Round 1

Reviewer 1 Report (Previous Reviewer 2)

In this study, authors discuss long-term trends of extreme climate indices in the southern part of Siberia, in comparison with other parts of Russia. Recently, many studies focused on the changes in climatic extremes in northern Eurasia (including Southern Siberia). However, in this study authors presents several novel results, in particular, monthly trends in extreme indices for various parts of Russia, and the results of clustering based on the monthly trends of these indices. The study is fully consistent with the topic of this special issue of the journal and can be published after a minor revision.

1.       Line 18 “…from observational data for 1950-2019…”

2.       Line 53: heavy rainfalls and floods in 2019 caused more substantial damage than in 2014, so these events can also be mentioned (see e.g. http://link.springer.com/article/10.1134/S187537284104006X

3.       Figure 1: The frequency of high temperature extremes has increased not only in Mongolia, but throughout Siberia, as noted in Section 1.2.

4.       Line 72: Remove "in the Russian Federation"

5.       Line 87-88: I recommend delete this sentence

6.       Line 89: hereinafter, instead of the term "precipitation-related indices," i recommend use "heavy precipitation extremes", since several precipitation-related indices like CDD, show the frequency of drought.

7.       Line 87-113: I recommend rewriting and shortening these two paragraphs, highlighting only the most significant patterns in climate extreme changes for the mentioned regions.

8.       Line 238: “Ward’s method [35] was  used for data agglomeration..”

9.       Line 284: Delete “In comparison with the trends in SI and FE”

10.   Line 297: replace “and whole Russia” to “in other parts of Russia”

I recommend authors to improve their English in terms of sentences construction. sentences look like a literal translation from Russian

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

This manuscript analyzes and explores the long-term trend of extreme climate change in southern Siberia and its surrounding areas. Previous research has mostly focused on specific regions of Siberia. The manuscript has to some extent filled the gap in extreme climate research in Siberia and its surrounding areas and has a certain guiding significance. However, there are still some problems in the manuscript, and it is recommended that the author modify it:

1.       The manuscript focuses on analyzing the long-term trend of extreme climate change in Siberia, but lacks an analysis of the causes of extreme climate change. In fact, extreme climate change is closely related to atmospheric circulation anomalies. It is recommended that the authors select appropriate atmospheric circulation factors, further, analyze the correlation between atmospheric circulation factors and extreme climate change, and deepen the understanding of extreme climate change in the research area.

2.       The manuscript itself has a certain degree of innovation and fills the gap in previous research. The article summarizes relevant research results, but the research significance of this article is only a passing remark. It is recommended that the author summarize the previous research results, summarize the shortcomings of previous research, propose the research significance of this article, and clarify the practical guiding significance of this study.

3.       The conclusion and arguments presented in the article are consistent and address the main issues raised. However, the description in the abstract section does not reflect the innovation of the article. The summary of the article is too flat and does not reflect the differences between this article and previous research. It is recommended to polish the abstract section of the manuscript to reflect the innovation and research significance of the article.

4.       More references to the latest research results from the past 5 years are necessary.

5.

1）The article lacks in-depth research on extreme temperatures

2）Suggest analyzing the causes of extreme climate in the research area

3）The selection of extreme rainfall indicators is limited and not representative

4）The abstract does not reflect the innovation of this article.

Minor editing of the English language required

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

General comments

This study examines long-term trends in extreme temperature and precipitation events observed at weather stations in Siberia. Standardized indices are calculated from available stations over the 1950-2019 period, and trends in these indices are compared with previous studies from surrounding areas. Monthly and annual trends are presented, and spatial patterns are explored with a cluster analysis. Overall, they show more extreme warming and precipitation events in Siberia, especially in spring. The results generally agree with previous studies, but also provide a more complete picture of extreme weather trends in their region of interest.

The manuscript is well-structured, easy to follow, and supported with quality graphics. The methods are well described and follow standard repeatable techniques, and the conclusions are well-supported by the analysis. I recommend publication in the special issue of Atmosphere after considering the following comments.

Specific comments

·       Regional names and references. Understanding region names is critical for this paper and could be done with greater care. While there are clear definitions for the ER/SI/FE regions used in the analysis, the description of regions referred to in other studies and descriptions of areas within ER/SI/FI is more ambiguous (e.g., southwestern Siberia, interior of Siberia, Central Asia, or even “southern part of Siberia” in the title). It would help to have a short study area section with an accompanying figure to identify all the regions referred to in the manuscript (and explain which are clearly defined regions and which are relative or general names). Figures 1 and 2 identify some regions from the manuscript, but not in entirety. Including brief terrain and climate descriptions in the study area section could help too (e.g., desert, mountains, grassland, taiga).

