Identification of Regional Drought Processes in North China Using MCI Analysis

Round 1

Reviewer 1 Report

Line 38. This definition of drought is not correct. Drought is always expressed in relative terms, i.e. with reference to the climatic conditions considered normal for the period and site considered. On the other hand, the index used by the authors (MCI) is not properly a drought index. The graphs of Fig. 3 demonstrate this, because they indicate a higher drought occurrence in specific months. Drought can occur in any month and in any weather. The drought impacts, instead, differ from month to month and from area to area. The MCI index, being dependent on the MI variable, is more an indicator of water stress ( or water scarcity or drought impact). But not of drought. I would like the authors to think carefully about this. I'm not saying their analysis is wrong, but the definitions are important.

Line 76: Please check the numbers associated to references. For example [27] is not related to Liao et al. (2017) and so on.

eq.(2) : is the index indicated as I_i the MCI computed at the generic station i? Why didn't you use the acronym MCI_i?

eq.(2) and eq.(3). I notice a certain degree of arbitrariness in the calculation of the MCI index. For example, in the work of Wang et al. (2021), the threshold for defining a drought process is 10 days (not 15). I would like a discussion and/or clarification on this.

1. (3). It is quite difficult for a reader to understand the calculation behind this equation. Maybe a numerical example could be helpful. Moreover the subscript i was already used in eq.(2) to indicate the generic site. Now it is used to indicate the generic drought day. Is the ratio (n^a/n) correct? In case of a=1 it would be useless.

line 175. Could you please add a reference in relation to "more appropriate"?

line 185 and 187: replace the n indicating the total number of years with N. Also in this case n was already used to in eq.(3) to indicate a different variable.

Line 245: replace figure 4 with figure 3.

Lines245-246. Really, I think it is better to avoid a reference to the figures because the mean values cannot be appreciated from the graphs.

Lines 247-248. Revise the sentence. It is not clear to which kind of drought 109.3d and 13.04d refers.

Lines 250-251. Unclear sentence

Line 254. Please, always use the same definition for extreme events (extreme or special)

Line 260. the highest drought days of special drought occurred in Shanxi occurred in 2001, and it is not 13.4d.

Lines 267-268. Some slopes don’t match with those reported in the figures (e.g. Beijing and Tianjing)

Lines 279-296. I think that the presence of continuous trend is not evident, given that in most cases, the last decade denotes a marked trend inversion. As for the previous analysis, a significance test for these trends should be provided.

Line 312. Not 12.3 and 2.4 but 10.1 and 2.3.

Figure 3. Please explain somewhere that Inner Mongolia and Niemeng are the same.

Figure 3. A significance test associated with these trend lines should be provided.

Figure 4. It seems unusual to me to fit a polynomial distribution to a sample frequency graph. Usually we reason by adapting a distribution of probabilities. Finally, the expression "reliability test" is not usual.

Figure.6 and lines 392-296. The source of the data related to the drought affected area must be indicated.

References

Wang S. et al. (2021) Atmosphere 12, 1274. https://doi.org/10.3390/atmos12101274

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments

The manuscript is interesting and worth publishing after a considerably careful and detailed revision. Currently the manuscript is a direct application to the specific case of China. The materials and methods section should be written in a more generalist manner, i.e. in such a way that the methodology could be applied in other parts of the world. After that, a new section “Application to China” or similar could detail the specific case of study. The paper is lacking The part of climate change assessment is lacking

• The English grammar/syntax must be carefully reviewed throughout the manuscript. A few minor mistakes found. For example, please add “the” before National Climate Center
• The abbreviations should be defined first time used in the main text. Please carefully review the text to make sure this happens. For example, PDSI (line 52), CI (line 52).
• Given the considerable amount of abbreviations, it is recommended adding an “Abbreviations” section after the Conclusions to include all of them.
• Authors need to deeply improve the format and presentation of the paper. (formulas, Figures, etc.)

