the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Aug 2024
A simplified system to quantify storage of carbon dioxide, water vapor and heat within a maize canopy
Abstract. The significance of canopy storage of CO2, latent energy and sensible heat within agricultural crops has not been fully examined. Reported canopy storage terms are consistently smaller than found for a forest ecosystem, such that they are often neglected. A novel multiport profile system has been developed to examine these storage terms. The system sequentially samples air from four heights to a single non-dispersive Infrared Gas Analyzer (IRGA). Following extensive laboratory testing, the system was used to measure CO2 and H2O within an eastern Tennessee maize canopy in 2023. The storage of latent and sensible heat was large enough to merit incorporation with conventional field measurements. The new system will enable profile measurements of CO2 sufficient to quantify canopy storage terms as are needed in agricultural field campaigns.
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RC1: 'Comment on egusphere-2024-2041', Anonymous Referee #1, 22 Aug 2024
The attached .pdf contains comments from the reviewer
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AC1: 'Reply on RC1', Taqi Raza, 26 Sep 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2041/egusphere-2024-2041-AC1-supplement.pdf
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AC1: 'Reply on RC1', Taqi Raza, 26 Sep 2024
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RC2: 'Comment on egusphere-2024-2041', Anonymous Referee #2, 19 Oct 2024
This manuscript (egusphere-2024-2041) discusses using a novel multiport vertical profile measurement system to examine energy balance closure in an agricultural setting and claims that this system provides an effective way to quantify the storage flux terms that are important but often ignored in the surface energy budget study. The novel system consisted of a single infrared gas analyzer (IRGA) and sampling intakes at four heights, which were adjusted as plants grew to ensure that two intakes were always within the canopy and the other two were above the canopy. The system sequentially sampled air at each height for 7.5 seconds, thus allowing a full cycle of 30 seconds for all the four intakes. The design of the system is scientifically sound and the authors have provided valuable research content and data, however the novelty is in question because the multi-level/gradient method has been adopted in a number of micrometeorological studies. The manuscript is overall presented in a concise and balanced way but there are several major concerns that need to be addressed:
1) the presentation of Fig. 2, especially regarding the transit/sampling time, needs further clarification. The first question is: should we expect the same pattern for intake 2 as shown for intake 1? I do see the first few seconds data of intake 1 should be discarded while the remaining data are stable and good for analysis. But where are the stable, equilibrium regions for intakes #2 and #4? I presume that a similar stable region and the same amount of data points are desired for each height/intake.
The second question is: at line 181, the authors mentioned that the 4.9 s delay time was improved to 3.2s but did not tell how this was achieved. Did the authors either increase the flow rate or change the tube length? Also, why not show a figure with 3.2 seconds delay since it's the most recent and reasonable result? Using 4.9 seconds delay is confusing here.
2) This concern is about section 3.1 Experimental Site. First, the authors started this section with introducing their field instruments and setup, then move to a subsection talking about the basics about the field site. Would it be logically better to introduce the experimental site first, then describe the field measurement setup? Second, should subsection 3.2 belong to Methodology? It's odd to put it under the section Field Measurement Setup.
3) Another concern is about section 4. First, starting at line 247, this paragraph delivers almost the same message as the paragraph above and adds nothing new. Second, starting at line 295, Fig.7b and 7c are mixed up in the figure and in the text, making it hard for readers to follow. The rest of this section lacks further discussion on the results, such as the advantages/limitations of this system compared to other similar studies/systems, a more comprehensive description on what aspects this system can be useful for in future micromet studies.
Minor comments are also listed below:
1) Highlights: the second and third bullet points convey the same meaning: neglecting the storage terms leads to inaccuracies (point 2) while considering it leads to an improved accuracy (point 3). In addition, how this consideration of storage fluxes improved the accuracy of energy closure was not shown in the study. Full budget calculations with/without the storage terms are needed to prove that.
2) Line 53, the previous two references (Lamas Galdo et al., 2021 and Wang et al., 2023) are very recent, can you find a more recent one to replace this 2004 paper?
3) Line 56, same as above. Replace this one with a more recent paper if possible.
4) Line 67, is there a newer paper discussing how many sites are measuring storage? This number must have increased since 2006.
5) Line 108, a period is missing before 'These'.
6) Line 115, the first 'and' changes to 'as'.
7) Line 115, 'To minimize consequences of individual sensor offsets". My comment: Actually you avoided the consequence of inconsistency in sensor offsets because you were using a single sensor rather than multiple, so I think you could just say "avoid" instead of "minimize" because it was no longer an issue.
