This website includes air-quality forecasts for nitrogen dioxide (NO2) and particles of under 10 microns (PM10). The system used is based on a pollution-dispersion model known as ADMS-Urban, the same one used for forecasts in London and Paris, among other cities. In Barcelona's case, the software is managed by Barcelona Regional, the Urban Development Agency.
To prepare forecasts, the system uses the whole emissions inventory for Barcelona and its surrounding area (traffic, industrial activity, commercial and domestic sectors, port, airport, etc.) as well as the exogenous background weather and pollution forecasts. This model has a 71% accuracy margin for the air-quality index.
There are other models, such as Spain's operational air-quality forecast system (CALIOPE) used by the Department of Earth Sciences at the Barcelona Supercomputing Centre (BSC-CNS), which provides the air-quality forecast for Europe and Spain, www.bsc.es/caliope/es