Analysis of summer O3 in the Madrid air basin with the LOTOS-EUROS chemical transport model
Tropospheric O3 remains a major air-quality issue in the Mediterranean region. The combination of large anthropogenic emissions of precursors, transboundary contributions, a warm and dry aestival climate, and topographical features results in severe cases of photochemical pollution. Chemical transport models (CTMs) are essential tools for studying O3 dynamics and for assessing mitigation measures, but they need to be evaluated specifically for each air basin. In this study, we present an optimisation of the LOTOS-EUROS CTM for the Madrid air basin. Five configurations using different meteorological datasets (from the European Centre for Medium-Range Weather Forecast, ECMWF; and the Weather Research and Forecasting Model, WRF), horizontal resolution and number of vertical levels were compared for July 2016. LOTOS-EUROS responded satisfactorily in the five configurations reproducing observations of surface O3 with notable correlation and reduced bias and errors. However, the best-fit simulations for surface O3 were obtained by increasing spatial resolution and using a large number of vertical levels to reproduce vertical transport phenomena and the formation of reservoir layers. Using the optimal configuration obtained in the evaluation, three characteristic events have been described: recirculation (REC) episodes and northern and southern advection (NAD and SAD, respectively) events. REC events were found to produce the highest O3 due to the reduced ventilation associated with low wind speeds and the contribution of reservoir layers formed by vertical transport of O3 formed near the surface in the previous days of the event. NAD events, usually associated with higher wind speeds, present the lowest ground-level O3 concentrations in the region. During SAD episodes, external contributions along with low wind speeds allow O3 to increase considerably but not as much as in REC events because steady southerly winds disperse local emissions and hinder the formation of reservoir layers. ; Funding text #1 1Centro Universitario de la Defensa (CUD) de Zaragoza, Academia General Militar, Ctra. de Huesca s/n, 50090 Zaragoza, Spain 2TNO, P.O. Box 80015, 3584 TA, Utrecht, the Netherlands 3Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain 4Department of Chemical and Environmental Engineering, Technical University of Madrid (UPM), c/José Gutiérrez Abascal 2, 28006 Madrid, Spain 5Escuela Técnica Superior de Ingeniería de Bilbao, Departamento de Ingeniería Química y del Medio Ambiente, Universidad del País Vasco (UPV/EHU), Urkixo Zumarkalea, s/n, 48013 Bilbao, Spain Funding text #2 Acknowledgements. This work was funded by the Ministry of Economy, Industry and Competitiveness and FEDER funds through the project HOUSE (CGL2016-78594-R); the Ministry of Agriculture, Fishing, Food and Environment; the Madrid City Council; the Madrid Regional Government; and by the Department of Research, Innovation and University of the Aragón Regional Government and the European Social Fund (project E23_17D). The study was also partially supported by the scientific programme TECNAIRE-CM funded by the Directorate General for Universities and Research of the Greater Madrid Region (S2013/MAE-2972). The authors gratefully acknowledge air-quality data provision by the following entities: Ministry for the Ecological Transition (MITECO); Madrid City Council; AEMET; and the autonomous communities of Madrid, Castilla y León and Castilla–La Mancha. Miguel Escudero received a grant from the José Castillejo programme of the Ministry of Education and Science of Spain (ref. CAS17/00108) for a 6-month research visit at TNO.View less Funding text #3 Ministry of Economy, Industry and Competitiveness of Spain and FEDER (grant no. CGL2016-78594-R); the Department of Research, Innovation and University of the Aragón Regional Government and the European Social Fund (grant no. E23_17D); the Directorate General for Universities and Research of the Greater Madrid Region (grant no. S2013/MAE-2972); and the Ministry of Education and Science of Spain (grant no. CAS17/00108). ; Peer reviewed