In my view, the paper is within the scope of ESD and presents some interesting new findings, however, there are some questions that I would like to authors to address to improve the presentation.

Abstract: I feel that it is too long and would suggest that you shorten it. For instance, discussions of the Saharan Low can go and the discussions of the Bjerknes feedback more focused.

L.20: I don’t understand how upper-level subsidence leads to the little dry season.

L.25: Does the little dry season occur in AMJ? One should expect this to correspond to the period between the double rainfall peaks?

L.40: Jouanno et al 2017 is just one of the numerous papers that discussed the Bjerknes feedback, so I don’t understand why this paper is presented as the final say. I think the point is that several processes drive the Atlantic Niño variability. The next paragraph, the upper-level links to the Indian and Pacific Oceans need to be better explained.

L.50: What destructive interference means or how it operates is not clear at all.

L.55: I don’t think that the discussion “...temperature and precipitation over the globe” is necessary here. I’d suggest that you remove that and keep the flow focused on the equatorial Atlantic.

L.100: Is it “realistic” or observed natural and anthropogenic forcing?

L.105: “These latter simulations…” Do you mean SSP-85?

L.115: Please use one rainfall, SST etc data to compare with the models. Comparing multiple observations is unnecessary and it makes following your discussions difficult.

L.130: Why do you use quadratic detrending, are the trends quadratic? I ask because we are more used to linear trends. More explanation is needed here.

Table 2: I don’t find the numerous acronyms here very useful and they can as well cause more confusion, given that we have the model names to deal with. Atl3 is widely known as the SST anomalies (well, or some other quantities) averaged in the Atlantic Niño region defined as 0-20W, 3N-3S; so it’s not necessary to introduce a new definition ATL3B. Why define TAB1, TAB2 when there are well known regions like Atl4, tropical North Atlantic (TNA) and tropical South Atlantic (TSA)?

Data and methods section: For easy navigation, I would suggest splitting this section, for instance “Data”, “CMIP6 Models”, “Analysis strategy” or something similar

section 3: I don’t find the line plots and discussions of bimodal structure and annual cycle necessary and I suggest that you remove these. I consider the question of annual cycles and seasonality as a separate question. Since this study is about JAS, it is enough to briefly describe the JAS patterns and biases and move to the Atlantic Niño related SST and rainfall and their future changes.

Fig. 2: How do you have strong easterly wind biases over warm SST biases? This pattern needs explanation because it is inconsistent with expectation and inconsistent with Richter and Tokinaga 2020 (see their Fig. 2).

Section 4: You are basically evaluating SST and rainfall patterns rather than “teleconnections”. Secondly, regression maps show rainfall, SST etc with units in mm/day, degC etc and I don’t see the need for the repeated use of regression coefficient, instead of referring to rainfall, SST etc.

L.225: Again, I don’t see the need to compare observations with other observations here. I suggest that the authors rather use just one observational data to compare the CMIP models.

Fig. 4: I suggest separating this Figure so that the maps stand as one Figure, and the Taylor diagram stands as a different Figure. In the Taylor diagram, the REF which is here ERA5 should correspond to a standard deviation of 1. The authors should explain why/how their scaling leads to a different value. Again I suggest that the authors discuss the overall model fidelity using using both pattern correlations and variance (that is closeness to REF).

Fig. 5: Again I suggest two different figures: one for the maps and the other for the Taylor diagram. One satellite rainfall data and one SST data should do, no need to compare different observations which I consider outside the scope of this manuscript.

L.260: It’ll be good to state what sea surface heights represent, what understanding you’ll like to gain by analyzing that. The same could be said of the atmospheric variables. The motivation and physical reasoning behind the analysis need to be better formulation. For instance, SSH-→SST(atl3) regression implying thermocline impact on the SSTs which is one element of the Bjerknes feedback (Keenlyside and Latif, 2007). Then the winds/SST regressions another element? Are the rainfall and divergence related to the ITCZ/atmospheric component of the Bjerknes feedback (Nnamchi et al. 2021)?

L.310: How you calculated the percentages should be explained in context here so that it’s understood what minus percentages, plus percentages mean.

L.315: This point needs more discussions/explanations of why your result is different from Brierley and Wainer (2018), Is it because the use different time slices, methods, models etc?

