Weekday and Seasonal Variations in NO2 in Southern Ontario, Canada using Data from the Ozone Monitoring Instrument (OMI)

Data from the Ozone Monitoring Instrument (OMI) are used to investigate the weekday and seasonal variations in nitrogen dioxide (NO₂) densities observed over southern Ontario, Canada. Total column and tropospheric density data gridded at 1deg times 1deg follow the weekday pattern observed by fixed monitoring stations on the ground, with decreased concentration on the weekends and highest values during mid-week. While seasonal patterns from tropospheric data are similar to ground observations, the total column vertical density pattern shows a summer NO₂ peak. Additional higher resolution tropospheric data, gridded at 0.25deg times 0.25deg for a smaller area encompassing the city of Hamilton, Ontario, show weekly and seasonal patterns which conform closely to those observed on the ground. While univariate linear regression indicate that OMI tropospheric NO₂ explain only 20% of ground observations (R² = 0.20), multivariate analyses with variables representing local meteorology, seasons and other pollutants, yield an R² value of 0.81.