·       Abbreviations. Excessive use of abbreviations impacts the readability of the manuscript. I suggest replacing the regional abbreviations of ER/SI/FE with full names to make it clearer when reading about trends between these regions. Similarly, there is no need to abbreviate the Mann-Kendall test as MK for the number of times it appears in the manuscript. Remembering abbreviations for 11 indices can be difficult when reading the manuscript, however, I think these should be preserved as is for precision. But to help the reader, it should always be clear whether an index is related to high temperatures, low temperatures, or precipitation.

·       Climate classification. I am not convinced it is appropriate to call the cluster analysis a “climate classification” when it is based on trends in extreme weather indices (lines 26, 143, 184, 329, 412, 523, etc.). Perhaps a more direct description such as “cluster analysis of spatial patterns in extreme climate events” would be more appropriate.

Technical comments

·        Line 26-28: This sentence is a little unclear and could be rewritten for clarity.

·        Line 58: Remove “related to this study” in the subheading, this is redundant.

·        Line 71: Is it correct to capitalize “W”estern Siberia but not “s”outhwestern Siberia as done in this section? Capitals imply a formal defined region and lower case implies a relative region.

·        Line 99: Could you be more specific than “adjacent to Siberia” (e.g., south of Siberia)?

·        Line 101: Do you mean the frequency of “extreme” high/low temperatures has increased? It is unclear what metric has increased in this study.

·        Line 118: Consider “because each study analyzed only a single region” rather than “only within each region”?

·        Line 149: Stating 527 stations were used in this study is misleading when in line 176 you state 128 for temperature and 142 for precipitation. Perhaps reword to something like “data from 527 stations covering Russia are available…”.

·        Line 152: Does “majority of stations began their observations during this period” mean that only a few stations cover the entire period. Knowing how many stations cover the full period seems important to weigh the relevance of the results. Or did you mean you only used stations that cover the entire 1950-2019 period?

·        Line 188-194: The number of indices is presented in a confusing way, in particular, how the 27 indices (16 temperature + 11 precipitation) relate to the 11 (6 + 5) presented in Table 1. From what I can tell only 11 indices are presented in the results. Also, it would be helpful to explicitly state that these are standardized indices used in climate studies as cited in [11], rather than definitions created for this study.

·        Line 196: Percentage of days may not capture some extreme events such as a short duration events with very extreme temperature or precipitation.

·        Line 226: Is it fair to say the Sen’s slope estimator provides the “magnitude” of the trend, which is the added value in addition to presenting the Mann-Kendall results?

·        Line 279: Is it correct to state the frequency of extreme cold in SI was “significantly reduced” compared to ER when Table 2 does not have bold trends, meaning the differences in trend were not significant at the 5% level?

·        Line 331: What criteria was used to determine the optimal number of clusters? I don’t think was provided in the methods.

·        Line 348-349: This would be easier to follow if it included east/west references such as “Comparing cluster 2 and 3, the cluster of station east of 75 *C had a stronger increasing trend…”

·        Line 361: Similar to previous comment; “Cluster 1, containing stations further north, had a smaller decrease…”

·        Line 424: Should this be 80 E instead of 80 N?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report (New Reviewer)

Report Review on the paper

Long-term trends of extreme climate indices in the southern part of Siberia in comparison with those of surrounding regions

This manuscript needs some improvements, namely:

1-  The author said that “To evaluate extreme climate events in Russia, especially in SI, this study calculated 27 extreme climate indices [11], which contain 16 temperature-related indices and 11 precipitation-related indices” but really, they used only 11 indices that are described in Table 1? I think there is a mistake.

2-  Depending on question (1). The authors retained only 11 indices in this study. What is the logic behind the selection of these indices. As we know, the Expert Team (ET) on Climate Change Detection and Indices (ETCCDI) defined of the 27 core indices. I think many other indices can be included in the analysis.

3-  This paper applies cluster analysis to identify climatic differences between the regions. More description of retained cluster method in the Method section is recommended.

4-  In light of your results, what are the main recommendations?

Acceptable

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report (New Reviewer)

It is recommended that the authors select appropriate atmospheric circulation factors, further, analyze the correlation between atmospheric circulation factors and extreme climate change, and deepen the understanding of extreme climate change in the research area.

