High resolution mapping of nitrogen dioxide with TROPOMI: First results and validation over the Canadian oil sands.

Unlabelled: TROPOMI, on-board the Sentinel-5 Precursor satellite is a nadir-viewing spectrometer measuring reflected sunlight in the ultraviolet, visible, near-infrared, and shortwave infrared spectral range. From these spectra several important air quality and climate-related atmospheric constituents are retrieved at an unprecedented high spatial resolution, including nitrogen dioxide (NO). We present the first retrievals of TROPOMI NO over the Canadian Oil Sands, contrasting them with observations from the OMI satellite instrument, and demonstrate its ability to resolve individual plumes and highlight its potential for deriving emissions from individual mining facilities. Further, the first TROPOMI NO validation is presented, consisting of aircraft and surface in-situ NO observations, as well as ground-based remote-sensing measurements between March and May 2018. Our comparisons show that the TROPOMI NO vertical column densities are highly correlated with the aircraft and surface in-situ NO observations, and the ground-based remote-sensing measurements with a low bias (15-30 %) over the Canadian Oil Sands.

Plain Language Summary: Nitrogen dioxide (NO) is a pollutant that is linked to respiratory health issues and has negative environmental impacts such as soil and water acidification. Near the surface the most significant sources of NO are fossil fuel combustion and biomass burning. With a recently launched satellite instrument (TROPOspheric Monitoring Instrument; TROPOMI) NO can be measured with an unprecedented combination of accuracy, spatial coverage, and resolution. This work presents the first TROPOMI NO measurements near the Canadian Oil Sands and shows that these measurements have an outstanding ability to detect NO on a very high horizontal resolution that is unprecedented for satellite NO observations. Further, these satellite measurements are in excellent agreement with aircraft and ground-based measurements.