the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 May 2026
Experiment design, nudging protocol, and models participating in Phase 2 of the APARC Quasi-Biennial Oscillation initiative (QBOi)
Abstract. We describe the protocol for coordinated experiments in phase-2 of the Quasi-Biennial Oscillation initiative (QBOi) and the participating models. The experiments involve nudging tropical stratospheric zonal-mean zonal winds in the models toward observations, enabling analysis of the impact of QBO biases on simulated teleconnections. Additionally, nudging the tropical winds allows investigation of the origins of QBO biases by examining the behaviour of resolved and parameterized equatorial waves under realistic equatorial wind shear conditions. We document here the scientific rationale and design of the nudging experiments, summarize the QBOi data request, and provide an overview of participating models. An initial evaluation is given of tropical stratospheric winds simulated by the multi-model ensemble for both nudged and free-running cases, and the overall impact of nudging on climatological aspects of the atmospheric circulation is examined.
Competing interests: JA serves as co-editor for the special issue to which this paper belongs.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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- RC1: 'Comment on egusphere-2026-1165', Anonymous Referee #1, 30 May 2026 reply
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CEC1: 'Comment on egusphere-2026-1165 - No compliance with the policy of the journal', Juan Antonio Añel, 20 Jun 2026
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Dear authors,
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
First, in your manuscript you present some preliminary results obtained with the models contributing to the QBOi. As you present results, you must publish the code of the models involved and that you have used to obtain them in a repository acceptable according to the policy of the journal. Also, we would expect that you provide in a repository the data for the variables plotted in the manuscript.
Please, therefore, publish your code and 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.
Later, if the Topical Editor decides to continue with the review or publication process of your manuscript and you are requested to upload a new version of it, then The 'Code and Data Availability’ section of your manuscript 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 EditorCitation: https://doi.org/10.5194/egusphere-2026-1165-CEC1 -
AC1: 'Reply on CEC1', J.A. Anstey, 30 Jun 2026
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Dear Editor,
Thank you for your helpful comments. We have updated the data availability statement accordingly and will include the updates at the revision stage.
Our paper references the original model documentation papers for full details of the participating models, including information on source code availability if applicable. However please note that models participating in QBOi generally do not have public code repositories due to their institutes’ licensing restrictions. Our approach here is similar to that of the recent multi-model experiment protocol description paper in GMD, Zhu et al. 2025 (https://doi.org/10.5194/gmd-18-5487-2025), who like us reference model description papers for further information on the participating models. Also this manuscript does not specifically report any further (new) developments to the models we use.
The manuscript doesn’t mention “preliminary results” but presents results for variables plotted using data from the QBOi multi-model archive hosted at the JASMIN supercomputing infrastructure (https://jasmin.ac.uk) which is part of the UK’s Centre for Environmental Data Analysis (CEDA). Our Data Availability statement already includes the Zenodo record for this data (https://doi.org/10.5281/zenodo.19059510) and describes how to request access to the archive. The HTHH-MOC project described by Zhu et al. (2025) similarly used a JASMIN group workspace to host their multi-model data archive.
ERA5 monthly-mean data was retrieved from the Copernicus Climate Change Service, https://doi.org/10.24381/cds.6860a573. This is the DOI of the Hersbach et al. 2023 data citation that was included in our Data Availability section.
The input4MIPs boundary condition data in Appendix B was described as being available from the input4MIPs project as the URL https://esgf-node.llnl.gov/search/input4mips/. We will include this data in the data availability section and add a new citation:
Durack, Paul J.; Taylor, Karl E.; Ames, Sasha; Po-Chedley, Stephen; Mauzey, Christopher (2022). PCMDI AMIP SST and sea-ice boundary conditions version 1.1.7. Version 20220201.Earth System Grid Federation. https://doi.org/10.22033/ESGF/input4MIPs.16485
We will make these revisions to the manuscript when we respond to all the reviewers comments.
