the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 May 2025
Natural Tropical Oscillations phase impact on stationary and westward travelling planetary waves
Abstract. We performed a series of numerical experiments to study the main patterns of the Quasi-Biennial Oscillation of the zonal wind in the equatorial stratosphere (QBO) and the El Niño-Southern Oscillation (ENSO) influence on stationary and westward travelling atmospheric planetary waves (PWs) with different zonal wave numbers and periods. The simulation was carried out for boreal winter conditions using the model of the middle and upper atmosphere (MUAM). The results showed that the joint effect of the considered tropical oscillations can significantly, up to tens of percent, change the amplitudes of the PW in the areas of their maxima. Under the El Niño, regardless of the QBO phase, the amplitude maxima of the stationary PW with wave number 1 (SPW1) shift toward high latitudes. The amplitude structure of SPW2 is basically opposite to the SPW1 structure. Increases of the upward wave activity fluxes of quasi- 5-, 10-, 7-day PWs, and the amplitudes of 10- and 7-day PWs are modelled when easterly QBO phase is superimposed on El Niño phase. Conversely, attenuations of the individual PW amplitudes and wave activity fluxes are typically observed under the westerly QBO, as well as under La-Niña/westerly QBO conditions combination in special cases, such as SPW1. The PW study is important due to their significant influence on the middle and upper atmosphere circulation, including the configuration of the stratospheric polar vortex whose deformation can influence the occurrence of extreme weather events, in particular, in the Arctic and Asia-Pacific region during the boreal winter.
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CC1: 'Comment on egusphere-2025-813', Maria Andreeva, 19 Jun 2025
As it became clear to me after reading the preprint, the study uses a fairly simple concept of numerical modeling. In the numerical model of global circulation, conditions are set correspond to different phases of the QBO and ENSO. The former are set by the nudging procedure, since the vertical resolution of the model does not allow reproducing the QBO independently. This even has a certain advantage: such QBO phases will exactly correspond to real ones. ENSO is set by implementing the parameterization of the release of latent heat by convective processes in the equatorial region, since the model does not have a realistic troposphere.
The results of the work demonstrate the main known trends, in particular, the weakening/strengthening of wave activity during the westerly/easterly QBO (Holton-Tan effect). In general, the MUAM model adequately reproduces the nuances of atmospheric circulation at different phases of the QBO, up to the heights of the thermosphere, which was demonstrated in previous works.
Consideration of the joint influence of the QBO/ENSO with this approach was made for the first time. The obtained results are new and, I think, deserve the attention of the scientific community, since they demonstrate in a simple form the basic trends in the change of the PW structures depending on the QBO and ENSO phases. Taking into account possible variations in atmospheric circulation caused by the QBO and ENSO phases is important primarily for improving the long-term forecast.
At the same time, I would like a more detailed analysis of what is the reason for such a difference in wave activity between the La Niña+wQBO phase and other phases. The second important point is how the obtained data correlate with other models.
Citation: https://doi.org/10.5194/egusphere-2025-813-CC1 -
AC1: 'Reply on CC1', Ksenia A. Didenko, 20 Jun 2025
Dear Ms Andreeva,
thank you for your appreciation of the publication.
Individual PW modes change significantly under La Niña+wQBO conditions as you correctly noted (in the case of SPW1 and 5-day PW (although the increments are insignificant for this wave), for an example). However, for other PW modes the greatest changes are determined either by the ENSO phase or by the QBO which was estimated in the work.
For numerical models the most important step is its validation, i.e. matching with observations. We pay a great attention to comparing model data and model PW structures with data from satellite observations, reanalysis (including modeling), and radar data in our researchers. The agreements of these data are published, for example, in Gavrilov et al., 2018 (https://doi.org/10 . 1016/j.asr.2017.08.022); Koval et al., 2018 (https://doi.org/10.1016/j.jastp.2017.04.013 ); Didenko et al., 2024 (https://doi.org/10.1186/s40623-024-02072-x ) and others. We will add relevant information during the revision.
Unfortunately, we are not aware of similar work on the study of wave activity with the allocation of individual combinations of QBO/ENSO. We think that comparing with other models is a good task for the future.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC1
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AC1: 'Reply on CC1', Ksenia A. Didenko, 20 Jun 2025
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CC2: 'Comment on egusphere-2025-813', Eugene Maurchev, 19 Jun 2025
Dear authors,
the proposed preprint is well written and the proposed investigation interesting and useful. Thanks to numerical modeling, in this case using the general atmospheric circulation model, it is indeed possible to estimate the effect of Natural tropical oscillations on the structures of atmospheric waves of a global scale. This task is currently very relevant due to the unquestionably influence of such waves on the thermal and dynamic regime of the atmosphere.
An interesting and impressive result, in my opinion, is the quantitative estimates of the amplitudes of planetary waves increments under conditions of various QBO and ENSO combinations, as well as the low sensitivity of the 5-day wave to these combinations. However, I have a few questions:
The panels b-e of the figures show the increments of amplitudes and wave activity fluxes. Which of these values was statistically evaluated?
What are the differences between runs within one ensemble when conducting numerical experiments?
Citation: https://doi.org/10.5194/egusphere-2025-813-CC2 -
AC2: 'Reply on CC2', Ksenia A. Didenko, 20 Jun 2025
Dear Mr Maurchev,
thank you for your attention to the publication and the questions. The answers are presented below.
The statistical significance was evaluated for all the increments presented: the amplitudes of individual PW and the wave activity fluxes. To avoid confusion, shaded in the figures areas with insufficient statistical significance are correspond the significance of the amplitude increments. Our estimates have shown that the areas of statistically significant increments of the EP fluxes roughly correspond to the amplitude regions.
