Round 1

Reviewer 1 Report

The authors compared planetary wave response and residual mean meridional circulation under various conditions caused by different El Niño types, an attempt was made to reveal identical features associated with any of this type. The topic is interesting. However, the manuscript is not well organized in general, and with plenty of English and grammar errors and some technical problems. I have listed some of the grammar errors below but there are still more. I would recommend the authors ask help from native speakers or English correction editors to improve the writing of the manuscript.

Detailed comments:

 “El Nino” should be “El Niño”.

This is a confusing sentence, “Sea Surface Temperature (SST) and pressure anomalies can affect even the stratosphere trough the teleconnections” may be modified to “Sea Surface Temperature (SST) and pressure anomalies can affect even the stratosphere through the teleconnections”.

“referred to” should be “referred to as”.

“The SOI index demonstrate…” should be “The SOI demonstrates”.

The full name of SOI, SPWs should be given.

Further analysis for Figure1 should be given. The main idea for Figure 1 needs to be further concluded.

In Figure 2, latitudes should be added.

The unit should be given on the color bars (Figure 1 to 4)

This is a confusing sentence, “… which are of about unit…”.

“This feature can be seen in the behavior of PW1 amplitude … ” do you mean “This feature are all the same for PW1, PW2 and PW3”?

I suggest to focus on analyzing the differences in Figure 1.

The amplitudes of planetary waves with zonal wave number under climate conditions can be given in Figure 1.

How about the results based on JRA55 for Figure 3 and 4.

I suggest to modified the results at 40km to 30km in Figure 5. This level is corresponding to the results from Figure 2.

I suggest to add the amplitudes of planetary waves with zonal wave number 1 in geopotential height (m) at 62.5° N.

The conclusion part should be reorganized.

Author Response

R E P L Y

to the reviewers’ comments on the revised version of the paper atmosphere-2024419 “Manifestations of different El Nino types in the dynamics of extratropical stratosphere”. We would like to thank the reviewer for useful comments that help to improve the paper.  Below is our response to the issues raised in the review. Our responses are following reviewer queries in the bold.

Reviewer #1
The authors compared planetary wave response and residual mean meridional circulation under various conditions caused by different El Niño types, an attempt was made to reveal identical features associated with any of this type. The topic is interesting. However, the manuscript is not well organized in general, and with plenty of English and grammar errors and some technical problems. I have listed some of the grammar errors below but there are still more. I would recommend the authors ask help from native speakers or English correction editors to improve the writing of the manuscript.

We are grateful to the Reviewer for the important remark. The new version of the manuscript has been reorganized to achieve more logic and focus, also it has been checked by a professional translator.

Detailed comments:

“El Nino” should be “El Niño”.

Corrected

This is a confusing sentence, “Sea Surface Temperature (SST) and pressure anomalies can affect even the stratosphere trough the teleconnections” may be modified to “Sea Surface Temperature (SST) and pressure anomalies can affect even the stratosphere through the teleconnections”.
Corrected

“referred to” should be “referred to as”.

Corrected

“The SOI index demonstrate…” should be “The SOI demonstrates”.
Corrected. Since it is the first use we added the expanded form of the abbreviation.

The full name of SOI, SPWs should be given.
Corrected

Further analysis for Figure 1 should be given. The main idea for Figure 1 needs to be further concluded.
Figure 1 was changed according to the comment of the second Reviewer. The amplitudes averaged over five investigated winters under different El Niño conditions are shown as contours. The anomalies relative to climatic distributions (November-March, 1964-2016) of planetary waves amplitudes are added with shading. Analysis for Figure 1 was expanded.

In Figure 2, latitudes should be added.
Done. Horizontal component of wave-activity flux (arrows) added according to the comment of the second reviewer.

