Signatures of the Madden-Julian Oscillation in Middle Atmosphere zonal mean Temperature: Triggering the Interhemispheric Coupling pattern

Hoffmann, Christoph G.; Buth, Lena G.; von Savigny, Christian

doi:https://doi.org/10.5194/egusphere-2022-998

Preprints

https://doi.org/10.5194/egusphere-2022-998

Preprints

13 Oct 2022

| 13 Oct 2022

Signatures of the Madden-Julian Oscillation in Middle Atmosphere zonal mean Temperature: Triggering the Interhemispheric Coupling pattern

Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

Abstract. The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal variability in the troposphere. The influence of the MJO on the middle atmosphere (MA) and particularly on its temperature is of interest for both the understanding of MJO-induced teleconnections and research on the variability of the middle atmosphere. However, only few studies dealing with the influence of the MJO on MA temperature are available.

We analyze statistically the connection of the MJO and the MA zonal mean temperature based on observations by the MLS satellite instrument. We consider all eight MJO phases, different seasons and the state of the quasi-biennial oscillation (QBO). We show that the MA temperature is influenced by the state of MJO in large areas of the MA and under roughly all considered atmospheric conditions. The zonal mean temperature response is characterized by a particular spatial pattern, which we link to the interhemispheric coupling (IHC) mechanism, a known dynamical feature of the MA. The strongest temperature deviations are on the order of ± 10 K and are found in the polar winter MA during boreal winter when the QBO is in the easterly phase. Other atmospheric conditions also show temperature responses with the characteristic spatial pattern, but weaker and more noisy. The QBO turns out to have a relatively big influence during boreal winter but only a small influence during austral winter. We also discuss the role of sudden stratospheric warmings (SSWs), which have an ambivalent influence on our interpretation, because they introduce strong temperature variability in the polar winter MA themselves. In addition, SSWs are one possibility to explain the QBO influence during boreal winter. Furthermore, we also analyze the change of the temperature response pattern while the MJO progresses from one phase to the next. We find a largely systematic reaction of the MA to the phase changes, particularly a gradual altitude shift of the MA temperature response pattern, which can be seen more or less clearly depending on the atmospheric conditions.

Overall, a major outcome of the present study is the finding that the tropospheric MJO can trigger the IHC mechanism, which affects many areas of the MA. It is therefore a noteworthy example for the complex couplings across different atmospheric layers and geographical regions in the atmosphere. Additionally, it highlights close linkages of known dynamical features of the atmosphere, particularly the MJO, the IHC, the QBO, and SSWs.

Because of the wide coverage of atmospheric regions and included dynamical features, the results might help to further constrain the underlying dynamical mechanisms and could be used as a benchmark for the representation of atmospheric couplings on the intraseasonal timescale in atmospheric models.

Received: 27 Sep 2022 – Discussion started: 13 Oct 2022

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Journal article(s) based on this preprint

12 Oct 2023

Signatures of the Madden–Julian oscillation in middle-atmosphere zonal mean temperature: triggering the interhemispheric coupling pattern

Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

Atmos. Chem. Phys., 23, 12781–12799, https://doi.org/10.5194/acp-23-12781-2023,https://doi.org/10.5194/acp-23-12781-2023, 2023

Short summary

Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

Interactive discussion

Status: closed

CC1:
'Comment on egusphere-2022-998', Paul PUKITE, 16 Oct 2022

One of the phases of MJO is shifted fom the high-resolution southern oscillation index (SOI) by 21 days.

So the signatures of the two are the same, only that MJO becomes a travelling wave left in the wake of ENSO

Citation: https://doi.org/10.5194/egusphere-2022-998-CC1
- CC2:
  'Reply on CC1', Paul PUKITE, 16 Oct 2022
  
  Brain dead interface -- here are the figures
  
  Citation: https://doi.org/10.5194/egusphere-2022-998-CC2
  - CC3: 'Reply on CC2', Paul PUKITE, 16 Oct 2022
    
    Apparently, can't just copy a link
    https://imagizer.imageshack.com/img921/7305/bXNFwm.png
    https://imagizer.imageshack.com/img923/8939/lzIRem.png
    
    Citation: https://doi.org/10.5194/egusphere-2022-998-CC3
RC1:
'Comment on egusphere-2022-998', Anonymous Referee #1, 14 Nov 2022
This paper investigates the statistical temperature feature in the middle atmosphere with respect to the Madden-Julian Oscillation, considering the interconnections of seasonal variation, the QBO, and SSW based on the analysis of the satellite observation. The authors suggested that the middle atmospheric temperature response to the MJO under different atmosphere conditions manifests an interhemispheric coupling with a “five-zone” pattern. The comprehensive comparisons show that this temperature response to the MJO agrees with those suggested by previous works. The result may benefit the models' coupling process within the intra-seasonal timescale. The issue addressed in this study is well within the journal's scope. However, the analysis and discussions presented in this study lack robust logic and verification. I would suggest major revisions before it is accepted for publication.

