Ozone attributed to Madrid and Barcelona on-road transport emissions: Characterization of plume dynamics over the Iberian Peninsula.

Despite the ~30% emission decrease of the main tropospheric ozone (O3) precursors in Spain in the 2001-2012 period, the O3 concentration in summer still exceeds the target value for the protection of the human health of the Air Quality Directive (2008/50/EC). On-road transport is the main anthropogenic contributor to O3 precursor's emissions in Madrid and Barcelona metropolitan areas (65%/59% of NOx, 40%/33% of NMVOC, and 67%/85% of CO emissions) but this contribution to O3 formation is not well understood. The present work aims at increasing the understanding on the role of on-road transport emissions from main Spanish urban areas in O3 dynamics over Spain under typical circulation types. For that purpose, the Integrated Source Apportionment Method is used within the CALIOPE modelling system (WRF/CMAQ/HERMES/BSC-DREAM8b). The results indicate that the daily maximum O3 concentration attributed to the on-road transport emissions from Madrid (O3T-MAD) and Barcelona metropolitan areas (O3T-BCN) contribute up to 24% and 8% to total O3 concentration, respectively, within an area of influence of 200 km. The contribution of O3T-MAD and O3T-BCN is particularly significant (up to 80-100 μg m(-3) in an hour) to the O3 concentration peak during the central hours of the day in the high O3 concentration season (April-September). The maximum O3T-MAD concentration is calculated within the metropolitan area of Madrid but the plume, channelled by the Tajo and the Henares valleys, affects large areas of the Iberian Peninsula. The O3T-BCN plume is more driven by sea-land and mountain-valley breezes than by the synoptic advection and its maximum concentration is usually registered over the Mediterranean Sea. The O3 concentration transported long-range to the Iberian Peninsula is significant in the area of influence of Madrid and Barcelona, being maxima under cold (70-96%) and minima in warm circulation types (35-70%).