The unit should be given on the color bars (Figure 1 to 4)
Done

This is a confusing sentence, “… which are of about unit…”.
The sentence was rephrased

“This feature can be seen in the behavior of PW1 amplitude … ” do you mean “This feature are all the same for PW1, PW2 and PW3”?
You are absolutely right. We extended this description.

I suggest to focus on analyzing the differences in Figure 1.
Additional analysis was added.

The amplitudes of planetary waves with zonal wave number under climate conditions can be given in Figure 1.
Done for PW1, PW2, and PW3 (with contours)

How about the results based on JRA55 for Figure 3 and 4.
An analysis based on Japanese reanalysis data was also carried out. The resulting RMC showed no significant difference. However, we chose MERRA2 as its vertical resolution is extended from the surface up to 0.1 hPa (JRA-55 – 1hPa). It should be noted that the correctness of the data in JRA and MERRA2 has been repeatedly verified by the scientific community, numerous comparisons have been made, so there is no reason to assume that the combined use of the two bases will distort the final result. E.g., in the article by Rakushina et al. 2018 (https://doi.org/10.1016/j.jastp.2017.08.005 http://ra.rshu.ru/mps/dwnl/lab/pub/RakushinaEtAl_JASTP_2018.pdf) four reanalysis have been used to estimate the climatic variability of the zonal mean flow, temperature, and Stationary Planetary Waves (SPW1, SPW2) from the
troposphere up to the lower mesosphere levels, mainly paying attention to interannual and intraseasonal variability. The comparison results of different reanalysis carried out. The results obtained show that only UK Met Office data demonstrate stronger changes and increase of the intraseasonal variability in comparison with other data sets.

I suggest to modified the results at 40km to 30km in Figure 5. This level is corresponding to the results from Figure 2.
The level has been changed, but vice versa. We lifted the level of wave activity flux in fig.2 up to 40 km. This was caused by two reasons:  the obtained results of RMC changes (figs. 3,4) showed greater values at 40 km. Also, PW amplitudes that cause circulation changes and transfer these changes to higher latitudes, it is more reasonable to consider at this height, because both the amplitudes themselves and their anomalies are greater there (see figure 1).   

I suggest to add the amplitudes of planetary waves with zonal wave number 1 in geopotential height (m) at 62.5° N.
We changed fig.5. Now Figure 5 demonstrates the amplitudes of standing waves at 62.5°N.

The conclusion part should be reorganized.

We extended and reorganized the conclusion.

Author Response File: Author Response.docx

Reviewer 2 Report

Please see my comments in the attached file. 

Comments for author File: Comments.pdf

Author Response

R E P L Y

to the reviewer comments on the revised version of the paper atmosphere-2024419 “Manifestations of different El Nino types in the dynamics of extratropical stratosphere”. We would like to thank the reviewer for useful comments and suggestions that help to improve the paper.  Below is our response to the issues raised in the review. Our responses are following reviewer queries in the bold.

Reviewer #2

“Manifestations of different El Nino types in the dynamics of extratropical stratosphere”, by Ermakova et al. This paper investigates behavior of planetary waves and their influence on the global circulation  of  the  Northern  Hemisphere  during  different  types  of  El  Nino  Modoki events  (Modoki  I,  II,  and  canonical  El  Niño). They  found  that  warming  of  the  polar stratosphere,  accompanied  by  strong  wave  activity  and  weakening  of  the  zonal   wind may  lead  to  earlier  stratospheric  polar  vortex  collapse  under  Modoki  I  conditions. They  further  showed  that  PW1  behavior  during  Modoki  I  and  II  types  of  El  Nino  is similar and can be associated with MEI values distribution. The results are interesting but  I  have  some  major  comments  that  need  to  be  addressed  in  order  to  improve  the representation of the results.

Major comments:
1. What is the underlying mechanism that leads to a stronger upward wave activity in Modoki  I  events  compared  to  Modoki  II  events?  Please provide evidence and explanation for this from a perspective of tropical-extratropical teleconnection.
2. How does tropical heating affect the mid-latitude standing waves during different types of the El Niño events? What are the implication of enhanced standing wave activity on the stability of stratosphere polar vortex? Which one is more important, standing  waves  or  traveling  waves  in  the  variability  of  polar  vortex  during  these events?