Major comments:

At a fundamental level, the analysis results in this article are consistent with the findings of previous studies, but the new findings are unclear. In my opinion, the results obtained from the analysis in this paper may be different from the existing studies about the MJO impact under different phases of the QBO, but an in-depth analysis of the reasons is missing, and only a simple discussion of the possibilities is given. There needs to be more, an in-depth discussion and analysis are necessary.

When analyzing the boreal winter response of atmospheric temperature to the MJO, the authors do not differentiate the effect of whether or not SSW events were included in the results. In particular, the authors recognize that the strong perturbation caused by SSWs cannot be effectively disentangled from the weak perturbation caused by the MJO itself. Thus, the MJO effect on atmospheric temperature during the boreal winter in this paper is of limited importance for related studies.

It has been shown in previous studies that it takes some time for the MJO to affect the polar stratosphere via planetary waves, but the analysis presented in this paper is based on a synthetic analysis with no time delay. The results obtained may, therefore, not capture true MJO effects. The temperature response seen in phase 5 is a superposition of delayed phase 2 and phase 4 effects. Therefore, it may be possible to make the results more convincing if the results of different statistical approaches could be demonstrated.

The structure of this paper consists primarily of the analysis of the MJO composite under different atmospheric conditions and a detailed comparison to the results of previous studies. As such, this paper appears to be a mixture of a simple statistical analysis of the data and a review of MJO effects on the middle and upper atmosphere rather than a research paper addressing a specific scientific question. To give the reader a better understanding of the main content of this article, I would suggest that the article should be revised, the logic of the article should be rearranged, and the focus of the article should be emphasized on the new findings.
Citation: https://doi.org/10.5194/egusphere-2022-998-RC1
RC2:
'Comment on egusphere-2022-998', Anonymous Referee #2, 15 Nov 2022
This paper studies the response of the middle atmosphere (MA, i.e. 261 hPa – 0.00046 hPa) to the MJO using daily MLS temperature for the period of 2004 to 2021. The MJO signature is studied using composite analysis for the eight MJO phases. The same analysis is repeated for easterly and westerly QBO phases and then for summer and winter months. I have some major concerns about the analyses which are stated below.

Major comments:

Physically speaking, high-frequency variability of stratospheric polar vortex is known to be controlled by wave drag in association with planetary and/or gravity waves. Figure 1a and Figure 4 suggest that the polar vortex has a MJO signature that is marked by cold anomalies in the earlier phases of the MJO but warm anomalies in the later phases. I believe that at least one of below is required: 1) Wavelet coherence analysis shows that daily MJO index and daily zonal mean temperature at 80N, 3hP are significantly coherent with each other and the MJO leads the temperature at 80N, 3hPa. See "A Practical Guide to Wavelet Analysis", C. Torrence and G. P. Compo, 1998 for detail. Some equivalent analysis to show that the polar vortex and the MJO share the same variability would also be helpful; 2) Significant anomalies in wave drag for the MJO phases that show significant temperature anomalies in the polar region; 3) The MJO leads temperature anomalies in the MA or the SSWs. In fact, 3) has been studied by Garfinkel et al. (2012) in terms of MJO influences on the SSWs. 2) is not easy to perform using temperature because wave drag or EP flux divergence require other parameters. 1) should be feasible to perform using temperature data.

The much-strengthened MJO-MA temperature connection could be physically real. But the authors need to make the mechanism clearer. For instance, how does the MJO affect the jet streams over the North Pacific whereby it affects the strength of planetary waves from the troposphere? Firstly, the strength or frequency of the MJO is enhanced during easterly QBO. Diabatic latent heating associated with extensive MJO convection can generate Rossby waves which propagate poleward and eastward toward North America, altering the atmospheric circulation as well as the planetary waves that propagate upward into the winter stratosphere. As it stands, this chain of effects is not clear either in the analysis or in the lengthy discussion.

