Preprints
https://doi.org/10.5194/egusphere-2023-1104
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2023-1104
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
22 Jun 2023
| 22 Jun 2023
An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture
Abstract. Ammonia (NH3) emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study introduces a novel methodology for evaluating uncertainties in NH3 emissions measurements using the Solar Occultation Flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method, utilizing solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between −31 % and +14 % on average, slightly larger than the estimated expanded uncertainty ranging from ±12 % to ±17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ±21 % and ±37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (~1 kg h−1) and large (~100 kg h−1) sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. The findings also have implications when using SOF to measure other gaseous species and in other applications.
How to cite. Mellqvist, J., Vechi, N. T., Scheutz, C., Durif, M., Gautier, F., Johansson, J., Samuelsson, J., Offerle, B., and Brohede, S.: An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1104, 2023.
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Journal article(s) based on this preprint
23 Apr 2024
An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production
Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede
Atmos. Meas. Tech., 17, 2465–2479, https://doi.org/10.5194/amt-17-2465-2024, https://doi.org/10.5194/amt-17-2465-2024, 2024
Short summary
Short summary
The solar occultation flux method retrieves ammonia gas columns from the solar spectrum. Emissions are obtained by multiplying the integrated plume concentration by the wind speed profile. The methodology for uncertainty estimation was established considering an error budget with systematic and random components, resulting in an expanded uncertainty in the range of 20 % to 30 %. The method was validated in a controlled release, and its application was demonstrated in different farms.
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
-
RC1: 'Comment on egusphere-2023-1104', Anonymous Referee #1, 26 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Johan Mellqvist, 24 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Johan Mellqvist, 24 Nov 2023
-
RC2: 'Comment on egusphere-2023-1104', Anonymous Referee #2, 25 Oct 2023
The authors address a comprehensive approach to quality uncertainties of measured ammonia emissions from livestock sources by using SOF & MeFTIR instruments, which is well fit for the scope of AMT. Meanwhile, scientifically speaking, understanding the level of uncertainty is crucial for the reliability and validity of the results in the Nitrogen domain.
The authors validated such error estimation method using tracer release experiment (single point source) and later aslo applied it into multiple livestock farms case studies (area sources), which can further help mitigate the possible causes of errors in real-world. In all, it is worthy for scientific publication. But before that, I do have some specific comments related the current error propagation methodology and the structural of the paper as well, which I’d hope the authors can remedy certain issues and deepen the discussion.'
some specific comments:
- It is well known that ammonia flux has its bidirectional character. Although notably the authors stated it is out of scope for the present work, I’d like to know how problematic would it be to fully ignore it from the error propagation? How large will it affect the error ranges? For example, the authors directly compared the tracer emitted NH3 value with the SOF measured value ~200 meter away from the source at the downwind direction. This possibly causes the current error propagation scheme (methodology) tentatively overestimate the actual ‘error’, because the ammonia ‘deposition loss’ is not corrected before the error propagation starts. In the other word, it might not be fair to name ammonia deposition loss as part of the total measurement error, isn't it?
- Some comprehensive discussions are missing from the current paper structure. I’d think it can add some extra for this paper if the authors can properly address the above mentioned issue, by adding some comparison cases studies, or discuss both limitations and advantages of the current method and results in the structural way.
- Both in the abstract and conclusion parts, the authors emphasized the SOF method estimated NH3 emission can be as low as 1 kg/h ± 21%. Does it somehow indicate the SOF method no longer trust worthy if the ammonia source emission below 1 kg/h? As it can influence the applications for potential users, can the authors justify your statement? Is such statement applicable for all agricultural sources or need further testing?
Some specific technical comments are listed below:
- The title of this paper is ‘An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture’. It seems too broad to cover all agricultural domain. The agricultural activities include fertilizer application, livestock operations, and other agricultural processes as well. However, none of the study cases listed in the present work demonstrated its application for fertilizer or manure field emission measurement yet. All cases are focused on livestock farms. Would it be more appropriate to narrow down the title to ‘livestock’ ?
