the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Oct 2023
Modelling reference evapotranspiration of green walls (ET0vert)
Abstract. Green walls, façade greenery, living walls – vertical building greening as part of urban green infrastructure are measures for climate sensitive urban design, for water management and microclimate regulation. Strategic integration of green walls into local water and energy cycles requires prediction of evapotranspiration, considering the individual design, plant species, and building characteristics. Available models address horizontal surfaces but disregard vertical particularities and urban conditions, e.g., reduced direct radiation, spatial patterns of radiation on the wall due to building orientation and shading obstacles, and very heterogeneous wind fields that are influenced by rough surfaces, canyons, and adjacent wind barriers. We present a verticalization model, ET0vert, for the reference crop evapotranspiration ET0 (FAO) based on a sensitivity analysis. It comprises the adaptation of solar radiation and wind to the individual situations in front of a wall or facade. The accuracies of the model predictions are evaluated for (i) remote climate station data (horizontal reference plane), (ii) interpolated climate data (both horizontal and vertical reference plane) and (iii) on-site measured climate data (vertical reference plane, both not height-adapted and height-adapted) as input. We validate the model with data for a one-month reference period (25/07/2014 – 29/08/2014) from a weighable lysimeter with Fallopia baldschuanica greening of a 12 m high wall in Berlin, Germany.
Regarding individual meteorological input parameters, we found high relevance of both vapor pressure deficit (VPD) and solar radiation (RS) for the study area. Using VPD and RS, respectively, a linear model could explain 90 % and 85 % of daily ET0 variances. No such relationship could be detected for wind speed, but for maximum and minimum wind speed.
Compared to remote horizontal input data, verticalization of input data (RS and wind) reduced overestimations of ET from about 90 % to 14 % and 27 % for the daily and hourly resolution, respectively. If onsite climate data is available, deviations are reduced to 9 % and 5 % for the daily and hourly resolution. Height-adaptation of input data resulted in further improvements of the prediction accuracies (1 % and 2 % deviation for hourly and daily resolution).
We conclude that simply using remote horizontal climate data for calculating ET of green walls is not advisable. Instead, any input data, onsite measured or remote climate station data, should be verticalized and preferably height-adapted.
The verticalized model predicts the hourly and daily evapotranspiration of green walls necessary for e.g., irrigation planning, building energy simulations or local climate modeling.
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Status: closed
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RC1: 'Comment on hess-2023-221', Anonymous Referee #1, 02 Nov 2023
The authors describe the quality of a methodology to estimate reference ET of a vertical green wall in an experimental setup.
My overall impression of the article is that it feels a bit shallow, especially in the methodology. The Introduction reads more like a review article, being quite extensive in digging up older studies on the subject of ET and vertical walls, and the relation to localised data usage. However, I was struggling to see exactly what the point is the authors are trying to make here with this extensive literature research. The subsection on Measuring ET just lists several ET values from different studies - is this really necessary? It would be much more easily accessible if it were tabulated for instance so the Introduction can be made much more concise and to the point. The authors don't reach their objective of the study until page 5, at which point it was still fairly unclear to me what the actual point of the paper is, how the authors will tackle the issue, exactly what the issue is etc.
In the Theory section, ne particular sentence that struck me as odd was in line 220-222, mentioning that VPD is highly influential on ET, is height-dependent on wind speed, but that would require CFD or local measurements so the authors just omit it...? I find it hard to justify this choice given that the authors explicitly state its importance on ET only to then ignore the variations.
The Material/Methods section then feels lacking in some details: the scientific quality of the article would benefit some more detailed description or visualization of the measurement setups (both at the experimental site and the external measurement sites). Especially the location of the sensors at the experimental site are important, given the strong non-linearity of environmental properties in the urban area, with wind speed as the most obvious one. The authors very briefly touch upon wind influence but seem to conclude that it is not important for ET estimation - this might also have to do with the location of the wind measurements and the behaviour of the wind at its microclimate. Another example of missing clarity of the interpolation of climatological data from the of-site stations - how is this done? Is the landscape taken into account at all? What method of interpolation has been used, has this been verified, is it susceptible to errors etc etc. These details are crucial since they can influence the validity of the conclusions.