If I understand the method correctly, the temperature anomalies globally are effectively band-pass filtered to a temporal width of 10-90days and a latitudinal band width of 10 degree. It is thus incorrect to state that the composite differences shown are MA response to the MJO. Even if the differences are statistically significant, they can be also interpreted as the co-signal of something else and/or be interpreted MA impact on the MJO. This is because the analysis perform does not ensure that the MJO leads the zonal mean signals in the MA. For instance, the so-call interhemispheric coupling could force both the MJO and the polar vortex. Hood (2017;2018) also showed both solar and QBO can influence the MJO.

I wonder how many of the samples in DJF QBOe subgroups are serially correlated. For instance, how many daily samples are adjacent to each other in time or how many daily samples belong to the same MJO event? The question applies for DJF QBOw and JJA QBOe etc. This is because the 10-day running average applied to the temperature data. Only one sample within the 10-day window should be regarded as independent statistically.

Is it possibility to detect MJO signature according to the QBO phases without contamination from many other factors, such as ENSO, QBO, solar and volcanic eruptions in this case? Given MLS data set only covers the period of 2004-2021, during which there has been only ~7.3 QBO cycles on average. Together with the band-pass filter applied, it could be very hard to interpret the results.

Specific comments:

Abstract requires to be shortened. Bring out the key results that are closely relevant to the tittle of the paper. It would be helpful if the authors can get the line “a major outcome of the present study is the finding that the tropospheric MJO can trigger the IHC mechanism, which affects many areas of the MA” sooner and start to explain the exact areas of the MA are affected by the MJO via the IHC mechanism.

Could the weaker MJO-MA temperature connection be due to QBO disruption? E.g. A westerly phase of the QBO was disrupted in 2015/16.

Section 4 is far too long. It could be very helpful if it is a review paper. But they do not really help the readers to better understand the results presented in this paper. The discussion should be shortened and focus on the key results obtained.

In several places, the authors stated that the MJO signal in the MA depends on atmosphere conditions. But what exactly does the “atmospheric conditions” mean? The MJO itself would be one of atmospheric conditions. Please define the term properly.

In the abstract, it mentioned that “the complex couplings across different atmospheric layers and geographical regions in the atmosphere”. It would be better to put this sentence in Conclusion section where the authors can be more specific about the complex couplings regarding the MJO influences with concrete results support such a statement.

References:

Hood, L. L. (2017), QBO/solar modulation of the boreal winter Madden-Julian oscillation: A prediction for the coming solar minimum, Geophys. Res. Lett., 44, 3849– 3857, doi:10.1002/2017GL072832.

Hood, L.L., 2018: Short-Term Solar Modulation of the Madden–Julian Climate Oscillation. J. Atmos. Sci., 75, 857–873, https://doi.org/10.1175/JAS-D-17-0265.1
Citation: https://doi.org/10.5194/egusphere-2022-998-RC2
AC1: 'Responses to all Reviewer and Community Comments', Christoph Hoffmann, 09 Feb 2023

Please see the attached .pdf file for the comments.

Citation: https://doi.org/10.5194/egusphere-2022-998-AC1

Interactive discussion

Status: closed

CC1:
'Comment on egusphere-2022-998', Paul PUKITE, 16 Oct 2022

One of the phases of MJO is shifted fom the high-resolution southern oscillation index (SOI) by 21 days.

So the signatures of the two are the same, only that MJO becomes a travelling wave left in the wake of ENSO

Citation: https://doi.org/10.5194/egusphere-2022-998-CC1
- CC2:
  'Reply on CC1', Paul PUKITE, 16 Oct 2022
  
  Brain dead interface -- here are the figures
  
  Citation: https://doi.org/10.5194/egusphere-2022-998-CC2
  - CC3: 'Reply on CC2', Paul PUKITE, 16 Oct 2022
    
    Apparently, can't just copy a link
    https://imagizer.imageshack.com/img921/7305/bXNFwm.png
    https://imagizer.imageshack.com/img923/8939/lzIRem.png
    
    Citation: https://doi.org/10.5194/egusphere-2022-998-CC3
RC1:
'Comment on egusphere-2022-998', Anonymous Referee #1, 14 Nov 2022
This paper investigates the statistical temperature feature in the middle atmosphere with respect to the Madden-Julian Oscillation, considering the interconnections of seasonal variation, the QBO, and SSW based on the analysis of the satellite observation. The authors suggested that the middle atmospheric temperature response to the MJO under different atmosphere conditions manifests an interhemispheric coupling with a “five-zone” pattern. The comprehensive comparisons show that this temperature response to the MJO agrees with those suggested by previous works. The result may benefit the models' coupling process within the intra-seasonal timescale. The issue addressed in this study is well within the journal's scope. However, the analysis and discussions presented in this study lack robust logic and verification. I would suggest major revisions before it is accepted for publication.

