Analysis of two heat wave driven ozone episodes in Barcelona and surrounding region: Meteorological and photochemical modeling

During the summer of 2019 unusual exceedances of ozone concentration affected NE Spain. A detailed study of two heat wave driven ozone episodes is presented based on the high resolution forecast air quality ARAMIS system, which integrates WRF and CMAQ models. The events occurred on June 28–29 and July 23 2019 and were characterized by synoptic anticyclonic conditions, surface temperatures over the 98th percentile (over the last 40 years), and high ozone values recorded inland due to precursors advection (NO x and VOCs) mainly from Barcelona Metropolitan Area (AMB), limited by an eastern and a western valley. The analysis of measured and ARAMIS modeled concentrations showed that advection on June 28 and July 23 made its way through the eastern Barcelona valley and on June 29 through the western one. Ozone concentration forecasts reflect a general tendency to overestimate peaks, underestimate in low concentration areas and to increase ozone concentrations earlier than observed. Additionally, a trajectory analysis confirmed the precursor advection from AMB and the recirculation between June 28 and June 29. Finally, NO 2 measured in Barcelona was found to have influence in urban and rural ozone concentrations (100 km from AMB).