Title

• Proposed change to: “Identification of regional drought processes in North China, using MCI analysis”

Abstract

• The novelty of the paper should be clearly stated as well as if/how the methodology/results can be applied to other regions of the world, and the key conclusion/recommendation (how the results can actually help in addressing drought resilience).
• Please review that all the abbreviations are defined in the Abstract. For example, “d” (167 days)
• “the maximum drought intensity was 119” – the number 119 needs to be explained (otherwise it is meaningless for the reader)

Introduction

• “The drought index can accurately reflect the characteristics and effects of drought.” – I disagree with this statement, as this is not always true (a drought index is only an approximation and each drought index has its own limitations, you also need good input data, a long period of data, etc.). Please modify the sentence or state in what circumstances that is true
• “However, the index only considers the influence of precipitation at a certain scale” - please define at what scale and add a supportive reference
• “and the influence of drought at different scales on the magnitude of drought at the later stage is not considered comprehensively” – please describe this in more detail

• It is required to add mention to Climate change projections and the significance of the study under climate change uncertainties

Data and Methods

• This section should be titled “Materials and Methods” – refer to the Instructions for Authors (https://www.mdpi.com/journal/remotesensing/instructions )
• Add a flowchart to show the steps in the methodology followed
• A location plan Figure is needed. Please add as well the location of the 403 meteorological          stations
• A Figure showing the mean annual precipitation, average temperature, maximum temperature, minimum temperature and average wind speed is needed
• A Figure showing the land use of the Study area is needed
• “semi-annual precipitation” – what does it mean?
• LN 134 – “(see GB/T 32136)” – what does it mean?
• “The values of northern China are 0.3, 0.5, 0.3 and 0.2, and the values of southern China are 0.5, 0.6, 0.2 and 0.1” – who has estimated them? Please explain in the text and add the relevant references
• “Table 1. Classification table of meteorological drought composite index grades.” – add the reference that defines this classification
• LN147: (QX/T 597-2021) - what does it mean?
• LN 182: 60a – please define abbreviations
• Figure 1. Refer to the instructions to authors for the presentation of Figures.
• Figure 2. – review the colour system. Usually red colour is used for the extreme drought

Spatial and temporal characteristics of drought days with different intensity

• This section should be titled “Results and discussion” – refer to the Instructions for Authors (https://www.mdpi.com/journal/remotesensing/instructions )
• The results need to be compared more thoroughly with other recent studies in this topic. I would also suggest the authors to see a recently published article on this topic of study: Yao, N.; Zhao, H.; Li, Y.; Biswas, A.; Feng, H.; Liu, F.; Pulatov, B. National-Scale Variation and Propagation Characteristics of Meteorological, Agricultural, and Hydrological Droughts in China. Remote Sens. 2020, 12, 3407.
• The spatio-temporal variation should be shown in maps (rather than only graphs). See this https://www.mdpi.com/2072-4292/12/20/3407
• Where is the climate warming assessment?

Conclusions

• Some of the major limitations of the data and methodology should be highlighted.
• Future research directions are not included in the section. What can be the factors which can be included/improved to refine the results?
• Please provide specific examples of how these results could be used by policy-makers and decision-makers, what type of strategies/actions could be taken to improve drought management
• Please state how these results could be integrated with future climate change projections to better forecast droughts

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Author Response

Thanks for the reviewer's insightful comments and suggestions for our manuscript.

Reviewer 2 Report

The definition of drought (provided in the first line) is wrong. Please review this reference Mishra, A.K.; Singh, V.P. A review of drought concepts. J. Hydrol. 2010, 391, 202–216.

The format, figures and presentation of the manuscript needs to be reviewed

Author Response

Thanks for your comment. Accepted. The reference “Mishra, A.K.; Singh, V.P. A review of drought concepts. J. Hydrol. 2010, 391, 202–216.” has been added as [1] in Line 40-42. And the format, figures and presentation of the manuscript also have been changed accordingly.  Please refer to the revised version of the manuscript in detail.

Author Response File: Author Response.docx