- In Line 19, how does the plume height estimation reducing the measurement uncertainty? I could not find detailed discussion in the main text. please reconsider its value when it is mentioned in the abstract?
- The last sentence in the abstract should be removed. The main paper does not provide concrete evidence or results demonstrating the applicability of the methodology to other gaseous species or purposes, it would not be appropriate to make such claims in the abstract. The abstract should accurately summarize the scope and results of the study based on what is presented in the main paper. It's better to phrase it as a potential avenue for future research or exploration rather than making definitive statements. Mentioning the potential for broader applications in the discussion section of the paper, along with the need for further research in those areas, would be more appropriate.
- The caption of Figure 2 mentioned case study C3 out of blue without any other context in the previous text, please add some extra information or consider reorder the main text structure.
- In line 170, both 2D sonic anemometer and vane wind meter are used in multiple campaigns. How do different types of wind meters contribute to the final measurement error? Do you take the instrument system error into account when estimating the wind profile error?
- In line 238 , absorption strength uncertainty of 2% was assigned from a previous study, is it always a fixed value for all SOF instrument in various application? If not so, can it be properly estimated or not?
- In line 255 equation 7, the 'abs' value is used. Can you please define what is it? As in equation 6 there is another abs(960-968). Are they the same? Similarly, in equation 8, it is Aabs. They become bit confusing.
- Some confusing statement occurred in both line 304 and 308. From the previous context, in line 304 C2 should be C1; and in line 308 C1 in fact refers to C2. Please double check.
- In line 317 Table 1. Case study C2 integrated wind profile is estimated using C3 data. Can you explain why C2 can use C3 wind profile data? I assume they were not measured in the same day nor the same location, so why do they share the same IWPavg value?
- Line 360, MeFTIR and SOF both used to estimate plume height. However, the current method did not mention MeFTIR measurement uncertainty at the ground level. How large uncertainty can be generated from MeFTIR system? and how large can it contribute to the total error prorogation?
- Line 367, the authors stated PTVS method result is slightly lower than VCGS method, but they are similar''. I would not agree so. In Figure 6b, it clearly shows PTVS results can be 2 times bigger than VCGC method in many cases.
- Figure 6b, what do you mean "farms" in the title of x-axis? It never mentioned in the main text. Or do you mean "transect" number from certain case study ? please clarify.
- Line 383, Figure 7b and line 403 all related to the Sep 22 measurement result, which was measured in a cloudy day. Does such data point still validate? Firstly, it is conflict with the previous statement that SOF is better used in sunny and less cloudy day. Secondly, even without ‘deposition loss’ correction, SOF measured downwind value is higher than the actual tracer release value. This strongly suggests such data may be too faulty to be trusted.
- In Table 4 , for C2 and C3a studies, 3 and 7 transects were measured, respectively. Elsewhere, the author stated that 12 to 16 transects should be applied. If so, will the small sampling size significantly enlarge the final error? Can you demonstrate it further?
- In Figure 8b caption, the flux on the figure corresponded to 0.55 kg/h. However, in the main text line 425 said ‘the SOF could measure concentration as low as 1 kg/h with an uncertainty of 21%’. But 0.55 kg/h is below such threshold. which statement is true? What is the lowest detection limitation to use SOF measuring Nh3 sources? Shall it be further explored or is it proved by current study?
Citation: https://doi.org/10.5194/egusphere-2023-1104-RC2 -
AC2: 'Reply on RC2', Johan Mellqvist, 24 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-AC2-supplement.pdf
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
-
RC1: 'Comment on egusphere-2023-1104', Anonymous Referee #1, 26 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Johan Mellqvist, 24 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Johan Mellqvist, 24 Nov 2023
-
RC2: 'Comment on egusphere-2023-1104', Anonymous Referee #2, 25 Oct 2023
The authors address a comprehensive approach to quality uncertainties of measured ammonia emissions from livestock sources by using SOF & MeFTIR instruments, which is well fit for the scope of AMT. Meanwhile, scientifically speaking, understanding the level of uncertainty is crucial for the reliability and validity of the results in the Nitrogen domain.
