Quantitative Analysis of the Impact of Meteorological Factors on Reference Evapotranspiration Changes in Beijing, 1958–2017

Round 1

Reviewer 1 Report

All my observations were introduced in the attached file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The paper "Difference analysis of potential evapotranspiration meteorological response factors in Beijing at different time scales" is focused on sensitivity analysis of FAO reference evapotranspiration to change of atmospheric conditions. The paper is in scope of J. Water, but the manuscript cannot be accepted for publication in its present form.

1. The English in the manuscript is not of publication quality and requires major improvement. Please carefully proof-read spell check to eliminate grammatical and stylistic errors. Native speaker manuscript spell-checking is preferable.
2. The manuscript title needs to be revised.
3. Authors declare that they analyze the potential evapotranspiration (PET). For this purpose they use the FAO method for estimation of reference evapotranspiration (ET0). The reference evapotranspiration is not absolutely equal to potential evapotranspiration. Reference evapotranspiration, that is sometimes incorrectly referred to as PET, is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop (grass), completely shading the ground, of uniform height and with adequate water status in the soil profile. Potential evapotranspiration is defined as the amount of evaporation that would occur if a sufficient water source in soil were available. PET of grassy and woody areas will be absolutely different. So, PET of your study area will be strictly dependent on vegetation cover. See e.g.: https://edis.ifas.ufl.edu/ae256

4. Keywords are available but they are incorrectly selected.
5. Study area is very poorly described. Map with geographical location of the study area is not shown. Climate and vegetation are not described. These points are very important especially in respect of spatial and temporal evaportanspiration analysis.
6. Discussion is very short and show comparisons with local studies only. There are no any comparisons with similar studies conducted in other geographical regions.
7. To analyze PET sensitivity I recommend to use a wider range of statistical methods.
8. A short report of the main achievements is presented in conclusion. Actually it is not enough for gut conclusion. I would like to see also e.g. "short addressing to opposing viewpoints and explaining why readers should align with your position; or any call for action or overview for future research possibilities".

Specific comments.

Line 15 Relative humidity is actually an atmospheric parameters depending on both air specific humidity and air temperature. So, in the study, authors looking for some relationships from PET and some dependent variables. It can result in increased uncertainties of data analysis.

Line 18 the same story. Relative humidity is actually dependent on air temperature (saturation water vapor pressure is a function of temperature). Following to P-M approach it is better to use water vapor deficit instead relative humidity.

Line 28 " PET change under climate change ". Sentence needs revision.

Lines 33-35 Such evapotranspiration definition was provided in many fundamental publications before 2010 .. I recommend to use appropriate reference.  

Line 42 The relationships between PET (not ET) and hydrological cycle are not clear.

Line 43 PET can be used as parameter in index to derive the climate moisture conditions.

" PET will likely cause regional climate variation ". I'm not sure that it is true.

Line 46 PET is independent on precipitation.

Lines 53-54 What is the sensitivity coefficient analysis method? Do you mean sensitivity analysis? Anyway, please provide some reference.

Lines 60-61 Sentences need revision

Lines 63-66 What is the difference between the selected method and any classical multivariate exploratory techniques?

Line 80 "Yin et al. (2010) found that" instead of " In 2010, Yin et al. (2010) found that "

Line 81 Is there any data about response of PET to various external factors in the areas situated outside of China?

Lines 84-85 It is doubtful statement, I guess.

Line 93 is situated at....

Line 94 Data from how many meteorological stations have been used?

Line 95 Rn was measured or calculated? It was calculated from sunshine duration, isn't it?

Line 97 Calculation of reference evapotranspiration.., it is more correct

Line 98 The reference evapotranspiration according to FAO ....

Line 103 psychrometric constant

Line 141 "multiannual averages" from all data sets?

Lie 147 Y- axis title is shifted to axis values

Line 152 Provided description of selected topic in the chapter is very shallow

Line 155 Units are not clear. What is it.... /10a ? 10 years or ..?

Line 157 Graph is shifted to the right

Line 158 evapotranspiration instead of "evapotranspiratio"

Line 163 " in the annual average daily sensitivity coefficient " is too long word-combination

Line 164 are shown

Line 189 Rn was measured or calculated?

Line 226 The sentence is disagreed with chapter title (daily time scale)

Lines 257-258 the sentence is unclear

Lines 280-281 the sentence needs revision

Line 285 Actually I cannot see in discussion any comparisons with results obtained in other geographical regions

Lines 297-303 It was already written in the result chapter

 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The paper was revised but it still needs significant improvements.

1. The English in the manuscript is not of publication quality and requires significant improvement. Very careful spell-checking is required to eliminate numerous grammatical and stylistic errors.