Major comments:

At a fundamental level, the analysis results in this article are consistent with the findings of previous studies, but the new findings are unclear. In my opinion, the results obtained from the analysis in this paper may be different from the existing studies about the MJO impact under different phases of the QBO, but an in-depth analysis of the reasons is missing, and only a simple discussion of the possibilities is given. There needs to be more, an in-depth discussion and analysis are necessary.

When analyzing the boreal winter response of atmospheric temperature to the MJO, the authors do not differentiate the effect of whether or not SSW events were included in the results. In particular, the authors recognize that the strong perturbation caused by SSWs cannot be effectively disentangled from the weak perturbation caused by the MJO itself. Thus, the MJO effect on atmospheric temperature during the boreal winter in this paper is of limited importance for related studies.

It has been shown in previous studies that it takes some time for the MJO to affect the polar stratosphere via planetary waves, but the analysis presented in this paper is based on a synthetic analysis with no time delay. The results obtained may, therefore, not capture true MJO effects. The temperature response seen in phase 5 is a superposition of delayed phase 2 and phase 4 effects. Therefore, it may be possible to make the results more convincing if the results of different statistical approaches could be demonstrated.

The structure of this paper consists primarily of the analysis of the MJO composite under different atmospheric conditions and a detailed comparison to the results of previous studies. As such, this paper appears to be a mixture of a simple statistical analysis of the data and a review of MJO effects on the middle and upper atmosphere rather than a research paper addressing a specific scientific question. To give the reader a better understanding of the main content of this article, I would suggest that the article should be revised, the logic of the article should be rearranged, and the focus of the article should be emphasized on the new findings.
Citation: https://doi.org/10.5194/egusphere-2022-998-RC1
RC2:
'Comment on egusphere-2022-998', Anonymous Referee #2, 15 Nov 2022
This paper studies the response of the middle atmosphere (MA, i.e. 261 hPa – 0.00046 hPa) to the MJO using daily MLS temperature for the period of 2004 to 2021. The MJO signature is studied using composite analysis for the eight MJO phases. The same analysis is repeated for easterly and westerly QBO phases and then for summer and winter months. I have some major concerns about the analyses which are stated below.

Major comments:

Physically speaking, high-frequency variability of stratospheric polar vortex is known to be controlled by wave drag in association with planetary and/or gravity waves. Figure 1a and Figure 4 suggest that the polar vortex has a MJO signature that is marked by cold anomalies in the earlier phases of the MJO but warm anomalies in the later phases. I believe that at least one of below is required: 1) Wavelet coherence analysis shows that daily MJO index and daily zonal mean temperature at 80N, 3hP are significantly coherent with each other and the MJO leads the temperature at 80N, 3hPa. See "A Practical Guide to Wavelet Analysis", C. Torrence and G. P. Compo, 1998 for detail. Some equivalent analysis to show that the polar vortex and the MJO share the same variability would also be helpful; 2) Significant anomalies in wave drag for the MJO phases that show significant temperature anomalies in the polar region; 3) The MJO leads temperature anomalies in the MA or the SSWs. In fact, 3) has been studied by Garfinkel et al. (2012) in terms of MJO influences on the SSWs. 2) is not easy to perform using temperature because wave drag or EP flux divergence require other parameters. 1) should be feasible to perform using temperature data.

The much-strengthened MJO-MA temperature connection could be physically real. But the authors need to make the mechanism clearer. For instance, how does the MJO affect the jet streams over the North Pacific whereby it affects the strength of planetary waves from the troposphere? Firstly, the strength or frequency of the MJO is enhanced during easterly QBO. Diabatic latent heating associated with extensive MJO convection can generate Rossby waves which propagate poleward and eastward toward North America, altering the atmospheric circulation as well as the planetary waves that propagate upward into the winter stratosphere. As it stands, this chain of effects is not clear either in the analysis or in the lengthy discussion.

