Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer&ndash;Dobson Circulation

Hollowed, Joseph P.; Jablonowski, Christiane; Ehrmann, Thomas; Bull, Diana; Wagman, Benjamin; Hillman, Benjamin

doi:10.5194/egusphere-2025-4598

Preprints

https://doi.org/10.5194/egusphere-2025-4598

Preprints

10 Oct 2025

| 10 Oct 2025

Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer–Dobson Circulation

Joseph P. Hollowed, Christiane Jablonowski, Thomas Ehrmann, Diana Bull, Benjamin Wagman, and Benjamin Hillman

Abstract. Great attention has been paid to the short-term climate response following large volcanic eruptions, in order to understand effects on zonal winds, the polar vortex, and surface temperature across latitude. In contrast, several works have shown that evidence of volcanic forcing can persist for much longer in the stratosphere's chemical composition, even after the instigating aerosol population has dissipated. Heating by volcanic aerosols accelerates tropical upwelling, and thus drives an acceleration of the Brewer–Dobson Circulation (BDC), and enhances troposphere--stratosphere mass exchange. Even after tropical motion returns to its climatological mean, the anomalous mass exchange remains detectable in the stratosphere for several years. In this work, we use an age-of-air (AoA) tracer to diagnose stratospheric composition changes following the simulated 1991 Mt. Pinatubo eruption. Specifically, we employ simulation ensembles from the E3SMv2 climate model to identify statistically significant effects on zonal-mean AoA. In addition, we use the Residual Circulation Transit Time (RCTT) diagnostic to separate the effects of advective transport and mixing. We find that the Mt. Pinatubo eruption lowers AoA in the middle-to-upper stratosphere globally, primarily due to an accelerated residual meridional circulation. We also observe a localized increase of AoA near 20–100 hPa in the hemisphere opposite the eruption, which we attribute to a dampening of the seasonal BDC cycle by the volcanic aerosols. We suggest that a dampened seasonal BDC cycle is perhaps a generic result of any heating process driven by aerosols that evolve on timescales beyond seasonal in the meridional plane.

Received: 28 Sep 2025 – Discussion started: 10 Oct 2025

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

Download & links

Preprint (PDF, 6067 KB)

Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Preprint (6067 KB)

Download & links

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Journal article(s) based on this preprint

21 May 2026

Volcanic aerosol modification of the stratospheric circulation in E3SMv2 – Part 2: Brewer–Dobson Circulation

Joseph P. Hollowed, Christiane Jablonowski, Thomas Ehrmann, Diana Bull, Benjamin Wagman, and Benjamin Hillman

Atmos. Chem. Phys., 26, 6889–6908, https://doi.org/10.5194/acp-26-6889-2026,https://doi.org/10.5194/acp-26-6889-2026, 2026

Short summary

Joseph P. Hollowed, Christiane Jablonowski, Thomas Ehrmann, Diana Bull, Benjamin Wagman, and Benjamin Hillman

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-4598', Anonymous Referee #1, 26 Nov 2025

Review of Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer–Dobson Circulation
The article discusses the modification of the stratospheric Brewer-Dobson circulation in response to the Pinatubo volcanic eruption, building upon the published results (Part I) on the stratospheric dynamics response. The results show that the heating-induced enhancement of tropical upwelling (~15ºN) results in reduced mean age of air (AoA) throughout the middle and upper stratosphere, while in the lower stratosphere (below ~30 hPa) in the SH there is a localized increase in AoA. The fact that the eruption is located in the NH tropics and the seasonal cycle in turnaround latitudes are found to explain the increased aging in the SH. A comprehensive analysis of the causes for AoA changes is carried out by combining the local tendency perspecive using the TEM budget of AoA, as well as the integrated transport perspective using RCTT and aging by mixing. The paper is very well written, the relevant literature is largely discussed, the analyses are well described to allow for reproducibility, the figures have high quality and support the results, and the conclusions are supported by the analyses shown. I therefore recommend publication after minor revisions. I do have some minor comments, which are aimed to improve the clarity of the paper and I strongly recommend addressing them.

