D2.14 Value of reactive trace gases observed by TROPOMI to improve quantitative analysis of ffCO2

File : D2.14

Author : Paul Palmer et al. (UEDIN)

We assess how nitrogen dioxide (NO₂), carbon monoxide (CO) and formaldehyde (HCHO) can be used as proxies to determine the combustion emission of CO₂ using satellite observations and in situ measurements. We focus our analysis on 2018 when there is a full complement of data. We find that that NO₂ and CO are the better candidates to identify incomplete combustion, but both have their own challenges associated with properly describing their atmospheric chemistry. We find a weak positive relationship (R<0.4) between national-scale emission inventory estimates of CO:CO₂ and NO_x:CO₂, reflecting the importance of different sectors within a country that have different combustion efficiencies. We also find a weak positive correlation between the CO:CO₂ inventory ratio and satellite observed column enhancements DXCO:DXCO₂ (R<0.2), suggesting some consistency and linearity in CO chemistry and transport. However, we find a stronger negative correlation between the NO_x:CO₂ inventory ratio and satellite observed column enhancements DXNO₂:DXCO₂ (R<0.50), driven by non-linear photochemistry. Both of these observed ratios are described well by a regional atmospheric chemistry transport model, providing confidence that the model is a useful tool for interpreting these tracer-tracer ratios. Our preliminary joint CO₂:CO inversion results using in situ data demonstrate the potential usefulness of including error correlations between CO₂ and CO to estimate combustion CO₂ emissions. During July 2018 we find that including CO₂:CO error correlations results in error reductions of up to 15% for combustion CO₂ estimates, and also improvements in natural fluxes of CO₂ and emissions of CO across Europe. This work paves the way for developing the method for satellite data.

Figure 1 : Overview of the work being shown in this technical note