From the point of view of conducting numerical experiments, the ensembles of solutions differ only in the specified distributions of zonal wind and latent heat release to account for QBO and ENSO. The initial, boundary, and background conditions do not change. Runs are formed within the same ensemble corresponding to different phases of oscillations between the mean flow and the PW in the middle atmosphere. These phases in the MUAM are controlled by changing the date of inclusion of diurnal variations in solar heating and generation of normal atmospheric modes. We will expand the description of the model experiment.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC2
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AC2: 'Reply on CC2', Ksenia A. Didenko, 20 Jun 2025
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CC3: 'Comment on egusphere-2025-813', Olga Zorkaltseva, 20 Jun 2025
This manuscript presents a timely and well-designed modeling study investigating the joint influence of QBO and ENSO phases on planetary wave (PW) dynamics in the boreal winter atmosphere. The authors effectively utilize the MUAM model to isolate the complex interactions between these major tropical oscillations and their significant impacts on both stationary (SPW1, SPW2) and traveling PWs. The study addresses a highly relevant problem with clear implications for understanding stratospheric polar vortex variability, SSW events, and downstream impacts on regional weather extremes in the Arctic and Asia-Pacific.
The explicit focus on the combined effect of QBO and ENSO phases on a broad spectrum of PWs is a significant strength of this work. I recommend expand the conclusion by synthesizing the key findings regarding the overall impact on the stratospheric polar vortex. How do the modeled PW changes under different QBO/ENSO combinations relate to vortex strength/position/stability and potential generation SSW likelihood? Or consider summarizing the primary atmospheric regions (Stratosphere / Mesosphere / Lower Thermosphere) most strongly affected by the different QBO/ENSO phase combinations based on the results. Addressing these points will further strengthen an already valuable contribution to the atmospheric science.Citation: https://doi.org/10.5194/egusphere-2025-813-CC3 -
AC3: 'Reply on CC3', Ksenia A. Didenko, 20 Jun 2025
Dear Ms Zorkaltseva,
thank you for your attention to the publication and high appreciation.
Your suggestions can definitely not only improve this manuscript, but also provide an opportunity to expand the research. Your suggestion for regional clarification of the results obtained will be taken into account at the next stage of the publication review.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC3
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AC3: 'Reply on CC3', Ksenia A. Didenko, 20 Jun 2025
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RC1: 'Comment on egusphere-2025-813', Anonymous Referee #1, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-813/egusphere-2025-813-RC1-supplement.pdf
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AC4: 'Reply on RC1', Ksenia A. Didenko, 23 Jun 2025
Dear Reviewer,
author and all co-authors would like to thank you for your attention to the publication, high valuation, and useful comments.
General Comments:
- Introduction: I really enjoyed reading this introduction, it is one of the best I’ve reviewed in some time. It was informative, well-structured, and comprehensive, and did a good job of motivating the work. Excellent.
- Results: Your results section presents a lot of information in a very concise manner. I would like a little bit more discussion of the implications of these results. For instance, you motivated the work very well by discussing the relationship of these waves with the polar vortex and SSWs. Based on these results, what can you say regarding the potential impacts of these oscillations on something like the polar vortex?
In one of our recent studies, we evaluated the effect of various combinations of QBO and ENSO phases on the SSW formation (Lifar et al., 2024). As you correctly noted, the formation in the SSW is inextricably linked to the intensity of the stratospheric polar vortex. We have found that SSW was observed in 9 out of 10 model runs under El Niño + eQBO in January-February with 4 major SSW. Under El Niño + wQBO SSW was modeled in 8 out of 10 runs with 2 major ones. SSW was modeled in half of the runs with one major during the cold phase of the QBO + eQBO. SSW is not modeled under La Niña + wQBO.
Lifar, V. D., Didenko, K. A., Koval, A. V., and Ermakova, T. S.: Numerical Simulation of QBO and ENSO Phase Effect on the Propagation of Planetary Waves and the Evolvement of Sudden Stratospheric Warming, Atmos. Ocean. Opt., 37, 415–421, doi:10.1134/S1024856024700489, 2024.
Particular thanks for the specific comments. Corrections have been made to the manuscript and will be displayed in the next version after a public discussion.
Specific Comments:
- Line 56: I would add the formation of cold waves across other regions in addition to east Asia, like North America for instance
The section and references have been expanded, thank you.
“This can lead to the alterations to the jet stream’s location, consequently affecting the storm trajectories, the formation of cold waves over East Asia, North America, and Europe, and the regional modulation of winter temperature and wind patterns, as well as the subsequent summer season, particularly when combined with tropical oscillations (Thompson et al., 2002; Yang et al., 2002; Lü et al., 2020; Zhang et al., 2020; Zhang et al., 2022; Yan et al., 2023). For example, Zhang et al. (2022) proposed a mechanism explaining the influence of major SSW, accompanied by the displacement of the stratospheric polar vortex on the unprecedented cold wave that occurred in East Asia in January 2021. An analysis of cold air outbreaks in Canada and midwestern USA after January, 2019 SSW in the presence of lower Barents-Kara Sea ice based on both observations and model experiments is presented in Zhang et al. (2020). Lü et al. (2020) showed that anomalous Siberian snow accumulation could have played an important role in the 2018 SSW occurrence. This SSW with a vortex split type and predominant planetary waves of zonal wave 2 regime has led to cold extremes over Europe.“
Lü, Z., Li, F., Orsolini, Y.J., Gao, Y. and He, S.: Understanding of European Cold Extremes, Sudden Stratospheric Warming, and Siberian Snow Accumulation in the Winter of 2017/18, J. Climate, 33, 527–545, doi:10.1175/JCLI-D-18-0861.1, 2020.
Zhang, P., Wu, Y., Chen, G., and Yu, Y.: North American cold events following sudden stratospheric warming in the presence of low Barents-Kara Sea sea ice, Environ. Res. Lett., 15, 124017, 2020.
- Line 93: Mention approximate heights of the F2 layer / top of the dataset. Additionally, more details about the vertical and horizontal resolutions of the model would be nice
The description of the MUAM spatial resolution has been expanded.
“As a result of the modelling, it was possible to obtain distributions of meteorological parameters from the level of 1000 hPa to the heights of the ionospheric layer F2 or approximately 300 km with 56 hight levels. The horizontal resolution is 5.625°×5° in longitude and latitude, respectively.”
- Line 103 – 104: consonant -> consistent
Revised.