If I understand the method correctly, the temperature anomalies globally are effectively band-pass filtered to a temporal width of 10-90days and a latitudinal band width of 10 degree. It is thus incorrect to state that the composite differences shown are MA response to the MJO. Even if the differences are statistically significant, they can be also interpreted as the co-signal of something else and/or be interpreted MA impact on the MJO. This is because the analysis perform does not ensure that the MJO leads the zonal mean signals in the MA. For instance, the so-call interhemispheric coupling could force both the MJO and the polar vortex. Hood (2017;2018) also showed both solar and QBO can influence the MJO.

I wonder how many of the samples in DJF QBOe subgroups are serially correlated. For instance, how many daily samples are adjacent to each other in time or how many daily samples belong to the same MJO event? The question applies for DJF QBOw and JJA QBOe etc. This is because the 10-day running average applied to the temperature data. Only one sample within the 10-day window should be regarded as independent statistically.

Is it possibility to detect MJO signature according to the QBO phases without contamination from many other factors, such as ENSO, QBO, solar and volcanic eruptions in this case? Given MLS data set only covers the period of 2004-2021, during which there has been only ~7.3 QBO cycles on average. Together with the band-pass filter applied, it could be very hard to interpret the results.

Specific comments:

Abstract requires to be shortened. Bring out the key results that are closely relevant to the tittle of the paper. It would be helpful if the authors can get the line “a major outcome of the present study is the finding that the tropospheric MJO can trigger the IHC mechanism, which affects many areas of the MA” sooner and start to explain the exact areas of the MA are affected by the MJO via the IHC mechanism.

Could the weaker MJO-MA temperature connection be due to QBO disruption? E.g. A westerly phase of the QBO was disrupted in 2015/16.

Section 4 is far too long. It could be very helpful if it is a review paper. But they do not really help the readers to better understand the results presented in this paper. The discussion should be shortened and focus on the key results obtained.

In several places, the authors stated that the MJO signal in the MA depends on atmosphere conditions. But what exactly does the “atmospheric conditions” mean? The MJO itself would be one of atmospheric conditions. Please define the term properly.

In the abstract, it mentioned that “the complex couplings across different atmospheric layers and geographical regions in the atmosphere”. It would be better to put this sentence in Conclusion section where the authors can be more specific about the complex couplings regarding the MJO influences with concrete results support such a statement.

References:

Hood, L. L. (2017), QBO/solar modulation of the boreal winter Madden-Julian oscillation: A prediction for the coming solar minimum, Geophys. Res. Lett., 44, 3849– 3857, doi:10.1002/2017GL072832.

Hood, L.L., 2018: Short-Term Solar Modulation of the Madden–Julian Climate Oscillation. J. Atmos. Sci., 75, 857–873, https://doi.org/10.1175/JAS-D-17-0265.1
Citation: https://doi.org/10.5194/egusphere-2022-998-RC2
AC1: 'Responses to all Reviewer and Community Comments', Christoph Hoffmann, 09 Feb 2023

Please see the attached .pdf file for the comments.

Citation: https://doi.org/10.5194/egusphere-2022-998-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Christoph Hoffmann on behalf of the Authors (23 Mar 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (11 Apr 2023) by Peter Haynes

RR by Anonymous Referee #1 (25 Apr 2023)

RR by Anonymous Referee #2 (01 Jun 2023)

Suggestions for revision or reasons for rejection

This paper studies the response of the middle atmosphere (MA, i.e. 261 hPa – 0.00046 hPa) to the MJO using daily MLS temperature for the period of 2004 to 2021. The MJO signature is studied using composite analysis for all the eight MJO phases. The same analysis is repeated for easterly and westerly QBO phases and for boreal and austral winters / summers. The paper the paper has benefited by considering of previous reviewers’ comments. The authors have done a relatively good job this round as it becomes easier to follow the motivation, the methods and the results. But I find the discussion section is unnecessarily long and hard to follow. I recommend the authors to consider the comments below before the paper is accepted for publication.

