The aim of this work is to simulate with high accuracy an episode of high NO2 pollution during December 2016 in the city of Madrid (Spain). For this purpose, a multiscale modelling system has been implemented that includes a mesoscale model (WRF/Chem) up to a horizontal resolution of 1 km and a computational fluid dynamics model (CFD; MICROSYS) with a resolution of 5 m. For the calculation of traffic emissions, a traffic simulation has been previously conducted with the SUMO microscopic model, calibrated from data measured with traffic counters. We show a substantial improvement in the results obtained with 5 m resolution with respect to those of 1 km, reproducing very closely the daily peaks of NO2 concentrations since a very detailed traffic emission source is being used and the CFD reproduces the interactions between the air flow and the buildings. The modelling system presented can be used as a tool to evaluate different emission reduction strategies at street level, as it would allow to have an orientation on their effectiveness without having to implement them.
Keywords: CFD model; Traffic emissions; Urban air pollution.
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