- Line 106: Friedrich et al. (1993); Wallace et al. (1993) à Friedrich et al. (1993) and Wallace et al. (1993)
Thanks, revised.
- Line 108: “In this work one of the latest versions of the MUAM was used”, which version exactly?
Historically, the model version is not explicitly specified in its name. As indicated in the section you mentioned, the latest version of the MUAM is determined by the parameterizations of atmospheric heating rates caused by the release of latent heat inclusion.
- Line 133: Important advantage -> An important advantage
Thanks, revised.
Yours sincerely. K.A. Didenko and co-authors
Citation: https://doi.org/10.5194/egusphere-2025-813-AC4
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AC4: 'Reply on RC1', Ksenia A. Didenko, 23 Jun 2025
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RC2: 'Comment on egusphere-2025-813', Anonymous Referee #3, 01 Jul 2025
The paper investigates the influence of the ENSO and QBO tropical oscillations on various planetary waves (PWs), namely the stationary PW with zonal wavenumbers 1 and 2 (SPW1, SPW2) and westward travelling quasy 5-, 10- and 7- day PWS. The authors use the MUAM code and consider an ensemble of 10 runs for each of the four combinations of El Niño/La Niña and easterly/westerly QBO. A total of 40 simulations was run.
The authors found that the tropical oscillations can significantly change the amplitudes of the PWs, and detail the specific changes that the different combinations produce. The design of the experiment is interesting and the science results a novel contribution to the literature. However I recommend major revisions to the manuscript before publication for the reasons below.
- The conclusion that the structure of SPW2 amplitudes is basically opposite to SPW1 is not entirely apparent to me. SPW2 under El Niño shows a decrease in amplitudes around the climatological peak, but SPW1 and SPW2 results at La Niña conditions just seem different, not opposite. Please could you clarify which part you mean is the opposite, otherwise please could you take another look at the conclusion
- The conclusion that similar features in are seen in SPW1 and SPW2 amplitude increments during El Niño regardless of QBO phase is not apparent to me. The distribution of positive and negative increments is different between SPW1 and SPW2. Please could you clarify which parts are similar, otherwise please could you take another look at reformulating this conclusion.
- You mention that the 5-day NM amplitude sees a change in flux direction to point from south to north for the eQBO phase, and vice versa for the wQBO phase, regardless of ENSO phase. However I see a decrease in fluxes around the climatological peak during the La Niña/eQBO phase, and an increase for El Niño/wQBO. Please could you clarify which parts of the figures you are drawing your conclusions from, or investigate the conclusion further.
- Whilst the overall presentation and figures is of high quality, there are a significant improvements required to the writing and grammar before I would recommend publication. I have detailed some below, but ask that the authors check the manuscript carefully and make the relevant sentence structure and grammatical changes.
Minor comments
- Please could you make your simulation set-up more clear. It is not clear to me what years you have picked for your simulations and how you have curated your ensemble. If you could perhaps show a table which details some more information about the simulations, e.g., what years are modelled and what stages of ENSO and QBO they are, that would be helpful.
- L134 - 140. This portion of the paragraph highlights how well MUAM reproduces the structures of PWs, however it is not shown how. I appreciate MUAM PW performance has been discussed in various studies, as you highlight, but perhaps you could at least give the reader an idea of how well MUAM performs in your wavelet analysis.
- L195 - You mention that the increase of PW amplitudes is attributed to secondary gravity waves by the authors, but then mention other processes such as tides and wave-wave interactions, and not secondary gravity waves. Could you please clarify what you are highlighting here?
- Paragraph starting on L 108. Could you comment on the accuracy of the parameterization and the dependence on ENSO, and the sensitivity of the results to the parameterization? Would the results be much different if a different parameterization was used?
- L133 “fidelity reproduction” should probably be “reproduction fidelity”
- L 138 “The accuracy of the simulated by the MUAM PWs and their temporal variability has recently been…” should probably be “The accuracy and temporal variability of the PWs simulated by the MUAM has recently been”
- L 145 “reaction” -> “reacting”
- L171 “40 model runs (for 4 combinations of ENSO and QBO, 10 runs each)” - no need to repeat
- L176 - “Figs.” -> figures
- L194 - “gray areas and arrows in Fig. 1a and 2a.” It’s not clear how this is relevant. Why is SPW2 wave activity flux mentioned separately? Is SPW1 and SPW2 not covered in the first part of the sentence?
- L195 - ““The reasons for the observed PW amplitude increases related to secondary waves generation are presented in … ” what observed PW amplitude increase do you mean here, the orange region around 60N and 90km in SPW1 and SPW2? Could you please clarify?
- L209 “Upon that in the area of SPW1 climatic maxima” -> “In the area of the SPW1 climatic maximum”
- L210 “4 times.” -> “A factor of 4”
- L 222 - I don’t see a large increase in amplitudes and fluxes in the lower thermosphere only in your Figs 1a and 1c. It looks like there is a 1-10% increase at various regions for all cases. It looks like the strongest increase of amplitude in the LT is around 60N 90 km in La Niña/eQBO. Could you please clarify what region you are highlighting?
- L 225 - It doesn’t look like SPW2 has a unique distinction between El Niño and La Niña in the thermosphere in Figs b - e. If you mean the changes in the local max at 60N 120km, which indeed show the behaviour you describe, please could you clarify that in the text.
- L 232 “transmitting” -> “transmission”
- L235 “mesosphere – the” -> “mesosphere and the”
- L 236 ““thermosphere, the mid-latitude” -> “thermosphere and the mid-latitude”Citation: https://doi.org/10.5194/egusphere-2025-813-RC2 -
AC5: 'Reply on RC2', Ksenia A. Didenko, 11 Jul 2025
Dear Reviewer,
Author and all co-authors would like to thank you for your attention to the manuscript and useful comments. We would also like to express our particular thanks for a constructive discussion of the planetary waves structures. The corrections and additions made to the manuscript in accordance with Reviewers comments are highlighted. Our response is provided below in bold font.
