Introduction and background
This report provides detailed background documentation of the air quality modelling and mapping activities carried out at NILU for the mapping of PM10 and NO2 in the Nord-Jæren region. This documentation supports the ‘summary report’ (in Norwegian) provided to Statens Vegvesen region west (NILU report TR 57/2013) entitled ‘Luftkvalitetskart av NO2 og PM10 for byområdet Stavanger, Sandnes, Randaberg og Sola (Nord-Jæren): oppsummeringsrapport’.
This report provides both background information for the summary report as well as providing internal documentation for the methodologies used. Good knowledge of air quality modelling is required in order to understand much of the description, though there are a large number of supporting figures that are self-explanatory.
Most modelling and mapping activities in the urban environment are carried out at NILU using AirQUIS (www.airquis.com), a comprehensive air quality management system that includes measurement and emission databases as well as modelling, analysis and presentation tools. However, AirQUIS is designed for specific types of applications and is limited in the ways it can both model and present data. As a result any application requiring alternative inputs or results must be carried out external to AirQUIS. This is the case for this particular application, the mapping of air quality in the Nord-Jæren region. Requirements concerning the mapping resolution and form as well as the use of state-of-the-science road dust emission models means that the emissions, model input data, model output, presentation and analysis are all carried out within the MATLAB programming environment for which a suite of codes have been developed.
Despite the differences in ‘packaging’ both AirQUIS and this current application use the same air quality model, the EPISODE model (Slørdal et al., 2003), which has been successfully applied on a large range of applications. Because of the non-standard nature of this application this documentation report has been written to describe the methodology applied and to present results in more detail than are given in the ‘Summary report’ of the results.
The model application and domain is the Nord-Jæren peninsula containing the municipalities of Stavanger, Sandnes, Randaberg and Sola. This same region is currently modelled using AirQUIS as part of the Better City Air (Bedre Byluft) forecasting system (Bedre byluft, 2013; Ødegaard et al., 2013). As such emissions inventories and other model input data already exist and are used as a starting point for the modelling and mapping. The model region is shown in Figure 1.
The maps to be created are required at 100 m resolution for the entire model domain and are to present annual mean concentrations of PM10 and NO2 as well as the percentile concentrations corresponding to the 19’th highest hourly mean NO2 concentrations and the 36’th highest PM10 daily mean concentrations. These maps are thus directly related to the European and national Air Quality Directives. For a description of these see the summary report.