The Results section has a lot of difficult to read text, formatted with Rs(remote_TXL) etc etc, with all the parentheses and mentioned values makes the text a slog to get through. I'd advise the authors to see if these cannot be summarized in a table as well, and to really get to the focus of the results. The figures themselves are also quite hard to read, especially in print. The results also feel like they don't quite go deep enough in explaining things, with some statements that feel fairly obvious (e.g. radiation values being of because the wall is shaded for a part of the day - something very obvious that you could have corrected for beforehand). So most of the results feel like quite generic statements, even though there are very interesting tidbits of knowledge in there that could really help judging the quality of using off-site data or not. For instance the possible influence of night-time longwave radiation on night-time ET - interesting stuff to explore.
In summary, the structure of the text and figures as well as the phrasing of the aim and results of the paper could use some serious work, but with some more in-depth information on the setup, as well as a more in-depth look at the actual results, would result in quite an interesting paper
Citation: https://doi.org/10.5194/hess-2023-221-RC1 -
CC1: 'Reply on RC1', Karin Hoffmann, 05 Nov 2023
Dear Referee,
thank you very much for reviewing our manuscript. We are thankful for your constructive comments. They will help us to improve the article and contribute to a better understanding of our work.
As soon as we have received feedback from the second reviewer, we will begin our revision and will answer all your comments in detail.
With best regards,
Karin Hoffmann for the author team
Citation: https://doi.org/10.5194/hess-2023-221-CC1 -
AC1: 'Reply on RC1', Thomas Nehls, 25 Mar 2024
Dear Reviewers,
we are very thankful, that you took the time to review our contribution. We discussed all your comments among the authors, and we will revise the manuscript thoroughly. From the constructive comments of both of you we learned that we:
- must sharpen and shorten our manuscript, including a concise presentation of the state of the art (table),
- must add information and a drawing on the experimental setup, now only given in a referenced paper, and
- must present model concept, deriving Kc and simulations using remote data clearer.
We compiled the detailed responses to your comments in the attached file.
Best regards
Thomas Nehls on behalf of the authors
-
CC1: 'Reply on RC1', Karin Hoffmann, 05 Nov 2023
-
RC2: 'Comment on hess-2023-221', Anonymous Referee #2, 02 Feb 2024
General:
- The manuscript is presenting a modelling concept for evapotranspiration determination of green walls, which is a relevant topic, specifically nowadays when greening infrastructure is a highly recommended measure to reduce urban heat and prevent drought. However, to the reviewer’s opinion, the method chosen is inappropriate due to violation of underlying (homogeneity) assumptions in the reference method chosen.
- Selecting (much) simpler approaches (e.g. Priestley-Taylor) might be more suitable and should be exploited.
- An additional analysis, examining the influence of actually received radiation, might provide interesting insights.
- Reasoning and explanations are often inaccurate/incomplete, possibly due to leaps of thought that are not well explained.
- Certain parameters are not taken into account in the analysis simply because they were not available: this is not justifiable reason (and in itself a reason to reject the manuscript).
- The added abbreviation list is appreciated, but still abbreviations should be explained at first use, to facilitate easy reading.
- English here and there might need slight polishing.
Summarizing I recommend either reject (and submit to other journal) or major revision. The above comments are detailed below:
Text:
Section 1. “Introduction”.
Page 2, line 42: Remove “on”
Page 3, line 56: “contributions of 13% up to 73%” ; reviewer assumes these percentages are the relative contribution to the total cooling effect. If yes, this should be explained more clear. In addition the total amount of cooling should be specified in one way or another to make more clear what are the quantitative effects.
Page 3, line 85: “results cannot be generalized”: it is unclear why not. Results can just be compared to nearby standard meteo station data as is the case with other ET observations; They often also do not show a straightforward relation to the ET observations in a standard meteo station, but that is not a reason not to use standard meteo station data for generalization.
Page 3, line 90: Replace “with” by “where” and replace “delivering” by “delivered the”
Page 3, line 93: Unclear which validation is meant here. Also unclear to what the correlation refers (correlation between what?).
