Reconstructions of droughts in Germany since 1500 – combining hermeneutic information and instrumental records in historical and modern perspectives

Glaser, Rüdiger; Kahle, Michael

doi:https://doi.org/10.5194/cp-16-1207-2020

Articles | Volume 16, issue 4

https://doi.org/10.5194/cp-16-1207-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Droughts over centuries: what can documentary evidence tell...

https://doi.org/10.5194/cp-16-1207-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 4

Research article

|

10 Jul 2020

Research article |

| 10 Jul 2020

Reconstructions of droughts in Germany since 1500 – combining hermeneutic information and instrumental records in historical and modern perspectives

Rüdiger Glaser and Michael Kahle

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Final revised paper (published on 10 Jul 2020)
Preprint (discussion started on 12 Sep 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review comments to “Reconstructions of droughts in Germany since 1500”', Anonymous Referee #1, 12 Oct 2019
- AC1: 'responses', Ruediger Glaser, 17 Dec 2019
RC2: 'Referee Comment. Manuscript CP-2019-104. Reconstruction of droughts in Germany since 1500', Anonymous Referee #2, 03 Dec 2019
- AC2: 'responses', Ruediger Glaser, 17 Dec 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (01 Feb 2020) by Günter Blöschl

The two reviews provide useful suggestions for strengthening the paper. I consider the paper interesting but more methodological detail is needed in order for the reader to understand what has been done. There are also a number of inconsistencies. I recommend that the authors address all comments of the two reviewers. The responses to the reviews seem to be an appropriate path to follow.

Additionally I have the following observations:

1. More detail on the data is needed. What is ‘information’ exactly? Are these 280000 pieces of information all relating to droughts – how many places, years? How did you get the monthly indices of Fig. 2? I would not expect there is information in every singly month of the past 500 years. The derivation of PI is completely missing, yet essential for understanding the paper.
2. CP has an open data policy. Please deposit data in a public repository
https://www.climate-of-the-past.net/about/data_policy.html
3. Fig. 3 is difficult to understand (in fact the figure captions are generally too short). Is each point a year, averaged over Germany? And if so, how?
4. Fig. 4 and the associated methods are unclear to me. They need a full description. Even though I do not know the details of the method, the correlation of 0.99 does not look right.
5. Correlations HDI-MDI is r=0.478 in line 191 but r=0.75 in line 273. The relevance of these correlations are difficult to assess unless the basis of the data becomes clearer. Have any systematic data been used in the historic data set? It would be good to demonstrate by a recent drought example how the documentation based data set compares with precipitation measurements.

Please address the comments of the reviewers and my observations and submit a revised paper.

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AR by Ruediger Glaser on behalf of the Authors (03 Mar 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Apr 2020) by Günter Blöschl

RR by Anonymous Referee #1 (06 May 2020)

Suggestions for revision or reasons for rejection

Dear Rüdiger Glaser and Michael Kahle,
Thank you for the revision of your manuscript “Reconstructions of Droughts in Germany since 1500 - combining hermeneutic information and instrumental records in historical and modern perspectives”. The new Figure 2 and the re-structuring of the text improved the clarity of your work. However, unfortunately there are still various unclear, not well explained aspects which need further improvement. The “results discussion and conclusion” section is rather weak, it contains a lot of repetition and summary of what has been shown before. The section needs to be re-written, focussed on the results of the study. A separate conclusions section is preferred.
I suggest major revision.
I hope my following comments help to further improve the manuscript:
Lines 105-108 & 140-209: It is unclear, if the derivation of the PI index and time series is part of this study, or if it is a dataset which was already available in the database tambora.org. It is described as an available dataset, but also in a quite long section in the methods chapter. It should be described either dataset, or as one step of the study, not both.
Lines 109-110: Please describe in more detail, what information these “early precipitation measurements and derived drought indices” contain and how these indices look like. Additionally, it should be described how this data was used to develop the PI; or was it only used for validating the PI?
Lines 117-125: This part does not fit into the data section, it seems to be more a result of a data analyses. This part might fit better towards the end of the paper, e.g. on lines 459-466 also outstanding flood events are discussed. Thus, these two different sources/indicators pointing to severe droughts could be evaluated against each other, e.g. consistency of indications checked.
Line 120: typo “outstanding”
Lines 118 & 121: the 1540 event is mentioned twice, why?
Lines 123: What does “reported as drought years” mean in respect to the indicator development?
Line 127: “these values” – you should better describe how the values look like, e.g. averaged monthly precipitation values for x stations in Germany (or is it only one aggregated value for Germany?)
Line 129-130: Are this the SPI values? In case these should be named as such here. Otherwise, it needs to be described how this data is related to the SPI.
Lines 191-193: This is double, the information has been given before.
Figure 2: This figure is very helpful and clarifies the process. However, it should be further improved. I suggest to include for each dataset/indicator the information how it looks like, e.g. PI 7 classes from -3 to +3; HHI unclear how many classes, from -4 to +4. This information needs to be given for all indicators mentioned (preferably with information what the extreme classes mean). If it does not fit into the Figure, you should provide an additional overview table. Also include in the figure, where the weather diaries as well as the “numerical records since 1800” come into play and how.
Lines 194-197: Describe in more detail, what information these weather diaries contain, for which years they are available (60 years between 1500 and 1800?) and most importantly how they were used for the development of the PI. Or have they been used for validation purposes only? The same is true for the “numerical records since 1800”
Lines 199 ff: Describe in more detail, what information these numerical records contain, for which years they are available (1800 until today?) and most importantly how they were used for the development of the PI.
Line 203: For which is the reference period good for? Average for the class 0? What doe it mean “These numerically derived indices were combined with the hermeneutically derived ones.” “Combined” how and why?
Chapter 3.2 Derivation of historical pathways and drought categories: it remains unclear to me how this part of the study fits into the process of index development.
Lines 263-264: what do you mean with “connectivity”? I guess you refer to correlation?
Lines 265: what do you mean by “inclination”? I guess you refer to slope?
Figure 4: What is the scale of the SPI and of the HPI? Y-axis labels are wrong.
Chapter 4 Results, discussion and conclusion: large parts of this section are a repetition or summary of what has been shown before. The whole section needs to be re-written. You need to be clear about what the results of this study are. This remains rather unclear.
A separate conclusions section is preferred.
General: It is important that you use consistent terminology throughout the manuscript. This is not given and confuses the reader (e.g. scale factor – compensation factor).

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RR by Anonymous Referee #2 (11 May 2020)

ED: Publish subject to minor revisions (review by editor) (11 May 2020) by Günter Blöschl

AR by Ruediger Glaser on behalf of the Authors (05 Jun 2020) Author's response Manuscript

ED: Publish as is (05 Jun 2020) by Günter Blöschl

AR by Ruediger Glaser on behalf of the Authors (13 Jun 2020)

Short summary

A new study on droughts in Germany since 1500 reveals the long-term trend of single extreme events, as well as drier periods. Extreme droughts appeared in 1540, 1590, 1615, 1706, 1834, 1893, 1921, 1949 and 2018. Like today, droughts had manifold impacts such as harvest failures, water deficits, low water levels and forest fires. This had different societal consequences ranging from famine, disease, rising prices, migration and riots leading to subsidies and discussions on climate change.