The additional explanation has been added: Considering the impacts of Modoki El Niño expressed in rainfall in southern China during boreal autumn (Wang and Wang 2013), the CP can be classified into Modoki I and Modoki II. The separation principle includes not only rainfall anomalies but also the spatio–temporal evolutions of SST anomalies. The origin of positive SST anomaly locates in the equatorial central Pacific and in the subtropical northeastern Pacific for Modoki I and Modoki II, respectively. As Wang et al 2018 showed in Figure 2 the origins and evolutions of SST anomalies for types of El Niño are quite different. Hence, the thermodynamic connections of El Niño three types with the extratropical climate variability may be different and need to be studied.

As it was shown in recent studies (Wang and Wang 2013; Weng et al. 2007; Kim et al. 2012) the distributions of precipitation rates under conditions of three El Niño types differ. Latent heat release connected with convective cloudiness and precipitation influence planetary waves at stratospheric heights in two ways: explicitly through their additional thermal forcing in the troposphere and implicitly via altering the mean zonal flow, whose distribution determines the PWs propagation conditions (e.g., Jacqmin and Lindzen 1985).

To determine the implication of the altered standing or travelling wave activity on the stability of stratosphere polar vortex, additional simulation studies are needed. We are going to continue this investigation with the MUAM in the nearest future. 

3.Since  the  classification  of  the  El  Niño  events  into  these  three  types  are  less common,  please  add  a  new  figure  in  the  manuscript  showing  the  distribution  of SST (overlay with OLR) during these three types, so the readers may aware of the convective system associated with these different types of the El Niño events.

We added reference to Wang et al. 2018, who demonstrated the evolution of composited SST anomalies and 850 hPa wind anomalies during canonical El Niño, El Niño Modoki I, and El Niño Modoki II from boreal spring to winter. Additional discussion was added to avoid misunderstanding.

4.Please improve the representation/robustness of the results:

• Figure 1: It it very hard to see and compare these figures for different types of the El  Niño  events.  I  suggest  to  show  the  amplitude  PW1  anomalies  (deviation  from daily climatology mean, as color shading) and the total amplitude as contour line.

Figure 1 was changed. The averaged amplitudes under different El Niño conditions are shown as contours. The anomalies relative to climatic distributions (November-March, 1964-2016) of planetary waves amplitudes are added with shading.

• Figure  2: Overlay  the  Fz  with  the  horizontal  vector  of  Plumb  fluxes  to  show  the horizontal  propagation  of  wave  energy  (group  velocity)  during  these  events. Also,  instead  of  showing  at  30  km,  I  encourage  the  authors  to  show  the  analysis  of  Fz (color shading) and Fx,Fy (vectors) at level of 100 hPa. This is an active level/layer where wave activity is highly correlated with the variability of the polar vortex.

Horizontal component of wave-activity flux (arrows) added. We decided to lift the level of wave activity flux up to 40 km. This was caused by two reasons:  the obtained results of RMC changes (figs. 3,4) showed greater values at 40 km. Also, PW amplitudes that cause circulation changes and transfer these changes to higher latitudes, it is more reasonable to consider at this height, because both the amplitudes themselves and their anomalies are greater there (see figure 1).

• 
  Figure  3:  The  figures  are  so  crowded.  Please  only  show  the significant  values  of the  U  response  as  color  shading  and  the  non-significant  values  as contour  line. Also only show the vectors that are significant at 95% level.
• Figure  4:  For  panel  (b-c)  and  (e-f)  please  calculate  the  response  at  95%  or  90% significant level (add them as dots).

