyon mean) ozone concentrations for typical urban areas, and that the performance of the averaged model is improved for more 'green' and/or less trafficked areas. Our findings also suggest that the trends of 2005-2020 in emissions, in isolation, reduce the error inherent in the averaged-emissions treatment. These new findings may be used to evaluate uncertainties in modelled urban ozone concentrations when grid-averaged emissions are adopted.
authors.affiliation: School of Geography, Earth & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhong
authors.affiliation: School of Geography, Earth & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Electronic address: x.cai@bham.ac.uk.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Cai
authors.affiliation: School of Geography, Earth & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: William James
authors.initials: WJ
authors.lastname: Bloss
mesh_terms: D000392:Air Movements; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D002947:Cities; D008956:Models, Chemical; D010126:Ozone / Q000032:analysis* / Q000737:chemistry; D055668:Photochemical Processes; D014186:Transportation; D035501:Uncertainty
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Emission heterogeneity; Photochemical box model; Segregation effect; Urban ozone concentrations; Urban street canyon