Keywords: air pollution modelling, chemical mechanisms, photochemistry, ozone, Spain
Photochemical modelling of summer ozone episodes in the Greater Madrid area
The mesoscale meteorological model TVM, coupled to a photochemical/transport module in which different chemical mechanisms (RACM, EMEP) are implemented, has been evaluated. Field measurements and numerical results are used to determine the impact of the mesoscale flows on the photochemical smog episodes observed in the Greater Madrid Area for two selected days, characterised by the presence of a thermal low-pressure system over the Iberian Peninsula. During the 14 July 1992, the synoptic flow from the southeast favoured the transport of the precursors to the Guadarrama mountain range, where high concentrations of ozone were registered, exceeding the population information threshold. On the 15 July 1995, the synoptic wind from the northwest interacted with the local thermally driven flows, pushing the pollutants far away from the metropolitan area with the result that high ozone concentrations were measured to the east-southeast of the city.