Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

Hu, Allen; Liu, Xiaohong; Ke, Ziming; Wagman, Benjamin; Brown, Hunter; Lu, Zheng; Bull, Diana; Peterson, Kara

doi:https://doi.org/10.5194/egusphere-2024-2227

Preprints

https://doi.org/10.5194/egusphere-2024-2227

Preprints

24 Jul 2024

| 24 Jul 2024

Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

Allen Hu, Xiaohong Liu, Ziming Ke, Benjamin Wagman, Hunter Brown, Zheng Lu, Diana Bull, and Kara Peterson

Abstract. Stratospheric sulfate aerosol produced by volcanic eruptions plays important roles in atmospheric chemistry and the global radiative balance of the atmosphere. The simulation of stratospheric sulfate concentrations and optical properties is highly dependent on the chemistry scheme and microphysical treatment. In this work, we implemented a sophisticated gas-phase chemistry scheme (full chemistry, FC) and a 5-mode version of the Modal Aerosol Module (MAM5) for the treatment of stratospheric sulfate aerosol in the Department of Energy’s Energy Exascale Earth System Model version 2 (E3SMv2) model to better simulate the chemistry-aerosol feedback following the Pinatubo eruption, and to compare it against a simulation using simplified chemistry (SC) and the default 4-mode version of the Modal Aerosol Module (MAM4). MAM5 experiments were found to better capture the stratospheric sulfate burden from the eruption of the volcano to the end of 1992 as compared to the High-resolution Infra Red Sounder (HIRS) observations, and the formation of sulfate in MAM5FC was significantly faster than in MAM4FC due to the addition of a OH replenishment reaction. Analyses of microphysical processes indicate that more sulfate aerosol mass was generated in total in FC experiments than in SC experiments. MAM5 performs better than MAM4 in simulation of aerosol optical depth (AOD); AOD anomalies from the MAM5 experiment have better agreement with AVHRR. The simulated largest changes in global mean net radiative flux at the top of the atmosphere following the eruption were about -3 W/m² in MAM5 experiments and roughly -1.5 W/m² in MAM4 experiments.

Received: 17 Jul 2024 – Discussion started: 24 Jul 2024

Competing interests: Some authors are members of the editorial board of Atmospheric Chemistry and Physics.

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.

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Journal article(s) based on this preprint

07 Oct 2025

Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

Allen Hu, Ziming Ke, Xiaohong Liu, Benjamin Wagman, Hunter Brown, Zheng Lu, Mingxuan Wu, Hailong Wang, Qi Tang, Diana Bull, Kara Peterson, and Shaocheng Xie

Atmos. Chem. Phys., 25, 12137–12157, https://doi.org/10.5194/acp-25-12137-2025,https://doi.org/10.5194/acp-25-12137-2025, 2025

Short summary

Allen Hu, Xiaohong Liu, Ziming Ke, Benjamin Wagman, Hunter Brown, Zheng Lu, Diana Bull, and Kara Peterson

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-2227', Anonymous Referee #1, 30 Aug 2024