Minor comments
- The top of the model at 60 km is located in the mesosphere and low in comparison with other state-of-the-art stratosphere-resolving models. I suggest adding a comment on the possible effects of this (relatively) low top, for instance on the BDC driving by gravity waves, the sponge layer, …
It could be perhaps affecting the longest-lived air parcels and explaining the misbehavior mentioned in the paper (missing trajectories, bouncing between the two hemispheres, e.g. L202-204).
- L115-125 (and Fig. 1): This discussion on the simulations is confusing. Why are a 3-year and a 7-year simulations needed? Why not carry out a single control simulation spanning the entire time period 1981-1998, and branch from it the different ensemble members, with and without perturbation? Please explain this in a simple and concise way in the paper.
- Throughout the paper, the term ‘tracer transport’ is used to denote ‘advection by the residual circulation’, in opposition to mixing. In my view, both advection and mixing lead to ‘tracer transport’ (while mixing alone does not lead to mass transport). Since this term is commonly used in the literature, and is the standard nomenclature of the TEM terms in Eqs. (5) and (6), I recommend to use it instead. For example in L154, L247, L254, L322, Fig. 10 title of panel (b) and figure caption.
- Fig. 4: Why do some trajectories seem to stop in the tropical lower stratosphere (below ~30 hPa) with transit times below 1 year?
- L281-282: ‘while the deep branch in the summer hemisphere is weakened’. I suggest specifying ‘the upwelling in the summer hemisphere is weakened’.
- The enhanced residual circulation is seen only above ~10 hPa in boreal winter. At lower levels it is actually weakened, as shown by the negative streamfunction response over the region of positive control streamfunction in Fig. 6. In the summer months instead there is an acceleration also in the lower stratosphere.
- Figure 9: In panel (c), the RCTT in the control simulation trajectories seem to stay constant after crossing the 20 hPa level, is this because the colorscale gets saturated? In this case it could be extended (otherwise it seems that they arrive to the final point with the same RCTT as the perturbed ensemble).
- Figure 10: In Fig. 7e the SH older-age region (SHLS) extends to July 1993, so Fig. 10 should be extended until that date to show the ‘abrupt’ termination of this feature. Is this what is referred to in L364-366? In that line it says the termination happens in June 1992, which is not what we see in Fig. 7e. Please clarify when does this aging terminate and show it in a figure (also ‘terminates after one year’ in L373 should be changed to ‘two years’?).
- Fig. 10 (less important than previous comment): For consistency with Figure 7e, this figure could show 40 hPa instead of 30 hPa. Finally, the black arrows in this figure are not necessary (the upwelling/downwelling regions are identified by the w*=0 contours) and in my opinion make the figure confusing, so I suggest removing them.
- Figure 12: Suggested modification of the schematic: Remove the annual mean picture, does not help to make the argument and it is not a realistic situaltion. Mark the turnaround latitudes (with vertical dotted/dashed lines, or shading the upwelling region), since the important point here is whether the anomalous downwelling falls into the climatological upwelling or downwelling region.
- Section 5.2: The damping of the seasonal cycle of AoA is interesting but could be shown more clearly. Fig. 11 shows that the eruption impact on AoA has the same sign as the boreal summer climatological tendency. But how that implies a reduced seasonality is not clear. Could you maybe show the reduced seasonal cycle for some specific region where it is most evident?

Technical:
- L199-201: This is already discussed above, consider reducing or removing and referencing back.
- ‘dampening’ should be ‘damping’ in L12 and L34.
- L380: ‘impact of’ should be ‘impact on’

Citation: https://doi.org/10.5194/egusphere-2025-4598-RC1
- AC1: 'Reply on RC1', Joseph Hollowed, 25 Jan 2026
  
  Our reply to Reviewer 1 is attached as a PDF document, where each comment was addressed in detail. We thank the reviewer for their hard work.
  
