Estimating the Evaporative Cooling Effect of Irrigation within and above Soybean Canopy
Round 1
Reviewer 1 Report
Abstract :
- Why the name of studied plant did not mention in abstract.
- What about generality of your model? Is it applicable for other plant species? This also can affect the title of your manuscript. If it is not a general method, then you should mention the name of specific plant species studied in title.
- You just applied the results of one-year experiment (1 August to 1 September 2020). Is it enough for your modeling?
- We know that the water shortage is an important problem for the future and “regular irrigation” is not possible in many critical regions of the world. How your model deal with this?
Introduction:
- Line 28-36: It is better to only focus on effects of global warming and heatwaves on crops, agricultural production, and sustainable food production, instead of human health and human mortality.
- Line 91: … above the canopy of what?
M&M:
- Lines 115-125: This section is not belonged to Materials and Methods section.
Other comments:
Abstract:
Line 20-24: Font is changed …
Table 3: Please correct the “R2”
Figures 4 and 5: Please correct the “R2”
Author Response
Dear reviewer,
thanks for the constructive comments. We provided point-by-point responses to them. please find the attachment.
Best regards,
Fatemeh Ghafarian
Author Response File: 
Author Response.docx
Reviewer 2 Report
General comment:
The study presents the modeling and experimental results of the evaporative cooling effect of irrigation within and above the crop canopy. The study is interesting but lacks the manuscript organization (intro and methods sections) and missing necessary information (for the experiment) in the methods section.
Introduction: This section is not comprehensive and not clear why this study was needed. Try to focus on the agricultural crops and impacts from heatwaves, remove the urban cooling literature (e.g., line 44-47) as the study is related to agricultural crops. Add relevant literature about the model used in this study.
Methods: not detailed and clear information on experimental set-up, for example, not clear if air temperature or canopy temperature difference was evaluated, no detailed information on based on rainfed vs irrigated experiment, and results reported based on what time after irrigation. Please see specific comments for further details:
Specific comments:
Line 20: ….performance of the model with….?
Line 94: report the grass type
Line 108-114: since the study was conducted during 1 August to 1 September 2020, why the weather information during 2019-2019?
Figure 1: 2017-2019 (label) or 2019-2020 (title)?
Line 115-137: this is not methods, either remove or move to the introduction section
Line 158: 1 August to 1 September 2020 reported in line 108.
Section 2.2.1: not clear if the experiment was setup for canopy temperature or air temperature, please distinguish these and explain clearly
Section 2.2.2: Why LAI was measured? and during July-August, which is out of the experiment period (1 August – 1 September)
Methods section: please add more on at what time after irrigation the measurement was taken, and results presented in this study (after 5 minutes? 30 minutes?)
Section 2.3.1: explain how temperature (air?) was estimated above canopy (eq. 2?) and below canopy (eq. 2?). If air temperature was measured, report how the above and below canopy sensor heights were adjusted during the experiment: above canopy (constant height above canopy?) and below canopy (constant height above ground surface?)
Line 231-233: under canopy is only evaporation?
Section 3.1: this is not the result, remove these paragraphs or move to the methods section
Results section: organize this section with respect to the revised methods section. Also, separate the results for grass and soybean as these crops response differently due to different canopy structures.
Author Response
Dear reviewer,
thanks for the constructive comments. We provided point-by-point responses to them. please find the attachment.
Best regards,
Fatemeh Ghafarian
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
All comments have been addressed by authors.
Author Response
Dear reviewer,
we appreciate the constructive suggestions of the reviewer.
Author Response File: Author Response.docx
Reviewer 2 Report
In response to my previous comments from lines 49-64: the authors mentioned that irrigation of crops may be the benefit to urban cooling, but the current form of the manuscript doesn’t have any results related to this presumption. If this is the presumption as highlighted in the introduction section, the authors much show how the irrigation-derived evaporative cooling benefits urban areas in the results section.
Line 108-114: the authors did not address my previous comment. If the study period is between 1 August to 1 September 2020, it’s irrelevant to show the climate data from 2019-2019. The authors responded that the data from 2017-2019 will provide historical climate change, two years (2017-2019) is not historical.
Figure 1: not addressed by authors
Line 117: …both crops’ canopies….? The study was conducted over soybean only?
Section 2.2.1: During the development phase, the canopy height did not change rapidly?
Line 173-178: if the main objective of this study was to evaluate the air temperature difference, the authors need to explain the need of canopy temperature measurement
Section 2.3.1: this section is not necessary, doesn’t provide any additional information. Already mentioned that PET can be estimated by FAO method in line 129-130.
Line 221-226: these sentences read as the authors are comparing canopy temperature (Tc) from model (Eq. 5) with measured Tc from thermal camera? If so, how these Tc comparisons relate with the evaporative cooling as suggested by the title of the manuscript?
Section 2.3.2: measurements were continuously taken at the 1-minute interval for 30 days, but the authors didn’t mention the time after irrigation that is presented in this study. For example, how the temperature difference varied with time, e.g., 2 degrees after 5 minutes, 4 degrees after 10 minutes, and so on. These will change all the results and interpretations from this study.
Author Response
Dear reviewer(s),
in the new version of the manuscript, we considered your valuable suggestions, which did not alter the original methodology of the study but improved it. We appreciate the constructive suggestions of the reviewer.