The paper investigates the influence of the ENSO and QBO tropical oscillations on various planetary waves (PWs), namely the stationary PW with zonal wavenumbers 1 and 2 (SPW1, SPW2) and westward travelling quasy 5-, 10- and 7- day PWS. The authors use the MUAM code and consider an ensemble of 10 runs for each of the four combinations of El Niño/La Niña and easterly/westerly QBO. A total of 40 simulations was run.
The authors found that the tropical oscillations can significantly change the amplitudes of the PWs, and detail the specific changes that the different combinations produce. The design of the experiment is interesting and the science results a novel contribution to the literature. However I recommend major revisions to the manuscript before publication for the reasons below.
- The conclusion that the structure of SPW2 amplitudes is basically opposite to SPW1 is not entirely apparent to me. SPW2 under El Niño shows a decrease in amplitudes around the climatological peak, but SPW1 and SPW2 results at La Niña conditions just seem different, not opposite. Please could you clarify which part you mean is the opposite, otherwise please could you take another look at the conclusion
Thank you, clarifications have been added to the Conclusion.
- The conclusion that similar features in are seen in SPW1 and SPW2 amplitude increments during El Niño regardless of QBO phase is not apparent to me. The distribution of positive and negative increments is different between SPW1 and SPW2. Please could you clarify which parts are similar, otherwise please could you take another look at reformulating this conclusion.
If we understood you correctly, the comment concerns the second point in the Conclusion. This result was obtained in the MLT region.
- You mention that the 5-day NM amplitude sees a change in flux direction to point from south to north for the eQBO phase, and vice versa for the wQBO phase, regardless of ENSO phase. However I see a decrease in fluxes around the climatological peak during the La Niña/eQBO phase, and an increase for El Niño/wQBO. Please could you clarify which parts of the figures you are drawing your conclusions from, or investigate the conclusion further.
Clarifications concerning the horizontal transfer area were included in the discussed paragraph of the Conclusion.
- Whilst the overall presentation and figures is of high quality, there are a significant improvements required to the writing and grammar before I would recommend publication. I have detailed some below, but ask that the authors check the manuscript carefully and make the relevant sentence structure and grammatical changes.
Thank you for your comments. The text of the publication has been revised.Minor comments
- Please could you make your simulation set-up more clear. It is not clear to me what years you have picked for your simulations and how you have curated your ensemble. If you could perhaps show a table which details some more information about the simulations, e.g., what years are modelled and what stages of ENSO and QBO they are, that would be helpful.
Paragraph 2.1 has been expanded to include a more detailed description of the MUAM simulation set-up.
- L134 - 140. This portion of the paragraph highlights how well MUAM reproduces the structures of PWs, however it is not shown how. I appreciate MUAM PW performance has been discussed in various studies, as you highlight, but perhaps you could at least give the reader an idea of how well MUAM performs in your wavelet analysis.
Paragraph 2.2 has been expanded.
- L195 - You mention that the increase of PW amplitudes is attributed to secondary gravity waves by the authors, but then mention other processes such as tides and wave-wave interactions, and not secondary gravity waves. Could you please clarify what you are highlighting here?
Different mechanisms for the formation of amplitude maxima above the region of waveguide interruption are indicated in the specified references, including modulation by gravity waves and planetary ones. Explanations have been added to paragraph 3.1.
- Paragraph starting on L 108. Could you comment on the accuracy of the parameterization and the dependence on ENSO, and the sensitivity of the results to the parameterization? Would the results be much different if a different parameterization was used?
The accuracy of parameterization and the dependence on ENSO used in current work were discussed in detail in Ermakova et al. (2019) (the reference is also presented in the manuscript). Parameterization development and evaluation of their accuracy are out of the scope of this study.Ermakova, T. S., Aniskina, O. G., Statnaya, I. A., Motsakov, M. A., and Pogoreltsev, A. I.: Simulation of the ENSO influence on the extra-tropical middle atmosphere, Earth Planets Space, 71, 8, doi:10.1186/s40623-019-0987-9, 2019.
- L133 “fidelity reproduction” should probably be “reproduction fidelity”
Corrected.
- L 138 “The accuracy of the simulated by the MUAM PWs and their temporal variability has recently been…” should probably be “The accuracy and temporal variability of the PWs simulated by the MUAM has recently been”
Corrected.
- L 145 “reaction” -> “reacting”
Corrected.
- L171 “40 model runs (for 4 combinations of ENSO and QBO, 10 runs each)” - no need to repeat
Thanks, revised.
- L176 - “Figs.” -> figures
Thanks, the above remarks have been revised.
- L194 - “gray areas and arrows in Fig. 1a and 2a.” It’s not clear how this is relevant. Why is SPW2 wave activity flux mentioned separately? Is SPW1 and SPW2 not covered in the first part of the sentence?
Clarifications were made in the first paragraph of paragraph 3.1.
- L195 - ““The reasons for the observed PW amplitude increases related to secondary waves generation are presented in … ” what observed PW amplitude increase do you mean here, the orange region around 60N and 90km in SPW1 and SPW2? Could you please clarify?
Comments were added to the first paragraph of paragraph 3.1.
- L209 “Upon that in the area of SPW1 climatic maxima” -> “In the area of the SPW1 climatic maximum”
Thanks, revised.
- L210 “4 times.” -> “A factor of 4”Thanks, revised.
- L 222 - I don’t see a large increase in amplitudes and fluxes in the lower thermosphere only in your Figs 1a and 1c. It looks like there is a 1-10% increase at various regions for all cases. It looks like the strongest increase of amplitude in the LT is around 60N 90 km in La Niña/eQBO. Could you please clarify what region you are highlighting?
We focused on effects up to 120 km in this article, although calculations were performed up to 300 km. However, a detailed review of the mechanisms of PW propagation into the thermosphere remains beyond the scope of this study, so we will focus on the upper atmosphere in the following works. The text of the article has been edited.
- L 225 - It doesn’t look like SPW2 has a unique distinction between El Niño and La Niña in the thermosphere in Figs b - e. If you mean the changes in the local max at 60N 120km, which indeed show the behaviour you describe, please could you clarify that in the text.
