From the Pacific to the Atlantic: Mesoscale Air Quality Modelling in Coastal Areas of Canada

The authors have been involved in regional air quality modeling programs in coastal areas of both eastern and western Canada, which allows for interesting contrasts to be drawn. In western Canada, the studies have focused on the Lower Fraser Valley (LFV) of British Columbia, where the City of Vancouver is located. The airshed is confined by the presences of large mountains to the north and south and is subject to relatively little long-range transport of pollutants. In eastern Canada, studies have focused on southern Ontario, Quebec and, most recently, the Maritime provinces. Unlike the LFV, the Maritime provinces are subject to a significant amount of long-range transport of pollutants.

For the LFV, high-resolution MC2 meteorological model outputs were used to drive SMOKE and CMAQ, resulting in good overall model performance on both 12km and 4km resolution model grids. Modelling results during the ‘Pacific 2001’ summer smog episode indicate that regional / synoptic weather patterns and localized sea breeze and terrain effects influence the trans-boundary movement of pollutants in this region. In the east, MM5, SMOKE, and CMAQ were used to simulate a regional smog event during the summer of 2001 summer in the Atlantic Provinces at a 36-km grid resolution. Long-range transport of O3, PM2.5, and precursors from U.S. eastern seaboard and southern Ontario and Quebec was found to play a major role in elevated O3 and PM2.5 levels in the Atlantic region, although local influences are evident, particularly for PM2.5. There is also evidence of regional flows that return some of the polluted airmass back to the U.S. east coast.