Analysis of an intense O₃ pollution episode in the Atlantic Coast of the Iberian Peninsula using photochemical modelling: characterization of transport pathways and accumulation processes

Abstract

Abstract. A tropospheric O3 pollution episode over the Atlantic Coast of the Iberian Peninsula during August 2–6 in 2018 has been analyzed. The episode was characterized by a permanent wind shear throughout the entire period, making the observed ozone surface distribution especially difficult to explain. A new methodology is described analyzing upper-level atmospheric parameters, such as temperature, wind direction, wind speed, and O3 concentrations, added to the traditional use of surface parameters, using WRF-CAMx models and available surface and upper-air observations. Results indicate that the episode was characterized by a first phase of a sudden increase in O3 concentrations produced by fumigation and interregional transport processes within the Iberian Peninsula, followed by a continental O3 transport from Europe to the Atlantic Coast. An Atlantic front produced the dissipation of the episode, generating an “ozone front” heading the cold front passage across the region.