Preprints
https://doi.org/10.5194/acp-2021-583
https://doi.org/10.5194/acp-2021-583

  13 Aug 2021

13 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Exploiting satellite measurements to reduce uncertainties in UK bottom-up NOx emission estimates

Richard J. Pope1,2, Rebecca Kelly1, Eloise A. Marais3, Ailish M. Graham1, Chris Wilson1,2, Jeremy J. Harrison4,5, Savio J. A. Moniz6, Mohamed Ghalaieny6, Steve R. Arnold1, and Martyn P. Chipperfield1,2 Richard J. Pope et al.
  • 1School of Earth and Environment, University of Leeds, Leeds, UK
  • 2National Centre for Earth Observation, University of Leeds, Leeds, UK
  • 3Department of Geography, University College London, London, UK
  • 4Department of Physics and Astronomy, University of Leicester, Leicester, UK
  • 5National Centre for Earth Observation, University of Leicester, Leicester, UK
  • 6Department for Environment, Food and Rural Affairs, 2 Marsham Street, London, UK

Abstract. Nitrogen oxides (NOx, NO+NO2) are potent air pollutants which directly impact on human health and which aid the formation of other hazardous pollutants such as ozone (O3) and particulate matter. In this study, we use satellite tropospheric column nitrogen dioxide (TCNO2) data to evaluate the spatiotemporal variability and magnitude of the United Kingdom (UK) bottom-up National Atmospheric Emissions Inventory (NAEI) NOx emissions. Although emissions and TCNO2 represent different quantities, for UK city sources we find a spatial correlation of ~0.5 between the NAEI NOx emissions and TCNO2 from the high-spatial-resolution TROPOspheric Monitoring Instrument (TROPOMI), suggesting a good spatial distribution of emission sources in the inventory. Between 2005 and 2015, the NAEI total UK NOx emissions and long-term TCNO2 record from the Ozone Monitoring Instrument (OMI), averaged over England, show decreasing trends of 4.4 % and 2.2 %, respectively. Top-down NOx emissions were derived in this study by applying a simple mass balance approach to TROPOMI observed downwind NO2 plumes from city sources. Overall, these top-down estimates were consistent with the NAEI, but for larger cities such as London and Manchester the inventory is significantly (> 25 %) less than the top-down emissions. This NAEI NOx emission underestimate is supported by comparing simulations from the GEOS-Chem atmospheric chemistry model, driven by the NAEI emissions, with satellite and surface NO2 observations over the UK. This yields substantial model negative biases, providing further evidence to demonstrate that the NAEI may be underestimating NOx emissions in London and Manchester.

Richard J. Pope et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on acp-2021-583 - by M. Pommier', Matthieu Pommier, 17 Sep 2021
  • RC1: 'Comment on "Exploiting satellite measurements to reduce uncertainties in UK bottom-up NOx emission estimates"', Anonymous Referee #1, 24 Sep 2021
  • RC2: 'Comment on acp-2021-583', Anonymous Referee #2, 07 Oct 2021
  • EC1: 'Editor comment on acp-2021-583', Andreas Richter, 18 Oct 2021

Richard J. Pope et al.

Richard J. Pope et al.

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Short summary
Nitrogen oxides (NOx) are potent air pollutants which directly impact on human health. In this study, we use satellite nitrogen dioxide (NO2) data to evaluate the spatial distribution and temporal evolution of the UK official NOx emissions inventory, with reasonable agreement. We also derived satellite based NOx emissions for several UK cities. In the case of London and Manchester, the NAEI NOx emissions are potentially too low by > 25 %.
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