  Citation: https://doi.org/10.5194/egusphere-2025-4598-AC1
RC2:
'Comment on egusphere-2025-4598', Anonymous Referee #2, 30 Nov 2025
Review of Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer–Dobson Circulation by Hollowed et al.
General comments: This study uses the E3SMv2 climate model to investigate the impacts of sulfate aerosols from the 1991 Pinatubo eruption on the Brewer-Dobson Circulation. The manuscript is very well written and follows a clear logical structure. The setup of the simulations is well described, and so is the analysis framework. The results are well and thoroughly presented. I strongly recommend publication and only have several minor comments as listed below.
Specific comments (minor):
line 1 and lines 16-17: Since volcanic eruptions are very diverse, I would appreciate if the authors would specify what kind of eruptions they are investigating upfront (for example, in the case of this study, explosive volcanic eruptions injecting large amount of SO2 into to stratosphere).

line 12: I would recommend specifying that the hemisphere opposite the eruption in the southern hemisphere as the authors do not simulate SH eruptions. This would be consistent with the wording of point 3 in Section 7.

line 66: The authors define the abbreviation SAI later in the manuscript but I would appreciate they did it here already.

lines 89-90: I assume the model is fully coupled.

line 98: Although the authors specify the altitude and the latitude of the volcanic SO2 injections in Part I, I would appreciate if they did it here as well.

line 171 (Eq. 11): The authors explain the variable X as the forcing by ‘parameterized processes and diffusion’, i.e. unresolved forcing. Later (for example in Fig. 5c and lines 247-251) they discuss this parameter only in terms of diffusion. Does this mean that unresolved processes other than diffusion are negligible in the TEM framework? If so, I would be interested in reading about it. And if not, I would be interested in reading more about which processes are not resolved and their relative importances.

line 220: ‘[...] whereas our reference point is close to the surface.’ Can you say that 700 hPa (ca. 3 km) is close to the surface? I suggest replacing ‘close’ with ‘closer’.

line 254: For clarity, I would appreciate if the authors specified panel (a) of which figure they are referring to (Fig. 3a).

line 257: For clarity, I would appreciate if the authors specified in which figure the ‘relatively small local diffusion tendencies’ can be seen (Fig. 5c).

line 259: For clarity, I would appreciate if the authors referred to Fig. 5e in the context of the net tendency.

lines 275-277: From Fig. 6, it looks like that not only has the significance of the features discussed ‘notably diminished by August of 1992’, but almost disappeared in the tropics (as the authors note in line 296).

Figure 13: Since the bulk of study focuses on the Pinatubo eruption (10 Tg SO2), I wonder why the authors choose to normalise the relative max impacts in the lower sub-panels to the results from their 15 Tg SO2 simulations.

lines 486-487: The authors expand on their study of the Pinatubo eruption by simulating similar eruptions (in terms of location and injection altitude) of different emission magnitudes (Section 6). In Section 7 (lines 486-487), they further suggest that a future study could explore the sensitivity of their results to variations in eruption latitude and season. I would like to add that exploring the sensitivity to injection altitude would be interesting. Particularly in the light of the recent study by Toohey et al. (https://doi.org/10.5194/acp-25-3821-2025) which showed how the lifetime of volcanic aerosols in the stratosphere is very sensitive to the injection altitude.
Citation: https://doi.org/10.5194/egusphere-2025-4598-RC2
- AC2: 'Reply on RC2', Joseph Hollowed, 25 Jan 2026
  
  Our reply to Reviewer 2 is attached as a PDF document, where each comment was addressed in detail. We thank the reviewer for their hard work.
  
  Citation: https://doi.org/10.5194/egusphere-2025-4598-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-4598', Anonymous Referee #1, 26 Nov 2025

Review of Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer–Dobson Circulation
The article discusses the modification of the stratospheric Brewer-Dobson circulation in response to the Pinatubo volcanic eruption, building upon the published results (Part I) on the stratospheric dynamics response. The results show that the heating-induced enhancement of tropical upwelling (~15ºN) results in reduced mean age of air (AoA) throughout the middle and upper stratosphere, while in the lower stratosphere (below ~30 hPa) in the SH there is a localized increase in AoA. The fact that the eruption is located in the NH tropics and the seasonal cycle in turnaround latitudes are found to explain the increased aging in the SH. A comprehensive analysis of the causes for AoA changes is carried out by combining the local tendency perspecive using the TEM budget of AoA, as well as the integrated transport perspective using RCTT and aging by mixing. The paper is very well written, the relevant literature is largely discussed, the analyses are well described to allow for reproducibility, the figures have high quality and support the results, and the conclusions are supported by the analyses shown. I therefore recommend publication after minor revisions. I do have some minor comments, which are aimed to improve the clarity of the paper and I strongly recommend addressing them.