The authors validated such error estimation method using tracer release experiment (single point source) and later aslo applied it into multiple livestock farms case studies (area sources), which can further help mitigate the possible causes of errors in real-world. In all, it is worthy for scientific publication. But before that, I do have some specific comments related the current error propagation methodology and the structural of the paper as well, which I’d hope the authors can remedy certain issues and deepen the discussion.'
some specific comments:
- It is well known that ammonia flux has its bidirectional character. Although notably the authors stated it is out of scope for the present work, I’d like to know how problematic would it be to fully ignore it from the error propagation? How large will it affect the error ranges? For example, the authors directly compared the tracer emitted NH3 value with the SOF measured value ~200 meter away from the source at the downwind direction. This possibly causes the current error propagation scheme (methodology) tentatively overestimate the actual ‘error’, because the ammonia ‘deposition loss’ is not corrected before the error propagation starts. In the other word, it might not be fair to name ammonia deposition loss as part of the total measurement error, isn't it?
- Some comprehensive discussions are missing from the current paper structure. I’d think it can add some extra for this paper if the authors can properly address the above mentioned issue, by adding some comparison cases studies, or discuss both limitations and advantages of the current method and results in the structural way.
- Both in the abstract and conclusion parts, the authors emphasized the SOF method estimated NH3 emission can be as low as 1 kg/h ± 21%. Does it somehow indicate the SOF method no longer trust worthy if the ammonia source emission below 1 kg/h? As it can influence the applications for potential users, can the authors justify your statement? Is such statement applicable for all agricultural sources or need further testing?
Some specific technical comments are listed below:
- The title of this paper is ‘An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture’. It seems too broad to cover all agricultural domain. The agricultural activities include fertilizer application, livestock operations, and other agricultural processes as well. However, none of the study cases listed in the present work demonstrated its application for fertilizer or manure field emission measurement yet. All cases are focused on livestock farms. Would it be more appropriate to narrow down the title to ‘livestock’ ?
- In Line 19, how does the plume height estimation reducing the measurement uncertainty? I could not find detailed discussion in the main text. please reconsider its value when it is mentioned in the abstract?
- The last sentence in the abstract should be removed. The main paper does not provide concrete evidence or results demonstrating the applicability of the methodology to other gaseous species or purposes, it would not be appropriate to make such claims in the abstract. The abstract should accurately summarize the scope and results of the study based on what is presented in the main paper. It's better to phrase it as a potential avenue for future research or exploration rather than making definitive statements. Mentioning the potential for broader applications in the discussion section of the paper, along with the need for further research in those areas, would be more appropriate.
- The caption of Figure 2 mentioned case study C3 out of blue without any other context in the previous text, please add some extra information or consider reorder the main text structure.
- In line 170, both 2D sonic anemometer and vane wind meter are used in multiple campaigns. How do different types of wind meters contribute to the final measurement error? Do you take the instrument system error into account when estimating the wind profile error?
- In line 238 , absorption strength uncertainty of 2% was assigned from a previous study, is it always a fixed value for all SOF instrument in various application? If not so, can it be properly estimated or not?
- In line 255 equation 7, the 'abs' value is used. Can you please define what is it? As in equation 6 there is another abs(960-968). Are they the same? Similarly, in equation 8, it is Aabs. They become bit confusing.
- Some confusing statement occurred in both line 304 and 308. From the previous context, in line 304 C2 should be C1; and in line 308 C1 in fact refers to C2. Please double check.
- In line 317 Table 1. Case study C2 integrated wind profile is estimated using C3 data. Can you explain why C2 can use C3 wind profile data? I assume they were not measured in the same day nor the same location, so why do they share the same IWPavg value?
- Line 360, MeFTIR and SOF both used to estimate plume height. However, the current method did not mention MeFTIR measurement uncertainty at the ground level. How large uncertainty can be generated from MeFTIR system? and how large can it contribute to the total error prorogation?
- Line 367, the authors stated PTVS method result is slightly lower than VCGS method, but they are similar''. I would not agree so. In Figure 6b, it clearly shows PTVS results can be 2 times bigger than VCGC method in many cases.
