EGU25-14161, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-14161
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Surface NO2 Derived from Pandora Column Measurements in Toronto and Detroit-Windsor
Darby Bates1, Ramina Alwarda1, Kimberly Strong1, Xiaoyi Zhao2, Vitali Fioletov2, Sum Chi Lee2, and Yushan Su3
Darby Bates et al.
  • 1Department of Physics, University of Toronto, Toronto, Canada
  • 2Air Quality Research Division, Environment and Climate Change Canada, Toronto, Canada
  • 3Ontario Ministry of the Environment, Conservation, and Parks, Toronto, Canada

Atmospheric trace gases near the Earth’s surface can have important human and environmental health impacts. In particular, the trace gas nitrogen dioxide (NO2), which is commonly emitted by traffic, biomass burning, and industrial sources, can be a major threat to human respiratory health, leading to increased rates of asthma, lung cancer, and overall mortality. In the Greater Toronto Area (GTA) and in the Detroit-Windsor Area (DWA), NO2 and other trace gases are being measured by ground-based Pandora UV-visible spectrometers that are part of the Pandonia Global Network. We present NO2 surface volume mixing ratios derived from Pandora direct sun total column measurements to monitor air quality in these two urban areas. The conversion method uses three inputs in addition to the Pandora total columns: (1) the stratospheric NO2 column from the Ozone Monitoring Instrument (OMI), (2) the free troposphere NO2 column from the GEOS-Chem chemical transport model, and (3) the ratio of NO2 surface volume mixing ratio to planetary boundary layer column from Environment and Climate Change Canada’s regional air quality forecast model, Global Environmental Multi-scale-Modelling Air quality and Chemistry (GEM-MACH). The derived estimates of surface NO2 are compared with in situ measurements, and their level of agreement is assessed for dependence on meteorological conditions, including wind speed and direction, temperature, and boundary layer height. The mean bias between the derived estimates and in situ measurements ranges from -1.0 ppbv to -2.6 ppbv. This bias has been found to vary with boundary layer height, so a method to account for this dependence has been developed to improve the results. This presentation will provide an overview of this column-to-surface conversion method, a summary of results for each site in the GTA and DWA, and an outline of plans toward using this approach to improve and validate satellite estimates of surface NO2.

How to cite: Bates, D., Alwarda, R., Strong, K., Zhao, X., Fioletov, V., Lee, S. C., and Su, Y.: Surface NO2 Derived from Pandora Column Measurements in Toronto and Detroit-Windsor, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14161, https://doi.org/10.5194/egusphere-egu25-14161, 2025.