Preliminary modelling results of an urban air quality model verifying the prediction of nitrogen dioxide, sulfur dioxide and ozone over the Sydney basin

Summary The air quality modelling system (HIRES-AIRCHEM) of The University of New South Wales is tested with regard to forecast distributions of sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and ozone (O₃) over the Sydney basin and surrounding area. This is achieved by assimilating the emissions inventory of the New South Wales State Environment Protection Authority. This inventory contains both road and non-road sources. The HIRES-AIRCHEM system was run over the greater Sydney metropolitan area for a four day period in February 1998. During this period O₃ readings, in particular, exceeded the EPAs threshold maximum of 80ppb. The model forecasts of the NO₂-, SO₂- and O₃-distributions verify well with the EPAs monitored readings. Diurnal concentrations are greatest in the late afternoon, as expected, when photochemical processes are most active. Furthermore, the forecast spatial distribution of NO₂ and SO₂ shows maximum values radiating out along major roads from the Sydney CBD and other population centres. This is consistent with NO₂ and SO₂ being major pollutants associated with vehicular traffic. These promising results have significant implications for possible future use of the system as a tool for routinely assessing air quality.