Clarifications were made to the text.
- L 232 “transmitting” -> “transmission”
Corrected.
- L235 “mesosphere – the” -> “mesosphere and the”
Corrected.
- L 236 ““thermosphere, the mid-latitude” -> “thermosphere and the mid-latitude”Thanks, the above remarks have been revised.
Yours sincerely.
K.A. Didenko and co-authors
Citation: https://doi.org/10.5194/egusphere-2025-813-AC5
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AC5: 'Reply on RC2', Ksenia A. Didenko, 11 Jul 2025
Status: closed
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CC1: 'Comment on egusphere-2025-813', Maria Andreeva, 19 Jun 2025
As it became clear to me after reading the preprint, the study uses a fairly simple concept of numerical modeling. In the numerical model of global circulation, conditions are set correspond to different phases of the QBO and ENSO. The former are set by the nudging procedure, since the vertical resolution of the model does not allow reproducing the QBO independently. This even has a certain advantage: such QBO phases will exactly correspond to real ones. ENSO is set by implementing the parameterization of the release of latent heat by convective processes in the equatorial region, since the model does not have a realistic troposphere.
The results of the work demonstrate the main known trends, in particular, the weakening/strengthening of wave activity during the westerly/easterly QBO (Holton-Tan effect). In general, the MUAM model adequately reproduces the nuances of atmospheric circulation at different phases of the QBO, up to the heights of the thermosphere, which was demonstrated in previous works.
Consideration of the joint influence of the QBO/ENSO with this approach was made for the first time. The obtained results are new and, I think, deserve the attention of the scientific community, since they demonstrate in a simple form the basic trends in the change of the PW structures depending on the QBO and ENSO phases. Taking into account possible variations in atmospheric circulation caused by the QBO and ENSO phases is important primarily for improving the long-term forecast.
At the same time, I would like a more detailed analysis of what is the reason for such a difference in wave activity between the La Niña+wQBO phase and other phases. The second important point is how the obtained data correlate with other models.
Citation: https://doi.org/10.5194/egusphere-2025-813-CC1 -
AC1: 'Reply on CC1', Ksenia A. Didenko, 20 Jun 2025
Dear Ms Andreeva,
thank you for your appreciation of the publication.
Individual PW modes change significantly under La Niña+wQBO conditions as you correctly noted (in the case of SPW1 and 5-day PW (although the increments are insignificant for this wave), for an example). However, for other PW modes the greatest changes are determined either by the ENSO phase or by the QBO which was estimated in the work.
For numerical models the most important step is its validation, i.e. matching with observations. We pay a great attention to comparing model data and model PW structures with data from satellite observations, reanalysis (including modeling), and radar data in our researchers. The agreements of these data are published, for example, in Gavrilov et al., 2018 (https://doi.org/10 . 1016/j.asr.2017.08.022); Koval et al., 2018 (https://doi.org/10.1016/j.jastp.2017.04.013 ); Didenko et al., 2024 (https://doi.org/10.1186/s40623-024-02072-x ) and others. We will add relevant information during the revision.
Unfortunately, we are not aware of similar work on the study of wave activity with the allocation of individual combinations of QBO/ENSO. We think that comparing with other models is a good task for the future.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC1
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AC1: 'Reply on CC1', Ksenia A. Didenko, 20 Jun 2025
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CC2: 'Comment on egusphere-2025-813', Eugene Maurchev, 19 Jun 2025
Dear authors,
the proposed preprint is well written and the proposed investigation interesting and useful. Thanks to numerical modeling, in this case using the general atmospheric circulation model, it is indeed possible to estimate the effect of Natural tropical oscillations on the structures of atmospheric waves of a global scale. This task is currently very relevant due to the unquestionably influence of such waves on the thermal and dynamic regime of the atmosphere.
An interesting and impressive result, in my opinion, is the quantitative estimates of the amplitudes of planetary waves increments under conditions of various QBO and ENSO combinations, as well as the low sensitivity of the 5-day wave to these combinations. However, I have a few questions:
The panels b-e of the figures show the increments of amplitudes and wave activity fluxes. Which of these values was statistically evaluated?
What are the differences between runs within one ensemble when conducting numerical experiments?
Citation: https://doi.org/10.5194/egusphere-2025-813-CC2 -
AC2: 'Reply on CC2', Ksenia A. Didenko, 20 Jun 2025
Dear Mr Maurchev,
thank you for your attention to the publication and the questions. The answers are presented below.
The statistical significance was evaluated for all the increments presented: the amplitudes of individual PW and the wave activity fluxes. To avoid confusion, shaded in the figures areas with insufficient statistical significance are correspond the significance of the amplitude increments. Our estimates have shown that the areas of statistically significant increments of the EP fluxes roughly correspond to the amplitude regions.
From the point of view of conducting numerical experiments, the ensembles of solutions differ only in the specified distributions of zonal wind and latent heat release to account for QBO and ENSO. The initial, boundary, and background conditions do not change. Runs are formed within the same ensemble corresponding to different phases of oscillations between the mean flow and the PW in the middle atmosphere. These phases in the MUAM are controlled by changing the date of inclusion of diurnal variations in solar heating and generation of normal atmospheric modes. We will expand the description of the model experiment.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC2
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AC2: 'Reply on CC2', Ksenia A. Didenko, 20 Jun 2025
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CC3: 'Comment on egusphere-2025-813', Olga Zorkaltseva, 20 Jun 2025
This manuscript presents a timely and well-designed modeling study investigating the joint influence of QBO and ENSO phases on planetary wave (PW) dynamics in the boreal winter atmosphere. The authors effectively utilize the MUAM model to isolate the complex interactions between these major tropical oscillations and their significant impacts on both stationary (SPW1, SPW2) and traveling PWs. The study addresses a highly relevant problem with clear implications for understanding stratospheric polar vortex variability, SSW events, and downstream impacts on regional weather extremes in the Arctic and Asia-Pacific.
