the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Feb 2026
A simple weather generator that converts statistical information from downscaled global climate models to 24-hr precipitation input for hydrological models
Abstract. A weather generator can provide a link between downscaled precipitation or temperature statistics on the one hand, and impact models that require daily data as input on the other. A simple design for a weather generator for daily precipitation is described together with results from an evaluation against rain gauge observations from Norway, Ghana and Romania. The results from the evaluation indicate that it gives a close approximation of the observed characteristics for daily precipitation in different climatological settings. A simple weather generator for daily temperature is also presented, and an assessment of its performance also suggests a reasonable skill level. These weather generators are part of the free and open-access R-package 'esd'.
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CEC1: 'Comment on egusphere-2026-351 - No compliance with the policy of the journal', Juan Antonio Añel, 25 Mar 2026
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CEC2: 'Reply on CEC1', Juan Antonio Añel, 25 Mar 2026
As an additional note to my previous comment, and to clarify, the data stored in FigShare are perfectly stored, and we can accept FigShare as a permanent repository.
Juan A. Añel
Geosci. Model Dev. Executive Editor
Citation: https://doi.org/10.5194/egusphere-2026-351-CEC2 -
AC1: 'Reply on CEC2', Rasmus Benestad, 26 Mar 2026
I have revised the Code and data availability by inclusding a reference to the ECA&D data: Klein Tank, A. J. B. W., Konnen, G. P., Böhm, R., Demarée, G., Gocheva, A., Mileta, M., Pashiardis, S., Hejkrlik, L., Kern-Hansen, C., Heino, R., Bessemoulin, P., Müller-Westermeier, G., Tzanakou, M., Szalai, S., Pálsdóttir, T., Fitzgerald, D., Rubin, S., Capaldo, M., Maugeri, M., Leitass, A., Bukantis, A., Aberfeld, R., Engelen, A. F. V. v., Førland, E., Mietus, M., Coelho, F., Mares, C., Razuvaev, V., Nieplova, E., Cegnar, T., López, J. A., Dahlström, B., Moberg, A., Kirchhofer, W., Ceylan, A., Pachaliuk, O., Alexander, L. V., and Petrovic, P.: Daily dataset of 20th-century surface air temperature and precipitation series for the European Climate Assessment, International Journal of Climatology, 22, 1441–1453, https://doi.org/https://doi.org/10.1002/joc.773, 2002.
I hope this is what was required.
Citation: https://doi.org/10.5194/egusphere-2026-351-AC1 -
CEC3: 'Reply on AC1', Juan Antonio Añel, 26 Mar 2026
Dear Dr. Benestad,
Thanks for the quick reply. Unfortunately, we can not accept this. You have cited a paper, not a repository. You must provide a repository (link and permanent handler, e.g. DOI) that contains all the data used and produced in your study.
Juan A. Añel
Geosci. Model Dev. Executive Editor
Citation: https://doi.org/10.5194/egusphere-2026-351-CEC3 -
AC2: 'Reply on CEC3', Rasmus Benestad, 27 Mar 2026
I have added the ECA&D data to Figshare with a DOI and revised the Code and data availability section:
Code and data availability. Code for the WGs is available as part of the open-source R-package ’esd’ version 1.11.21 from FigShare DOI:10.6084/m9.figshare.1160493.v18 (Benestad and Mezghani, 2026). Some of the data is provided as a part of the R-package, except for the rain gauge data from Ghana. The ECA&D (Klein Tank et al., 2002) data used as an example here is public and available from https://www.ecad.eu/dailydata/, however, similar demonstrations can be done with other daily rain gauge data. A copy of the Romanian Cluj Napoca ECA&D record is provided in DOI:10.6084/m9.figshare.31869940 where it is stored as an esd-station object stored in the native R-binary ’.rda’ format that can be read using ’load(<file name>)’. The Met Ghana record used in the SPRINGS project is not open and nor free to share, but there is a record available from Akuse in GHCND with doubtful quality which is also provided in DOI:10.6084/m9.figshare.31869940. The data in this case is not important, as it merely serves for demonstration purposes, and an evaluation of the WG should also involve other data records.
Citation: https://doi.org/10.5194/egusphere-2026-351-AC2 -
CEC4: 'Reply on AC2', Juan Antonio Añel, 27 Mar 2026
Dear Dr. Benestad,
Many thanks for the quick reply. I have checked the repositories and we can consider now the current version of your manuscript in compliance with the code policy of the journal.
Juan A. Añel
Geosci. Model Dev. Executive Editor
Citation: https://doi.org/10.5194/egusphere-2026-351-CEC4
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CEC4: 'Reply on AC2', Juan Antonio Añel, 27 Mar 2026
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AC2: 'Reply on CEC3', Rasmus Benestad, 27 Mar 2026
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CEC3: 'Reply on AC1', Juan Antonio Añel, 26 Mar 2026
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AC1: 'Reply on CEC2', Rasmus Benestad, 26 Mar 2026
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CEC2: 'Reply on CEC1', Juan Antonio Añel, 25 Mar 2026
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RC1: 'Comment on egusphere-2026-351', Anonymous Referee #1, 26 Apr 2026
Review of 'A simple weather generator that converts statistical information from downscaled global climate models to 24-hr precipitation input for hydrological models’ by Rasmus E. Benestad
This manuscript is submitted to GMD as a ‘Development and technical paper’. The manuscript describes a simple weather generator (WG) and demonstrates the performance of the WG at a few locations. While the methodology is well documented and the text is straightforward to follow, the following comments must be addressed before this manuscript can be considered for publication.