Sincerely,
James AnsteyCitation: https://doi.org/10.5194/egusphere-2026-1165-AC1 -
CEC2: 'Reply on AC1', Juan Antonio Añel, 30 Jun 2026
reply
Thanks for the reply. Unfortunately, it does not address the outstanding issues, and additional work will be necessary.First, we understand that some of the models used in the work presented are not allowed to be distributed; however, several of them can be distributed, and we expect you to provide a valid repository for them. For those that cannot be distributed, the Code Availability section of the manuscript should state this, provide clear instructions for accessing them (contact form, etc.), and include information on how they are preserved. That is, the fact that the authors cannot distribute the model does not mean they should not take the necessary steps to preserve it internally. For example, Copernicus and GMD have an agreement with the Met Office to access the Met Office's model code, which is stored on the Met Office's supercomputers. For others, you could provide a Zenodo private repository.Regarding citation to other papers, although I have not checked them here case by case, it is often the case that citations to papers presenting the specific version of a model do not reflect the exact code and routines used in an experiment, which often are modified to include for example nudged data or specific parametrisations or small improvements since the original version of the model was released. Therefore, please, if you are going to cite papers, ensure that the repository linked in the mentioned paper: a) contains exactly the same code used for your experiments, b) is a repository that we can accept (not Git sites, webpages of research centers, etc.).We could accept JASMIN to deposit the QBOi data. We realize that it is a large dataset and that a decision was made to host it there; however, it is hard to move elsewhere. You need to provide specific information about how to access the data openly. If you cannot provide an open link, please provide a rationale and clear instructions for how readers can access the data.We usually do not accept the Copernicus Climate Data Store as a data repository. It does not offer the preservation period or the guarantees that the policy of the journal requests. For example, several old reanalyses that were available there are no longer accessible. This is because the Copernicus Climate Data Store is designed more as a service than as a large-scale storage repository. Therefore, the ideal approach is to store the monthly datasets in a repository. If the size is excessive (for example, over 150 GB), an exception can be made.We can accept that you cite data (input4MIPs) hosted on the ESGF; however, please provide specific information about the files used and the sources from which they were obtained. A link to the main webpage or a generic description is not enough to ensure access to the data used in your work.The Zenodo repository linked in your manuscript does not contain any assets, but only three links to external webpages, which we cannot accept.In your reply, you state, "We will include this data in the data availability section". The mentioned issues have to be solved at this point, not later. Therefore, please provide a new "Code and Data Availability" statement for your manuscript in your next replies. Also, it speeds up the evaluation of compliance with the code and data policy.Also, please, understand that while we try to maintain uniformity in requirements across papers submitted to the journal and in requests for code and data, we evaluate each paper individually. Perceived discrepancies in the requirements for different papers can have a variety of causes, from editorial oversights to other considerations taken into account when reviewing the manuscript. Therefore, a judgment made from a published paper can be biased.Juan A. Añel
Geosci. Model Dev. Executive EditorCitation: https://doi.org/10.5194/egusphere-2026-1165-CEC2
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CEC2: 'Reply on AC1', Juan Antonio Añel, 30 Jun 2026
reply
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AC1: 'Reply on CEC1', J.A. Anstey, 30 Jun 2026
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- 1
review of "Experiment design, nudging protocol, and models participating in Phase 2 of the APARC Quasi-Biennial Oscillation initiative (QBOi)" by Anstey et al
This study introduces the protocol for phase 2 of the QBOi project, with the main addition being two nudged experiments. In Exp1-ObsQBO, the tropical stratospheric zonal winds are nudged to observed reanalysis wind, and in Exp1-NoQBO they are nudged to the climatological wind over the 1979-2020 period. The paper also introduces key aspects of the participating models, and also describes the data request. The paper also demonstrates that the models respond to nudging as expected.
I have no major comments - this study is very appropriate for GMD - and I look forward to reading the subsequent papers that report results. To be explicit, I don't think the authors should be asked to include any additional results in the current paper. It should be promptly accepted subject to the technical edits described below.
technical edits:
line 59-62 this sentence could be reworded for clarity
line 87 "seasonal" -> "subseasonal"
caption of figure 1: give- > given
line 227 "Sensitivity of QBO simulations to vertical resolution is not well quantified," is confusing. Do you mean "mechanisms are poorly understood"?
line 245, 502 Garfinkel et al 2025 seems appropriate in these two locations. Consider citing it.
line 275: therefore **are** not
line 302 nudged -> nudge
line 355 "responding" is superfluous
line 368 "and" is missing between Exp1-NoQBO and Exp1-ObsQBO
line 375 **the** simulated
line 396 consider a comma after "winds"
line 465 GCMs
line 506 superfluous "is"
section A2: it might be worth stating explicitly that the profile for Exp1-noQBO is the climatological mean over 1979-2020 to match the period for obsQBO, though this is probably obvious. For SNAPSI, the specific wind and temperature profiles to be relaxed towards were provided to model developers. For SNAPSI this was done because the initial spinup in the first few days after initialization needed to be handled somewhat carefully to avoid shocks for the runs nudged to climatology due to the fast nudging timescale. Presumably this is less of a problem for the QBOi runs.
Garfinkel, C. I., Avisar, D., Osprey, S., & Smith, D. (2025). The response of the QBO to external forcings: implications for disruption events. Journal of Geophysical Research: Atmospheres, 130(22), e2025JD044438.