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This work aims to create background and roadside maps of pollutant concentrations for Scotland and compare them with similar maps for the UK. The maps provide complete coverage and can identify local and national "hotspots" where no monitoring is present. These maps can also be used to assess the impact of policy scenarios and project future pollutant concentrations. The Scottish mapping exercise examines the performance of the model for specific regions and highlights areas for improvement. The model was developed using Scottish monitoring and meteorological data, as well as emissions data. Verification of the model's performance shows promising results, but more monitoring sites are needed to improve accuracy. Overall, modeling and mapping can complement monitoring campaigns and provide valuable information for air quality assessments.
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Introduction • The aim of this work was to create background and roadside maps of pollutant concentrations for Scotland and to compare these with similar maps created for the whole of the UK. • Work undertaken within Netcen’s Pollution Climate Mapping Team by Andrew Kent, supervised by John Stedman. • Technical queries can be directed to: andrew.kent@aeat.co.uk • The technical aspects of this work will be available in a report soon.
Why modelling and mapping? • A good question – given the extensive national monitoring campaigns undertaken by Defra and the DAs and by LAs • Maps provide complete coverage over the modelled area, so filling in the gaps where no monitoring is present. • Can help identify local and national scale ‘hotspots’ where there is no monitoring – i.e. selection of monitoring site location. • At an advanced level, the maps can be used to illustrate the impact of policy scenarios – e.g. the impact of changing emissions legislation • Maps for future years can be made based on projected emissions – e.g. to show whether an area is likely to meet future legislative objectives
Examples… Background map Roadside map
The national maps – what are they used for? • These cover the whole of the UK. • The map outputs are provided to the Commission each year, together with the UK monitoring data for the purposes of the Daughter Directives. • Defra and the DAs use them for policy guidance: • Policy scenario impacts • Identify future compliance with AQS Objectives and Daughter Directive Limit Values. • Local Authorities – use background concentrations published on the national Air Quality Archive as an important component of the Review and Assessment process – to determine air quality on a local level and decide on AQMA declaration.
The Scottish mapping exercise • Follows on from a similar comparison performed in Wales between national maps and Welsh monitoring data. • Useful to examine the performance of the model for specific regions: • Promotes confidence in use of mapped background concentrations for Review and Assessment. • Highlights areas of model improvement for future. • Scotland’s different meteorological conditions, northerly position and more rural characteristics may be better represented in a Scotland-specific model
The Scottish model • Developed from the national model • Changes included: • Calibration relationships defined using only Scottish monitoring data • Dispersion based on Scottish meteorological data (Edinburgh Airport, 2004)
About the data… • A model is only as good as what you feed it! These models are dependent on as much good quality monitoring data as possible. • Monitoring data is used to calibrate the model and to verify the results. • Fully ratified monitoring data from the national networks for 2004 was used – 11 AURN monitoring sites available (9 background and 3 roadside) in 2004. • NAEI 2003 emissions data were also used in the models. • Meteorological data – national model uses data from Waddington; the Scotland model uses met data from Edinburgh. • A data capture threshold was set for the monitoring data so that sites with untrustworthy amounts of data were removed.
Testing the model performance - verification • Scatter plots of modelled concentrations vs. measured concentrations • Shows position of modelled results about the 1:1 line to illustrate the variation and any over or under prediction • Tabulated results including averages of the modelled and monitored data, correlation coefficients • Data Quality Objectives – set a defined target range for modelled data in the 1st and 2nd Daughter Directives • Additional lines included for illustrative purposes where no formal DQOs for these metrics • The data used to calibrate was the same data used to verify the results
CO annual mean verification 2004, mg m-3 CO annual mean map 2004, mg m-3 CO annual mean results
NO2 annual mean verification 2004, µg m-3 NO2 annual mean map 2004, µg m-3 NO2 annual mean results
PM10 (TEOM) annual mean model 2004, µg m-3 PM10 (TEOM) annual mean map 2004, µg m-3 PM10 (TEOM) annual mean results
SO2 p99.9 of 15-min mean verification 2004, µg m-3 SO2 99.9%ile of 15-min mean map 2004, µg m-3 SO2 15-minute results
Conclusions Modelling and mapping can provide a useful source of information to supplement monitoring campaigns. The national models can be tailored to Scotland, producing more accurate results for most pollutants/metrics provided that adequate monitoring data are available to support the model. • The improvement resulting from Scottish calibration may be offset by the additional uncertainties resulting from such a small number of sites used for calibration. • For the year 2004, there are not really sufficient monitoring data available in Scotland – a meaningful repeat of the exercise would require a greater number of monitoring sites.