Minor comments
- The top of the model at 60 km is located in the mesosphere and low in comparison with other state-of-the-art stratosphere-resolving models. I suggest adding a comment on the possible effects of this (relatively) low top, for instance on the BDC driving by gravity waves, the sponge layer, …
It could be perhaps affecting the longest-lived air parcels and explaining the misbehavior mentioned in the paper (missing trajectories, bouncing between the two hemispheres, e.g. L202-204).
- L115-125 (and Fig. 1): This discussion on the simulations is confusing. Why are a 3-year and a 7-year simulations needed? Why not carry out a single control simulation spanning the entire time period 1981-1998, and branch from it the different ensemble members, with and without perturbation? Please explain this in a simple and concise way in the paper.
- Throughout the paper, the term ‘tracer transport’ is used to denote ‘advection by the residual circulation’, in opposition to mixing. In my view, both advection and mixing lead to ‘tracer transport’ (while mixing alone does not lead to mass transport). Since this term is commonly used in the literature, and is the standard nomenclature of the TEM terms in Eqs. (5) and (6), I recommend to use it instead. For example in L154, L247, L254, L322, Fig. 10 title of panel (b) and figure caption.
- Fig. 4: Why do some trajectories seem to stop in the tropical lower stratosphere (below ~30 hPa) with transit times below 1 year?
- L281-282: ‘while the deep branch in the summer hemisphere is weakened’. I suggest specifying ‘the upwelling in the summer hemisphere is weakened’.
- The enhanced residual circulation is seen only above ~10 hPa in boreal winter. At lower levels it is actually weakened, as shown by the negative streamfunction response over the region of positive control streamfunction in Fig. 6. In the summer months instead there is an acceleration also in the lower stratosphere.
- Figure 9: In panel (c), the RCTT in the control simulation trajectories seem to stay constant after crossing the 20 hPa level, is this because the colorscale gets saturated? In this case it could be extended (otherwise it seems that they arrive to the final point with the same RCTT as the perturbed ensemble).
- Figure 10: In Fig. 7e the SH older-age region (SHLS) extends to July 1993, so Fig. 10 should be extended until that date to show the ‘abrupt’ termination of this feature. Is this what is referred to in L364-366? In that line it says the termination happens in June 1992, which is not what we see in Fig. 7e. Please clarify when does this aging terminate and show it in a figure (also ‘terminates after one year’ in L373 should be changed to ‘two years’?).
- Fig. 10 (less important than previous comment): For consistency with Figure 7e, this figure could show 40 hPa instead of 30 hPa. Finally, the black arrows in this figure are not necessary (the upwelling/downwelling regions are identified by the w*=0 contours) and in my opinion make the figure confusing, so I suggest removing them.
- Figure 12: Suggested modification of the schematic: Remove the annual mean picture, does not help to make the argument and it is not a realistic situaltion. Mark the turnaround latitudes (with vertical dotted/dashed lines, or shading the upwelling region), since the important point here is whether the anomalous downwelling falls into the climatological upwelling or downwelling region.
- Section 5.2: The damping of the seasonal cycle of AoA is interesting but could be shown more clearly. Fig. 11 shows that the eruption impact on AoA has the same sign as the boreal summer climatological tendency. But how that implies a reduced seasonality is not clear. Could you maybe show the reduced seasonal cycle for some specific region where it is most evident?

Technical:
- L199-201: This is already discussed above, consider reducing or removing and referencing back.
- ‘dampening’ should be ‘damping’ in L12 and L34.
- L380: ‘impact of’ should be ‘impact on’

Citation: https://doi.org/10.5194/egusphere-2025-4598-RC1
- AC1: 'Reply on RC1', Joseph Hollowed, 25 Jan 2026
  
  Our reply to Reviewer 1 is attached as a PDF document, where each comment was addressed in detail. We thank the reviewer for their hard work.
  
