On the origin of the elevated ozone concentration in Spain

The objective of this work is to study the influence of three mechanisms in the high surface concentration of the Spanish EMEP stations. These mechani sms are: Photochemical production from organic compounds and nitrogen oxide s, exchange of air between the Planetary Boundary Layer and the free tropos phere and the advection of ozone. To do this we have designed a new method that use multivariate analysis and the average ozone concentrations, NOx co ncentrations, lenght of the air mass trajectories reaching the stations and emissions of NOx. Results suggest that high surface ozone concentrations a re controled by photochemical production if the source is close to the stat ion. If the distance from the source to the station rises, the influence of the NOx emissions become more important. (C) 1999 ElsevierScience Ltd. All rights reserved.