L.360: It’s important to first outline the elements of the Bjerknes feedback as the basis for your analysis and then build the subsequent discussions around that.

L.370: I think that this paper is about weakening equatorial Atlantic variability rather than teleconnections. Please note that equatorial Atlantic doesn’t mean the same thing as tropical Atlantic.

Fig. 11: I don’t really find the discussions of Saharan Low interesting at all because I feel the an equatorial region is enough to interpret the results here. The Sahara/Sahel matter is a different topic.

References

Brierley, C. and Wainer, I.: Inter-annual variability in the tropical Atlantic from the Last Glacial Maximum into future climate projections simulated by CMIP5/PMIP3, Climate of the Past, 14, 1377–1390, https://doi.org/10.5194/cp-14-1377-2018, 2018.

Jouanno, J., Hernandez, O., and Sanchez-Gomez, E.: Equatorial Atlantic interannual variability and its relation to dynamic and thermodynamic

processes, Earth System Dynamics, 8, 1061–1069, https://doi.org/10.5194/esd-8-1061-2017, 2017.

Keenlyside, N. S., & Latif, M. (2007). Understanding Equatorial Atlantic Interannual Variability, Journal of Climate, 20(1), 131-142. https://journals.ametsoc.org/view/journals/clim/20/1/jcli3992.1.xml

Nnamchi, H.C., Latif, M., Keenlyside, N.S. et al. Diabatic heating governs the seasonality of the Atlantic Niño. Nat Commun 12, 376 (2021). https://doi.org/10.1038/s41467-020-20452-1

Richter, I., Tokinaga, H. An overview of the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts. Clim Dyn 55, 2579–2601 (2020). https://doi.org/10.1007/s00382-020-05409-w

Review of the manuscript ESD-2021-46, “Weakened impact of the Atlantic Niño on the future equatorial Atlantic and Guinean Coast rainfall”, by Koffi Worou, Hugues Goosse, Thierry Fichefet, and Fred Kusharski.

The submitted manuscript explores the rainfall annual cycle in the Guinea Coast, gives a detailed analysis of the future changes in the Atlantic Niño and their impact on the rainfall, and the modulation of the Bjerknes feedback in the future climate change projection. The investigation is based in 31 historical simulations from General Circulation Models of CMIP6 with some observations and reanalysis. The authors found that these models are able to simulate reasonably well the rainfall annual cycle in the Guinea Coast with a wet bias in boreal summer (July-August-September). They also found a rainfall decrease in the Tropical Atlantic region due to a weakening of the Bjerknes feedback over the equatorial Atlantic in future climate projection. This work will be a valuable contribution to Earth System Dynamics journal after some revisions.

The paper is well written, well documented, easy to follow and understand from the beginning up to section 4. In section 5, there are lots of information, and it’s a bit dense. Please, what is the purpose of defining all the groups you defined? I am referring to group GC+, GC-, GC+-, GC++, OC+, OC-, ect… It will be nice if you could resume your findings about the previous mentioned groups in a table.  Moreover, it is better to name the figure you are referring too early in the text than in the middle or at the end of a paragraph.

Minor

Line 35: “deepens” not “deepen”

Please, add a figure in the supplement material to show the different boxes of Table 2.

Provide a statement on how the data used for the study could be accessed.

Line 68: Precise the figure you refer to after giving the interval of the RMSE.

Line 160 and line 193: Which figures are you referring to? If it is not shown, please precise.

Line 197: Why you did not represent the bias relative to ERA5 instead of the mean state?

Line 216: The multimodel mean “underestimates” the SST STD in relation to ERA5 in the time period you have highlighted. Compared to other observations, the multimodel underestimates the SST STD in May-June and overestimates it the rest of the year.

L256-259: There are 24 GC+ and 6 GC- models. It seems like 1 model is missing because there are 31 GCMs in total.

Title of figure 6d: It is better to write ERA5 (ORAS5) than ERA5/ORAS5, or use only ORAS5, because it is confusing.

L260: Please, precise “not shown” after “nor in the observations”.

L282: Please, precise the figure you are referring too at the end of the sentence (Fig. A4?).

Caption of figure A4, add the color of the box for each region.

