Ozone episodes in Catalonia during the summer of 2019. A meteorological and photochemical modeling analysis

Abstract

During the summer of 2019 unusual exceedances of ozone concentration affected Catalan territory. In the present work, a deep study of two ozone episodes is performed, focusing on the flow circulation and potential sources. Episode A occurred on June 28 and June 29 and Episode B on July 23. Both episodes are characterized by synoptic anticyclonic conditions, surface temperatures over the 95th percentile and high ozone values recorded inland due to precursors advection (NOx and VOCs) mainly from Barcelona Metropolitan Area (AMB). The analysis of measured time series and the comparison with ARAMIS modeled concentrations showed that advection on June 28 and July 23 made its way through the eastern Barcelona valley and through the western one on June 29. Modeled-observation comparison maps reflect the general tendency of the model to overestimate modeled peak areas, to slightly underestimate in the rest of the territory and to rise ozone values few hours before they are measured. Moreover, a trajectory analysis confirmed recirculation between June 28 and June 29 and concentration weighted trajectory maps determined the pathways linking the receptors with the AMB as the main potential sources for the cities of Vic and Manresa. Finally, NO2 measured in Barcelona was found to have in uence in urban and rural ozone concentrations.