Index Geophysics

Novel application of satellite and in-situ measurements to map surface-level NO2 in the Great Lakes region

Ozone Monitoring Instrument (OMI) tropospheric NO₂ vertical column density data were used in conjunction with in-situ NO₂ concentrations collected by permanently installed monitoring stations to infer 24 h surface-level NO₂ concentrations at 0.1&deg; (~11 km) resolution. The region examined included rural and suburban areas, and the highly industrialised area of Windsor, Ontario, which is situated directly across the US-Canada border from Detroit, MI. Photolytic NO₂ monitors were collocated with standard NO₂ monitors to provide qualitative data regarding NO_z interference during the campaign. The accuracy of the OMI-inferred concentrations was tested using two-week integrative NO₂ measurements collected with passive monitors at 18 locations, approximating a 15 km grid across the region, for 7 consecutive two-week periods. When compared with these passive results, satellite-inferred concentrations showed an 18% positive bias. The correlation of the passive monitor and OMI-inferred concentrations (<i>R</i>=0.69, <i>n</i>=115) was stronger than that for the passive monitor concentrations and OMI column densities (<i>R</i>=0.52), indicating that using a sparse network of monitoring sites to estimate concentrations improves the direct utility of the OMI observations. OMI-inferred concentrations were then calculated for four years to show an overall declining trend in surface NO₂ concentrations in the region. Additionally, by separating OMI-inferred surface concentrations by wind direction, clear patterns in emissions and affected down-wind regions, in particular around the US-Canada border, were revealed.

Lee, C. J.

Brook, J. R.

Evans, G. J.

Martin, R. V.

Mihele, C.

2018-01-15

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application/pdf

10.5194/acp-11-11761-2011

https://acp.copernicus.org/articles/11/11761/2011/

eISSN: 1680-7324

eng