Prediction of Future Spatial and Temporal Evolution Trends of Reference Evapotranspiration in the Yellow River Basin, China

Round 1

Reviewer 1 Report

Thank you for inviting me to review the paper “Prediction of future spatial and temporal evolution trends of potential evapotranspiration in the Yellow River Basin, China” by Jian et al.   Papers on what might be expected of PET change in semi-arid regions continue to be of particular importance. The impact of climate change raises the risk of impacting a very large number of people, as well as affecting local biomes. Hence this manuscript includes important information.   Please find below a set of main points:   1. Why did not use the Penman–Monteith to calculate PET? the Hargreaves does not consider net radiation and vapor presure deficit, which are very imporant factors influencing PET. It is better to compare PET calculated by the Hargreaves model and by the Penman-Monteith model.   2. There is some difference between pan evaporation and PET. It is inappropriate to call pan evaporation as measured PET. This should be noticed in the analysis of Fig. 7.   3. The authors attribute the enhanced increase in PET over the west region of YRB to higher elevation. This is one aspect. However, the more important reason may be related to regional climate. The west part, belong to semi-arid climate, would experience enhanced warming under global change due to land-atmosphere feedback. Therefore, the influence of soil moisure or precipitation on the climate tendency of PET should be analyzed or disscused.  

4. In figure 10, it is better to use more contrasting colors.

Author Response

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Reviewer 2 Report

Yellow River Basin is one of two longest rivers in China and plays a significant role in the ecology of the river basin. Its water balance state has an important impact on the utilization of water resources in the basin. As the key variable of land-atmosphere interaction, evapotranspiration is of great significance for water resources planning in the Yellow River basin to study its maximum evaporation potential in the context of climate change. This study shows that the Yellow River basin may face the problem of accelerated loss of surface water in the future. The analysis is sufficient, but there are still several questions to be further clarified:

 

1. In the introduction, this study chose statistical downscaling. Would you like to supplement its superiority over dynamic downscaling or the deficiency of dynamic downscaling in the Yellow River basin?

 

2. In figure 8, would you like to interpret the abrupt increase of PET between observation and prediction basing model output? And please show the fitting formulas for predicting PET under different emission scenarios.

 

3. In figure 11a, please explain why the principal component time coefficient increases first and then decreases in the low emission scenario (SSP126).

 

Author Response

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Reviewer 3 Report

 

 

The topic of this manuscript is very interesting. The authors use the latest CMIP6 climate model data and delta statistical downscaling to predict the spatial and temporal characteristics of potential evapotranspiration in the Yellow River Basin of China under future climate change scenarios, which is highly relevant for water resources research in global climate change sensitive areas. However, the following problems need to be addressed for accepting the paper for publication.

(1) The paper can be accepted for publication provided that it will be scientifically edited to follow strictly instructions of the journal. The list of references could be updated and enriched with more recent papers on the subject.

(2) Lines 7-24: In the abstract section, please consider whether to add the results of Morlet wavelet analysis and EOF analysis, while taking care not to exceed 300 characters.

(3) Line 137: “where it was located”, please check if this phrase is necessary here.

(4) Line 242: Please revise the way Fig. 8 expresses the different periods in the future to make it consistent with the full text.

(5) Line 256: The legend in Fig. 9g is missing the maximum value, please complete it.

(6) Lines 391-395: The sentence is convoluted and not that clear.

To sum up, the revision opinion of the manuscript is minor revision.

Author Response

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Reviewer 4 Report

Dear Authors,

Given that evapotranspiration is perhaps the most important and most difficult to monitor natural phenomenon/parameter, its assessment and precise prediction is extremely important. I think that you did a great job. You methodically, in detail explained all the steps that led to the final goal of your work, i.e. the results.

I have a few simple suggestions:

The term Potential Evapotranspiration (PET) is used less and less. I think it should be put out of use.. Most scientists in this field agree that the good term is Reference Evapotranspiration (ET0). And even the research you cite, such as the FAO (FAO 56 Drainage and Irrigation paper) recommendation for the alternative Penman-Monteith equation, it refers to Hargreaves Reference Evapotranspiration (ET0).

153 - give, cite some research that confirms the statement.

189 - you are showing a formula according to Hargreaves. This formula has undergone several modifications. So, here please be precise, specify exactly which formula was used and from which year.

The work is exciting and it was a pleasure to be its reviewer.

Author Response

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Round 2

Reviewer 1 Report

My concerns  have been fully addressed.