L295: “The models show a poor to modest spatial correlation with ERA5, which ranges from −0.4 to 0.6”. Precise the figure you are referring to, is it (Fig. 5a?)

L298: Is OC+ the sum of GC+ and GC- when referring to EAB region?

You did not use Figure A6. Please, remove the figure if it is not needed.

Figure 7b: Please, keep the same color in (a) and (b) for the period 2015-2039, 2040-2069, and 2070-2099.

L320: Refer the figure after 0.32°C.

L397: Remove one “zonal”.

1. General Comments

The authors of this manuscript investigate the present-day and future boreal summer (JAS) rainfall and sea surface temperature (SST) variability in the eastern and equatorial Atlantic using 31 historical and scenario simulations from the sixth phase of the Coupled model Intercomparison Project (CMIP6). They show that the rainfall annual cycle, computed for the period 1985-2014, in the Guinea Coast is generally well simulated. Yet, a wet bias persists in boreal summer due to a large SST bias in the eastern equatorial Atlantic and south Atlantic regions. The rainfall variability is strongly linked to the SST variability in this region and therefore the SST variability in the eastern equatorial Atlantic is also investigated. The authors show that relative to the present-day situation, in a climate with a high anthropogenic emission of greenhouse gases, the eastern equatorial Atlantic JAS SST variability weakens. They show that the reduced SST variability in the equatorial Atlantic could be due to a weakening of the Bjerknes feedback. As a result, relative to the present-day situation, in the future they also find a reduction of the rainfall variability over the equatorial Atlantic Ocean and Guinea coast in a majority of the CMIP6 considered.     

The article is well written and addresses an important topic with detailed results. In my view the results are within the scope of ESD and therefore, I recommend minor revision before publication following the different aspects provided bellow.

2. Specific Comments

Abstract

L3. I would state that both historical and scenario (SSP5-8.5)  simulations from 31 GCMs from CMIP6 are used throughout the study.

L6. Add “boreal” to the sentence “This bias is associated with too high mean summer SSTs”

Introduction

L31. The acronym ATL3 is used in this study to refer to the Atlantic Niño. It is generally more used to define the region where the Atlantic Niños occur (20˚W-0˚; 3˚S-3˚N). The authors have defined this region with the acronym ATL3B in Table 2 but ATL3B is never used in the manuscript.

Data and methods

L132. Please, can you explain how the anomalies were computed. Do you remove the climatological monthly-mean seasonal cycle?

Section 3.2

L200. The title of the section says “JAS mean” but the JAS mean is not discussed.

L214. “The winter Atlantic Niño” was defined as the “Atlantic Niño II” by Okumara and Xie (2006).

Okumura, Y., & Xie, X. (2006). Some overlooked features of tropical atlantic climate leading to a new Nino-like phenomenon. Journal Of Climate, 19, 5859-5874. doi:10.1175/JCLI3928.1

Figures 1 and 3:

I would like to see the cross-correlation between the GC rainfall anomalies and ATL3 SST anomalies. As in the CMIP6 ensemble, both the ATL3 SST variability and the GC rainfall variability peak in JJA and assuming that the maximum of correlation is found at 0 lag then why not regressing JJA SST (rainfall) anomalies on the standardized JJA ATL3 index in Figure 4 (Figure 5)?

Section 4.1:

To investigate the boreal summer Atlantic Niño pattern why not regressing the JJA SST anomalies onto the standardized JJA ATL3 index?

As shown and discussed in section 3.2 the ATL3 variability peaks in JJA in the CMIP6 ensemble corresponding to the Atlantic Niño activity in the ATL3 region. Therefore, when looking at future Atlantic Niño changes, I would recommend to use JJA and not JAS.

Figure 4: One could draw the TAB1 and TAB2 boxes on Figure 4 if it stays legible. 

Section 4.2:

L241. Should be: “Figure 5(a) displays the regression maps of the JAS rainfall anomalies onto the standardized JAS ATL3 index”, correct?

L254-L256: 31 models are present on Figures 4, 5 and 6 but only 30 models are in the GC groups (24 + 6).

Figure 6. caption: Should “associated with the standardized ATL3 index” be “associated with the JAS standardized ATL3 index”?

Section 5.1:

Figure 7: From (a) to (b) I recommend the authors to keep the same color for the different periods.