The explicit focus on the combined effect of QBO and ENSO phases on a broad spectrum of PWs is a significant strength of this work. I recommend expand the conclusion by synthesizing the key findings regarding the overall impact on the stratospheric polar vortex. How do the modeled PW changes under different QBO/ENSO combinations relate to vortex strength/position/stability and potential generation SSW likelihood? Or consider summarizing the primary atmospheric regions (Stratosphere / Mesosphere / Lower Thermosphere) most strongly affected by the different QBO/ENSO phase combinations based on the results. Addressing these points will further strengthen an already valuable contribution to the atmospheric science.Citation: https://doi.org/10.5194/egusphere-2025-813-CC3 -
AC3: 'Reply on CC3', Ksenia A. Didenko, 20 Jun 2025
Dear Ms Zorkaltseva,
thank you for your attention to the publication and high appreciation.
Your suggestions can definitely not only improve this manuscript, but also provide an opportunity to expand the research. Your suggestion for regional clarification of the results obtained will be taken into account at the next stage of the publication review.
Citation: https://doi.org/10.5194/egusphere-2025-813-AC3
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AC3: 'Reply on CC3', Ksenia A. Didenko, 20 Jun 2025
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RC1: 'Comment on egusphere-2025-813', Anonymous Referee #1, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-813/egusphere-2025-813-RC1-supplement.pdf
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AC4: 'Reply on RC1', Ksenia A. Didenko, 23 Jun 2025
Dear Reviewer,
author and all co-authors would like to thank you for your attention to the publication, high valuation, and useful comments.
General Comments:
- Introduction: I really enjoyed reading this introduction, it is one of the best I’ve reviewed in some time. It was informative, well-structured, and comprehensive, and did a good job of motivating the work. Excellent.
- Results: Your results section presents a lot of information in a very concise manner. I would like a little bit more discussion of the implications of these results. For instance, you motivated the work very well by discussing the relationship of these waves with the polar vortex and SSWs. Based on these results, what can you say regarding the potential impacts of these oscillations on something like the polar vortex?
In one of our recent studies, we evaluated the effect of various combinations of QBO and ENSO phases on the SSW formation (Lifar et al., 2024). As you correctly noted, the formation in the SSW is inextricably linked to the intensity of the stratospheric polar vortex. We have found that SSW was observed in 9 out of 10 model runs under El Niño + eQBO in January-February with 4 major SSW. Under El Niño + wQBO SSW was modeled in 8 out of 10 runs with 2 major ones. SSW was modeled in half of the runs with one major during the cold phase of the QBO + eQBO. SSW is not modeled under La Niña + wQBO.
Lifar, V. D., Didenko, K. A., Koval, A. V., and Ermakova, T. S.: Numerical Simulation of QBO and ENSO Phase Effect on the Propagation of Planetary Waves and the Evolvement of Sudden Stratospheric Warming, Atmos. Ocean. Opt., 37, 415–421, doi:10.1134/S1024856024700489, 2024.
Particular thanks for the specific comments. Corrections have been made to the manuscript and will be displayed in the next version after a public discussion.
Specific Comments:
- Line 56: I would add the formation of cold waves across other regions in addition to east Asia, like North America for instance
The section and references have been expanded, thank you.
“This can lead to the alterations to the jet stream’s location, consequently affecting the storm trajectories, the formation of cold waves over East Asia, North America, and Europe, and the regional modulation of winter temperature and wind patterns, as well as the subsequent summer season, particularly when combined with tropical oscillations (Thompson et al., 2002; Yang et al., 2002; Lü et al., 2020; Zhang et al., 2020; Zhang et al., 2022; Yan et al., 2023). For example, Zhang et al. (2022) proposed a mechanism explaining the influence of major SSW, accompanied by the displacement of the stratospheric polar vortex on the unprecedented cold wave that occurred in East Asia in January 2021. An analysis of cold air outbreaks in Canada and midwestern USA after January, 2019 SSW in the presence of lower Barents-Kara Sea ice based on both observations and model experiments is presented in Zhang et al. (2020). Lü et al. (2020) showed that anomalous Siberian snow accumulation could have played an important role in the 2018 SSW occurrence. This SSW with a vortex split type and predominant planetary waves of zonal wave 2 regime has led to cold extremes over Europe.“
Lü, Z., Li, F., Orsolini, Y.J., Gao, Y. and He, S.: Understanding of European Cold Extremes, Sudden Stratospheric Warming, and Siberian Snow Accumulation in the Winter of 2017/18, J. Climate, 33, 527–545, doi:10.1175/JCLI-D-18-0861.1, 2020.
Zhang, P., Wu, Y., Chen, G., and Yu, Y.: North American cold events following sudden stratospheric warming in the presence of low Barents-Kara Sea sea ice, Environ. Res. Lett., 15, 124017, 2020.
- Line 93: Mention approximate heights of the F2 layer / top of the dataset. Additionally, more details about the vertical and horizontal resolutions of the model would be nice
The description of the MUAM spatial resolution has been expanded.
“As a result of the modelling, it was possible to obtain distributions of meteorological parameters from the level of 1000 hPa to the heights of the ionospheric layer F2 or approximately 300 km with 56 hight levels. The horizontal resolution is 5.625°×5° in longitude and latitude, respectively.”
- Line 103 – 104: consonant -> consistent
Revised.
- Line 106: Friedrich et al. (1993); Wallace et al. (1993) à Friedrich et al. (1993) and Wallace et al. (1993)
Thanks, revised.
- Line 108: “In this work one of the latest versions of the MUAM was used”, which version exactly?
Historically, the model version is not explicitly specified in its name. As indicated in the section you mentioned, the latest version of the MUAM is determined by the parameterizations of atmospheric heating rates caused by the release of latent heat inclusion.
- Line 133: Important advantage -> An important advantage
Thanks, revised.
Yours sincerely. K.A. Didenko and co-authors
Citation: https://doi.org/10.5194/egusphere-2025-813-AC4
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AC4: 'Reply on RC1', Ksenia A. Didenko, 23 Jun 2025
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RC2: 'Comment on egusphere-2025-813', Anonymous Referee #3, 01 Jul 2025
The paper investigates the influence of the ENSO and QBO tropical oscillations on various planetary waves (PWs), namely the stationary PW with zonal wavenumbers 1 and 2 (SPW1, SPW2) and westward travelling quasy 5-, 10- and 7- day PWS. The authors use the MUAM code and consider an ensemble of 10 runs for each of the four combinations of El Niño/La Niña and easterly/westerly QBO. A total of 40 simulations was run.
