Evaluation of a regional air-quality model (AURAMS) for two field campaign periods over south-eastern Canada and U.S. northeast: impact of meteorology on air quality

The Environment Canada regional air quality modeling system, AURAMS, has been used to provide real-time forecast for several recent field campaigns. Two of the campaigns were conducted over eastern North America: the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) during the summer of 2004, mainly focused on air quality over the east coast, New England area, and the outflow to the North Atlantic; and the Border Air-Quality Study - Meteorology (BAQSMet) which was conducted in the summer of 2007 over southern Ontario focused on the impact of lake-breeze meteorological conditions on air pollution in the region. Retrospective model runs over similar domains for the two campaign periods (6 weeks in 2004 and three months in 2007) have since been conducted and detailed evaluation of model performance against field study data and network observations is being carried out.

The two summers (2004 and 2007) are quite different, in the sense that the summer of 2004 was characterized as been cooler and wetter than normal over eastern North America while the summer of 2007 was closer to normal over the region. The ozone monitoring data from the AIRNOW network shows an average of 4 ppb difference between ICARTT period (lower) and the BAQSMet period (higher) both in terms of ozone1-hour daily maximum and daily mean. As for PM2.5 mass, although the average levels are comparable between the two periods, the speciated PM data from the IMPROVE network indicates a distinct difference in the composition of PM2.5 over the region, namely the sulfate fraction is significantly higher in the summer of 2004 than the summer of 2007.

This paper will focus on the comparison of model performance between the two periods, model's ability in capturing the impact of meteorology on air quality in the region as seen from the network monitoring data, aiming at shedding light to the roles of different processes affecting ozone and PM in the region.