Major Comments
As per the requirements of the journal - “Development and technical papers usually include a significant amount of evaluation against standard benchmarks, observations, and/or other model output as appropriate”. I am not fully convinced about the performance of the WG. I recommend the author to provide more robust performance evaluation at several other locations.
The text inside the figures, the axis labels, and the legends are too small and often extremely difficult to read. It seems that the figures were prepared in a rush. I recommend the author to improve the figure quality.
Minor Comments
L1: If possible, simplify this sentence.
L3: Mention how many stations are used.
L4, L6: Explain ‘close approximation’ and ‘reasonable skill level’ with a number or error metric.
L6: Consider removing this sentence.
L1-7: The abstract seems more like a plain language summary. I recommend the author to think carefully about the abstract.
L20: Please add a couple of citations.
L23: Please add a couple of relevant citations, to which a new reader can refer to if they want more information about downscaling.
L39: Please provide a sentence describing why previous weather generators were not designed to connect with ESD.
L40: Provide full name of the SPRINGS project. Additionally, the relevance of the SPRINGS project is not clear.
L45: Mentioning names of a couple of relevant and popular hydrological models might be useful.
L55: I recommend adding one sentence better describing the cut-off threshold.
L69: A sentence or two describing the equation would be helpful.
L75: The choice of default smudge factor should be explained.
L93, 94, 102: ‘good agreement’, ‘modest deviations’, ‘comparable to the observations’ - These qualitative descriptions should be avoided and the author must provide quantitative metrics for evaluation of the Weather Generator.
Figure1: The schematic could be improved. In my opinion, the description provided in the caption is not properly reflected in the figure.
Figure2: It is not clear what the colors represent.
Citation: https://doi.org/10.5194/egusphere-2026-351-RC1 - AC3: 'Reply on RC1', Rasmus Benestad, 02 Jun 2026
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RC2: 'Comment on egusphere-2026-351', Anonymous Referee #2, 01 Jul 2026
General comments:
The manuscript presents a simple weather generator designed to translate downscaled annual precipitation statistics, mainly wet-day frequency and wet-day mean precipitation, into daily precipitation sequences for hydrological and impact models. The topic is relevant because many impact models require daily inputs. The implementation in the open-source 'esd' R package is useful and improves reproducibility.
However, the current manuscript would benefit from stronger evaluation and clearer framing of the method’s limitations. The proposed weather generator reproduces some marginal precipitation statistics reasonably well, but it does not yet adequately reproduce wet-spell and dry-spell duration, which are important for hydrological applications, flood generation, soil moisture, and drought-related impacts. The manuscript should more clearly explain when this simple generator is appropriate and when a more advanced weather generator may be needed.
Major comments:
First, the evaluation should be strengthened beyond visual comparison. Most results are shown as QQ plots and time-series comparisons, but the manuscript would benefit from quantitative metrics for wet-day frequency, wet-day mean precipitation, annual totals, extremes, and wet/dry spell durations. These metrics would help readers assess performance more objectively.
Second, the underestimation of wet-spell and dry-spell duration is an important limitation. The author notes that the WG tends to generate too many short wet and dry spells, but this issue should be discussed more centrally. Spell persistence strongly affects hydrological model outputs, especially runoff generation, antecedent moisture, flood peaks, and drought duration. The manuscript should either improve the method to better preserve spell statistics or clearly state that the current WG is less suitable for applications that depend strongly on precipitation persistence.
Finally, the temperature generator is presented rather briefly. The precipitation WG is the main focus, but the manuscript also reports reasonable skill for daily temperature. The temperature section should either be expanded with more complete evaluation across sites and seasons or shortened and framed as a preliminary extension.
Specific comments:
1. Please consider evaluating the WG at more sites or across a broader range of climate regimes to better demonstrate transferability.
2. Please add quantitative performance metrics to complement the figures.
3. Please discuss the lack of spatial dependence among multiple stations. This may limit applications to basin-scale hydrological modeling.
4. Please discuss the lack of dependence between precipitation and temperature. This may matter for snow and evapotranspiration applications.
5. Some figures are difficult to read because labels and legends are small. Please improve figure readability.
6. The conclusion should include a concise limitations paragraph, such as spell-duration bias, stationary seasonality, single-site design, lack of spatial correlation, and limited temperature evaluation.Citation: https://doi.org/10.5194/egusphere-2026-351-RC2
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Dear Dr. Benestad,
Unfortunately, after checking your manuscript, it has come to our attention that it does not comply with our "Code and Data Policy".
https://www.geoscientific-model-development.net/policies/code_and_data_policy.html
In the Code and Data Availability section you have not provided permanent repositories for all the data used in your work. Instead, you provide some data in the FigShare repository, stating that the data for Ghana are not accessible, and linking a site (ECA&D) which is not a trusted repository for long-term archival, and therefore is not acceptable according to the policy of the journal. Because of it, your manuscript should not have been accepted for Discussions or peer review.
The GMD review and publication process depends on reviewers and community commentators being able to access, during the discussion phase, the code and data on which a manuscript depends, and on ensuring the provenance of replicability of the published papers for years after their publication. Please, therefore, publish your data in one of the appropriate repositories and reply to this comment with the relevant information (link and a permanent identifier for it (e.g. DOI)) as soon as possible. We cannot have manuscripts under discussion that do not comply with our policy.
The 'Code and Data Availability’ section must also be modified to cite the new repository locations, and corresponding references added to the bibliography.
I must note that if you do not fix this problem, we cannot continue with the peer-review process or accept your manuscript for publication in GMD.
Juan A. Añel
Geosci. Model Dev. Executive Editor