The revised manuscript doesn’t meet the requirement, and some comments I proposed last time are not adopted.

Author Response

Please see the attachment.

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.

Round 1

Reviewer 1 Report

In the manuscript entitled "Long-term trends of extreme climate indices in the Southern part of Siberia" (atmosphere-2143347), the authors examined 128 stations for air temperature and 142 stations for precipitation (1950-2019) and estimated the ETCCDI extreme rainfall indices using the Mann-Kendall test and the Sen slope estimator. The characteristics were examined in terms of the Welch’s t-test and Cluster analysis.

Comments for the authors

Minor remarks
1-Figure 1  Change reagion to region.
2-Delete the brackets
3-Lines 190-193 : Add “low-temperature, respectively” after high-temperature events
4-Figure 4-5 : Change WR to ER
5-Lines 283-284: Change latitude to longitude
6- Line 406 :  Change precipitation to RX5day

Major remarks
1-Line 17 : this line talks about methods. I suggest authors include Mann-Kendall test, Sen slope estimator, Welch’s t-test and Cluster analysis in the methods of the abstract.
2-Line 18 :The study area is in southern Siberia. Why tell you about Russia?
3- Lines 18-20 :Similar results were also found by [16] in the southwestern part of Siberia. Why study the temperature trend again? Where is the originality of your study?
4- Lines 21-23 : Which part of your study showed this?
5- Lines 23-24 : Similar results were also found by [16] in the southwestern part of Siberia.
6- Lines 30-33 : It is better to use a single citation for both sentences.
7- Line 39 : Frequency is a component of extreme events so it needs to be rewritten.


According to the authors, the originality of their paper is that their case study (Southern part of Siberia), to elucidate the differences in the long-term trends of extreme climate events between Siberia and the other Russian regions and compare the surrounding areas of Siberia with previous studies and to evaluate the long-term trends in extreme events in Siberia at a finer scale. However, the methods regarding the extreme rainfall used in both are almost the same [16, 28-31]. Therefore, the original part of the manuscript is the Welch’s t-test and Cluster analysis in southern Russia, which is considered an entire part of Russia including the southern part of Siberia.

Unfortunately, I have to suggest rejection for this manuscript on the grounds; because the exposition of the topics is confusing, abstract used are not clear, also there are some results that are described in section 3 but which have been investigated as temperature in a previous study [16]. There are some incomprehensible statements in the description of the results. A rewrite of the article is recommended. In my opinion, the authors should initially correct the aims (for example, to choose to study the long-term of extreme precipitations of southern part of Siberia), and add new methodologies. I suggest applying the modified MK test in order to address the problem of autocorrelation structures in time series and then comparing the findings to those of the MK test. If similar results are found, the authors can proceed with the MK test. However, if differences are found, I suggest adopting the modified MK test.

Reviewer 2 Report

In this study, the authors discuss long-term trends of extreme climate indices in the southern part of Siberia, in comparison with other parts of Russia. Recently, many studies focused on the changes in climatic extremes in northern Eurasia (including Southern Siberia). However, in this study authors presents several novel results, in particular, monthly trends in extreme indices for various parts of Russia, and the results of clustering based on the monthly trends of these indices. The study is fully consistent with the topic of this special issue of the journal and can be published after a minor revision.

1.       I recommend the authors to more clearly emphasize the differences between the presented results and those previously published in the conclusion, and possibly in the abstract

2.       Replace “extreme climate” to “extreme indices” or “climatic extremes” (which is more suitable) in Keywords and throughout the text

3.       Line 16: this study calculated → we calculated

4.       Line 18: the entire country of Russia → the entire territory of Russia

5.       Line 146: this study calculated → we calculated

6.       Line 229 - 231: “the trends in the low temperature-related indices, such as TN10P and  CSDI,  in  SI  were  smaller  than  those  in  ER.  Therefore,  the  frequency  of  extreme  cold  weather in the SI was significantly reduced compared to that in the ER”. I think, there is an erroneous conclusion in the second sentence

7.       Figure 4: replace WE (western Russia?) to ER in the legend

8.       Figure 5: replace WE (western Russia?) to ER in the legend

9.       Line 265: rainfall intensity in winter was the largest → precipitation intensity in winter was the strongest

- -  Line 342 – 343: It is likely that, that the identified strong warming trend in spring (especially in March) may be associated with a change in the characteristics of the snow cover, in particular, the snow water equivalent or the snow-covered area in the ER or in Kazakhstan in early spring. Authors can mention these hypotheses in the discussion

1-   Line 345: I assume that the risk of snowmelt flooding will just decrease as the duration of the snow accumulation season decreases. In Siberia and Ural mountains, the most hazardous spring floods were associated with cold waves in the first half of spring, when snowmelt period was shifted to the end of April or even to May.