NATIVE SPEAKER MANUSCRIPT SPELL-CHECKING IS VERY NECESSARY.

2. The manuscript title is horribly formulated and cannot be accepted.
3. Appropriate keywords must be provided.
4. Study area is very poorly described. Climate and vegetation are not described. These points are very important especially in respect of spatial and temporal evaportanspiration analysis.
5. Discussion shows comparisons with local studies only. There are no any comparisons with similar studies conducted in other geographical regions. Some paragraphs repeat information from the result section. 
6. Reference evapotranspiration in the paper was calculated by PM approach. It was not measured. Thus, in this case authors try to find in the study some obvious relationships between dependent (included in PM model) variables. What is the novelty of such study?
7. Standard deviations must be shown in all graphs (figure 2) illustrating annual variability of meteorological parameters.
8. A short report of the main achievements is presented in conclusion. Actually it is not enough for conclusion. I would like to see also e.g. "short addressing to opposing viewpoints and explaining why readers should align with your position; or any call for action or overview for future research possibilities".

Author Response

Dear editor:

We sincerely appreciate the hard work of you on this manuscript. You have provided constructive comments to improve the quality of our manuscript. We have carefully revised the manuscript after considering all the comments. The following is the point-by-point response to all of the comments.

1 The English in the manuscript is not of publication quality and requires significant improvement. Very careful spell-checking is required to eliminate numerous grammatical and stylistic errors. Native speaker manuscript spell-checking is preferable.

Re: Thanks for the comments. According your suggestion, the grammar and spelling in the manuscript have been modified. by Liwen Bianji, Edanz Editing China (www.liwenbianji.cn/ac), and the Certificate of Editing as follows:

 

2 The manuscript title is horribly formulated and cannot be accepted.

Re: Thanks for your kind suggestion. The manuscript title has be revised. We carefully considered the research method and research content of the manuscript. Finally, we think that " Quantitative analysis of the impact of meteorological factors on ET₀ changes in Beijing, 1958–2017" is more suitable as the title of the article.

 

3 Appropriate keywords must be provided.

Re: Thanks for your reminder. The keywords have been modified to “meteorological factors; reference evapotranspiration; sensitivity coefficient; Penman-Monteith; contribution amount”.(Line28-29,P2)

 

4 Study area is very poorly described. Climate and vegetation are not described. These points are very important especially in respect of spatial and temporal evapotranspiration analysis.

Re: Thanks for your kind suggestion. We have added more description of the climate about the study area. The study area is situated in Beijing (39.4°–41.6° N; 115.7°–117.4° E), with an average elevation of 43.5 meters (Figure 1). It has a temperate semi-arid continental monsoon climate. The multi-year average temperature, wind speed and relative humidity are 12.1°C, 1.2 m/s and 52%, respectively. There are 2502h of annual sunshine, the effective accumulated temperature over 10°C is 4730°C, and the average daily solar net radiation is 171 W/m2. There are 185 frost-free days throughout the year on average. The annual rainfall and average evaporation are 540mm and 1021mm, respectively. More than 80% of the annual rainfall occurs from June to September. The soil is mainly sandy loam, suitable for the growth of various crops. A wheat-corn rotation is the traditional cultivation system in Beijing. With this system, the annual crop water requirement is 876mm, 453mm of which is for winter wheat and 423mm for summer corn(Liu et al., 2002; Zhang et al., 2011). Historical meteorological data from 1958 to 2017, including sunshine hours, T, RH and U, were obtained from China Meteorological Science(http://cdc.cma.gov.cn). (Line91-102, P2-3)

 

5 Discussion shows comparisons with local studies only. There are no any comparisons with similar studies conducted in other geographical regions. Some paragraphs repeat information from the result section.

Re: Thanks for your reminder. We have made further changes to the discussion section. In terms of sensitivity coefficient research，Suat et al (2006) found that the wind speed sensitivity coefficient fluctuated greatly, while the changes in the sensitivity coefficients of the other three meteorological factors (T_max, T_min and R_s)were smaller at the eight rigions in the United States. Liu et al.(2014) found that the first important factor was relative humidity in March, August, October, November and December, but in July was sunshine. Meanwhile, We found that RH was most sensitive to ET₀ at the start and end of the doy, while RN was the most sensitive factor in the middle part of the doy, which consistent with results of Hupet et al (2001), and Liu et al. (2009) and Zhao et al. (2013). In terms of contribution analysis, Zhao et al (2013) found that VPD contributes greatly to the annual scale ET₀ change. Huan et al.(2015) got different results and found that the wind speed was major contributes to ET₀ change. Also, Kang at al (2018) found that T, U and RH contribute greatly to monthly ET₀ changes and only T contributes greatly to the change of ET₀ in winter and spring, while wind speed and humidity contribute greatly to ET₀ in summer and annual scale. Yin et al. (2010) found that U and sunshine hours were the main meteorological factors controlling changes in ET₀ in China, with minor contributions from RH and T.It is worth noting that studies that combine the sensitivity coefficient of meteorological factors with the relative rate of change to characterize their contribution to ET₀ changes are rare in regions outside China.(Line287-294, 305-311,P12-13)