- Figure 6b, what do you mean "farms" in the title of x-axis? It never mentioned in the main text. Or do you mean "transect" number from certain case study ? please clarify.
- Line 383, Figure 7b and line 403 all related to the Sep 22 measurement result, which was measured in a cloudy day. Does such data point still validate? Firstly, it is conflict with the previous statement that SOF is better used in sunny and less cloudy day. Secondly, even without ‘deposition loss’ correction, SOF measured downwind value is higher than the actual tracer release value. This strongly suggests such data may be too faulty to be trusted.
- In Table 4 , for C2 and C3a studies, 3 and 7 transects were measured, respectively. Elsewhere, the author stated that 12 to 16 transects should be applied. If so, will the small sampling size significantly enlarge the final error? Can you demonstrate it further?
- In Figure 8b caption, the flux on the figure corresponded to 0.55 kg/h. However, in the main text line 425 said ‘the SOF could measure concentration as low as 1 kg/h with an uncertainty of 21%’. But 0.55 kg/h is below such threshold. which statement is true? What is the lowest detection limitation to use SOF measuring Nh3 sources? Shall it be further explored or is it proved by current study?
Citation: https://doi.org/10.5194/egusphere-2023-1104-RC2 -
AC2: 'Reply on RC2', Johan Mellqvist, 24 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1104/egusphere-2023-1104-AC2-supplement.pdf
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Johan Mellqvist on behalf of the Authors (12 Dec 2023)
Author's response
Author's tracked changes
Manuscript
ED: Publish subject to minor revisions (review by editor) (12 Jan 2024) by Jochen Stutz
AR by Johan Mellqvist on behalf of the Authors (22 Jan 2024)
Author's response
Author's tracked changes
Manuscript
ED: Publish as is (02 Feb 2024) by Jochen Stutz
AR by Johan Mellqvist on behalf of the Authors (11 Feb 2024)
Manuscript
Post-review adjustments
AA: Author's adjustment | EA: Editor approval
AA by Johan Mellqvist on behalf of the Authors (10 Apr 2024)
Author's adjustment
Manuscript
EA: Adjustments approved (10 Apr 2024) by Jochen Stutz
Journal article(s) based on this preprint
23 Apr 2024
An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production
Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede
Atmos. Meas. Tech., 17, 2465–2479, https://doi.org/10.5194/amt-17-2465-2024, https://doi.org/10.5194/amt-17-2465-2024, 2024
Short summary
Short summary
The solar occultation flux method retrieves ammonia gas columns from the solar spectrum. Emissions are obtained by multiplying the integrated plume concentration by the wind speed profile. The methodology for uncertainty estimation was established considering an error budget with systematic and random components, resulting in an expanded uncertainty in the range of 20 % to 30 %. The method was validated in a controlled release, and its application was demonstrated in different farms.
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Department of Space, Earth and Environment, Chalmers University of Technology, Göteborg, Sweden
Nathalia T. Vechi
Department of Space, Earth and Environment, Chalmers University of Technology, Göteborg, Sweden
Department of Environmental Engineering, Technical University of Denmark, Lyngby, Denmark
Charlotte Scheutz
Department of Environmental Engineering, Technical University of Denmark, Lyngby, Denmark
Marc Durif
INERIS, Verneuil-en-Halatte, France
Francois Gautier
INERIS, Verneuil-en-Halatte, France
John Johansson
Fluxsense AB, Göteborg, Sweden
Jerker Samuelsson
Fluxsense AB, Göteborg, Sweden
Brian Offerle
Fluxsense AB, Göteborg, Sweden
Samuel Brohede
Fluxsense AB, Göteborg, Sweden
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Short summary
The solar occultation flux method retrieves ammonia gas columns from the solar spectrum. Emissions are obtained by multiplying the integrated plume concentration by the wind speed profile. The methodology for the method uncertainty estimation was established considering an error budget with systematic and random components, resulting in an expanded uncertainty in the range of 20 to 30 %. The method was validated in a controlled release, and its application was demonstrated in different farms.
The solar occultation flux method retrieves ammonia gas columns from the solar spectrum....