A regional modelling study of the high ozone episode of June 2001 in southern Ontario

High ozone levels were observed in southern Ontario in the summer of 2001, particularly in June, when the observed maximum was 137 ppb at Long Point. Development of effective ozone abatement strategies to prevent such episodes requires acknowledge of the chemistry in the appropriate source regions. Comprehensive high-resolution Eulerian chemical transport models, when used with accurate emissions data and meteorology, can elucidate the atmospheric chemical and physical processes responsible for episodes like these. In this work, the MM5/SMOKE/CMAQ   regional air quality modelling system was used to investigate the chemistry involved in ozone formation during the episode in question and also more generally in the target domain. Some of the important simulations were further developed using Taylor diagrams to explore the ozone background and understand the sensitivity of ozone to NOXNOX and VOC concentrations. Results from an arbitrary reduction of road traffic are discussed, based on NOXNOX and VOC species in the traffic emission inventory. The ozone production rate was extracted from the model and mapped for June 2001 to assist in the identification of the source regions contributing to the ozone episode.