Articles | Volume 25, issue 19
https://doi.org/10.5194/acp-25-12379-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.Global atmospheric inversion of the anthropogenic NH3 emissions over 2019–2022 using the LMDZ-INCA chemistry transport model and the IASI NH3 observations
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- Final revised paper (published on 08 Oct 2025)
- Supplement to the final revised paper
- Preprint (discussion started on 17 Feb 2025)
- Supplement to the preprint
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
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RC1: 'Comment on egusphere-2025-162', Anonymous Referee #1, 22 Mar 2025
- AC1: 'Reply on RC1', Pramod Kumar, 08 Jun 2025
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RC2: 'Comment on egusphere-2025-162', Anonymous Referee #2, 31 Mar 2025
- AC2: 'Reply on RC2', Pramod Kumar, 08 Jun 2025
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Pramod Kumar on behalf of the Authors (08 Jun 2025)
Author's response
Author's tracked changes
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ED: Referee Nomination & Report Request started (15 Jun 2025) by Jayanarayanan Kuttippurath
RR by Anonymous Referee #2 (18 Jun 2025)
RR by Anonymous Referee #1 (25 Jun 2025)

RR by Anonymous Referee #3 (27 Jun 2025)

ED: Publish subject to minor revisions (review by editor) (03 Jul 2025) by Jayanarayanan Kuttippurath

AR by Pramod Kumar on behalf of the Authors (15 Jul 2025)
Author's response
Author's tracked changes
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ED: Publish as is (16 Jul 2025) by Jayanarayanan Kuttippurath

AR by Pramod Kumar on behalf of the Authors (17 Jul 2025)
Author's response
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General comments
The paper describes the application of global ammonia (NH3) emission inversion estimates over 2019-2022. As the current top-down emissions of NH3 are rather inconsistent across spatiotemporal scales, this approach provides a new insight into the NH3 emission budget, at relatively high resolution and daily scales. The inversion uses an IASI averaging kernel (AK) to constrain the profile of NH3 concentrations; results are compared with two global inventories and two top-down estimates. The average estimate shows a higher value, compared to previous budgets, either globally or regionally. The emission results are used to analyze the impact of COVID-19 lockdowns in 2020, as compared with that in 2019. However, the rise of emissions in 2020 seems to be likely due to the decrease in atmospheric NH3 sinks (e.g., NOx and SO2) and induces large uncertainty to these emission estimates.
The inversion now uses IASI observations to constrain emissions, and other bottom-up inventories and top-down inversions for validation. Would it be possible to use simulated NH3 concentration based on updated emissions to compare with the IASI (or CrIS) concentration or in-situ observations? The current emission validation shows quite large differences between emission products, would the simulated concentration based on this emission estimate also give very different results with NH3 concentration observations? The consistency of this inversion method would be very necessary to check first.
Although the finite difference mass-balance (FDMB) inversion approach has been applied to update the anthropogenic NOx emission inventories, it has been rarely used in NH3 emission. Actually, the emission perturbation of 10-20 % is sometimes applied to get the scaling factor (beta). Could the authors further explain why a larger 40 % is applied in NH3 emission and distribution of the beta could be shown to clarify why it should be within the range of 0 to 10?
The spatial resolution of the model is 1.27° × 2.5°, which challenges the assumption that there is no transport in a grid, considering the normal wind speed of more than 100 km in a day and the lifetime of NH3 around a day. And the prior inventory (in 0.5°) may not be able to capture the NH3 concentration dynamics at a finer scale, if not overridden by some regional inventories. Moreover, the NH3 is actively reacted with NH4+, so it is worth discussing whether the sensitivity of NH3 and NH4+ together would be better to capture the sensitivity of the NHx (NH3 + NH4+) family to the emission.
The longer period has been used for spin-up (2010-2018), by using the CEDS global bottom-up gridded inventories as a prior. However, post-2019 was set with the carbon emission growth rate, which I think is inappropriate for the NH3 since 1) NH3 does not have an intense relationship with fossil fuel emissions, as an agricultural-based emission, and 2) they have different trends in anthropogenic sources, but may have a similar reflection on the biomass burning. Instead, the post-2019 prior could be set as invariant and adjust the simulated NH3 columns with the IASI observations, and the derived NH3 emission could be corrected by SO2/NOx change during the COVID lockdown. Or authors could just update it after the release of new CEDS emissions.
Although the paper focuses on the application of the inversion system in a high spatiotemporal resolution, the setup and suitability of the system are not sufficient enough to publish, before more tests and discussions on its sensitivity and consistency. For some parts a more detailed and cleared description could be useful, as described below in the Specific Comments. Overall, the paper is easy to read with a good structure, but could still not be published in the ACP in terms of the above scientific concerns.
Specific comments
Technical corrections