An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture

Mellqvist, Johan; Vechi, Nathalia T.; Scheutz, Charlotte; Durif, Marc; Gautier, Francois; Johansson, John; Samuelsson, Jerker; Offerle, Brian; Brohede, Samuel

doi:https://doi.org/10.5194/egusphere-2023-1104

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https://doi.org/10.5194/egusphere-2023-1104

Preprints

22 Jun 2023

| 22 Jun 2023

An uncertainty methodology for solar occultation flux measurements: ammonia emissions from agriculture

Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede

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 NH₃concentration 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.

Received: 24 May 2023 – Discussion started: 22 Jun 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

Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede

Interactive discussion

Status: closed

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

Citation: https://doi.org/10.5194/egusphere-2023-1104-RC1
- 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
  
  Citation: https://doi.org/10.5194/egusphere-2023-1104-AC1
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 NH₃emission 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
  
  Citation: https://doi.org/10.5194/egusphere-2023-1104-AC2

Interactive discussion

Status: closed

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

Citation: https://doi.org/10.5194/egusphere-2023-1104-RC1
- 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
  
  Citation: https://doi.org/10.5194/egusphere-2023-1104-AC1
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 NH₃emission 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
  
  Citation: https://doi.org/10.5194/egusphere-2023-1104-AC2

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

Dear Dr. Mellqvist,

Thank you for submitting your manuscript to AMT. I have read the two anonymous reviews, your response, as well as the revised manuscript. Overall, your response and revisions address the reviewer’s concerns and I the manuscript has improved from its previous version. However, I found several minor issues in the text that I would like you to correct before making a final decision on the manuscript (see below).
Please also review the AMT data policy (https://www.atmospheric-measurement-techniques.net/policies/data_policy.html), which calls for making data publicly available as well as citable. Please provide a link and/or DOI for the data in this manuscript in the “Data availability” section.

Sincerely
Jochen Stutz

Minor comments (line numbers in revised, not red-lined, manuscript):
Line 105: Consider removing one “ideally”.
Line 110: “ introduce” should be “introducing”. Maybe consider if this entire sentence is even necessary.
Section 2.2.1 and 3.3: the mathematical symbol /alpha is used for two different quantities in the manuscript (relative wind angle in eq 1 and in eq. 10). Please rename it for one of these instances.
Line 185: Ineris is an acronym. Please spell out the full name.
Line 193. Add “Inc.” to Fluxsense. Not everyone knows this is a company.
Line 199. Add “distance” after 250 – 900m (assuming this is what you meant)
Line 258: I agree with reviewer 1 that adding a sentence explaining the factor 1.96 would improve the manuscript. It is not well enough known for every reader to understand where this number is coming from.
Line 489: replace “their” with “its” since you are referring to the “stickiness” of NH3 not of its emissions.
Line 507: Replace “very” with “vary”
Line 539: “instrument" should be “instruments”

Hide

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

Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede

Supplement

https://doi.org/10.5194/egusphere-2023-1104-supplement

Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede

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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.


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