the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Dec 2024
Decrease of the European NOx anthropogenic emissions between 2005 and 2019 as seen from the OMI and TROPOMI NO2 satellite observations
Abstract. There are great expectations about the detection and the quantification of NOx emissions using NO2 tropospheric columns from satellite observations and inverse systems. This study assesses the potential of the OMI-QA4ECV and TROPOMI satellite observations to improve the knowledge on European NOx emissions at the regional scale and to inform about the spatio-temporal variability of NOx anthropogenic emissions from 2005 to 2019, at the resolution of 0.5° over Europe. Starting from European emission estimates from the TNO-GHGco-v3 inventory for the year 2005, regional inversions using the Community Inversion Framework coupled to the CHIMERE chemistry-transport model and assimilating satellite NO2 tropospheric columns from OMI and TROPOMI have been performed to estimate the European annual and seasonal budgets for the year 2019. Both the OMI and TROPOMI inversions show decreases in European NOx anthropogenic emission budgets between 2005 and 2019 but the magnitude of the reductions differs with OMI and TROPOMI data (-16 % and -45 %, respectively). A TROPOMI in-version giving more weight to the satellite data becomes consistent with the independent TNO-GHGco-v3 inventory for the year 2019, with annual budgets for EU-27+UK showing absolute relative difference of only 4 %. These TROPOMI inversions are therefore in agreement with the magnitude of the decline in NOx emissions declared by countries, when aggregated at the European scale. However, our results —with OMI and TROPOMI data leading to different magnitudes of corrections on NOx anthropogenic emissions—suggest that more observational constraints would be required to sharpen the European emission estimates.
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RC1: 'Comment on egusphere-2024-3679', Anonymous Referee #1, 11 Dec 2024
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Overall, it is clear that a large amount of work was done by the authors. However, in its current state, I cannot recommend publication. I do encourage the authors to carefully consider my comments and resubmit the revised manuscript.
A major concern of mine is that this article doesn’t present new science, so it may be better suited to another journal, such as Earth System Science Data (ESSD). The title and introduction actually sound somewhat appropriate for ACP, but the manuscript content is really not appropriate for ACP.
Another issue is that the manuscript is poorly organized and, therefore, difficult to read. ACP gives handy recommendations on the structure of a manuscript: https://www.atmospheric-chemistry-and-physics.net/policies/guidelines_for_authors.html. I highly suggest that the authors review these recommendations. Here are two examples of what I mean:
- The title doesn’t reflect what the paper is about. The paper title indicates that the paper is focused on discussing the causes of trends in European NOx emissions. At least, that’s what I thought when reading the title. This isn’t the case. Please revise the title to reflect the actual manuscript content.
- The paper is wordy (by 30-50%); the introduction is particularly wordy and needs paragraph indents for clarity. Note that a goal of technical writing is to clearly and concisely convey a particular message. As an example, the purpose of your paper should be given in one sentence, such as in the abstract and as a topic sentence of a paragraph in the introduction. I had to piece it together over a very long paragraph, but I still don’t know the overall goal of the paper given the vague title, vague abstract, and vague conclusions. An overview diagram of the steps in your work would be helpful.
Another major concern is the lack of validation of the data products and emission estimates. Why don’t you compare results with independent in situ observations, such as from the Pandora network? That would certainly strengthen your conclusions about how your method impacts the emissions estimates. In fact, you say in the last sentence of the abstract “…our results —with OMI and TROPOMI data leading to different magnitudes of corrections on NOx anthropogenic emissions—suggest that more observational constraints would be required to sharpen the European emission estimates.” You haven’t even used the existing observational constraints!
Section 2.1: What are the strengths and limitations of this inversion system for your work? Has it been applied and validated with independent observations (e.g., Pandora)? Why are you using it relative to other inversion systems?
Citation: https://doi.org/10.5194/egusphere-2024-3679-RC1
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