the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Dec 2023
Estimating scalar turbulent fluxes with slow-response sensors in the stable atmospheric boundary layer
Abstract. Conventional and recently developed approaches for estimating turbulent scalar fluxes under stable conditions are evaluated. The focus is on methods that do not require fast scalar sensors such as the relaxed eddy accumulation (REA) approach, the disjunct eddy-covariance (DEC) approach, and a novel mixing length parametrization labelled as A22. Using high-frequency measurements collected from two contrasting sites (Utqiagvik, Alaska and Wendell, Idaho "during winter"), it is shown that the REA and A22 models outperform the conventional Monin-Obukhov Similarity Theory (MOST) utilized in Earth System Models. With slow trace gas sensors used in disjunct eddy-covariance (DEC) approaches and the more complex signal filtering associated with REA devices (here simulated using filtered signals from fast-response sensors), A22 outperforms REA and DEC in predicting the observed unfiltered (total) eddy-covariance (EC) fluxes. However, REA and DEC can still capture the observed filtered EC fluxes computed with the filtered scalar signal. This finding motivates the development of a correction, blending the REA and DEC methods, for the underestimated net averaged fluxes to incorporate the effect of sensor filtering. The only needed parameter for this correction is the mean velocity at the instrument height, a surrogate of the advective timescale.
-
Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
-
Preprint
(3116 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3116 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2620', Anonymous Referee #1, 16 Feb 2024
Review of the manuscript “Estimating scalar turbulent fluxes with slow-response sensors in the stable atmospheric boundary layer” by M. Allouche et al.
General comments
This manuscript aims to evaluate the performance of different scalar flux quantification methods that can be applied to measurements at one height, especially when only slow-response sensors are available that do not suffice for direct eddy covariance (EC); these methods are disjunct eddy covariance (DEC), relaxed eddy covariance (REA) and the mixing length model of A22. They are tested for two real-world data sets of high-frequency turbulence measurements that are artificially deteriorated or filtered. The paper is generally well written and clearly structured, but I have one main concern, which is that the authors do not apply the DEC and REA method as is it usually applied in other studies, thereby potentially giving the false impression that these methods create a systematic bias in flux estimates. This should not be the case if everything is done properly. Normally, only the random uncertainty or the scatter should increase. At least from this manuscript, I cannot rule that the authors have a fundamental misconception about the DEC method. It still requires a fast sampling, even if a slow-response sensor is applied, and the sampled air can then be analysed for a while before the next fast (instantaneous) grab sample is taken. Hence there is no low-pass filtering involved. Only the number of samples per averaging period is decreased, which usually leads to a larger random error but no systematic error (Karl et al. 2002, Rinne et al. 2001, 2008). Similarly, it should be clear to any micrometeorological practitioner that the REA method requires fast switching valves that can change the air flow in less than 0.1 s. However, the authors apply filtering time scales of several seconds. This is not how REA is done in reality. Because of this shortcoming, I can only recommend a major revision of this manuscript.
Specific comments
L4: The abstract is rather short, I would welcome one or two more sencentes describing the two field experiments.
L8-9: I am not sure what you try to say with this sentence, be more specific. Under which circumstances?
L120-125: Any references for the DEC method?
L167: What sonic anemometer model was used?
L187-193: I am not sure about the purpose of this paragraph here. I is not really suited as an overarching introduction to section 4, but rather belongs to only to section 4.1, since it does not mention DEC, which is treated in section 4.2 and 4.3
L205-210: Based on this text passage I have the impression the authors have a misconception about the DEC method, since normally only grab samples are analyses but now low-pass filtering is applied.
L239: As the authors rightfully state, REA with fast-switching valves will lead to a good agreement with EC, and that is the only way REA should be applied in the first place. The authors should make sure to avoid the impression that this strong bias shown in Fig. 2 is the result of the REA method itself, while it is actually an effect of the strong (artificial) low-pass filtering.
