Modelled air quality data

Introduction

Air pollution concentration maps are prepared annually for Scotland under the Scottish Air Quality Database (SAQD) project, using Scotland-specific versions of the UK Pollution Climate Mapping (PCM) modelling methods. The UK maps are published in the year following the model year. The Scotland-specific modelling requires elements from the UK modelling and as such, the Scottish maps are published the year following the UK publication (two years after the model year).

Background concentrations are mapped at a spatial resolution of 1 km² (1 km x 1 km grid). Roadside concentrations are mapped for urban major road links across Scotland. The maps provide annual mean concentrations of NO_X, NO₂, PM₁₀ and PM_2.5 (from 2020).

The background and roadside maps are available to download in the sections below. Please acknowledge the Scottish Government as the source for this data if using the maps for your work.

You can view interactive versions of the maps via the Maps of annual concentrations page.

Methodology

The PCM methodology has been developed over several decades and is subject to an annual improvement programme. Please bear in mind these year-to-year changes in methodology, when comparing model outputs between years. The most recent methodology is detailed in the report linked on the Maps of annual concentrations page. Please note that model outputs for 2019 were produced using meteorological data from RAF Leuchars. Model outputs from 2020 onwards, were produced using meteorological data from the Weather Research and Forecasting (WRF) model.

Queries

For any queries about these maps, please contact us at info@scottishairquality.co.uk

Background maps

The background maps are downloadable as .csv files for each modelled base year from 2019 to the current model year. Background concentrations of NO_X, NO₂, PM₁₀ and PM_2.5 (from 2020) are available using the links in the tables below. The coordinate system is OSGB (British National Grid). Each file states the pollutant, model year, metric and units on rows one to four. The data begin on row six and contain the following fields:

• “gridcode” – a unique code for each 1 km x 1 km grid cell
• “x” – the x coordinates (easting) for the centroid of each grid cell, in metres
• “y” – the y coordinates (northing) for the centroid of each grid cell, in metres
• The annual mean concentration for the selected pollutant, where the column name is comprised of the pollutant name and the model year e.g. “nox2022”. The units are µg m^-3 (see tables below for further information).

The gridcode field allows several maps to be joined in a single file using that code as the lookup column.

The data can be imported into GIS software. Alternatively, the data can be viewed via the interactive map on the Maps of annual concentrations page.

Other maps

These maps should not be mistaken for the Local Authority specific maps which are alternative maps based on the same model results as presented here but which provide source-sector splits and projections to future years by Local Authority to aid the Local Air Quality Management process.

These maps should also not be mistaken for the UK maps, which are similar to the maps presented here, but which provide data for the whole of the UK and are produced to satisfy the annual Air Quality Standards Regulations reporting requirements.  

Directory of maps

NO_x

NO₂

PM₁₀

PM_2.5

Roadside maps

The roadside maps are downloadable as GIS shapefiles for each modelled base year from 2019 to the current model year. Roadside concentrations of NO_X, NO₂, PM₁₀ and PM_2.5 (from 2020) are provided within one shapefile, per model year, via the links in the table below. The coordinate system is OSGB (British National Grid). Each file contains the following fields:

• "census_id" – a unique code identifying the road traffic count point (modelled road)
• "roadnumber" – the road number of the modelled road
• "length_m" – the length of the modelled road, in metres
• "rno2XXXX" – the annual mean roadside concentration of NO₂, where XXXX is the model year, in µg m^-3
• "rnoxXXXX" – the annual mean roadside concentration of NO_X, where XXXX is the model year, in µg m^-3 (NO_X as NO₂)
• "rpm10XXXX" – the annual mean roadside concentration of PM₁₀, where XXXX is the model year, in µg m^-3, gravimetric equivalent
• "rpm25XXXX" – the annual mean roadside concentration of PM_2.5, where XXXX is the model year, in µg m^-3, gravimetric equivalent (available from 2020)

The data can be imported into GIS software. Alternatively, the data can be viewed via the interactive map on the Maps of annual concentrations page.

Other maps

These maps should not be mistaken for the UK maps, which are similar to the maps presented here, but which provide data for the whole of the UK and are produced to satisfy the annual Air Quality Standards Regulations reporting requirements.

Directory of maps