8) Line 162, '3.2 seconds were ignored' changes to 'The first 3.2 seconds of data were discarded, and the remaining ...'
9) Line 162, maybe I missed that but I don't think you have mentioned the frequency of your data so far. Is it 10Hz, 20Hz or else? Since you start to talk about data here, readers may wonder how many data points are there in 4.3 seconds.
10) Line 164, I don't get this 1.8 seconds. You just said 3.2 seconds is the delay time but now you have another delay time. Is the 3.2 seconds delay for the entire switching system and the 1.8 s delay for the IRGA separately? If you did not use this 1.8s delay time for your flux data calculation, I think it would be better to not mention it to avoid confusion.
11) I don't see any results about the environmental data such as precipitation, temperature, wind, etc. Such data could provide useful information or at least context about this specific location.
12) Line 211, 'A)' for what?
13) Line 213, font size changed.
14) Line 260, times of sunrise and sunset are NOT shown.
15) Line 262, '15-minute'. My comment: this is the only place you mentioned the average time for flux calculation. You should do this earlier in the method section.
16) Fig. 5 and Fig. 6: Need to provide a separate table/graph showing how the heights of the intakes were adjusted during the two-month study period (at least in the supplementary materials). Moreover, the sampling heights in these figures are not consistent with what the authors described earlier. For instance, in the figures, the maximum height for the second level is 1.4 m (0.5h), which means max canopy height h is 2.8 m. Then the max height for the third level (1+h) should be 3.8 m and the max for the top level (2+h) should be 4.8 m. However, in either figure the maximum heights are only 3 m for the third level and 4.4 m for the fourth level. This inconsistency needs explanation.
17) Line 303, there were both positive and negative storage before 2000LT.
18) Fig.7: figure letters a-c need to be placed at the same corner.
Overall, in my opinion, this paper is not ready yet for publication until major revisions are done.
Citation: https://doi.org/10.5194/egusphere-2024-2041-RC2 -
AC2: 'Reply on RC2', Taqi Raza, 12 Nov 2024
Dear Sir,
Greetings of the day, I hope you are doing well!
The authors are grateful to the reviewer for a careful and helpful analysis of our manuscript. Undoubtedly, due to the Reviewer`s comments, the manuscript has been significantly improved. All the reviewer`s comments are reasonable, and we have corrected the MS according to the comments and suggestions.
Answers to the reviewer's comments are given next to comments in bullets.
the presentation of Fig. 2, especially regarding the transit/sampling time, needs further clarification. The first question is: should we expect the same pattern for intake 2 as shown for intake 1? I do see the first few seconds data of intake 1 should be discarded while the remaining data are stable and good for analysis. But where are the stable, equilibrium regions for intakes #2 and #4? I presume that a similar stable region and the same amount of data points are desired for each height/intake.
- Yes, not only 1 and 2 but all intake tubes have the same sampling time. After careful consideration, we decided to remove Table 1 (IRGA output for the multiport air sampling system, for CO2 conc. (430 ppm) fed through the sampling lines at ambient pressure) and Figure 2 (The time-dependent relationship between the infrared gas analyzer (IRGA) in the multiport air sampling apparatus for a gas concentration of 430 ppm CO2 flowing at <1 L/min) from the manuscript, as it raised additional questions and complexities not central to the primary objectives of our study. The initial purpose of this figure was to demonstrate that the instrument was accurately measuring a known CO2 concentration (430 ppm) using different intake tubes, which was a verification step supporting the field trial described in the text that follows. In the revised manuscript, we have clarified that both N2 (0 ppm CO2) and CO2 (430 ppm) were used to test the stability of the system and confirm that the analyzer and switching mechanism were functioning correctly. We believe that the removal of this figure enhances the clarity and focus of the manuscript.
The second question is: at line 181, the authors mentioned that the 4.9 s delay time was improved to 3.2s but did not tell how this was achieved. Did the authors either increase the flow rate or change the tube length? Also, why not show a figure with 3.2 seconds delay since it's the most recent and reasonable result? Using 4.9 seconds delay is confusing here.
- Thank you for bringing this to our attention. We made a mistake. In fact, actual timing for measurement was 3.1 seconds and 4.4 seconds were ignored during the CO2 reading by the analyzer. This has been briefly explained in the revised manuscript.