Page 4, line 94: Replace “included” by “used”
Page 4, line 97/98: Unclear why surface temperature is just a proxy for ET; please explain more.
Page 4, line 101: Unclear to which regression the correlation figures refer and unclear what are the “panel system” and the “planter box system”; please explain further.
Page 5, line 136: “To refine ….in the model”: Unclear what is meant here; please explain further.
Section 2. “Theory”Page 6, line 179: “all these parameters need to be verticalized”. Reviewer would like to remark that other plants, also in a non-urban area, have vertical dimensions and, especially in a non-homogeneous environment, may or may not experience sensitivity to the parameters mentioned (Rn, Rs, u, T, VPD) in a manner that is not independent of height. Whereas it is obvious that the influence of mentioned parameters is varying with height in such circumstances, employing (simple linear) regressions to correct for this (multiple) influences is violating the original homogeneity assumptions underlying the PM approach (so-called “big leave approach”), reason for which it would be more just to employ such regressions to much simpler approaches, or simply to standard met-station observations of ET (when fully 3-D models, which in principle are required for conditions like the present, are not an option). Moreover, every individual site would require on-site calibration (which will depend on its surroundings), making the approach unsuitable for “universal” application. In this context one would expect considerations such as relatively homogeneous units (the well-known Local Climate Zone concept by Stewart and Oke (2012) for example) to be applied, or at least mentioned.
Page 7, section “Wall heat flux”: it is unacceptable that based on an observation/estimation during summer period the decision is taken that “G might be 0 on a daily basis and during the day”
Page 7, lines 220-221: the fact that certain measurements or simulations are not available does not justify simply ignoring them!
Page 7, line 232: Reference is missing for the “formula” presented. The windspeed profile depends on (effective) surface roughness and atmospheric stability; the approach presented is way too simplistic in an urban area.
Section 3. “Material and Methods”
Page 8, line 256: “It”; what is meant here?
Page 9, line 265: “Both” is used whereas there are 4 parameters mentioned.
Page 9, line 283: Remove “in”
Page 9, line 283/284: “calculated according to Perez et.al., 1991” mentioning only the reference when discussing a crucial calculation is insufficient; provide the equation(s) used and explain what is done. This is also valid for several other parts of the manuscript; it is not clear what is done exactly; see also next remark(s).
Page 9, line 291: “factors ku…were derived”: unclear what has happened here exactly (other than a logarithmic model was fitted. More detailed explanation is required.
Page 9, line 292: “Temperature …height dependent”: No justification is provided for this assumption.
Page 10, line 297: “therefore eq. 4 has been used”: No justification is provided.
Page 10, lines 307-308: “using the mapped horizon”: Again; unclear what has been done exactly; more detailed explanation is required.
Page 11, lines 343-354: these figures will vary dramatically from site to site and presumably are driven (only) by shadows received at the urban location (“on-site”); either caused by the immediate surrounding of the site, or by clouds passing by (as is mentioned). To the reviewers opinion an exercise investigating solely the influence of radiation on the regression (using a simple ET-approach, or directly met-station data of ET, instead of Penman-Monteith) would be more useful here.
Page 12, line 367: “climate station”: guess this is “meteo station”? if not, mention/define the difference.
Page 12, line 370: Replace “comparably” by “relatively”
Page 13, line 400: “However, ….accuracy”: add the reference.
Page 13, line 412: “based on the PM equation”: as mentioned previously; the underlying assumptions of PM are violated, instead a 3D model should in principle be used. If that is not possible/desirable, a simple regression of ET meteo station data with onsite data and some parameters (radiation being the most important one) would be a more logical approach.
Page 13, line 413: “which climate variable to focus”; as also mentioned by the authors themselves, Rs is the most relevant, especially for green walls.
Page 13, line 420: “Kc = 1.21”: from where is this value taken/calculated?
