Assessment of mesoscale and microscale simulations of a NO2 episode supported by traffic modelling at microscopic level

The aimof 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. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study aimed to simulate a high NO2 pollution episode in Madrid in December 2016 with high accuracy. Using a multiscale modelling system, including a mesoscale model with a resolution of 1 km and a CFD model with a resolution of 5 m, substantial improvement in results was achieved with the higher resolution. The modelling system can be used to evaluate emission reduction strategies at street level effectively.