The authors set up 2 modal aerosol models, each with both simple and full chemistry, in the Dept. of Energy’s Earth system model and compare the model output for 1991-1993. The object is to characterize the development of stratospheric aerosol from the Pinatubo eruptions from the 4 different aerosol models. The models are compared to AVHRR and HIRS observations.
The paper is mostly well written with a specific purpose but there are difficulties. The first difficulty is the limited comparisons with observations, just two sets of observations and two figures. Both figures raise questions about the comparison, but little discussion is given to the disagreements. A lot of papers have been published describing the post Pinatubo aerosol from a variety of instruments. Why aren’t additional comparisons made with a much wider set of data? The model has pretty fine resolution, so it should not be limited to comparisons to measurements with global coverage. The authors spend a lot of energy comparing the various size distribution modes from the different model configurations, but make no attempt to compare any of these size distributions to observed size distributions. The authors offer no explanation for their limited comparison with observations.
The second difficulty has to do with the figures, their discussions, and the language used to describe processes related to aerosol moving between modes. Details related to these issues follow here by line number. Within this are also a few minor suggestions.
119-120 In terms of size order aren’t the modes: Aitken, accumulation, coarse, rather than accumulation first? If so then they should be listed in that order.
Fig. 1 What happens to particles in MAM4 when they exceed Dg_hi (0.48 µm), which is not that large for sulfate particles following Pinatubo? See e.g. Deshler et al., GRL, 1992.
178-179 The parenthetical clause is so long the reader has lost the thread as to what limits the aerosol formation rates.
Fig. 2 and its discussion. What is the explanation for the aerosol in the Southern Hemisphere, which appears at most longitudes almost simultaneous with the Pinatubo eruption, particularly in MAM5FC? The presence of this aerosol clearly above background should be acknowledged and if possible explained.
284-286 Why does the smaller geometric standard deviation in MAM5 lead to more persistence? Is it because the particles are smaller in MAM5 compared to MAM4 and therefore less sedimentation? In any case there should be a sentence to describe the physics involved.
Fig. 4 and its discussion. The discussion mostly consists of describing the figure providing specific dates and sulfate burden peaks for the various modes. While perhaps these details are interesting they are all available in the figure for the interested reader. More interesting for the reader would be more discussion of the model / measurement discrepancies. Why do all models except MAM4FC over estimate the peak observed sulfur burden by 20%? Are the HIRS data reliable at the peak or are they suffering a saturation problem? Why does HIRS fall off so much faster than the MAM5 models in 1993? Additional interesting detail would be the range of median sizes involved in the large particle mode.
Because MAM4 doesn’t have a coarse mode and MAM5 has a very narrow accumulation mode, both Figs 4 and 5 show the same thing, no contribution in the accumulation mode (or very little) from MAM5 and no contribution in the coarse mode from MAM4. Why then show the accumulation mode at all? Combine the MAM4 accumulation mode and MAM5 coarse mode into one figure. MAM5 accumulation mode could be included as a dotted line in the coarse mode plot. Then the two models can be more easily compared in terms of sulfate burden carried in the large particle mode.
Fig. 5 Same comments as Fig. 4 but in addition the ordinates should all be the same scale (0-4 Tg S), so the relative contributions from the different latitude zones can be seen directly. Without that the reader immediately wonders about the Southern Hemisphere signal which seems to persist at high levels. The label on the ordinate is wrong. It should be Sulfur burden (Tg S). Label the rows in some other way or describe them in the figure caption. Again combine accumulation and coarse mode into one plot then there will only be three rows. The latitudes of the eruptions should be listed in the figure caption.
331-332 What is the reason for this oscillation, when the sulfur burden is declining everywhere else? A somewhat similar oscillation, but offset, is observed in the Northern Hemisphere. Why does the sulfur burden persist to 1994 in the Southern Hemisphere while it decays everywhere else?
341-343 This point would be a lot clearer for the reader if the ordinate scale on all plots was the same. But this statement, “Starting from 1993, the stratospheric burden south of 30 S in MAM5 begins to make up at least half of the total between 80 S and 80 N (about 0.8 Tg S out of the total of 1.7 Tg S)”, doesn’t make sense. Between 80 S and 80 N includes 30 S – 30 N, so the total sulfur burden in early 1993 for MAM5FC is ~4.1 Tg S.
349-350 Suggest rephrasing to. “The tendencies are the integrals over three-dimensions of: all longitudes, …”
Fig. 6 is problematic. There are too many rows making the figure so small that most readers have to blow it up to see it. This could be fixed by breaking it into two figures: the first containing the first 4 rows, the next containing the last 3. Another suggestion is to combine the right and left panels into a single plot with separate ordinates on the right and left. Since the left shows a rate and right shows an accumulation the lines will generally not overlap but rather complement each other. Again the ordinate labels are incorrect. They should be tendency (kg/s) for the left plots and their integrals (or cumulative) (Tg S) for the right. Include the name of the row as a label in each plot. The labels RNMxx are too tied to the inner workings of the model, “renaming”. But physically what is happening? The particles are growing to the next largest size distribution mode. If labels were added to the plots to identify them RNMaa could become Aitken->Accumulation mode and RNMasc Accumulation->Coarse mode.
Fig 6 e, f) shows the growth from Aitken to accumulation mode presumably by several processes including growth by condensation and coagulation, correct? If that is the case then why are the ordinate scales on COAG so much larger than for RNMaa? Both are showing mass loss rate and total mass lost. It seems it should be the other way around with COAG less than RNMaa. Why is this one process coagulation singled out for a special plot?
Fig 6 i – n) Condensation? Why are these processes now called condensation? Condensing from what? Weren’t these earlier called renaming, which is also not that helpful or descriptive. Isn’t this particle growth from one mode to another? Ordinate problems again. What is on the left and right ordinates? Is it again rate (kg/s) and cumulative mass (Tg S)? The reader doesn’t know and the figure caption does not help.
351-415 Again the figure discussion consists primarily of describing the figure, pointing out maximum values and dates when they occur. Relatively little is describing what can be learned from the figure which is the importance of the figure. Here and elsewhere, if these dates and amounts are particularly important organize them into a table. Then they could really be compared. It is not clear how listing them in the text helps the reader.
Figs. 4-8, 11 The plotting for these figures could be made much more intuitive, so the reader doesn’t constantly have to refer to the legend to remember which is which. It would be quite easy to do. Use one color for MAM4 and one for MAM5, then one line style (e.g. solid) for FC and another (dashed or dotted) for SC. Then each figure can be immediately understood without referring to the legend but once.
Figs 7 and 8 suffer from the same problem as Fig. 6. There are too many panels and they are too small. What are Figs. 7 and 8 adding to what we learned from Fig. 6? Are all these rows necessary? Which ones are the most informative?
420-430 In fact the discussion of Figs. 7 and 8 acknowledges that not much new is added. “The same patterns as above apply between 30 S and 30 N. Above 30 N and below 30 S the same signal from the Pinatubo is still present, though slightly delayed due to the time that it took for the aerosol to transport poleward. Signals from other eruptions (Spurr and Lascar) are also present” Then a few interesting differences are discussed. Just show the interesting panels and combine Figs 7 and 8 into one figure with the few interesting panels.
503 condensation? Same questions as above. What does this mean?
503-505 What is the reason for quoting these numbers? How will the reader use such information rather than the already stated comparison about the difference rates? Too detailed.
506 Here COAG is separated from RNMaa, but aren’t both processes doing the same thing? There is only the transition from Aitken to accumulation. Is it important how it happens? If so why isn’t that mentioned earlier?
509 deposition? Does this mean sedimentation out of the stratosphere? Generally deposition refers to losing aerosol due to contact with a surface.