Figure 2: The results for DEC are confusing since such a systematic bias is not to be expected based on the literature on DEC. If DEC is applied properly, only the time interval between grab samples should be altered, and any low-pass filtering should be avoided. The REA results are also misleading, since they imply that slow-switching valves are used or some other form of low-pass filtering is applied. This is not how REA is or should be done in practice.
Karl TG, Spirig C, Rinne J, et al (2002) Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry. Atmos Chem Phys 2:279–291. https://doi.org/10.5194/acp-2-279-2002
Rinne HJI, Guenther AB, Warneke C, Gouw JA De (2001) Disjunct eddy covariance technique for trace gas flux measurements. Geophys Res Lett 28:3139–3142
Rinne J, Douffet T, Prigent Y, Durand P (2008) Field comparison of disjunct and conventional eddy covariance techniques for trace gas flux measurements. Environ Pollut 152:630–635
Citation: https://doi.org/10.5194/egusphere-2023-2620-RC1 -
AC1: 'Reply on RC1', Mohammad Allouche, 16 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2620/egusphere-2023-2620-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Mohammad Allouche, 16 May 2024
-
RC2: 'Comment on egusphere-2023-2620', Anonymous Referee #2, 10 Mar 2024
The objective of this study is to assess and compare the performance of relaxed eddy accumulation (REA), disjunct eddy-covariance (DEC), and a mixing length parameterization labelled A22 in comparison to the eddy covariance (EC) technique using high-frequency measurements collected at two sites. The high-frequency measurements of scalars were filtered to supply scalar quantities that were then used with high-frequency wind speed measurements to compute the REA and DEC fluxes. I concur with Referee 1 that by low-pass filtering the scalar signal, the authors unrealistically deteriorated it for input into both the REA and DEC flux calculation. Fast valve switching is done in REA, and fast (instantaneous) sampling is done in DEC, in order to avoid apparent biases as are depicted in Figure 2. As such, I recommend that the authors undertake a major revision of the work in this manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-2620-RC2 -
AC2: 'Reply on RC2', Mohammad Allouche, 16 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2620/egusphere-2023-2620-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Mohammad Allouche, 16 May 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2620', Anonymous Referee #1, 16 Feb 2024
Review of the manuscript “Estimating scalar turbulent fluxes with slow-response sensors in the stable atmospheric boundary layer” by M. Allouche et al.
General comments
This manuscript aims to evaluate the performance of different scalar flux quantification methods that can be applied to measurements at one height, especially when only slow-response sensors are available that do not suffice for direct eddy covariance (EC); these methods are disjunct eddy covariance (DEC), relaxed eddy covariance (REA) and the mixing length model of A22. They are tested for two real-world data sets of high-frequency turbulence measurements that are artificially deteriorated or filtered. The paper is generally well written and clearly structured, but I have one main concern, which is that the authors do not apply the DEC and REA method as is it usually applied in other studies, thereby potentially giving the false impression that these methods create a systematic bias in flux estimates. This should not be the case if everything is done properly. Normally, only the random uncertainty or the scatter should increase. At least from this manuscript, I cannot rule that the authors have a fundamental misconception about the DEC method. It still requires a fast sampling, even if a slow-response sensor is applied, and the sampled air can then be analysed for a while before the next fast (instantaneous) grab sample is taken. Hence there is no low-pass filtering involved. Only the number of samples per averaging period is decreased, which usually leads to a larger random error but no systematic error (Karl et al. 2002, Rinne et al. 2001, 2008). Similarly, it should be clear to any micrometeorological practitioner that the REA method requires fast switching valves that can change the air flow in less than 0.1 s. However, the authors apply filtering time scales of several seconds. This is not how REA is done in reality. Because of this shortcoming, I can only recommend a major revision of this manuscript.
Specific comments
L4: The abstract is rather short, I would welcome one or two more sencentes describing the two field experiments.