  Citation: https://doi.org/10.5194/egusphere-2025-4598-AC1
RC2:
'Comment on egusphere-2025-4598', Anonymous Referee #2, 30 Nov 2025
Review of Volcanic Aerosol Modification of the Stratospheric Circulation in E3SMv2 Part II: Brewer–Dobson Circulation by Hollowed et al.
General comments: This study uses the E3SMv2 climate model to investigate the impacts of sulfate aerosols from the 1991 Pinatubo eruption on the Brewer-Dobson Circulation. The manuscript is very well written and follows a clear logical structure. The setup of the simulations is well described, and so is the analysis framework. The results are well and thoroughly presented. I strongly recommend publication and only have several minor comments as listed below.
Specific comments (minor):
line 1 and lines 16-17: Since volcanic eruptions are very diverse, I would appreciate if the authors would specify what kind of eruptions they are investigating upfront (for example, in the case of this study, explosive volcanic eruptions injecting large amount of SO2 into to stratosphere).

line 12: I would recommend specifying that the hemisphere opposite the eruption in the southern hemisphere as the authors do not simulate SH eruptions. This would be consistent with the wording of point 3 in Section 7.

line 66: The authors define the abbreviation SAI later in the manuscript but I would appreciate they did it here already.

lines 89-90: I assume the model is fully coupled.

line 98: Although the authors specify the altitude and the latitude of the volcanic SO2 injections in Part I, I would appreciate if they did it here as well.

line 171 (Eq. 11): The authors explain the variable X as the forcing by ‘parameterized processes and diffusion’, i.e. unresolved forcing. Later (for example in Fig. 5c and lines 247-251) they discuss this parameter only in terms of diffusion. Does this mean that unresolved processes other than diffusion are negligible in the TEM framework? If so, I would be interested in reading about it. And if not, I would be interested in reading more about which processes are not resolved and their relative importances.

line 220: ‘[...] whereas our reference point is close to the surface.’ Can you say that 700 hPa (ca. 3 km) is close to the surface? I suggest replacing ‘close’ with ‘closer’.

line 254: For clarity, I would appreciate if the authors specified panel (a) of which figure they are referring to (Fig. 3a).

line 257: For clarity, I would appreciate if the authors specified in which figure the ‘relatively small local diffusion tendencies’ can be seen (Fig. 5c).

line 259: For clarity, I would appreciate if the authors referred to Fig. 5e in the context of the net tendency.

lines 275-277: From Fig. 6, it looks like that not only has the significance of the features discussed ‘notably diminished by August of 1992’, but almost disappeared in the tropics (as the authors note in line 296).

Figure 13: Since the bulk of study focuses on the Pinatubo eruption (10 Tg SO2), I wonder why the authors choose to normalise the relative max impacts in the lower sub-panels to the results from their 15 Tg SO2 simulations.

lines 486-487: The authors expand on their study of the Pinatubo eruption by simulating similar eruptions (in terms of location and injection altitude) of different emission magnitudes (Section 6). In Section 7 (lines 486-487), they further suggest that a future study could explore the sensitivity of their results to variations in eruption latitude and season. I would like to add that exploring the sensitivity to injection altitude would be interesting. Particularly in the light of the recent study by Toohey et al. (https://doi.org/10.5194/acp-25-3821-2025) which showed how the lifetime of volcanic aerosols in the stratosphere is very sensitive to the injection altitude.
Citation: https://doi.org/10.5194/egusphere-2025-4598-RC2
- AC2: 'Reply on RC2', Joseph Hollowed, 25 Jan 2026
  
  Our reply to Reviewer 2 is attached as a PDF document, where each comment was addressed in detail. We thank the reviewer for their hard work.
  
  Citation: https://doi.org/10.5194/egusphere-2025-4598-AC2

Peer review completion

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

AR by Joseph Hollowed on behalf of the Authors (25 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (26 Jan 2026) by Petr Šácha

RR by Anonymous Referee #2 (28 Jan 2026)

RR by Anonymous Referee #1 (09 Feb 2026)

ED: Publish subject to minor revisions (review by editor) (11 Feb 2026) by Petr Šácha

Dear authors,

thank you very much for carefully considering all of the referee comments.
I am happy that both experts found the revisions successful and unequivocally recommend the manuscript for publication.
However, I am myself interested in the fundamental topic of the BDC driving and after reading your manuscript carefully,
I have found some minor issues concerning the theoretical aspects of your methodology and typological errors that need to be addressed before publication.
Hence, I reached the editorial decision of "Publish subject to minor revisions".
The list of my comments is given below in chronological order.