1-   Line 359 – 360: “the monthly trend of RX5day in SI showed an increasing trend” word “trend” is doubled.

1-   Line 415: I encourage the authors to compare this data with the recent study of the trends in convective and stratiform precipitation in Northern Eurasia (Chernokulsky et al., 2019) in this paragraph.

Reviewer 3 Report

Long-term trends of extreme climate indices in the Southern  part of Siberia

Takanori Watanabe, Hiroshi Matsuyama, Irina Kuzhevskaia, Olga Nechepurenko, Vladislav Chursin  and Valerii Zemtsov

Information about long-term trends of extreme climate indices is important to improve understanding of future climatic changes over different parts of globe. The manuscript considers information about trends of extreme climate indices over three parts of Russian Federation. So it is important but Title of article is incorrectly reflects the content of the article in this case.

I think the manuscript need reject and resubmit. Some of my common comments are below:

L15–L17. «To evaluate the long-term trends of extreme climate events in Siberia, this study calculated extreme climate indices from observed data from to 1950-2019 and analyzed their characteristics and trends over the entire country of Russia».

The phrase is illogical. It is not clear why it is necessary to use data for the whole of Russia to study trends in Siberia. This is a study of trends in Russia. Thus you need to change the statement of the problem and the name of the work.

L18–L26.

The rest of the text of the abstract talks about a comparative analysis of temperature and precipitation trends in Siberia and other regions of Russia, a comparative analysis of temperature and precipitation trends in areas inside Siberia, as well as seasonal features of climatic trends in temperature and precipitation. It is difficult to understand what exactly will be discussed in the article itself. If about all this at once, then this is a very large amount of too heterogeneous information.

L42–44. «This event was caused by a prolonged anticyclonic circulation over Russia, which was generated by quasi-stationary Rossby waves…»

The phrase is incorrect from a meteorological point of view. This is an unrealistic situation when circulation of the same type would be simultaneously observed over the entire territory of Russia.

L46–48. «Subsequently, Siberia experienced a severe drought in 2012….»

In combination with the previous phrase in one paragraph, this reads as a consideration of Siberia as a state separate from Russia. The paragraph is structured incorrectly.

L92–94. «Because Southwestern Siberia is located near the borders of China, Mongolia, and Kazakhstan, the periphery of these countries may have affected the results of previous studies [15,16,20–27].»

A very strange phrase about the influence of the periphery of countries on the results of research…

L94–95. «Therefore, long-term trends in extreme climate events in Siberia must be investigated.»

Following the logic of the authors, due to the influence of the periphery of countries on previous studies, there is an urgent need to study the climate trends in Siberia. This is an extremely illogical and strange statement of the problem.

L101–107. «The aim of this study was to elucidate the differences in the long-term trends of extreme climate events, such as extreme hot or cold weather, drought, and heavy precipitation between Siberia and the other Russian regions. Since regional and seasonal variations in extreme climatic events have been reported within Siberia [28–31], climate classification of the interior of Siberia is conducted based on the long-term trends of extreme events. This analysis also aimed compare the surrounding areas of Siberia with previous studies  and to evaluate the long-term trends in extreme events in Siberia at a finer scale»

Too many aims at the same time. It is not clear what exactly the authors want to find out. Climatic trends in different regions of Russia? Trends within Siberia? Comparing of trends in different regions of Russia or in different regions of Siberia? Comparing of trends in Siberia with trends in neighboring countries?.. But climate trends are indifferent to administrative boundaries, it is incorrect to set such boundaries initially. Climate trend areas can be described by enumerating administrative areas to give the reader a better understanding of the area covered by the trend. But doing the opposite is incorrect.

 …

Reviewer 4 Report

The authors present interesting results of their research on observational data regarding the trends of extrem climate indices in the Southern part of Siberia for th period 1950-2019.

The paper is appropriately organized, the results are convincingly discused and put in context of other findngs published in peer reviewed journals.

Only few / minor corretions are needed, in my opinion:

Lines: 190-195: Please, provide a reference for the cluster analysis (Ward method) , and the softaware used for your calculations.

Figures 4 & Figure  5: Please, match the figure caption and Figures for WR and ER