Exploring the nature of air quality over southwestern Ontario: main findings from the Border Air Quality and Meteorology Study

Abstract

Abstract. This paper serves as an overview and discusses the main findings from the Border Air Quality and Meteorology Study (BAQS-Met) in southwestern Ontario in 2007. This region is dominated by the Great Lakes, shares borders with the United States and consistently experiences the highest ozone (O 3 ) and fine particulate matter concentrations in Canada. The purpose of BAQS-Met was to improve our understanding of how lake-driven meteorology impacts air quality in the region, and to improve models used for forecasting and policy scenarios. Results show that lake breeze occurrence frequencies and inland penetration distances were significantly greater than realized in the past. Due to their effect on local meteorology, the lakes were found to enhance secondary O 3 and aerosol formation such that local anthropogenic emissions have their impact closer to the populated source areas than would otherwise occur in the absence of the lakes. Substantial spatial heterogeneity in O 3 was observed with local peaks typically 30 ppb above the regional values. Sulfate and secondary organic aerosol (SOA) enhancements were also linked to local emissions being transported in the lake breeze circulations. This study included the first detailed evaluation of regional applications of a high-resolution (2.5 km grid) air quality model in the Great Lakes region. The model showed that maxima in secondary pollutants occur in areas of convergence, in localized updrafts and in distinct pockets over the lake surfaces. These effects are caused by lake circulations interacting with the synoptic flow, with each other or with circulations induced by urban heat islands. Biogenic and anthropogenic emissions were both shown to play a role in the formation of SOA in the region. Detailed particle measurements and multivariate receptor models reveal that while individual particles are internally mixed, they often exist within more complex external mixtures. This makes it difficult to predict aerosol optical properties and further highlights the challenges facing aerosol modelling. The BAQSMet study has led to a better understanding of the value of high-resolution (2.5 km) modelling for air quality and meteorological predictions and has led to several model improvements.

Sensitivity of Ozone Production to NOx and VOC Along the Lake Michigan Coastline

“…high pollution events due to lake breeze circulation (Foley et al, 2011). Coastal regions in the United States where this phenomenon has been observed include Lake Michigan (Dye et al, 1995), Lake Erie (Brook et al, 2013), the Gulf of Mexico (Mazzuca et al, 2016), and the Chesapeake Bay (Loughner et al, 2014;Stauffer & Thompson, 2012;Sullivan et al, 2019). There is still significant uncertainty regarding the conditions driving coastal O 3 production, which limits confidence in proposed emission control strategies for reducing O 3 exceedances in such regions.…”

Using computational fluid dynamics and field experiments to improve vehicle-based wind measurements for environmental monitoring

“…The calibration of vehicle-based measurements is important for integration with stationary measurements and with mobile measurements from differing vehicle platforms. Studies evaluating the trends in near-surface ocean winds demonstrated that systematic bias in measurement methods contributed to an increasing trend in global wind speed in reported climate data (Cardone et al, 1990;Ramage, 1987;Peterson and Hasse, 1987). The International Comprehensive Ocean Atmosphere Data Set (ICOADS) documents wind measurements from Voluntary Observing Ships (VOSs) and other marine platforms (Thomas et al, 2008).…”

“…The datasets date back prior to the 1940s and provide data for observed changes in climate patterns (Ramage, 1987). The datasets have been studied extensively to explain the increasing trend in global wind speed after the 1940s (Cardone et al, 1990), when archived data prior to the 1940s showed a decreasing trend (Thomas et al, 2008). Peterson and Hasse (1987) and Ramage (1987) attributed the shift from decreasing to increasing wind speed to the change in the method of reporting ship-based wind measurements.…”

“…Many scientific applications require local measurements of wind speed and direction in the lower atmosphere. Currently, vehicle-based wind measurements are used to study severe weather-related meteorology (Belušić et al, 2014;Straka et al, 1996;Taylor et al, 2011) and lake meteorology (Brook et al, 2013;Curry et al, 2017), and they are integrated into methane measurement studies to detect, quantify, and map emission plumes from oil and gas developments (Atherton et al, 2017;Rella et al, 2015;Zazzeri et al, 2015).…”

A Survey of Regional-Scale Blocking Patterns and Effects on Air Quality in Ontario, Canada

“…In Ontario, meteorology is affected primarily by the midlatitude westerly jet and the eastward progression of cyclones, anticyclones, and fronts across eastern North America, and significant modification by the three Great Lakes surrounding southern Ontario often affects local weather and air quality [34]. Local air pollutant concentrations are mainly determined by the combination of emissions, chemistry and local meteorology, but an estimated 55% of air pollution impacts result from transboundary flow of emissions from the United States [35].…”