Comments and Suggestions for Authors
In response to my previous comments from lines 49-64: the authors mentioned that irrigation of crops may be the benefit to urban cooling, but the current form of the manuscript doesn’t have any results related to this presumption. If this is the presumption as highlighted in the introduction section, the authors much show how the irrigation-derived evaporative cooling benefits urban areas in the results section.
In the literature, the cooling effect of vegetation is predominantly discussed in the context of urban heat islands and the broader context of anthropogenic climate change [1][2][3]. Our experimental research for this study focused on agricultural land use. However, a cooling effect as such of irrigated land has, in general, no imminent agricultural usefulness but provides an added microclimatic and ecological effect services of land use. The basic experimental setup of the study can be adapted to other crop types - we compare irrigated and non-irrigated crops of the same type, here soybeans.
In the context of urban cooling strategies, it can demonstrate the effects of irrigation of urban vegetation on microclimate. Nevertheless, we kept the conclusion general: (line 404-412): “With this model, we are now able to assess the potential cooling effect of crop irrigation as a possible contribution to a cooling-service design at the landscape scale.” An incidental application to non-rural landscapes, e.g. for the irrigation of urban grass, is evident.”
Line 108-114: the authors did not address my previous comment. If the study period is between 1 August to 1 September 2020, it’s irrelevant to show the climate data from 2019-2019. The authors responded that the data from 2017-2019 will provide historical climate change, two years (2017-2019) is not historical.
The reviewer is right, these 4 years of local climate change cannot be represented as historical climate changes. Considering the scale of the field in this study, we wanted to give an impression of how the weather has varied during recent years in certain months (June, July, and August).
- Figure 1: not addressed by authors
This is now corrected in the manuscript (line 114).
- Line 117: …both crops’ canopies….? The study was conducted over soybean only?
The observation is correct, it is now replaced by “crop’s canopy “.
- Section 2.2.1: During the development phase, the canopy height did not change rapidly?
The crop passed the initial stage of its growth by the end of July and its height reached 60.5cm. During the development stage of growth, the crop grows slowly to reach the highest length (64.8cm) and in the last stage crop’s height started to decrease (60.3cm). Therefore, the rapid height change of this crop occurred in the initial stage, not the development or last stage.
- Line 173-178: if the main objective of this study was to evaluate the air temperature difference, the authors need to explain the need of canopy temperature measurement.
In this section, we refer to the ancillary use of thermal cameras not as input data for the model. Thermal camera measurements relate to surface temperature helped us to identify the surface temperature differences of the irrigated and non-irrigated sides. We need exact sensor measurements, both above and below the canopy, which differ significantly. We also refer to the subject of our study which relates to “evaporative cooling effect of irrigation within and above a soybean canopy”.
- Section 2.3.1: this section is not necessary, doesn’t provide any additional information. Already mentioned that PET can be estimated by FAO method in line 129-130.
We agree with the reviewer. The section is now merged with section 2.3.2 under the new section ‘2.2 modelling the air temperature differences under adiabatic processes’.
- Line 221-226: these sentences read as the authors are comparing canopy temperature (Tc) from model (Eq. 5) with measured Tc from thermal camera? If so, how these Tc comparisons relate with the evaporative cooling as suggested by the title of the manuscript?
No, in this study, we are comparing canopy temperature from the model with the air temperature measured by sensors (TFD 500; Temperatur–Feuchte–Datenlogger). Tc in Eq.5 is the air temperature after evapotranspiration and was compared with Tc measured by sensors that are located in the field above and below the canopy.
We checked the lines 221-226 and did not find any mentioning of the thermal camera (data).
The Tc from the thermal camera was just used as ancillary information to prove the difference in the absolute surface temperatures between irrigated and non-irrigated sides of the field.
- Section 2.3.2: measurements were continuously taken at the 1-minute interval for 30 days, but the authors didn’t mention the time after irrigation that is presented in this study. For example, how the temperature difference varied with time, e.g., 2 degrees after 5 minutes, 4 degrees after 10 minutes, and so on. These will change all the results and interpretations from this study.
The timing of the irrigation was presented in Table 1. The cooling effect we are examining does not relate to the process of irrigating the field as such. In fact, the six days where irrigation took place were omitted (line 247). The specific type of irrigation management explained in lines 126-135 is based on the cumulative daily water deficit with an eye to avoid the water stress of the plant.
The different timing of the irrigation along with different meteorological conditions during the experimental period influenced the pattern of the evaporative cooling effect of the crop in the following days. Our model can simulate this pattern between each two irrigation practices when the crops are under no water stress.
References:
[1] K. Gao, M. Santamouris, and J. Feng, “On the cooling potential of irrigation to mitigate urban heat island,” Sci. Total Environ., vol. 740, p. 139754, Oct. 2020.
[2] Q. Yang, X. Huang, and Q. Tang, “Irrigation cooling effect on land surface temperature across China based on satellite observations,” Sci. Total Environ., vol. 705, p. 135984, Feb. 2020.
[3] C. Wang, Z. H. Wang, and J. Yang, “Urban water capacity: Irrigation for heat mitigation,” Comput. Environ. Urban Syst., vol. 78, p. 101397, Nov. 2019.
Author Response File: Author Response.docx