Page 14, line 425: Replace “could be” by “is”
Page 14, lines 431-434: The authors mention here that the variation in received shortwave radiation between the distant and on-site locations is not very drastic in summer (i.e. the period of study) and therefore the relation found is valid. However, they also state that shortwave radiation is the main driver (showing the highest correlation), which would plee (if not demand) for examining this effect in the other seasons as well. In this context instead of “summing” & “verticalizing” the PM approach it would be good to see:
- What if simply radiation reduction (due to shadow) is taken into account?
- What if a very simple ET model/regression (e.g. the Priestley-Taylor approach) is used instead of PM? Especially given the fact that a (rather arbitrarily) Kc coefficient of 1.21 is applied (to reduce differences)
Page 15, lines 459-460: “First, ET is generally estimated too high”: This is not a reason but an observation.
Page 15, lines 462-466: It is unclear to the reviewer what the authors exactly mean here; please provide a more clear description of the processes that occur between the plant, soil and water transport out and into the lysimeter observation.
Page 15, line 473: What is meant with “vegetation period”? Please explain, also to clarify the remarks made with respect to soil evaporation versus transpiration rates.
Page 16, line 477: “Adjusting Kc”: unclear how it was adjusted, for which period and on what grounds. Please explain further.
Page 16, line 487: “might impede the accuracy of the lysimeter”: Unclear why this would impede the accuracy of the lysimeter; water is still in the plant so it would still be weighed by the lysimeter, is it not? In addition it is not clear how the lysimeter functions when plants are connected to vertical walls; would this not affect the weighing? Please explain n more detail these aspects.
Page 16, line 498: “Penman-Monteith approach”, probably Priestley-Taylor approach (which is using radiation/conduction mainly) would be better suited.
Page 16, line 498: What is meant with “greater comparability”?
Page 16, line 499: “empirically adjust it with a crop factor”; could also be valid for (all) other approaches to correct/adjust them with a (crop)factor.
Page 16, line 499: “Stomatal resistance is not (only) a plant-specific parameter.
Figures.
Figure 2:
- It is unclear on which equations the shown profiles are based (especially those for windspeeds and, thus, ET).
- I assume the Rs correction-profile is based on local site DEM specifics, but this remains unclear from the text. Instead of speaking of “verticalization”, one could also reason that this is just a manner of “calculating” the correct (i.e. real) amount of Rs that should be input to the PM-equation.
Figure 3:
- In the figure there is only 1 y-axis (showing ET0(remote_TXL) (mm d-1), but the values in the left panel are lower than in the middle and right panel, which is not possible. Middle and right panel (seem to) show similar y-values.
Figure 6:
- It would be interesting to also plot the net radiation (or shortwave during day and longwave radiation during the night) in the different panels.
Citation: https://doi.org/10.5194/hess-2023-221-RC2 -
AC2: 'Reply on RC2', Thomas Nehls, 25 Mar 2024
Dear Reviewers,
we are very thankful, that you took the time to review our contribution. We discussed all your comments among the authors, and we will revise the manuscript thoroughly. From the constructive comments of both of you we learned that we:
- must sharpen and shorten our manuscript, including a concise presentation of the state of the art (table),
- must add information and a drawing on the experimental setup, now only given in a referenced paper, and
- must present model concept, deriving Kc and simulations using remote data clearer.
We compiled the detailed responses to your comments in the attached file.
Best regards
Thomas Nehls on behalf of the authors
Status: closed
-
RC1: 'Comment on hess-2023-221', Anonymous Referee #1, 02 Nov 2023
The authors describe the quality of a methodology to estimate reference ET of a vertical green wall in an experimental setup.
My overall impression of the article is that it feels a bit shallow, especially in the methodology. The Introduction reads more like a review article, being quite extensive in digging up older studies on the subject of ET and vertical walls, and the relation to localised data usage. However, I was struggling to see exactly what the point is the authors are trying to make here with this extensive literature research. The subsection on Measuring ET just lists several ET values from different studies - is this really necessary? It would be much more easily accessible if it were tabulated for instance so the Introduction can be made much more concise and to the point. The authors don't reach their objective of the study until page 5, at which point it was still fairly unclear to me what the actual point of the paper is, how the authors will tackle the issue, exactly what the issue is etc.
