Evaluation of a Regional Air Quality Model Using Ground-based Observations in North-eastern Canada and United States

The 3-dimensional regional air quality model (MC2AQ) was used to simulate the high ozone episode recorded at numerous ground-based observations over North-eastern Canada and United States in July 1999. The model, driven by a non-hydrostatic mesoscale compressible community meteorological model (MC2), includes online oxidant chemistry of inorganic and organic species, as well as emissions and deposition. Two different standard emissions inventories for the year 1990 and year 1985 were used separately as the model input from anthropogenic and natural sources. The comparisons using various statistical methods between model predictions and the ground based observations show that the model can capture ozone (O3) diurnal variation, peak concentration, and geographical distribution very well. Over the entire MC2AQ domain, the values of 18.5% for normalized gross error (NGE) and -10.9% for normalized bias (NB) are found to be within acceptable ranges. About 80% of the monitoring sites have an index of agreement (between the predicted and the measured ozone) larger than 0.8. The predictions for other gaseous species, such as SO2, NO, NO2 and NOx, were also compared to the measurements and show some discrepancies, but they are consistent with the results from other models evaluated by others in the literature. In addition, the predictions of wind speed and direction showed good agreement with the use of the MC2 meteorology driver. Further model development and evaluation will focus on particulate matter.