When you revise the manuscript and reply to my comments, I will swiftly review the revision and accept it for publication, if no other issues arise.
Thank you again for publishing with ACP
and wishing you all the best for your future work.
Best regards,
Petr Šácha.

Comments from the editor review:
General: Over the whole manuscript and also in captions of the figures - an overbar is missing for w* and delta w*. You refer to the circulation as residual mean (I think this shortcoming comes from the Birner and Boenish paper), which is probably acceptable, but do not forget that it is in fact the residual mean circulation and reflect this with the overbar.

Chronological:
L39-L41 "Tracer isopleths (surfaces of constant mixing ratio) are raised and lowered in the tropics and polar regions, respectively, by the thermally-direct
overturning cell that is the residual circulation. In the midlatitudes, isopleths are homogenized by two-way adiabatic mixing of
mass along isentropes, caused by breaking planetary waves in the surf-zone (e.g. Plumb (2007))...."
- Nowhere you mention the fundamental effect of the Stokes drift, very important in the midlatitudinal LS, where it smears out the indirect Eulerian mean cell. Also, you should make clear that mixing is active not only in the midlatitudes and, generally, also vertical mixing is very important.

L48-49: ".. and local concentrations corresponding to mean age."
- The whole statement here is a bit vague, as it obscures the whole underlying theory of Age-of-air and the fact that your method is able to derive the mean AoA only. At least, I would ask you to highlight the fact that the mean stratospheric age-of-air is analyzed in your manuscript.

L58-L60: "Later, Garny et al. (2014) pointed out that the difference (AoA−RCTT) could be used to isolate aging by isentropic mixing, which throughout much of the upper atmosphere was shown to be at least as important as aging by residual circulation advection. While this type of differencing is a useful procedure, it is also a blunt one, as it cannot separate contributions of mixing by resolved wave breaking, and diffusion..."
-You should be aware that the difference between AoA and RCTT is partly also due to the advective processes. For one, already Garny et al. (2014) mention the effect of recirculation on AbM.
However, there is also an additional mechanism arising from the fact that the residual mean circulation approximates the Lagrangian mean circulation only to the second order of wave amplitude and for steady waves. Hence, for the transport connected with wave transience events and finite amplitude waves the residual mean circulation is not accurate and the difference goes to AbM.

Subsection 3.2, 3.3 - please state what version of TEM and residual mean circulation you use (I suppose that it is a hydrostatic primitive equation version in geometric coordinates, and not in the log-pressure coordinates or the QG version).

Subsection 3.3 In relation with the previous comment, the reader needs to know more details on the p->z transformation (around L191). Hopefully, actual geopotential height and not the log-pressure formula is used. Because the log-pressure relation may result in uncertainties in measuring the vertical distances due to changes in the thickness of atmospheric layers induced by variable heating (see e.g. Eichinger and Šácha, 2020, QJRMS or Šácha et al., 2019, ACP for the impact of vertical shifts on AoA and AbM, which can be also relative to pressure levels).

Fig. 4 - the colorbar includes white for the values between 5 and 6. Is this intentional?

Fig. 5 - Are the units [day/day] correct here given the large tendencies that are resulting (even though these are only the partial tendencies)? Further, there is a typo in the caption.. "resiudal".
Also, the reader would welcome more information on how the tendencies are computed. From daily data and then averaged over the year/season?

L338 "Whatever the dynamical explanation of the advection-mixing balance at play here.."
-Let me suggest a possible dynamical mechanism - the Stokes drift, which influences the Lagrangian mean transport (and the residual mean circulation) is connected with the pure presence of Rossby waves, when the Rossby waves break, they induce the quasi-horizontal mixing but also their amplitude is lowered and hence also the Stokes drift and the residual mean circulation are affected.
I assume that the majority of Rossby waves will be upward propagating modes and in the full picture they will also be affected by the anomalies in the zonal wind field you describe around L329 (possible critical level occurence/shift for some modes).

L418 What is the global EP wave activity? You mean Rossby wave activity?

L472 "..climatological w∗zero-line"
-This line has a name - the turn-around latitude.

