Global catalog of NOx point sources derived from the divergence of the NO2 flux

Abstract

<p>Satellite observations of NO<sub>2</sub> provide valuable information on the location and strength of NO<sub>x</sub> emissions, but spatial resolution is limited by horizontal transport and smearing of temporal averages due to changing wind fields. The divergence (spatial derivative) of the mean horizontal flux, however, is highly sensitive for point sources like power plant exhaust stacks.</p><p>In a previous study, point source emissions have been identified and quantified exemplarily for Riyadh, South Africa, and Germany with a detection limit of about 0.11 kg/s down to 0.03 kg/s for ideal conditions, based on TROPOMI NO<sub>2</sub> columns and ECMWF wind fields (Beirle et al., Science Advances, 2019).</p><p>Here we extend this study and derive a global catalog of NO<sub>x</sub> emissions from point sources. The specific challenges for e.g. high latitudes (longer NO<sub>x</sub> lifetime) or coastlines (potentially persistent diurnal wind patterns) are investigated.</p>