Air Quality downscaling

The urban downscaling is achieved through a high resolution model simulation over the city, using local emission data. The success of the downscaling is completely depending on user’s contribution of high resolution emission data.

The Common Services Air Quality model is named MATCH, an Eulerian off-line chemistry-transport model developed at SMHI. The photochemical scheme contains around 70 chemical species and around 130 chemical reactions.

Pre-calculated air quality data on the European scale, with a spatial resolution of 25-50 km, do not represent the true air pollution for urban residents - a downscaling with much higher spatial resolution is needed (see the two figures on the right hand side comparing NO2 levels in Stockholm without and with this downscaling).

The much higher spatial resolution given by a downscaling simulation will only be meaningful if the emission input to the dispersion model has the same degree of accuracy. Common Services therefore require the users to contribute with annually averaged emission grids for some pollutants like NOX, SO2, PM, CO and VOC, at least separated in traffic and other sources. Also tables for temporal variation can be introduced (there are default variations for mobile sources).

Before being used for climate scenario modelling, it is important to validate the downscaling model (see figure here below).

Validation of Air Quality downscaling
Simulated monthly mean NO2 levels together with a time series comparison between simulated and monitored hourly NO2 data. Enlarge Image