Models-3/CMAQ Simulations to Estimate Transboundary Influences on Ozone and Particulate Matter Concentrations Over Ontario in Spring – Summer 1998

This study describes the application of atmospheric modelling to assess transboundary transport from the USA and the influence of natural emissions sources for the 12 most populated sub regions across Ontario, Canada. The impact of Ontario emissions was determined by the difference between model runs including all emissions and model runs with Ontario’s anthropogenic NOx, SO2, VOC and primary particulate matter emissions shut off. The modelling has been done for the entire May through September 1998 period. Since there were many days with high ozone and/or high PM2.5 that summer, the model runs provide estimates of the variations in Ontario’s impact from episode to episode and from the spring to the summer.