Citation: https://doi.org/10.5194/egusphere-2024-2227-RC1
- AC1: 'Reply on RC1', Allen Hu, 26 Dec 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2227/egusphere-2024-2227-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2227-AC1
RC2:
'Comment on egusphere-2024-2227', Anonymous Referee #2, 03 Sep 2024

Overview:
This paper explores simulations of the Pinatubo eruption using different configurations of the Modal Aerosol Module (MAM) in E3SMv2. MAM is used with 4 modes and extended with a 5^th mode to better capture large stratospheric aerosol particles. Additionally, both simplified and full chemistry modes are tested. The paper is well written and structured with clear explanations of the differences for full chemistry due the importance of OH reactions and inclusion of a larger mode to more accurately capture growth and sedimentation processes. I think this paper is a good contribution to the literature on prognostic aerosol modelling in the stratosphere and I would recommend publication with minor clarifications provided it falls within the scope of ACP.
General Comment:
I think the article is well written and a nice advancement to stratospheric aerosol modeling but may be better suited in its current form for a journal such as Geoscientific Model Development. While the differences in aerosol loading due to model configuration are made clear, it is left to the reader to interpret how this improves understanding of atmospheric chemistry or physics. The authors provide in-depth discussion on the relative importance of coagulation, nucleation and renaming/growth in the model, but have little discussion on the physical processes this may help resolve. Similarly, few comparisons are made with measurements for AOD, particle size or radiative flux, with no discussion given to possible sources of disagreement, or what implications these results may have for observations (e.g. the assumptions going into the HIRS results used here). Personally, I think addressing any of these points would help expand the applicability of the paper to a more general audience.
Specific Comments:
Line 50-65: This geoengineering section seems a bit out of place to me. I'm sure this work has implications for geoengineering studies, but no indication of exactly what those may be is provided. I recommend clarifying the link to this work or removing this paragraph. Perhaps the geoengineering discussion and the link to this work would be better placed in the discussion/conclusion?
Line 415: “MAM4 also generally has stronger nucleation and coagulation processes than MAM5.” From Figure 6 it isn’t clear whether MAM4FC has greater coagulation tendencies for physical reasons or if it is just due to the increased NUCL. This is discussed in the conclusion of the paper (Line 503), but I think should be mentioned here. I would suggest rewording to something like: “MAM4 also generally has stronger nucleation than MAM5, and due to these higher concentrations, increased coagulation processes as well” Or, if there are other reasons for increased COAG then this should also be discussed.
Line 490: “large differences in both the temporal variations and the spatial distributions of sulfate concentrations” It is difficult to tell from Figures 7/8, but in Figures 9/10 there doesn’t appear to be much change in spatial distribution. Both MAM4 and MAM5 show large increase in the tropics and later transport to the NH. Some expansion on the spatial differences the authors are referring to would be welcome.
Line 521-522: If the use of full chemistry and MAM5 helped improve agreement with AVHRR, why is the TOA flux more comparable to Brown (2024) and Mills (2017) results than the MAM4 version? Is this related to the geometric standard deviation that was used?

