Various studies have reported that the photochemical nucleation of new ultrafine particles (UFPs) in urban environments within high insolation regions occurs simultaneously with high ground ozone (O 3 ) levels. In this work, we evaluate the atmospheric dynamics leading to summer O 3 episodes in the Madrid air basin (central Iberia) by means of measuring a 3-D distribution of concentrations for both pollutants. To this end, we obtained vertical profiles (up to 1200 m above ground level) using tethered balloons and miniaturised instrumentation at a suburban site located to the SW of the Madrid Metropolitan Area (MMA), the Majada-honda site (MJDH), in July 2016. Simultaneously, measurements of an extensive number of air quality and meteorological parameters were carried out at three supersites across the MMA. Furthermore, data from O 3 soundings and daily radio soundings were also used to interpret atmospheric dynamics.The results demonstrate the concatenation of venting and accumulation episodes, with relative lows (venting) and peaks (accumulation) in O 3 surface levels. Regardless of the episode type, the fumigation of high-altitude O 3 (arising from a variety of origins) contributes the major proportion of surface O 3 concentrations. Accumulation episodes Published by Copernicus Publications on behalf of the European Geosciences Union.