In the Theory section, ne particular sentence that struck me as odd was in line 220-222, mentioning that VPD is highly influential on ET, is height-dependent on wind speed, but that would require CFD or local measurements so the authors just omit it...? I find it hard to justify this choice given that the authors explicitly state its importance on ET only to then ignore the variations.
The Material/Methods section then feels lacking in some details: the scientific quality of the article would benefit some more detailed description or visualization of the measurement setups (both at the experimental site and the external measurement sites). Especially the location of the sensors at the experimental site are important, given the strong non-linearity of environmental properties in the urban area, with wind speed as the most obvious one. The authors very briefly touch upon wind influence but seem to conclude that it is not important for ET estimation - this might also have to do with the location of the wind measurements and the behaviour of the wind at its microclimate. Another example of missing clarity of the interpolation of climatological data from the of-site stations - how is this done? Is the landscape taken into account at all? What method of interpolation has been used, has this been verified, is it susceptible to errors etc etc. These details are crucial since they can influence the validity of the conclusions.
The Results section has a lot of difficult to read text, formatted with Rs(remote_TXL) etc etc, with all the parentheses and mentioned values makes the text a slog to get through. I'd advise the authors to see if these cannot be summarized in a table as well, and to really get to the focus of the results. The figures themselves are also quite hard to read, especially in print. The results also feel like they don't quite go deep enough in explaining things, with some statements that feel fairly obvious (e.g. radiation values being of because the wall is shaded for a part of the day - something very obvious that you could have corrected for beforehand). So most of the results feel like quite generic statements, even though there are very interesting tidbits of knowledge in there that could really help judging the quality of using off-site data or not. For instance the possible influence of night-time longwave radiation on night-time ET - interesting stuff to explore.
In summary, the structure of the text and figures as well as the phrasing of the aim and results of the paper could use some serious work, but with some more in-depth information on the setup, as well as a more in-depth look at the actual results, would result in quite an interesting paper
Citation: https://doi.org/10.5194/hess-2023-221-RC1 -
CC1: 'Reply on RC1', Karin Hoffmann, 05 Nov 2023
Dear Referee,
thank you very much for reviewing our manuscript. We are thankful for your constructive comments. They will help us to improve the article and contribute to a better understanding of our work.
As soon as we have received feedback from the second reviewer, we will begin our revision and will answer all your comments in detail.
With best regards,
Karin Hoffmann for the author team
Citation: https://doi.org/10.5194/hess-2023-221-CC1 -
AC1: 'Reply on RC1', Thomas Nehls, 25 Mar 2024
Dear Reviewers,
we are very thankful, that you took the time to review our contribution. We discussed all your comments among the authors, and we will revise the manuscript thoroughly. From the constructive comments of both of you we learned that we:
- must sharpen and shorten our manuscript, including a concise presentation of the state of the art (table),
- must add information and a drawing on the experimental setup, now only given in a referenced paper, and
- must present model concept, deriving Kc and simulations using remote data clearer.
We compiled the detailed responses to your comments in the attached file.
Best regards
Thomas Nehls on behalf of the authors
-
CC1: 'Reply on RC1', Karin Hoffmann, 05 Nov 2023
-
RC2: 'Comment on hess-2023-221', Anonymous Referee #2, 02 Feb 2024
General:
- The manuscript is presenting a modelling concept for evapotranspiration determination of green walls, which is a relevant topic, specifically nowadays when greening infrastructure is a highly recommended measure to reduce urban heat and prevent drought. However, to the reviewer’s opinion, the method chosen is inappropriate due to violation of underlying (homogeneity) assumptions in the reference method chosen.
- Selecting (much) simpler approaches (e.g. Priestley-Taylor) might be more suitable and should be exploited.
- An additional analysis, examining the influence of actually received radiation, might provide interesting insights.
- Reasoning and explanations are often inaccurate/incomplete, possibly due to leaps of thought that are not well explained.
- Certain parameters are not taken into account in the analysis simply because they were not available: this is not justifiable reason (and in itself a reason to reject the manuscript).
- The added abbreviation list is appreciated, but still abbreviations should be explained at first use, to facilitate easy reading.