2) This concern is about section 3.1 Experimental Site. First, the authors started this section with introducing their field instruments and setup, then move to a subsection talking about the basics about the field site. Would it be logically better to introduce the experimental site first, then describe the field measurement setup?
- This is the valid question of the reviewer, and we agree that logically experiment site should first and then the field measurement setup. In the revised manuscript we have incorporated the reviewer’s suggestion
Second, should subsection 3.2 belong to Methodology? It's odd to put it under the section Field Measurement Setup.
- Thank you for bringing this to our attention. We have moved subsection 3.2 under the result section.
3) Another concern is about section 4. First, starting at line 247, this paragraph delivers almost the same message as the paragraph above and adds nothing new. Second, starting at line 295, Fig.7b and 7c are mixed up in the figure and in the text, making it hard for readers to follow. The rest of this section lacks further discussion on the results, such as the advantages/limitations of this system compared to other similar studies/systems, a more comprehensive description on what aspects this system can be useful for in future micromet studies.
- Thank you for your feedback. We have addressed the concerns you raised in the revised manuscript. We have removed the reputation you mentioned in the revised manuscript. We have also fixed the figure 7 a, b & c in the revised manuscript. We have given a complete paragraph describing how this study can be useful for future micromet studies at the end of the result section. Similarly, the limitation of the study has been given in the conclusion and summary. See the revised manuscript.
Minor comments are also listed below:
Highlights: the second and third bullet points convey the same meaning: neglecting the storage terms leads to inaccuracies (point 2) while considering it leads to an improved accuracy (point 3). In addition, how this consideration of storage fluxes improved the accuracy of energy closure was not shown in the study. Full budget calculations with/without the storage terms are needed to prove that.
- Yes, we agree with that highlight 2 & 3 conveying same message. We have removed point 2 and added new highlights. We agree with the reviewer that how this consideration of storage fluxes improved the accuracy of energy closure was not shown in the study. Actually, this paper focuses on the development of the system to measure the storage terms for considering them in the energy balance closure. How this instrument can advance science involve in modeling etc. Our 2nd study focused on calculations of full budget with/without the storage terms.
2) Line 53, the previous two references (Lamas Galdo et al., 2021 and Wang et al., 2023) are very recent, can you find a more recent one to replace this 2004 paper?
- Recent references have been added in the revised manuscript (e.g., Hoeltgebaum and Nelson, 2023).
3) Line 56, same as above. Replace this one with a more recent paper if possible.
- Recent reference (Varmaghani et al., 2016) have been added in the revised manuscript
4) Line 67, is there a newer paper discussing how many sites are measuring storage? This number must have increased since 2006.
- We have updated the number of sites in the revised manuscript and also provided recent references (Fluxnet; Pastorello et al., 2020).
Line 108, a period is missing before 'These'.
- Thak you for your attention. A period has been added before “these” in the revised manuscript.
Line 115, the first 'and' changes to 'as'.
- Thak you for your attention. “as” has been replaced with “and” in the revised manuscript.
Line 115, 'To minimize consequences of individual sensor offsets". My comment: Actually you avoided the consequence of inconsistency in sensor offsets because you were using a single sensor rather than multiple, so I think you could just say "avoid" instead of "minimize" because it was no longer an issue.
- Thank you for your comments. “minimize” has been replaced with “avoid” in the revised manuscript.
Line 162, '3.2 seconds were ignored' changes to 'The first 3.2 seconds of data were discarded, and the remaining ...'
- Thank you for bringing this to our attention. We made a mistake. In fact, actual timing for measurement was 3.1 seconds and 4.4 seconds were ignored during the CO2 reading by the analyzer. This has been briefly explained in the revised manuscript. These time was monitored during the laboratory evaluation of the system for our understanding.
9) Line 162, maybe I missed that but I don't think you have mentioned the frequency of your data so far. Is it 10Hz, 20Hz or else? Since you start to talk about data here, readers may wonder how many data points are there in 4.3 seconds.
- The frequency of data was 10Hz which is mentioned in 1 Apparatus design and operation. After careful consideration, we decided to remove Table 1 (IRGA output for the multiport air sampling system, for CO2 conc. (430 ppm) fed through the sampling lines at ambient pressure) and Figure 2 (The time-dependent relationship between the infrared gas analyzer (IRGA) in the multiport air sampling apparatus for a gas concentration of 430 ppm CO2 flowing at <1 L/min) from the manuscript, as it raised additional questions and complexities not central to the primary objectives of our study. The initial purpose of this figure was to demonstrate that the instrument was accurately measuring a known CO2 concentration (430 ppm) using different intake tubes, which was a verification step supporting the field trial described in the text that follows. In the revised manuscript, we have clarified that both N2 (0 ppm CO2) and CO2 (430 ppm) were used to test the stability of the system and confirm that the analyzer and switching mechanism were functioning correctly. We believe that the removal of this figure enhances the clarity and focus of the manuscript.
