High‐Resolution Mapping of Nitrogen Dioxide With TROPOMI: First Results and Validation Over the Canadian Oil Sands

TROPOspheric Monitoring Instrument (TROPOMI), on-board the Sentinel-5 Precursersatellite, is a nadir-viewing spectrometer measuring reflected sunlight in the ultraviolet, visible,near-infrared, and shortwave infrared. From these spectra several important air quality and climate-relatedatmospheric constituents are retrieved, including nitrogen dioxide (NO2) at unprecedented spatialresolution from a satellite platform. We present the first retrievals of TROPOMI NO2over the Canadian OilSands, contrasting them with observations from the Ozone Monitoring Instrument satellite instrument,and demonstrate TROPOMI's ability to resolve individual plumes and highlight its potential for derivingemissions from individual mining facilities. Further, the first TROPOMI NO2validation is presented,consisting of aircraft and surface in situ NO2observations, and ground-based remote-sensingmeasurements between March and May 2018. Our comparisons show that the TROPOMI NO2verticalcolumn densities are highly correlated with the aircraft and surface in situ NO2observations, and theground-based remote-sensing measurements with a low bias (15–30 %); this bias can be reduced byimproved air mass factors.

Plain Language Summary:
Nitrogen dioxide (NO2) is a pollutant that is linked to respiratoryhealth issues and has negative environmental impacts such as soil and water acidification. Near thesurface the most significant sources of NO2are fossil fuel combustion and biomass burning. With a recentlylaunched satellite instrument (TROPOspheric Monitoring Instrument [TROPOMI]), NO2can be measuredwith an unprecedented combination of accuracy, spatial coverage, and resolution. This work presents thefirst TROPOMI NO2measurements near the Canadian Oil Sands and shows that these measurements havean outstanding ability to detect NO2on a very high horizontal resolution that is unprecedented for satelliteNO2observations. Further, these satellite measurements are in excellent agreement with aircraft andground-based measurements.