The authors found that the tropical oscillations can significantly change the amplitudes of the PWs, and detail the specific changes that the different combinations produce. The design of the experiment is interesting and the science results a novel contribution to the literature. However I recommend major revisions to the manuscript before publication for the reasons below.
- The conclusion that the structure of SPW2 amplitudes is basically opposite to SPW1 is not entirely apparent to me. SPW2 under El Niño shows a decrease in amplitudes around the climatological peak, but SPW1 and SPW2 results at La Niña conditions just seem different, not opposite. Please could you clarify which part you mean is the opposite, otherwise please could you take another look at the conclusion
- The conclusion that similar features in are seen in SPW1 and SPW2 amplitude increments during El Niño regardless of QBO phase is not apparent to me. The distribution of positive and negative increments is different between SPW1 and SPW2. Please could you clarify which parts are similar, otherwise please could you take another look at reformulating this conclusion.
- You mention that the 5-day NM amplitude sees a change in flux direction to point from south to north for the eQBO phase, and vice versa for the wQBO phase, regardless of ENSO phase. However I see a decrease in fluxes around the climatological peak during the La Niña/eQBO phase, and an increase for El Niño/wQBO. Please could you clarify which parts of the figures you are drawing your conclusions from, or investigate the conclusion further.
- Whilst the overall presentation and figures is of high quality, there are a significant improvements required to the writing and grammar before I would recommend publication. I have detailed some below, but ask that the authors check the manuscript carefully and make the relevant sentence structure and grammatical changes.
Minor comments
- Please could you make your simulation set-up more clear. It is not clear to me what years you have picked for your simulations and how you have curated your ensemble. If you could perhaps show a table which details some more information about the simulations, e.g., what years are modelled and what stages of ENSO and QBO they are, that would be helpful.
- L134 - 140. This portion of the paragraph highlights how well MUAM reproduces the structures of PWs, however it is not shown how. I appreciate MUAM PW performance has been discussed in various studies, as you highlight, but perhaps you could at least give the reader an idea of how well MUAM performs in your wavelet analysis.
- L195 - You mention that the increase of PW amplitudes is attributed to secondary gravity waves by the authors, but then mention other processes such as tides and wave-wave interactions, and not secondary gravity waves. Could you please clarify what you are highlighting here?
- Paragraph starting on L 108. Could you comment on the accuracy of the parameterization and the dependence on ENSO, and the sensitivity of the results to the parameterization? Would the results be much different if a different parameterization was used?
- L133 “fidelity reproduction” should probably be “reproduction fidelity”
- L 138 “The accuracy of the simulated by the MUAM PWs and their temporal variability has recently been…” should probably be “The accuracy and temporal variability of the PWs simulated by the MUAM has recently been”
- L 145 “reaction” -> “reacting”
- L171 “40 model runs (for 4 combinations of ENSO and QBO, 10 runs each)” - no need to repeat
- L176 - “Figs.” -> figures
- L194 - “gray areas and arrows in Fig. 1a and 2a.” It’s not clear how this is relevant. Why is SPW2 wave activity flux mentioned separately? Is SPW1 and SPW2 not covered in the first part of the sentence?
- L195 - ““The reasons for the observed PW amplitude increases related to secondary waves generation are presented in … ” what observed PW amplitude increase do you mean here, the orange region around 60N and 90km in SPW1 and SPW2? Could you please clarify?
- L209 “Upon that in the area of SPW1 climatic maxima” -> “In the area of the SPW1 climatic maximum”
- L210 “4 times.” -> “A factor of 4”
- L 222 - I don’t see a large increase in amplitudes and fluxes in the lower thermosphere only in your Figs 1a and 1c. It looks like there is a 1-10% increase at various regions for all cases. It looks like the strongest increase of amplitude in the LT is around 60N 90 km in La Niña/eQBO. Could you please clarify what region you are highlighting?
- L 225 - It doesn’t look like SPW2 has a unique distinction between El Niño and La Niña in the thermosphere in Figs b - e. If you mean the changes in the local max at 60N 120km, which indeed show the behaviour you describe, please could you clarify that in the text.
- L 232 “transmitting” -> “transmission”
- L235 “mesosphere – the” -> “mesosphere and the”
- L 236 ““thermosphere, the mid-latitude” -> “thermosphere and the mid-latitude”Citation: https://doi.org/10.5194/egusphere-2025-813-RC2 -
AC5: 'Reply on RC2', Ksenia A. Didenko, 11 Jul 2025
Dear Reviewer,
Author and all co-authors would like to thank you for your attention to the manuscript and useful comments. We would also like to express our particular thanks for a constructive discussion of the planetary waves structures. The corrections and additions made to the manuscript in accordance with Reviewers comments are highlighted. Our response is provided below in bold font.
The paper investigates the influence of the ENSO and QBO tropical oscillations on various planetary waves (PWs), namely the stationary PW with zonal wavenumbers 1 and 2 (SPW1, SPW2) and westward travelling quasy 5-, 10- and 7- day PWS. The authors use the MUAM code and consider an ensemble of 10 runs for each of the four combinations of El Niño/La Niña and easterly/westerly QBO. A total of 40 simulations was run.
The authors found that the tropical oscillations can significantly change the amplitudes of the PWs, and detail the specific changes that the different combinations produce. The design of the experiment is interesting and the science results a novel contribution to the literature. However I recommend major revisions to the manuscript before publication for the reasons below.
- The conclusion that the structure of SPW2 amplitudes is basically opposite to SPW1 is not entirely apparent to me. SPW2 under El Niño shows a decrease in amplitudes around the climatological peak, but SPW1 and SPW2 results at La Niña conditions just seem different, not opposite. Please could you clarify which part you mean is the opposite, otherwise please could you take another look at the conclusion
Thank you, clarifications have been added to the Conclusion.