We use GRADS for creating figures. Еhere is no technical possibility to make changes as requested by the Reviewer. However, we calculated statistical significance of the obtained increments (using paired t-test) and added hatched areas of insignificant values (et 95%) in Fig.4.

Fig.3 is indeed so crowded, therefore have not added areas with insignificant data to it. Our calculation showed that ΔT over 1K and ΔV* over 1 m/s are significant, which corresponds to most of the distributions. We have added additional discussion to the text.

• Figure  5:  Very  hard  to  see  these  figures.  I suggest  show  the  anomalies  in color shading and the total value as contour line.

The figure has been replaced with the similar one but for 62.5°N. This one is easier for understanding and interpreting, and correlates with Figure 1.

• Figure  6: This  is  super  confusing  plots.  Instead of  plotting  like  this,  I  suggest  the authors show the PDF of each wave type for different El Niño types calculated from November to March.

We are not sure, that we understand comment clearly. The averaged over winter amplitudes of waves have been shown to demonstrate, first of all, the overestimated amplitudes of the atmospheric tides and the fast waves before 1979 (pre-satellite era), as well as the similarity between canonical type and Modoki II. Another interesting fact shown in Fig.5 is variability of PW amplitudes for different years having the same El-Nino index. Therefore, we cannot average these amplitudes over the sets of years (if the reviewer has this in mind. On the other hand, examination of individual figures averaged over individual months (if the reviewer has this in mind) showed an even greater variability that is impossible to interpret. We have expanded the discussion of figure 5 in the new version of the manuscript.     

5. 
   The other thing that is unclear in this paper is how do you calculate/define the standing wave. Could you add the formulation or method how did you do  this.  Can standing  waves  be  considered  as  stationary  waves  or  they  are  more  likely  a  be considered as wave resonance? Please explain this in detail in the manuscript.

To extract the traveling planetary waves existing in the stratospheric data (only the waves with zonal wave numbers m = 1-3 have been considered), a space-time spectral analysis of the geopotential height fields based on the Morlet wavelet transform (Torrence and Compo, 1998) has been performed. As was suggested in Pogoreltsev et al. (2002 and 2009), it is possible to extract the westward and eastward propagating planetary waves using the phases of geopotential height oscillations obtained at different longitudes. Separation of these oscillations into the westward and eastward propagating parts is to a certain degree artificial. Two waves with the same amplitudes propagating in different directions represent the so-called ‘‘standing’’ wave, i.e., oscillations with zero phase speed (relative to Earth surface). We have expanded the description of the calculation of PW amplitudes in the new version of the manuscript.

6. 
   The introduction needs to be improved. •Please  discuss  the  role  of  ocean  (SST)  variability  on  stratospheric  polar  vortex variability  from  previous  studies  (e.g.,  Richter  et  al.,  2011;  Lubis  et  al.,  2016). Please include these in the introduction

Lubis,  et  al.,  (2016).  Influence  of  the  Quasi-Biennial  Oscillation  and  Sea  Surface Temperature Variability on Downward Wave Coupling in the Northern Hemisphere. Journal of the Atmospheric Sciences 73, 5, 1943-1965.

Richter, J. H., Matthes, K., Calvo, N., and Gray, L. J. (2011), Influence of the quasi-biennial  oscillation  and  El  Niño–Southern  Oscillation  on  the  frequency  of  sudden stratospheric warmings, J. Geophys. Res., 116, D20111.

The discussion was added.

• Please  add  one  paragraph  to  discuss  the  implication  of  enhanced  upward  wave activity  (in  your  case  due  to  different  types  of  El-Nino)  on  the  surface  extreme events, for example, why do we care about the variability of the polar vortex in the presence of  these  forcing?  

The paragraph was added.