 

6 Reference evapotranspiration in the paper was calculated by PM approach. It was not measured. Thus, in this case authors try to find in the study some obvious relationships between dependent (included in PM model) variables. What is the novelty of such study ?

Re: Reference evapotranspiration is indeed calculated by the PM method in this paper. The input variables in the equation are simplified to four meteorological factors, including temperature (T), relative humidity (RH), wind speed (U) and net radiation (Rn). Although the ET₀ calculation method is systematic, the response law of meteorological factors in different time scales and regions to the reference evapotranspiration changes is quite different. Based on this, many scholars have done a series of studies.

Suat at al (2006) found that the wind speed sensitivity coefficient fluctuated greatly, while the changes in the sensitivity coefficients of the other three meteorological factors (T_max, T_min and Rs)were smaller at the eight rigions in the United States. Yin et al. (2010) found that U and sunshine hours were the main meteorological factors controlling change in ET₀ in China, with minor contributions from RH and T. Zhao et al (2013) found that VPD contributes greatly to the annual scale ET₀ change in Beijing area.Liu et al.(2014) found that the first important factor to ET₀ was relative humidity in March, August, October, November and December, but in July was sunshine in Beijing area. Huan et al. (2015) got different results and found that the wind speed was major contributes to ET₀ change in the middle area of Shandong province (China). Also, Kang et al (2018) found that T, U and RH contribute greatly to monthly ET₀ changes and only T contributes greatly to the change of ET₀ in winter and spring, while wind speed and humidity contribute greatly to ET₀ in summer and annual scale in Altay region (China). Yin et al. (2010) found that U and sunshine hours were the main meteorological factors controlling changes in ET₀ in China, with minor contributions from RH and T.

However, most research focuses only on certain time scales and does not consider the response of meteorological factors to ET₀ changes at different time scales. Meanwhile, the quantitative analysis of the impact of meteorological factors on ET₀ changes is imperfect in Beijing under different time perspectives. In this paper, we qualitatively analyzed the major meteorological factors on ET₀, and estimate the contributions of these meteorological factors to ET₀ combining sensitivity coefficient with the factor’s relative change rate on different time scales (including daily scale, monthly scale, seasonal scale and annual scale). Determining the causes of ET₀ change on different time scales will provide a theoretical basis for water resources regulation, irrigation system design and crop water management in Beijing.

 

7 Standard deviations must be shown in all graphs (figure 2) illustrating annual variability of meteorological parameters.

Re: Thanks for your kind suggestion. We have added the standard deviations in Figure 2.(Line155-165,P4-7)

 

8. A short report of the main achievements is presented in conclusion. Actually it is not enough for conclusion. I would like to see also e.g. "short addressing to opposing viewpoints and explaining why readers should align with your position; or any call for action or overview for future research possibilities".

Re: The future research hotspots have been proposed in the manuscript. The ET₀ response to climate change will differ with region and season because of the large spatial-temporal variability of the sensitivity coeffificients, at the same time, the characteristics of the relative change rate of meteorological factors are also closely related to the spatiotemporal scale, which leads to variability in the main ET₀ control factors on different time scales. Thus, an important focus area for research will be analyzing the contribution of meteorological factors to changes in ET₀ on larger spatial scales and different temporal scales.

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

The paper was significantly revised. But, some additional improvements of the manuscript before publishing are still very necessary.

English in revised manuscript is much better but not yet perfect. Writing style and grammar must be improved (especially in abstract and introduction).

I suggest to replace in the title "ETo" by "reference evapotranspiration"

What is delta in figures 2?

Result descriptions are too short in 3.1.

Conclusion is too short, includes the main results only, and needs revision. It should show the importance of the paper, restate the main ideas and arguments, clarify the result importance, suggest possible future research on the topic, etc.

Author Response

Dear editor:

We sincerely appreciate the hard work of you on this manuscript. You have provided constructive comments to improve the quality of our manuscript. We have carefully revised the manuscript after considering all the comments. The following is the point-by-point response to all of the comments.

 

1.English in revised manuscript is much better but not yet perfect. Writing style and grammar must be improved (especially in abstract and introduction).

