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Data Analysis

In addition to analysis of data obtained in our group, we have support from Environment Canada to analyze observations from many federal and provincial monitoring networks (e.g. NAPS, CAPMON)

Ozone in GTA 

An examination of the last decade of observations of ozone and its precursors in the Greater Toronto Area has demonstrated why emission controls that have been so successful for primary pollutants have resulted in only minor reductions in photochemical ozone. This figure displays contours of predicted ozone production rates as a function of NO2 concentration and VOC reactivity, while the shaded arrow shows the chemical space over which the atmosphere has changed in the last eight years, resulting in minimal decreases in ozone.

Acid Deposition in Canada

Our analysis of the chemical composition of gases, particulate matter and precipitation from CAPMON sites across Canada between 1990 and 2007 found that decreases in sulphate yielded increases in the pH of precipitation, but also altered the partitioning between HNO3 and particulate nitrate. The lack of routine measurements of gas phase ammonia complicates the interpretation of trends and underlines the need for the type of accurate measurements we are pursuing.

Ground-based evaluation of OMI NO2

Applications of remotely sensed chemical composition data include evaluation of air quality models, assimilation into air quality forecast models, identification of previously unrecognized pollution hot spots or emission sources, and assessments of chronic pollutant exposure in epidemiological studies. There is interest in ascertaining to what degree observations of tropospheric columns of pollutants (e.g. NO2) observed from space can replicate/replace data from sparse networks of traditional in situ monitors, particularly in urban areas where there is a high degree of spatial variability. One caveat is the presence of clouds, which obscure the satellite instrument’s field of view. We are assessing this by using the fractional cloud cover observed by the Ozone Monitoring Instrument (OMI) to screen the ground-based measurements, and calculate whether there is a significant selection bias in NO2 and SO2.