Keywords: urban meteorology, blending height, dispersion modelling, surface exchange, roughness sublayer, friction velocity, air pollution, air quality, urban pollution, pollution emissions
Sensitivity of urban dispersion calculations to urban meteorology (COST 715)
Generally, the worst air pollution occurs in cities. This paper describes the COST 715 programme, which is a European activity supporting scientific exchange and networks on 'meteorology applied to urban air pollution problems'. For urban pollution assessments one needs the input of pollution near the ground, 'averaged' over an area containing a mixture of houses, gardens, streets, etc. The properties of the urban surface vary enormously over very short distances making this difficult. COST 715 has considered most of the available methods. As no single solution to the averaging problem has emerged, computer models with finer grid resolutions are seen as the best way of approaching this complex issue, as well as improving the forecasting of air pollution episodes. The sensitivity and accuracy of air quality predictions to assumptions regarding urban meteorological parameterisations in computer models appear to be hidden by other uncertainties associated with dispersion and emissions within the overall calculation.