Re: Thanks for the comments. Writing style and grammar has been improved by Liwen Bianji, Edanz Editing China (www.liwenbianji.cn/ac) in the last revision. Of course, there will be some small mistakes inevitably, we have made changes. Such as “Therefore, using the meteorological data from 1958 to 2017 of Beijing, China, ET₀ values over the last 60 years were calculated using Penman–Monteith method. The variation in ET₀ values was thus analyzed against four meteorological factors over different time scales.Over annual time scales, relative humidity and net radiation alternated as the main sensitivity factor; while over interannual time scales, the most sensitive factor was relative humidity during 1958–1979 and net radiation thereafter.(Line18-21, P1) ET₀ is also regarded as a key parameter for evaluating the efficiency of agricultural water-use.( Line41-42, P1) Ma et al. (2012) found that ET₀ within the Heihe River Basin was sensitive to climate factors on monthly and seasonal scales, identifying wind speed (U) as the dominant factor causing the change in ET₀ in this region.( Line70-73, P2) Historical daily meteorological data from 1958 to 2017, including sunshine hours, T, RH and U, were obtained from China Meteorological Science(http://cdc.cma.gov.cn).( Line102-104, P3) The format of Figure 5 and 6 has been modified.( Line244-245, P10-11; Line258-259, P11)”

 

2.I suggest to replace in the title "ETo" by "reference evapotranspiration"

Re: Thanks for your kind suggestion. The manuscript title has be revised. We carefully considered the “ET₀” and “reference evapotranspiration”, found that abbreviations in the title of the manuscript is neither standardized nor appropriate. Thus, we think that " Quantitative analysis of the impact of meteorological factors on reference evapotranspiration changes in Beijing, 1958–2017" is more suitable as the title of the article.( Line1-3, P1)

 

3. What is delta in figures 2?

Re: Thanks for your comments. The delta (δ) means standard deviations which is the content requested by the reviewer in the last revision, illustrating annual variability of meteorological parameters. A higher standard deviation indicates meteorological factor values are more dispersed, while a lower value indicates more concentrated. (Line174-177, P7)

 

4. Result descriptions are too short in 3.1.

Re: Thanks for your kind suggestion we added more description of the 3.1. And the more detail description has been added. Such as “On monthly scales, RN, T, RH, U and ET₀ ranges were 1.29-13.57MJ/m²/d, −3.65–26.48°C, 43.39%–75.25%, 1.30–2.31m/s and 29.10–154.14mm, with average values of 7.68MJ/m²/d, 12.45°C, 55.94%, 1.79m/s and 87.92mm, respectively, the changes in these four meteorological factors and ET₀ were consistent with those observed at daily scales, with similar trends in RN, T, RH, U and ET₀ (Figure. 2). The ranking of standard deviations of four climatic factors and ET₀ at daily scales was as follows: RH > T > RN > ET₀ >U, while in monthly, this ranking became ET₀ >RH > T > RN > U. This shows that RH and ET₀ are the most concentrated factors at daily and monthly time scale, respectively, while the U are the most scattered factor Whether it is daily or monthly time scale.( Line154-162,P4) The δ means standard deviations, illustrating annual variability of meteorological parameters. A higher standard deviation indicates meteorological factor values are more dispersed, while a lower value indicates more concentrated.( Line174-177,P7) The ranking of the four climate factors and ET₀ changes as follows ET₀ > T > RN > U> RH. Significance test results show that at a significant level of 0.05, the four climate factors and ET₀ all show significant changes. The five factors are all fitted with a linear function, and the ranking of correlation coefficients is RN> T> RH> U> ET₀.( Line182-186,P7) ”.

 

5. Conclusion is too short, includes the main results only, and needs revision. It should show the importance of the paper, restate the main ideas and arguments, clarify the result importance, suggest possible future research on the topic, etc.

Re: Thanks for your kind suggestion. The conclusion of the manuscript already contains main ideas and arguments, so we restate the importance of the paper and the future research on the topic. And the more contents have been added, such as “The contribution of each factor to ET₀ change was quantified by combining this sensitivity coefficient with the factor’s relative change rate over multiple time scales. Determining the main control factors of ET₀ change on different time scales will provide a theoretical basis for water resources regulation, irrigation system design and crop water management in Beijing. A limitation of this research is that the application of contribution rate analysis method was only done for Beijing, also, the ET₀ response to climate change will differ by region and season because of the large spatiotemporal variability of the sensitivity coefficients and relative change rate. Thus, an important focus area for research will be analyzing the contribution of meteorological factors to changes in ET₀ on larger spatial scales and different temporal scales.( Line377-384, P14) ”.

 

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.