10) Line 164, I don't get this 1.8 seconds. You just said 3.2 seconds is the delay time but now you have another delay time. Is the 3.2 seconds delay for the entire switching system and the 1.8 s delay for the IRGA separately? If you did not use this 1.8s delay time for your flux data calculation, I think it would be better to not mention it to avoid confusion.
- 8 seconds mean system takes 1.8 second to produce steady or continuous reading of CO2, and H2O. After 1.8 seconds there is no gap (missing data points) recorded. Yes, we did not use this data recorded during this delay period for flux calculation. The 1.8 second is out of 3.2 seconds. The timing was just for our record to check the response time.
11) I don't see any results about the environmental data such as precipitation, temperature, wind, etc. Such data could provide useful information or at least context about this specific location.
- A new table 1 is added where precipitation, temperature and storage terms data are provided along the cop height and growth stage. For wind speed see the figure 4. Both table 1 and figure 4 are added into the revised manuscript.
12) Line 211, 'A)' for what?
- Thank you for pointing out the mistake. “A)” has been deleted in the revised manuscript.
13) Line 213, font size changed.
- The front size has been fixed in the revised manuscript.
14) Line 260, times of sunrise and sunset are NOT shown.
- We have deleted “times of sunrise and sunset are shown” from the description of figure 5 and described the time of sunrise and sunset in section 3 experimental site in the revised manuscript.
15) Line 262, '15-minute'. My comment: this is the only place you mentioned the average time for flux calculation. You should do this earlier in the method section.
- Thank you for bringing your attention. “constructed from 15-minute” has been deleted as It was already described in the methodology section (2.1 Apparatus design and operation).
16) Fig. 5 and Fig. 6: Need to provide a separate table/graph showing how the heights of the intakes were adjusted during the two-month study period (at least in the supplementary materials). Moreover, the sampling heights in these figures are not consistent with what the authors described earlier. For instance, in the figures, the maximum height for the second level is 1.4 m (0.5h), which means max canopy height h is 2.8 m. Then the max height for the third level (1+h) should be 3.8 m and the max for the top level (2+h) should be 4.8 m. However, in either figure the maximum heights are only 3 m for the third level and 4.4 m for the fourth level. This inconsistency needs explanation.
- The instrument evaluation study was conducted for six weeks from May to the end of June 2023 (for your clearance, results are provided for only 6 weeks of measurement). The maximum height for H1, H2, H3, and H4 was 0.11m, 1.27m, 3m and 4.36m respectively. In the revised manuscript the measurements along the height and growth stage are provided in Table 1.
17) Line 303, there were both positive and negative storage before 2000LT.
- Latent heat storage (Fig. 7c) fluctuated about zero for most of the daylight hours, after exhibiting a major positive excursion (> 4 W m-2) during the few hours after sunrise. After about 2100 LT, similar fluctuations occurred until sunrise, with an average of about –0.5 W m-2. We have explained it clearly in the revised manuscript.
18) Fig.7: figure letters a-c need to be placed at the same corner.
- We apologize for the misplaced letter a-c in fig 7 but they are placed correctly in the same corner in the revised manuscript.
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AC2: 'Reply on RC2', Taqi Raza, 12 Nov 2024
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RC3: 'Comment on egusphere-2024-2041', Anonymous Referee #3, 26 Nov 2024
This manuscript (egusphere-2024-2041) deals with the use of a new multiport vertical profile measurement system to examine energy balance closure in an agricultural environment. It is conventionally assumed that storage in the canopy is negligible compared with the other terms, and the procedures for closing the energy balance are not completely standardised.
The methodology used is appropriate for identifying and quantifying this storage term. It aims to respond to the usual technical difficulties (loss of data, multiple devices not operating over common periods, or multiple sensor drifts/offsets, etc.). The system implemented is therefore based on a single device that simultaneously measures temperature, water vapour and CO2. The sampling system therefore enables these variables to be analysed at several heights over short time steps (a few seconds).
On the pure technical elements, it is clear that the analysis for each of the tubes merits the exclusion of residual air, estimated at 3.2 seconds, but it is not clear how this calculation of the purge delay is made. You could better explain this section.