- English here and there might need slight polishing.
Summarizing I recommend either reject (and submit to other journal) or major revision. The above comments are detailed below:
Text:
Section 1. “Introduction”.
Page 2, line 42: Remove “on”
Page 3, line 56: “contributions of 13% up to 73%” ; reviewer assumes these percentages are the relative contribution to the total cooling effect. If yes, this should be explained more clear. In addition the total amount of cooling should be specified in one way or another to make more clear what are the quantitative effects.
Page 3, line 85: “results cannot be generalized”: it is unclear why not. Results can just be compared to nearby standard meteo station data as is the case with other ET observations; They often also do not show a straightforward relation to the ET observations in a standard meteo station, but that is not a reason not to use standard meteo station data for generalization.
Page 3, line 90: Replace “with” by “where” and replace “delivering” by “delivered the”
Page 3, line 93: Unclear which validation is meant here. Also unclear to what the correlation refers (correlation between what?).
Page 4, line 94: Replace “included” by “used”
Page 4, line 97/98: Unclear why surface temperature is just a proxy for ET; please explain more.
Page 4, line 101: Unclear to which regression the correlation figures refer and unclear what are the “panel system” and the “planter box system”; please explain further.
Page 5, line 136: “To refine ….in the model”: Unclear what is meant here; please explain further.
Section 2. “Theory”Page 6, line 179: “all these parameters need to be verticalized”. Reviewer would like to remark that other plants, also in a non-urban area, have vertical dimensions and, especially in a non-homogeneous environment, may or may not experience sensitivity to the parameters mentioned (Rn, Rs, u, T, VPD) in a manner that is not independent of height. Whereas it is obvious that the influence of mentioned parameters is varying with height in such circumstances, employing (simple linear) regressions to correct for this (multiple) influences is violating the original homogeneity assumptions underlying the PM approach (so-called “big leave approach”), reason for which it would be more just to employ such regressions to much simpler approaches, or simply to standard met-station observations of ET (when fully 3-D models, which in principle are required for conditions like the present, are not an option). Moreover, every individual site would require on-site calibration (which will depend on its surroundings), making the approach unsuitable for “universal” application. In this context one would expect considerations such as relatively homogeneous units (the well-known Local Climate Zone concept by Stewart and Oke (2012) for example) to be applied, or at least mentioned.
Page 7, section “Wall heat flux”: it is unacceptable that based on an observation/estimation during summer period the decision is taken that “G might be 0 on a daily basis and during the day”
Page 7, lines 220-221: the fact that certain measurements or simulations are not available does not justify simply ignoring them!
Page 7, line 232: Reference is missing for the “formula” presented. The windspeed profile depends on (effective) surface roughness and atmospheric stability; the approach presented is way too simplistic in an urban area.
Section 3. “Material and Methods”
Page 8, line 256: “It”; what is meant here?
Page 9, line 265: “Both” is used whereas there are 4 parameters mentioned.
Page 9, line 283: Remove “in”
Page 9, line 283/284: “calculated according to Perez et.al., 1991” mentioning only the reference when discussing a crucial calculation is insufficient; provide the equation(s) used and explain what is done. This is also valid for several other parts of the manuscript; it is not clear what is done exactly; see also next remark(s).
Page 9, line 291: “factors ku…were derived”: unclear what has happened here exactly (other than a logarithmic model was fitted. More detailed explanation is required.
Page 9, line 292: “Temperature …height dependent”: No justification is provided for this assumption.
Page 10, line 297: “therefore eq. 4 has been used”: No justification is provided.
Page 10, lines 307-308: “using the mapped horizon”: Again; unclear what has been done exactly; more detailed explanation is required.
Page 11, lines 343-354: these figures will vary dramatically from site to site and presumably are driven (only) by shadows received at the urban location (“on-site”); either caused by the immediate surrounding of the site, or by clouds passing by (as is mentioned). To the reviewers opinion an exercise investigating solely the influence of radiation on the regression (using a simple ET-approach, or directly met-station data of ET, instead of Penman-Monteith) would be more useful here.