Main comments:
1) The results shown in figure 6 are most interesting and possibly most robust as well. Although the magnitudes of the MA temperature anomalies are smaller than those in boreal winter, the statistical significance of those MJO signals in Austral winter is evidently higher, thus more believable in terms of the so-called “interhemispheric coupling”. The magnitude of the signal is also agreeable with existing literature, e.g. Karlsson et al. (2009a).
2) The MJO signal in MA temperature during boreal winter peaks at the north pole (Figs. 2-5) but during Austral winter, the largest temperature anomalies are found near the polar vortex edge, i.e. at 60S, e.g. Figs. 6-8. This characteristic difference should be mentioned in the text.
3) The entire paper can be written much more concisely than its current form. There are a lot of repetition and detailed comparison with previous studies. In particularly, Section 4, i.e. the discussion section is currently 7-8 pages. If the detailed comparison is removed, the same message can be delivered in two pages at most. Furthermore, some of the phrases, e.g. “more or less”, “roughly”, “probably”, or “appears” should not be used so frequently. Sentences that are unsupported by the results or only remotely related should be removed to improve the readership.
4) The authors need to be very careful with their expression in terms of the statistical linkage between the MJO and the MA temperatures. Try to avoid using words such as influence, affect, or response. “Signal” is more appropriate.
Specific comments
Lines 5-9, the word “influenced” is too strong as there is no mechanisms revealed by this study. I suggest changing to “We show that the MA temperature anomalies are significantly related to the MJO and its temporal development. The MJO signal in the zonalmean MA temperature is marked by a particular spatial pattern in the MA, which we link to the …. The signal with the largest magnitude is found in the polar MA during boreal winter in the order of ±10 K when the QBO at 50 hPa is in its easterly phase”.
Line 11, remove “found”.
Lines13-14, remove “Because of the wide coverage … included dynamical features” as it does not add anything to the content.
Line 45, “inner-tropospheric connections” -> “internal variability of the troposphere”.
Line 82, remove “key parameter”.
Line 89, “consider instead” -> “instead consider”
Line 125, remove “Nevertheless, we might check our boreal summer results with a special BSISO index in future.”
Lines 133-135, I wonder how the days are defined for the composite analysis. Are the temperature anomalies are estimated using 90-day or 10-day forward windows? I would recommend using a 91-day or 11-day windows if the temperature anomalies are estimated based on centred averages.
Lines 141-142, “We take generally only days into account, during
which the MJO strength was greater than 1” -> We only consider those days when the strength of the MJO is greater than 1.
Line 143, citations to other MJO related studies are required here. Also remove “apparent on all considered days”.
Lines 149-151, Again, it is not clear to me how the days in the MA temperature anomalies are defined, e.g. centred or forward from the day of a given MJO phase?
Line 189, “if a we” -> “if we”
Line 200, “present manuscript” -> “this study”
Lines 201-202, “On the other hand, by considering previous publications, which overlap in particular aspects, it becomes expectable that a physical mechanism actually exists (i.e. that we do not describe a purely statistical artifact) as we will outline in Sect. 4.” This does not add anything to the manuscript; consider removing for better flow of the paper.

Lines 204-214, these sentences can be either removed or placed in discussion section. They stop the flow of the paper.

Line 217, citations required after “during that season” to support the statement.

Line 230, “Put in other words, areas …” can be dropped.

Line 232, “whereas these four zones” -> “Whereas these two dipole patterns”.

Line 234, “the first four zones” -> “the quadrupole pattern lowerdown”

Line 235: “we will call it temporarily ” -> “ we denote these MA anomalies temporarily to”

Line 236: “in the following” -> “in sect. 4.1”. And remove the sentence after.

Line 254: “the temperature signals” -> “the MJO signal in the MA zonal-mean temperatures”

Lines 259-260: “It is obvious the temperature anomalies are even stronger than …” -> “It is evident that the temperature anomalies in the boreal winter are of larger magnitude than those shown in Fig. 2.”
Line 264: “Important is” -> “The importance is”

Line 274: “the negative polar winter anomaly” -> “the cold anomalies in the boreal polar winter”

Lines 290-295, I am completely lost from “However, …” onwards. Consider rephrasing.

Lines 296-305: Condense and move these sentences to Discussion / conclusion section, which would help the follow of the main results.

Line 310: I suggest further condensing the discussion in this section or merge it with section 3.3. The five-zone response is only recognizable during MJO phases 5 and 7 (with opposite signed signals to phase 5). There is no clear evidence in terms of signal descent.

Line 356: remove “(whereas it was …)” to get the main message across better.