This would be helpful if the authors include a few sentences to explain a dynamical process of such coupling to the surface, for example the role of internal tropospheric eddy-mean flow feedbacks leading to the tropospheric response/surface impacts to  SSWs  is  essential  (e.g.,    and  Song  and  Robinson  (2004),  ,  Lubis  et  al. (2018a,b)).  
Please include all these references.
Kunz,  T.,  and  R.  J.  Greatbatch,  2013:  On  the  Northern  Annular  Mode  Surface Signal   Associated   with   Stratospheric   Variability. J.   Atmos.   Sci., 70,   2103–2118, https://doi.org/10.1175/JAS-D-12-0158.1.

Lubis,   S.   W.,   et   al.,   2018a:   Role   of   Finite-Amplitude   Rossby   Waves   and Nonconservative   Processes   in   Downward   Migration   of   Extratropical   Flow Anomalies. J.   Atmos.   Sci., 75,   1385–1401,   https://doi.org/10.1175/JAS-D-17-0376.1.

Lubis, S. W., Huang, C. S. Y., and Nakamura, N. 2018b. Role of Finite-Amplitude Eddies and Mixing in the Life Cycle of Stratospheric Sudden Warmings. J. Atmos. Sci, 75, 11, 3987-4003.

Wittman,  M.  A.  H.,  L.  M.  Polvani,  R.  K.  Scott,  and  A.  J.  Charlton,  2004: Stratospheric  influence  on  baroclinic  lifecycles  and  its  connection  to  the  Arctic O s c i l l a t i o n .   G e o p h y s .   R e s .   L e t t . ,   3 1 ,   L 1 6 1 1 3 ,   h t t p s : / / d o i . o r g /10.1029/2004GL020503.

Song,  Y.,  and  W.  A.  Robinson,  2004:  Dynamical  mechanisms  for  stratospheric influences  on  the  troposphere.  J.  Atmos.  Sci.,  61,  1711–1725,  https://doi.org/10.1175/1520-0469(2004) 061,1711:DMFSIO.2.0.CO;2.

The introduction has been rewritten. All references mentioned above have been included. We thank the Reviewer, taking into account the clarifications provided by the Reviewer, the introduction has become more detailed.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

It can be accepted in present form.

Author Response

We would like to apologize if the presentation of the material was not always up to the reviewer’s expectations. We would like to thank the reviewer for his careful consideration of our manuscript. The reviewer’s thoughtful comments helped us refine the manuscript in preparation for publication. We asked to check our manuscript by a native English-speaking colleague. He checked our text for grammar and style mistakes.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors have considered some of my comments, as a result the paper has been much more improved and clearer (in terms of presentation and content) compared to the previous (old) version. I just have a few minor comments before accepting this work for publication on MDPI Atm:

1. Make sure all the new citations you cited in the manuscript are listed in the new references.

2. Please add a significant test for Fig. 3. You can do a t-test/bootstrap on both vector and contour to show the robustness of the results.

3. I recommend the authors to have an English professional proofreader to improve the clarity of the texts. 

Author Response

R E P L Y

to the reviewers’ comments on the revised version of the paper atmosphere-2024419 “Manifestations of different El Nino types in the dynamics of extratropical stratosphere”. We would like to apologize if the presentation of the material was not always up to the reviewer’s expectations. We would like to thank the reviewer for his careful consideration of our manuscript. The reviewer’s thoughtful comments helped us refine the manuscript in preparation for publication.

Reviewer #2
The authors have considered some of my comments, as a result the paper has been much more improved and clearer (in terms of presentation and content) compared to the previous (old) version. I just have a few minor comments before accepting this work for publication on MDPI Atm:

1. Make sure all the new citations you cited in the manuscript are listed in the new references.

Thank you for pointing this out. We admit that missed some references. We checked the reference list once again and included the missing references.

2. Please add a significant test for Fig. 3. You can do a t-test/bootstrap on both vector and contour to show the robustness of the results.

Added

3. I recommend the authors to have an English professional proofreader to improve the clarity of the texts.

We asked to check our manuscript by a native English-speaking colleague. He checked our text for grammar and style mistakes.

Author Response File: Author Response.docx