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Volume 18, issue 9
Atmos. Chem. Phys., 18, 6511-6533, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Chem. Phys., 18, 6511-6533, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 May 2018

Research article | 08 May 2018

Phenomenology of summer ozone episodes over the Madrid Metropolitan Area, central Spain

Xavier Querol1, Andrés Alastuey1, Gotzon Gangoiti2, Noemí Perez1, Hong K. Lee3, Heeram R. Eun3, Yonghee Park3, Enrique Mantilla4, Miguel Escudero5, Gloria Titos1, Lucio Alonso2, Brice Temime-Roussel6, Nicolas Marchand6, Juan R. Moreta7, M. Arantxa Revuelta7, Pedro Salvador8, Begoña Artíñano8, Saúl García dos Santos9, Mónica Anguas10, Alberto Notario11, Alfonso Saiz-Lopez10, Roy M. Harrison12,13, Millán Millán4, and Kang-Ho Ahn3 Xavier Querol et al.
  • 1Institute of Environmental Assessment and Water Research (IDAEA-CSIC), C/ Jordi Girona 18-26, Barcelona, 08034, Spain
  • 2Escuela Técnica Superior Ingeniería de Bilbao, Departamento Ingeniería Química y del Medio Ambiente, Universidad del País Vasco UPV/EHU, Urkixo Zumarkalea, S/N, Bilbao, 48013, Spain
  • 3Department of Mechanical Engineering, Hanyang University, Ansan 425-791, Republic of Korea
  • 4Centro de Estudios Ambientales del Mediterráneo, CEAM, Unidad Asociada al CSIC, Parque Tecnológico C/ Charles R. Darwin, 14 Paterna, Valencia, 46980, Spain
  • 5Centro Universitario de la Defensa de Zaragoza, Academia General Militar, Ctra. de Huesca s/n, Zaragoza, 50090, Spain
  • 6Aix Marseille Univ, CNRS, LCE, Marseille, France
  • 7Agencia Estatal de Meteorología, AEMET, C/ Leonardo Prieto Castro, 8, Madrid, 28071, Spain
  • 8Department of Environment, CIEMAT, Joint Research Unit Atmospheric Pollution CIEMAT-CSIC, c/ Avenida Complutense 40, Madrid, 28040, Spain
  • 9Centro Nacional de Sanidad Ambiental – Instituto de Salud Carlos III (ISCIII), Ctr Majadahoda a Pozuelo km 2, Majadahonda (Madrid), 28222, Spain
  • 10Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, 28006, Spain
  • 11University of Castilla-La Mancha, Physical Chemistry Department, Faculty of Chemical Science and Technologies, Ciudad Real, Spain
  • 12National Centre for Atmospheric Science, University of Birmingham, B15 2TT, UK
  • 13Department of Environmental Sciences/Centre for Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract. 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 (O3) levels. In this work, we evaluate the atmospheric dynamics leading to summer O3 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 1200m above ground level) using tethered balloons and miniaturised instrumentation at a suburban site located to the SW of the Madrid Metropolitan Area (MMA), the Majadahonda 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 O3 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 O3 surface levels. Regardless of the episode type, the fumigation of high-altitude O3 (arising from a variety of origins) contributes the major proportion of surface O3 concentrations. Accumulation episodes are characterised by a relatively thinner planetary boundary layer (<1500m at midday, lower in altitude than the orographic features), light synoptic winds, and the development of mountain breezes along the slopes of the Guadarrama Mountain Range (located W and NW of the MMA, with a maximum elevation of >2400ma.s.l.). This orographic–meteorological setting causes the vertical recirculation of air masses and enrichment of O3 in the lower tropospheric layers. When the highly polluted urban plume from Madrid is affected by these dynamics, the highest Ox (O3+NO2) concentrations are recorded in the MMA.

Vertical O3 profiles during venting episodes, with strong synoptic winds and a deepening of the planetary boundary layer reaching >2000ma.s.l., were characterised by an upward gradient in O3 levels, whereas a reverse situation with O3 concentration maxima at lower levels was found during the accumulation episodes due to local and/or regional production. The two contributions to O3 surface levels (fumigation from high-altitude strata, a high O3 background, and/or regional production) require very different approaches for policy actions. In contrast to O3 vertical top-down transfer, UFPs are formed in the planetary boundary layer (PBL) and are transferred upwards progressively with the increase in PBL growth.

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Short summary
We show the main drivers of high O3 episodes in and around Madrid. High levels of ultrafine particles (UFPs) are evidenced, but we demonstrate that most O3 arises from the fumigation of high atmospheric layers, whereas UFPs are generated inside the PBL. O3 contributions from the fumigation of the vertical recirculation of regional air masses, hemispheric transport, and horizontally from direct urban plume transport are shown. Complexity arises from the need to quantify them to abate surface O3.
We show the main drivers of high O3 episodes in and around Madrid. High levels of ultrafine...