Results from Three Field Tracer Experiments on the Neighbourhood Scale in the City of Birmingham UK |
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Authors: | R E Britter S Di Sabatino F Caton K M Cooke P G Simmonds G Nickless |
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Institution: | (1) Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, U.K;(2) Laboratorie d'Energétique et de Mécanique Théorique et Appliquée CNRS UMR 7563, 160, 54404 Vandoeuvre Cedex, France;(3) SIRA Ltd, South Hill, Chislehurst, Kent, BR7 5EH, U.K;(4) School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, U.K |
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Abstract: | The physical processes governing flow and pollutantdispersion at the neighbourhood scale, a spatial scaleintermediate between the street scale and the city scale, is notwell understood. Furthermore, it is not clear whether a traditional approach using averaged characteristics such as theaerodynamic roughness length is sufficient to predict the concentration field at this scale. To investigate pollutant dispersion in a real urban area, three field experiments were designed within the UK-URGENT programme sponsored by NERC. Theexperiments were performed in the City of Birmingham using a finite duration release of inert, non-toxic and non-depositingtracers, vis. perfluoromethylcyclohexane (PMCH) and perfluoromethylcyclopentane (PMCP). Measurements were taken using air bag samplers placedin an arc at 3.5 km (first experiment) and 1 km (second andthird experiments) from the source; some trap samplers wereplaced outside the main arc in the outskirts of the city. Measurements were analysed in the laboratory using anovel gas-chromatography technique. Data so obtained werecompared with predictions from a simple steady-state modeland a time-dependent model. The concentration-time serieswere very asymmetrical with a sharp rise, a plateau followedby a relatively slow decrease and finally a long-livedplateau above (or possibly very slow decrease to) thebackground level. |
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Keywords: | atmospheric dispersion neighbourhood scale tracer experiments urban air quality |
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