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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Oct 2018

Research article | 15 Oct 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).

Assessing London CO2, CH4 and CO emissions using aircraft measurements and dispersion modelling

Joseph Pitt1, Grant Allen1, Stéphane Bauguitte2, Martin Gallagher1, James Lee3, Will Drysdale3, Bethany Nelson3, Alistair Manning4, and Paul Palmer5 Joseph Pitt et al.
  • 1School of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
  • 2Facility for Airborne Atmospheric Measurements (FAAM), Cranfield University, Cranfield, MK43 0AL, UK
  • 3Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
  • 4Met Office, FitzRoy Road, Exeter, EX1 3PB, UK
  • 5School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UK

Abstract. We present a new modelling approach for assessing atmospheric emissions from a city, using an aircraft measurement sampling strategy similar to that employed by previous mass balance studies. Unlike conventional mass balance methods, our approach does not assume that city-scale emissions are confined to a well-defined urban area and that peri-urban emissions are negligible. We apply our new approach to a case study conducted in March 2016, investigating CO, CH4 and CO2 emissions from London using aircraft sampling of the downwind plume. For each species, we simulate the flux per unit area that would be observed at the aircraft sampling locations based on emissions from the UK national inventory, transported using a Lagrangian dispersion model. To reconcile this simulation with the measured flux per unit area, assuming the transport model is not biased, we require that inventory values of CO, CH4, and CO2 are scaled by 1.00, 0.70, and 1.57, respectively. However, our result for CO2 must be treated with strong caution as we do not account for the influence of the land and ocean biosphere in this work.

For comparison, we also calculate fluxes using a conventional mass balance approach and compare these to the emissions inventory aggregated over the Greater London area. Using this method we derive much higher inventory scale factors for all three gases, as a direct consequence of neglecting emissions outside the Greater London boundary. That substantially different conclusions are drawn using the conventional mass balance method demonstrates the danger of using this technique for cities whose emissions cannot be separated from significant surrounding sources.

Joseph Pitt et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Joseph Pitt et al.
Joseph Pitt et al.
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Publications Copernicus
Short summary
This paper presents a new method to assess inventory estimates of greenhouse gas and air pollutant emissions for large cities. A case study using data sampled by a research aircraft around London was used to test the method. We found that the UK national inventory agrees with our observations for CO, but needed lower emissions for CH4 to agree with the measured data. Repeated studies could help determine how these emissions vary on different timescales.
This paper presents a new method to assess inventory estimates of greenhouse gas and air...