Page 12, line 367: “climate station”: guess this is “meteo station”? if not, mention/define the difference.
Page 12, line 370: Replace “comparably” by “relatively”
Page 13, line 400: “However, ….accuracy”: add the reference.
Page 13, line 412: “based on the PM equation”: as mentioned previously; the underlying assumptions of PM are violated, instead a 3D model should in principle be used. If that is not possible/desirable, a simple regression of ET meteo station data with onsite data and some parameters (radiation being the most important one) would be a more logical approach.
Page 13, line 413: “which climate variable to focus”; as also mentioned by the authors themselves, Rs is the most relevant, especially for green walls.
Page 13, line 420: “Kc = 1.21”: from where is this value taken/calculated?
Page 14, line 425: Replace “could be” by “is”
Page 14, lines 431-434: The authors mention here that the variation in received shortwave radiation between the distant and on-site locations is not very drastic in summer (i.e. the period of study) and therefore the relation found is valid. However, they also state that shortwave radiation is the main driver (showing the highest correlation), which would plee (if not demand) for examining this effect in the other seasons as well. In this context instead of “summing” & “verticalizing” the PM approach it would be good to see:
- What if simply radiation reduction (due to shadow) is taken into account?
- What if a very simple ET model/regression (e.g. the Priestley-Taylor approach) is used instead of PM? Especially given the fact that a (rather arbitrarily) Kc coefficient of 1.21 is applied (to reduce differences)
Page 15, lines 459-460: “First, ET is generally estimated too high”: This is not a reason but an observation.
Page 15, lines 462-466: It is unclear to the reviewer what the authors exactly mean here; please provide a more clear description of the processes that occur between the plant, soil and water transport out and into the lysimeter observation.
Page 15, line 473: What is meant with “vegetation period”? Please explain, also to clarify the remarks made with respect to soil evaporation versus transpiration rates.
Page 16, line 477: “Adjusting Kc”: unclear how it was adjusted, for which period and on what grounds. Please explain further.
Page 16, line 487: “might impede the accuracy of the lysimeter”: Unclear why this would impede the accuracy of the lysimeter; water is still in the plant so it would still be weighed by the lysimeter, is it not? In addition it is not clear how the lysimeter functions when plants are connected to vertical walls; would this not affect the weighing? Please explain n more detail these aspects.
Page 16, line 498: “Penman-Monteith approach”, probably Priestley-Taylor approach (which is using radiation/conduction mainly) would be better suited.
Page 16, line 498: What is meant with “greater comparability”?
Page 16, line 499: “empirically adjust it with a crop factor”; could also be valid for (all) other approaches to correct/adjust them with a (crop)factor.
Page 16, line 499: “Stomatal resistance is not (only) a plant-specific parameter.
Figures.
Figure 2:
- It is unclear on which equations the shown profiles are based (especially those for windspeeds and, thus, ET).
- I assume the Rs correction-profile is based on local site DEM specifics, but this remains unclear from the text. Instead of speaking of “verticalization”, one could also reason that this is just a manner of “calculating” the correct (i.e. real) amount of Rs that should be input to the PM-equation.
Figure 3:
- In the figure there is only 1 y-axis (showing ET0(remote_TXL) (mm d-1), but the values in the left panel are lower than in the middle and right panel, which is not possible. Middle and right panel (seem to) show similar y-values.
Figure 6:
- It would be interesting to also plot the net radiation (or shortwave during day and longwave radiation during the night) in the different panels.
Citation: https://doi.org/10.5194/hess-2023-221-RC2 -
AC2: 'Reply on RC2', Thomas Nehls, 25 Mar 2024
Dear Reviewers,
we are very thankful, that you took the time to review our contribution. We discussed all your comments among the authors, and we will revise the manuscript thoroughly. From the constructive comments of both of you we learned that we:
- must sharpen and shorten our manuscript, including a concise presentation of the state of the art (table),
- must add information and a drawing on the experimental setup, now only given in a referenced paper, and
- must present model concept, deriving Kc and simulations using remote data clearer.
We compiled the detailed responses to your comments in the attached file.
Best regards
Thomas Nehls on behalf of the authors
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