Regarding figure 2, I didn't understand the change from 4.9 seconds to 3.2 seconds. You could better explain this section.
Lines 205 and 206 give an average temperature and precipitation, but two values (a range of values) are given. I didn't understand the reason for this two averages. In my opinion, only one average is possible.
Figure 4 doesn't provide much information. I suggest deleting it.
In my opinion, there is a lack of information on the maize crop. At the very least, we need information on the sowing and harvest dates, if the ris no infiormation about the average LAI over the period, and ideally the maize variety. It would be important to provide the soil depth that can be explored by the root system to get an idea of the water reserve (large or small) available to the plant (and therefore potential water stress).
Figures 5 and 6 could be improved (font size, box, grid, etc.).
I do not recommend using "approximately" or "around" (line 298), which are not « countable ». I suggest giving a range or an average value or any other indication that is not open to interpretation by the reader.
Figures 5, 6 and 7 show envelope curves. What does the envelope correspond to? Unless I'm mistaken, I don't have the information. I think it's important to mention this in the legends so that each of these figures can stand on its own.
Despite these comments, many of which are formal, I find this new system interesting and relevant for such energy storage estimates
Citation: https://doi.org/10.5194/egusphere-2024-2041-RC3 -
AC3: 'Reply on RC3', Taqi Raza, 01 Dec 2024
- On the pure technical elements, it is clear that the analysis for each of the tubes merits the exclusion of residual air, estimated at 3.2 seconds, but it is not clear how this calculation of the purge delay is made. You could better explain this section.
- Air sampling through the system is controlled by the four, 3-way solenoid valves. Data logger controls the switching of the valves that switch the air between the sampling pump and purging pump sequentially. The sampling pump draws air from the height of interest and passes it to the analyzer (IRGA) for 7.5 seconds. The first 4.4 seconds of data allows the logger to equilibrate and the next 3.1 seconds with the reading of the sample. The delay of 4.4 seconds before the reading of the data logger is based on the equilibration of the system and purging of air from a separate height. This has been briefly explained in the revised manuscript.
- Regarding figure 2, I didn't understand the change from 4.9 seconds to 3.2 seconds. You could better explain this section.
- We made a mistake. In fact, the actual timing for measurement was 3.1 seconds and 4.4 seconds were ignored during the CO2 reading by the analyzer. This has been briefly explained in the revised manuscript.
- Lines 205 and 206 give an average temperature and precipitation, but two values (a range of values) are given. I didn't understand the reason for these two averages. In my opinion, only one average is possible.
- We have changed into average temperature and precipitation 5 oC and 54 in respectively.
- Figure 4 doesn't provide much information. I suggest deleting it.
- We have removed figure 4 in the revised manuscript.
- In my opinion, there is a lack of information on the maize crop. At the very least, we need information on the sowing and harvest dates, if the ris no infiormation about the average LAI over the period, and ideally the maize variety. It would be important to provide the soil depth that can be explored by the root system to get an idea of the water reserve (large or small) available to the plant (and therefore potential water stress).
- The current study was for 6 weeks from growth stage V2 to growth stage VT (last week of April 2023 to last week of June 2023). We have not recorded the LAI till July 2023. The maize variety was “Dent corn”. We have not measured the root systems but in literature, it is reported that maize root length varies between 1 and 1.5 meters.
- Figures 5 and 6 could be improved (font size, box, grid, etc.).
- Figures 5 and 6 have been improved according to reviewer suggestion.
- I do not recommend using "approximately" or "around" (line 298), which are not « countable ». I suggest giving a range or an average value or any other indication that is not open to interpretation by the reader.
- We have replaced it with an average value of 3 W m-2
- Figures 5, 6 and 7 show envelope curves. What does the envelope correspond to? Unless I'm mistaken, I don't have the information. I think it's important to mention this in the legends so that each of these figures can stand on its own.
- We have changed the figure 5, 6, and 7 in the revised manuscript. In the revised figures, symbols correspond to different heights of measurements with bands corresponding to +/- one standard error.
Despite these comments, many of which are formal, I find this new system interesting and relevant for such energy storage estimates.
Thank you for your thoughtful feedback and for finding our system interesting and relevant for energy storage estimates. We greatly appreciate your recognition of the potential of our work.
We have carefully considered all the comments you provided and have addressed them in the revised manuscript.
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AC3: 'Reply on RC3', Taqi Raza, 01 Dec 2024
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