L8-9: I am not sure what you try to say with this sentence, be more specific. Under which circumstances?
L120-125: Any references for the DEC method?
L167: What sonic anemometer model was used?
L187-193: I am not sure about the purpose of this paragraph here. I is not really suited as an overarching introduction to section 4, but rather belongs to only to section 4.1, since it does not mention DEC, which is treated in section 4.2 and 4.3
L205-210: Based on this text passage I have the impression the authors have a misconception about the DEC method, since normally only grab samples are analyses but now low-pass filtering is applied.
L239: As the authors rightfully state, REA with fast-switching valves will lead to a good agreement with EC, and that is the only way REA should be applied in the first place. The authors should make sure to avoid the impression that this strong bias shown in Fig. 2 is the result of the REA method itself, while it is actually an effect of the strong (artificial) low-pass filtering.
Figure 2: The results for DEC are confusing since such a systematic bias is not to be expected based on the literature on DEC. If DEC is applied properly, only the time interval between grab samples should be altered, and any low-pass filtering should be avoided. The REA results are also misleading, since they imply that slow-switching valves are used or some other form of low-pass filtering is applied. This is not how REA is or should be done in practice.
Karl TG, Spirig C, Rinne J, et al (2002) Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry. Atmos Chem Phys 2:279–291. https://doi.org/10.5194/acp-2-279-2002
Rinne HJI, Guenther AB, Warneke C, Gouw JA De (2001) Disjunct eddy covariance technique for trace gas flux measurements. Geophys Res Lett 28:3139–3142
Rinne J, Douffet T, Prigent Y, Durand P (2008) Field comparison of disjunct and conventional eddy covariance techniques for trace gas flux measurements. Environ Pollut 152:630–635
Citation: https://doi.org/10.5194/egusphere-2023-2620-RC1 -
AC1: 'Reply on RC1', Mohammad Allouche, 16 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2620/egusphere-2023-2620-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Mohammad Allouche, 16 May 2024
-
RC2: 'Comment on egusphere-2023-2620', Anonymous Referee #2, 10 Mar 2024
The objective of this study is to assess and compare the performance of relaxed eddy accumulation (REA), disjunct eddy-covariance (DEC), and a mixing length parameterization labelled A22 in comparison to the eddy covariance (EC) technique using high-frequency measurements collected at two sites. The high-frequency measurements of scalars were filtered to supply scalar quantities that were then used with high-frequency wind speed measurements to compute the REA and DEC fluxes. I concur with Referee 1 that by low-pass filtering the scalar signal, the authors unrealistically deteriorated it for input into both the REA and DEC flux calculation. Fast valve switching is done in REA, and fast (instantaneous) sampling is done in DEC, in order to avoid apparent biases as are depicted in Figure 2. As such, I recommend that the authors undertake a major revision of the work in this manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-2620-RC2 -
AC2: 'Reply on RC2', Mohammad Allouche, 16 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2620/egusphere-2023-2620-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Mohammad Allouche, 16 May 2024
Peer review completion
Journal article(s) based on this preprint
Data sets
Data Sets: Estimating scalar turbulent fluxes with slow-response sensors in the stable atmospheric boundary layer Mohammad Allouche, Vladislav I. Sevostianov, Einara Zahn, Mark A. Zondlo, Nelson Luís Dias, Gabriel G. Katul, Jose D. Fuentes, and Elie Bou-Zeid https://doi.org/10.5281/zenodo.10073726
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 319 | 110 | 38 | 467 | 27 | 27 |
- HTML: 319
- PDF: 110
- XML: 38
- Total: 467
- BibTeX: 27
- EndNote: 27
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Cited
1 citations as recorded by crossref.
Mohammad Allouche
Vladislav I. Sevostianov
Einara Zahn
Mark A. Zondlo
Nelson Luís Dias
Gabriel G. Katul
Jose D. Fuentes
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3116 KB) - Metadata XML