L511 - The possible role of the QBO phase is very important and would be nice to mention in the methodology, how QBO is treated in the simulations you use (internally generated, nudged, constant phase...)

Hide

AR by Joseph Hollowed on behalf of the Authors (24 Feb 2026) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (25 Feb 2026) by Petr Šácha

Dear authors,

I would like to thank you very much for considering my additional comments, revising the text, where it was needed, and replying in a great detail.
Especially I would like to applaud the part of your response concerning the effect of constant H. Your clean analytical argument would make a nice stand-alone technical paper in my eyes.
I indicate "Publish subject to technical corrections" in the system, because there is one remaining minor issue in the revision (see below).
When you revise it and upload the manuscript back to us, it will be immediately and automatically accepted (already without my control).

Having said that, I would like to thank you again for publishing in ACP
and would like to inform you that I nominated your paper for a highlight article, which is up to the executive editors to decide.

Best regards,
Petr Šácha.

Minor comment:
"This circulation describes the transport of mass in the meridional plane, as the superposition
of an advective component which approximates the Lagrangian mass flow, and an eddy-driven component, which approximates the effects of Stokes drift, wave transience and dissipation."

I think that the statement is even more confusing this way and suggest rephrasing similarly to:
"This circulation approximates the mean Lagrangian transport of mass in the meridional plane as a superposition of the Eulerian mean circulation and an eddy-driven component accounting for the Stokes drift induced by the wave field."

As for the wave transience and dissipation - I suggest not to mention them here, because it is these two factors that make the relationship between the Lagrangian mean and residual mean circulation complicated. To this point, I add a private note to the system, which will not emerge in the public justification.

Hide

AR by Joseph Hollowed on behalf of the Authors (10 Apr 2026) Author's response Manuscript

Journal article(s) based on this preprint

21 May 2026

Volcanic aerosol modification of the stratospheric circulation in E3SMv2 – Part 2: Brewer–Dobson Circulation

Joseph P. Hollowed, Christiane Jablonowski, Thomas Ehrmann, Diana Bull, Benjamin Wagman, and Benjamin Hillman

Atmos. Chem. Phys., 26, 6889–6908, https://doi.org/10.5194/acp-26-6889-2026,https://doi.org/10.5194/acp-26-6889-2026, 2026

Short summary

Joseph P. Hollowed, Christiane Jablonowski, Thomas Ehrmann, Diana Bull, Benjamin Wagman, and Benjamin Hillman

Viewed

Total article views: 2,279 (including HTML, PDF, and XML)

HTML	PDF	XML	Total	BibTeX	EndNote
1,573	520	186	2,279	133	114

HTML: 1,573
PDF: 520
XML: 186
Total: 2,279
BibTeX: 133
EndNote: 114

Views and downloads (calculated since 10 Oct 2025)

Month	HTML	PDF	XML	Total
Oct 2025	520	100	40	660
Nov 2025	203	35	35	273
Dec 2025	175	140	50	365
Jan 2026	233	89	20	342
Feb 2026	164	69	24	257
Mar 2026	187	52	15	254
Apr 2026	79	30	1	110
May 2026	12	5	1	18

Cumulative views and downloads (calculated since 10 Oct 2025)

Month	HTML	PDF	XML	Total
Oct 2025	520	100	40	660
Nov 2025	203	35	35	273
Dec 2025	175	140	50	365
Jan 2026	233	89	20	342
Feb 2026	164	69	24	257
Mar 2026	187	52	15	254
Apr 2026	79	30	1	110
May 2026	12	5	1	18

Viewed (geographical distribution)

Total article views: 2,271 (including HTML, PDF, and XML) Thereof 2,271 with geography defined and 0 with unknown origin.

Country	#	Views	%

Latest update: 25 May 2026

Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Preprint (6067 KB)
Metadata XML

Short summary

Large volcanic eruptions introduce huge quantities of aerosols into the stratosphere. Volcanic aerosols heat the stratosphere, thereby altering the global circulation of air. This research uses simulations of the 1991 Mt. Pinatubo eruption to study the resulting circulation changes, and the dynamical processes which govern them. We find that stratospheric composition is altered by increased tropical vertical motion, and that the seasonal cycle of the global circulation is significantly dampened.


Total:	0
HTML:	0
PDF:	0
XML:	0