01 Oct 2021
01 Oct 2021
Status: this preprint is currently under review for the journal ACP.

Understanding the influence of combustion on atmospheric CO2 over Europe by using satellite observations of CO2 and reactive trace gases

Mehliyar Sadiq1, Paul I. Palmer1,2, Mark F. Lunt1, Liang Feng1,2, Ingrid Super3, Stijn N. C. Dellaert3, and Hugo A. C. Denier van der Gon3 Mehliyar Sadiq et al.
  • 1School of GeoSciences, University of Edinburgh, Edinburgh, UK
  • 2National Centre for Earth Observation, University of Edinburgh, Edinburgh, UK
  • 3Department of Climate, Air and Sustainability, TNO, P.O. Box 80015, 3508 TA Utrecht, the Netherlands

Abstract. We assess how nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO) and formaldehyde (HCHO) can be used as proxies to determine the combustion contribution to atmospheric carbon dioxide (CO2) using satellite observations. We focus our analysis on 2018 when there is a full complement of column data from the TROPOspheric Monitoring Instrument (NO2, CO, and HCHO) and the Orbiting Carbon Observatory-2 (CO2). We use the nested GEOS-Chem atmospheric chemistry model to relate high-resolution emission inventories over Europe to these atmospheric data, taking into account scene-dependent averaging kernels. We find that that NO2 and CO are the better candidates to identify incomplete combustion and fingerprints of different combustion sectors, but both have their own challenges associated with properly describing their atmospheric chemistry. The secondary source of HCHO from oxidation of biogenic volatile organic compounds, particularly over southern European countries, compromises its use as a proxy for combustion emissions. We find a weak positive correlation between the CO : CO2 inventory ratio and observed column enhancements of ΔCO : ΔCO2 (R < 0.2), suggesting some consistency and linearity in CO chemistry and transport. However, we find a stronger negative correlation between the NOx : CO2 inventory ratio and observed column enhancements of ΔNO2 :ΔCO2 (R < 0.50), driven by non-linear photochemistry. Both of these observed ratios are described well by the GEOS-Chem atmospheric chemistry transport model, providing confidence of the quality of the emission inventory and that the model is a useful tool for interpreting these tracer-tracer ratios. Our results also provide some confidence in our ability to develop a robust method to infer combustion CO2 emission estimates using satellite observations of reactive trace gases that have up until now mostly been used to study surface air quality.

Mehliyar Sadiq et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Not convincing', Maarten Krol, 03 Oct 2021
    • RC1: 'CC1 again as RC', Maarten Krol, 07 Oct 2021
      • AC1: 'Reply on RC1', Mehliyar Sadiq, 05 Dec 2021
  • RC2: 'Comment on acp-2021-816', Josh Laughner, 13 Dec 2021

Mehliyar Sadiq et al.

Mehliyar Sadiq et al.


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Short summary
We make use of high-resolution emission inventory of CO2 and co-emitted tracers, satellite measurements, together with nested atmospheric transport model simulation, to investigate how reactive trace gases such as nitrogen dioxide and carbon monoxide can be used as proxies to determine the combustion contribution to atmospheric CO2 over Europe. We find stronger correlation in ratios of nitrogen dioxide and carbon dioxide between emission and satellite observed and modelled column concentration.