Keywords: air pollution modelling, field measurements, street pollution models, traffic-induced turbulence, traffic pollution
Dependence of street canyon concentrations on above-roof wind speed - implications for numerical modelling
For microscale numerical modelling of street canyon air pollution, the traffic-related component of the total ambient pollutant concentration is often assumed to be inversely dependent on the wind-speed at rooftops for idealised conditions of neutral stratification, no solar radiation, and no traffic-induced turbulence. Detailed data analyses of two comprehensive datasets from Gottinger Strase (Hannover) and Jagtvej (Copenhagen), including concentration and wind-field measurements in the street and above the rooftops, are presented to test these idealised assumptions, and to improve numerical modelling for a wider range of conditions. The experimental results show systematic deviation from the idealised inverse wind-speed law, when rooftop wind-speeds were less than 10 m/s. It was found that turbulence associated with traffic is a parameter, which is increasingly important for lower wind-speeds.