- The conclusion that similar features in are seen in SPW1 and SPW2 amplitude increments during El Niño regardless of QBO phase is not apparent to me. The distribution of positive and negative increments is different between SPW1 and SPW2. Please could you clarify which parts are similar, otherwise please could you take another look at reformulating this conclusion.
If we understood you correctly, the comment concerns the second point in the Conclusion. This result was obtained in the MLT region.
- You mention that the 5-day NM amplitude sees a change in flux direction to point from south to north for the eQBO phase, and vice versa for the wQBO phase, regardless of ENSO phase. However I see a decrease in fluxes around the climatological peak during the La Niña/eQBO phase, and an increase for El Niño/wQBO. Please could you clarify which parts of the figures you are drawing your conclusions from, or investigate the conclusion further.
Clarifications concerning the horizontal transfer area were included in the discussed paragraph of the Conclusion.
- Whilst the overall presentation and figures is of high quality, there are a significant improvements required to the writing and grammar before I would recommend publication. I have detailed some below, but ask that the authors check the manuscript carefully and make the relevant sentence structure and grammatical changes.
Thank you for your comments. The text of the publication has been revised.Minor comments
- Please could you make your simulation set-up more clear. It is not clear to me what years you have picked for your simulations and how you have curated your ensemble. If you could perhaps show a table which details some more information about the simulations, e.g., what years are modelled and what stages of ENSO and QBO they are, that would be helpful.
Paragraph 2.1 has been expanded to include a more detailed description of the MUAM simulation set-up.
- L134 - 140. This portion of the paragraph highlights how well MUAM reproduces the structures of PWs, however it is not shown how. I appreciate MUAM PW performance has been discussed in various studies, as you highlight, but perhaps you could at least give the reader an idea of how well MUAM performs in your wavelet analysis.
Paragraph 2.2 has been expanded.
- L195 - You mention that the increase of PW amplitudes is attributed to secondary gravity waves by the authors, but then mention other processes such as tides and wave-wave interactions, and not secondary gravity waves. Could you please clarify what you are highlighting here?
Different mechanisms for the formation of amplitude maxima above the region of waveguide interruption are indicated in the specified references, including modulation by gravity waves and planetary ones. Explanations have been added to paragraph 3.1.
- Paragraph starting on L 108. Could you comment on the accuracy of the parameterization and the dependence on ENSO, and the sensitivity of the results to the parameterization? Would the results be much different if a different parameterization was used?
The accuracy of parameterization and the dependence on ENSO used in current work were discussed in detail in Ermakova et al. (2019) (the reference is also presented in the manuscript). Parameterization development and evaluation of their accuracy are out of the scope of this study.Ermakova, T. S., Aniskina, O. G., Statnaya, I. A., Motsakov, M. A., and Pogoreltsev, A. I.: Simulation of the ENSO influence on the extra-tropical middle atmosphere, Earth Planets Space, 71, 8, doi:10.1186/s40623-019-0987-9, 2019.
- L133 “fidelity reproduction” should probably be “reproduction fidelity”
Corrected.
- L 138 “The accuracy of the simulated by the MUAM PWs and their temporal variability has recently been…” should probably be “The accuracy and temporal variability of the PWs simulated by the MUAM has recently been”
Corrected.
- L 145 “reaction” -> “reacting”
Corrected.
- L171 “40 model runs (for 4 combinations of ENSO and QBO, 10 runs each)” - no need to repeat
Thanks, revised.
- L176 - “Figs.” -> figures
Thanks, the above remarks have been revised.
- L194 - “gray areas and arrows in Fig. 1a and 2a.” It’s not clear how this is relevant. Why is SPW2 wave activity flux mentioned separately? Is SPW1 and SPW2 not covered in the first part of the sentence?
Clarifications were made in the first paragraph of paragraph 3.1.
- L195 - ““The reasons for the observed PW amplitude increases related to secondary waves generation are presented in … ” what observed PW amplitude increase do you mean here, the orange region around 60N and 90km in SPW1 and SPW2? Could you please clarify?
Comments were added to the first paragraph of paragraph 3.1.
- L209 “Upon that in the area of SPW1 climatic maxima” -> “In the area of the SPW1 climatic maximum”
Thanks, revised.
- L210 “4 times.” -> “A factor of 4”Thanks, revised.
- L 222 - I don’t see a large increase in amplitudes and fluxes in the lower thermosphere only in your Figs 1a and 1c. It looks like there is a 1-10% increase at various regions for all cases. It looks like the strongest increase of amplitude in the LT is around 60N 90 km in La Niña/eQBO. Could you please clarify what region you are highlighting?
We focused on effects up to 120 km in this article, although calculations were performed up to 300 km. However, a detailed review of the mechanisms of PW propagation into the thermosphere remains beyond the scope of this study, so we will focus on the upper atmosphere in the following works. The text of the article has been edited.
- L 225 - It doesn’t look like SPW2 has a unique distinction between El Niño and La Niña in the thermosphere in Figs b - e. If you mean the changes in the local max at 60N 120km, which indeed show the behaviour you describe, please could you clarify that in the text.
Clarifications were made to the text.
- L 232 “transmitting” -> “transmission”
Corrected.
- L235 “mesosphere – the” -> “mesosphere and the”
Corrected.
- L 236 ““thermosphere, the mid-latitude” -> “thermosphere and the mid-latitude”Thanks, the above remarks have been revised.
Yours sincerely.
K.A. Didenko and co-authors
Citation: https://doi.org/10.5194/egusphere-2025-813-AC5
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AC5: 'Reply on RC2', Ksenia A. Didenko, 11 Jul 2025
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- 1
Andrey V. Koval
Tatiana S. Ermakova
Aleksey S. Fadeev
Luyang Xu
Ke Wei
The results showed that the joint effect of the considered tropical oscillations, originating in low latitudes, significantly affect the structure of planetary waves, not only in the regions of their climatic maxima but also throughout the middle atmosphere and thermosphere of both hemispheres.