Lines 360-363: the gradual descent of the temperature could start in MJP phase 2 in the Austral winter. The signal intensifies during phases 3-4 while they move downwards. Another cold anomaly zone then appears at 40-50S, 0.02-0.07hPa during MJO phase 5 and then gradually descends to the lower levels.

Lines 363-369: the abrupt pattern reverse shown in Figure 4 between MJO phase 4 and 5 might be just an artefact, e.g. the signal in the MA during phase 4 is rather weak and statistically insignificant.

Lines 386-389: “in both directions” -> “in terms of two aspects”. Then: 1) to provide a broader picture that integrate and interrelate current and previous studies; 2) to put forward some possible physical explanation in terms of the responsible mechanisms.

Line 395: be specific about “first publications”.

Lines 394: It would be very helpful to properly state the mechanism of the IHC if it is identified to be the most important mechanism that is responsible for the MJO signal in the MA temperature. Changes in planetary wave drag is not enough to explain IHC. Gravity wave drag must be involved.

Lines 419-439: need to be much condensed to bring out the key message. It is currently too detailed to grasp the main idea that the authors want to deliver.

Lines 485-486 and line 491: No evidence provided for the MJO influences on the PW activity in this study. These statements are pure speculation and should either be removed or rewrite as hypothesis.

Lines 497-505: my quick examination of Fig. 2 signal suggests that the temperature responses in the boreal winter stratosphere is almost entirely agreeable to the finding of Wang et al. (2018a). Note that stratospheric response may involve one month lag in relation to tropospheric wave forcing. I do agree that this work adds additional information in terms of mesospheric responses, which should be emphasised. The apparent downward descent of the high latitude anomalies is just dynamical response of initial wave forcing. Thus, there is no need to make such a lengthening discussion.

Lines 562-564: Remove “This can be seen …” to improve the readership.

Lines 565-579: section 4.5.2. I do not think that this section is needed or adds any new information. The QBO influence on the stratospheric polar vortex is on the seasonal time-scale while the MJO influence is sub-seasonal. The mainly reason that the boreal winter signal of the MJO becomes stronger during eQBO is the MJO becomes more active, and deeper during eQBO. Thus, there is a stronger poleward propagation of wave activity during MJO phase 4, which induces more planetary waves entering the winter stratosphere, as it has been reported by Wang et al. (2018a).

Line 615: “For the sake of brevity …” This statement should be in methodology or introduction section. Not in conclusion. If it has already stated, remove it.

Line 635: no evidence provided for this, i.e. the MJO can lead to the initial planetary wave drag disturbances of the IHC mechanism. As far as I understand, part of the IHC mechanism involves changes in gravity wave drag not just planetary waves. I would recommend remove this paragraph entirely as it has been discussed in Section 4 in detail.

Lines 655-659: This is not true. During winter, the stratospheric polar vortex descends with time climatologically. Once it is disturbed by a large-enough wave forcing, the associated warm temperature anomalies would also descend with time. On the timescale of the MJO, the descent of stratospheric anomalies in the polar region is thus fully expected as long as the initial wave drag is sufficiently large. The downward descent of polar vortex anomalies is one well-known pathway whereby the stratosphere influences the troposphere.

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ED: Publish subject to minor revisions (review by editor) (14 Jun 2023) by Peter Haynes

AR by Christoph Hoffmann on behalf of the Authors (04 Aug 2023) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (28 Aug 2023) by Peter Haynes

AR by Christoph Hoffmann on behalf of the Authors (01 Sep 2023) Author's response Manuscript

Journal article(s) based on this preprint

12 Oct 2023

Signatures of the Madden–Julian oscillation in middle-atmosphere zonal mean temperature: triggering the interhemispheric coupling pattern

Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

Atmos. Chem. Phys., 23, 12781–12799, https://doi.org/10.5194/acp-23-12781-2023,https://doi.org/10.5194/acp-23-12781-2023, 2023

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Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

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https://doi.org/10.5194/egusphere-2022-998-supplement

Christoph G. Hoffmann, Lena G. Buth, and Christian von Savigny

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The Madden–Julian oscillation is an important feature of weather in the Tropics. Although it is mainly active in the troposphere, we show that it systematically influences the air temperature in the layers above – up to about 100 km altitude and from pole to pole. We have linked this to another known far-reaching process, the interhemispheric coupling. This is basic research on atmospheric couplings and variability, but might also be of interest for intraseasonal weather forecasting models.


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