Figure 9 caption: Should “Rainfall anomalies associated with ATL3” be “JAS rainfall anomalies associated with JAS standardized ATL3 index”? Same question for the rest of the subpanels.  

L384. Should “First, the GC+ group (the 24 models in Sect. 4.2 which simulate a realistic GCB rainfall associated with one standard deviation of the ATL3)” be “First, the GC+ group (the 24 models in Sect. 4.2 which simulate a realistic JAS GCB rainfall associated with the standardized JAS ATL3 index)”?

Section 5.2:

Throughout this section, the authors should state that they investigate the JAS rainfall, SST, 850 hPa zonal wind, moisture flux associated with the JAS standardized ATL3 index.

Figure 10 caption: Should “Long-term changes of the JAS rainfall (a-e), SST (f-j), 850 hPa zonal wind (k-o), sea surface height (p-t), moisture flux (vectors) and moisture flux divergence (in colors) (u-y) regression patterns associated with the standardized ATL3 index ”  be “Long-term changes of the JAS rainfall (a-e), SST (f-j), 850 hPa zonal wind (k-o), sea surface height (p-t), moisture flux (vectors) and moisture flux divergence (in colors) (u-y) regression patterns associated with the standardized JAS ATL3 index”?

Appendix:

Figure A8, A9, A10. caption: Should “regression maps of rainfall anomalies onto the standardized ATL3 index” be “regression maps of the JAS rainfall anomalies onto the JAS standardized ATL3 index”?

Figure A6 is not discussed.

General comments:

This paper investigates the present and future characteristics of the Atlantic Niño and its influence in the Gulf of Guinea and Equatorial Atlantic precipitation, using CMIP6 simulations. It shows that models project a weakening in the variability of the ATL3 region which would then lead to a weakening in the rainfall variability in the equatorial Atlantic and Guinean Coast.

In my opinion the paper has valuable information that is within the scope of ESD and deserves publication after the some revisions.

The paper has a lot of information that not always is presented in the clearest way. Specially when the authors divide the 31 models in different groups (GC+, GC-, OC+). I fell that the group OC+ is not at all necessary in section 4, and makes the discussion of the results a bit messy. Also section 5 is hard to follow in some places.

Specific cmments:

Introduction:

ATL3 is an index that reflects the variability of the Atlantic Niño region, but I don’t think it is correct to use ATL3 acronym to refer to the Atlantic Niño.

Data and methods:

Why do you perform a quadratic detrend of the data?

Section 3.1:

Figure 2: I don’t understand the wind pattern. It is not consistent with Richter and Tokinaga (2020).

Please add in figure 2 or in any aditional figure the boxes defined in table 2.

Section 3.2:

L. 213: I think that the statement “the winter Atlantic Niño has greatly influenced the ENSO events” is a bit too strong.

Also you should refer to Okumura and Xie (2006) when talking about the winter Alantic Niño for the first time.

Okumura, Y., & Xie, X. (2006). Some overlooked features of tropical atlantic climate leading to a new Nino-like phenomenon. Journal Of Climate, 19, 5859-5874. doi:10.1175/JCLI3928.1

Section 4:

I would reorganize this section. I fell that section 4.1 belongs to section 3, in which the model performance of the patterns are described. Then, in section 4, the authors can focus in the impact of the Atlantic Niño on rainfall.

The authors jump from figure 5 to figure 6 and back in a confusing way.

I don’t think that the analysis of OC+ models is necessary here.

Section 5:

Again is difficult to follow. I would rearange figures 8 an 9 by areas, to make the discussion in the section easier to follow.

I would talk about OC+ models only from section 5.3 onwards. I doesn’t seem necessary before and makes the discussion hard to follow.

Figure 7: Please use the same colors for each period in (a) and (b).

L. 406: I don’t agree with the sentence “ The projected ATL3-rainfall signal in the GC+- group is … hardly robust over the Guinea Coast”. I see a very robust decreas of rainfall over the green box in figure 10a.

Supplementary material:

Figure A6 is not discussed in the text

Technical corrections:

L. 23: Please replace “has moved” by “moves”.

L. 45: Losada et al. 2009 should be Losada et al. 2010a.

L. 143 to 145: I find this description of the sign-dependent average a bit confusing.

L. 248: Change “Mohino and Losada (2015)” by “Mohino and Losada (2015), among others”.

L. 355: Pleas move the sentence “ This indicates a weakening… in the eastern equatorial Atlantic” to the end of the paragraph.

