Air pollution causes adverse effects on human health as well as ecosystems and crop yield and also has an impact on climate change trough short-lived climate forcers. To design mitigation strategies for air pollution, 3D Chemistry Transport Models (CTMs) have been developed to support the decision process. Increases in model resolution may provide more accurate and detailed information, but will cubically increase computational costs and pose additional challenges concerning high resolution input data. The motivation for the present study was therefore to explore the impact of using finer horizontal grid resolution for policy support applications of the European Monitoring and Evaluation Programme (EMEP) model within the Long Range Transboundary Air Pollution (LRTAP) convention. The goal was to determine the “optimum resolution” at which additional computational efforts do not provide increased model performance using presently available input data. Five regional CTMs performed four runs for 2009 over Europe at different horizontal resolutions. The models’ responses to an increase in resolution are broadly consistent for all models. The largest response was found for NO2 followed by PM10 and O3. Model resolution does not impact model performance for rural background conditions. However, increasing model resolution improves the model performance at stations in and near large conglomerations. The statistical evaluation showed that the increased resolution better reproduces the spatial gradients in pollution regimes, but does not help to improve significantly the model performance for reproducing observed temporal variability. This study clearly shows that increasing model resolution is advantageous, and that leaving a resolution of 50 km in favour of a resolution between 10 and 20 km is practical and worthwhile. As about 70% of the model response to grid resolution is determined by the difference in the spatial emission distribution, improved emission allocation procedures at high spatial and temporal resolution are a crucial factor for further model resolution improvements.

The EMEP MSC-W team received funding through EMEP under UN-ECE, as well as through the EU FP7 ECLAIRE project (Project No. 282910). INERIS was funded by the French Ministry in charge of Ecology the European project EC4MACS (EU LIFE, www.ec4macs.eu). The LOTOS-EUROS modelling team was funded by the Dutch Ministry for Infrastructure and Environment. The RCGC modelling team was funded by Umweltbundesamt Germany, project number 21981. The CMAQ modelling team received funding from the Severo Ochoa Program awarded by the Spanish Government (grant number SEV-2011-00067) and the postdoctoral grant in the Beatriu de Pinós programme (file number 2011 BP-A 00427).

Peer Reviewed