Revision of "Weakened impact of the Atlantic Niño on the future equatorial Atlantic and Guinean Coast rainfall" by K. Worou, H. Goose, T. Fichefet and F. Kucharski

General comments:

The article is a detailed analysis of the rainfall over the Guinean coast and the relation with Atlantic Niño using a pool of CMIP6 simulations in the historical period compared with observed data. The analysis is relevant, and the article convincingly shows that the rainfall will decrease over the Guinean coast as the Atlantic Niño variability will also decrease in the future.

The paper addresses relevant scientific questions and the conclusions are important for the climate science community.

I have, however, some suggestions for improving the paper from my point of view.  I recommend shortening the article; I found a very large document with unnecessary figures. It is, however, good to see a lot of more information in the additional material. I have some ideas of how to reduce it below together with some typos and minor comments

specific comments and technical corrections:

• Typo in line 10 (and more). Please be aware that Bjerknes feedback is referred to Jacob Bjerknes, use Bjerknes feedback instead of Bjerkness feedback.
• Line 31 (and also the abstract), You referred to the Atlantic Niño as ATL3, but the community usually defines ATL3 as an index (SST averaged over 20W-0, 3S-3N, Zebiak 1993). Please define the index first and then explain why you identify the Atlantic Niño with ATL3 (you could also use a different acronym).
• Line 42, a reference should be added.
• Table 2. It would be good to see the boxes within the map (for instance in figure 2)
• Figure 3b and d, why ERA5 is used as a reference for the std when it is clearly biased in relation with the other observed SST datasets?, please explain in the text or in the figure caption.
• Line 132. Why do you remove the quadratic trend instead of the linear trend?  It is quite clear the linear trend in the Atl3 SST in the historical period. Please show the trend of the rainfall and SST for the indexes to understand your choice.
• Figure 4a and line 255. From figure 3b and the observations, it is clear the main season for Atl3 would be JJA, why do you decide to compare the observed and simulated Atlantic Niño in JAS?. It would be useful to show correlation between SST and rainfall indexes for different seasons to realize which of the seasons is more realistic (maybe in the observation the maximum correlation is between Atl3 SST index in JJA and precipitation GG in JAS).
• As you exposed in the introduction, deconstructive interaction of Atlantic Niño and ENSO events onto the WA rainfall in some time-periods can conduct into a dipole or monopole of the rainfall anomalies (Losada et al 2012). It would be nice to see how many of those simulated and observed Atl3 indexes are correlated with Niño3 index. Thus, the rainfall pattern in figure 5 could be a mix between local and remote SST drivers.
• Line 264. Stronger correlation between Atl3-SST and SSH in models than in ORAS5 implies stronger Bjerknes feedback in the models, which I did not expected from CMIP5 models analysis (for instance Dippe et al 2018, DOI 10.1007/s00382-017-3943-z). It would be nice to see surface wind superimposed on figures 6 u-x to illustrate the 3 elements of the Bjerknes feedback.
• Paragraph from line 280 please reduce or suppress, I do not see that OC+ models are explaining important differences from GC+ models. Remove (or reduce) and explain later in the text (beginning of section 5.2)
• Figure 8 is a very interesting and illustrative view of the processes and the trends, however, Figure 9 is not necessary (figure 9a is certainly illustrative of where the mean change occurs but figure 9 overall is redundant). From my point of view figure 9 should be removed or put in the additional material. Conclusions on this part could be explained with figure 8 alone.
• Line 380 should start a new section 5.2
• Line 397 typo zonal
• I found all the discussion about figure 10 of OC models very unnecessary, indeed in your abstract you don’t mention such differences. The main result about this in the abstract is “higher confidence in the reduction of the rainfall associated with atl4 over the Atlantic Ocean than over the Guinea coast”. It is appreciated the detailed analysis of the different model flavours but It doesn’t give any light into the main conclusion. I will leave the GG models alone, and the OC models in the additional material. Also, figure 11 b is not necessary for the conclusions, I would go for 11a alone. Please enlarge Figure 11a.
• Line 471 remove more