Citation: https://doi.org/10.5194/egusphere-2024-2227-RC2
- AC2: 'Reply on RC2', Allen Hu, 26 Dec 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2227/egusphere-2024-2227-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2227-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-2227', Anonymous Referee #1, 30 Aug 2024

The authors set up 2 modal aerosol models, each with both simple and full chemistry, in the Dept. of Energy’s Earth system model and compare the model output for 1991-1993. The object is to characterize the development of stratospheric aerosol from the Pinatubo eruptions from the 4 different aerosol models. The models are compared to AVHRR and HIRS observations.
The paper is mostly well written with a specific purpose but there are difficulties. The first difficulty is the limited comparisons with observations, just two sets of observations and two figures. Both figures raise questions about the comparison, but little discussion is given to the disagreements. A lot of papers have been published describing the post Pinatubo aerosol from a variety of instruments. Why aren’t additional comparisons made with a much wider set of data? The model has pretty fine resolution, so it should not be limited to comparisons to measurements with global coverage. The authors spend a lot of energy comparing the various size distribution modes from the different model configurations, but make no attempt to compare any of these size distributions to observed size distributions. The authors offer no explanation for their limited comparison with observations.
The second difficulty has to do with the figures, their discussions, and the language used to describe processes related to aerosol moving between modes. Details related to these issues follow here by line number. Within this are also a few minor suggestions.
119-120 In terms of size order aren’t the modes: Aitken, accumulation, coarse, rather than accumulation first? If so then they should be listed in that order.
Fig. 1 What happens to particles in MAM4 when they exceed Dg_hi (0.48 µm), which is not that large for sulfate particles following Pinatubo? See e.g. Deshler et al., GRL, 1992.
178-179 The parenthetical clause is so long the reader has lost the thread as to what limits the aerosol formation rates.
Fig. 2 and its discussion. What is the explanation for the aerosol in the Southern Hemisphere, which appears at most longitudes almost simultaneous with the Pinatubo eruption, particularly in MAM5FC? The presence of this aerosol clearly above background should be acknowledged and if possible explained.
284-286 Why does the smaller geometric standard deviation in MAM5 lead to more persistence? Is it because the particles are smaller in MAM5 compared to MAM4 and therefore less sedimentation? In any case there should be a sentence to describe the physics involved.
Fig. 4 and its discussion. The discussion mostly consists of describing the figure providing specific dates and sulfate burden peaks for the various modes. While perhaps these details are interesting they are all available in the figure for the interested reader. More interesting for the reader would be more discussion of the model / measurement discrepancies. Why do all models except MAM4FC over estimate the peak observed sulfur burden by 20%? Are the HIRS data reliable at the peak or are they suffering a saturation problem? Why does HIRS fall off so much faster than the MAM5 models in 1993? Additional interesting detail would be the range of median sizes involved in the large particle mode.
Because MAM4 doesn’t have a coarse mode and MAM5 has a very narrow accumulation mode, both Figs 4 and 5 show the same thing, no contribution in the accumulation mode (or very little) from MAM5 and no contribution in the coarse mode from MAM4. Why then show the accumulation mode at all? Combine the MAM4 accumulation mode and MAM5 coarse mode into one figure. MAM5 accumulation mode could be included as a dotted line in the coarse mode plot. Then the two models can be more easily compared in terms of sulfate burden carried in the large particle mode.
Fig. 5 Same comments as Fig. 4 but in addition the ordinates should all be the same scale (0-4 Tg S), so the relative contributions from the different latitude zones can be seen directly. Without that the reader immediately wonders about the Southern Hemisphere signal which seems to persist at high levels. The label on the ordinate is wrong. It should be Sulfur burden (Tg S). Label the rows in some other way or describe them in the figure caption. Again combine accumulation and coarse mode into one plot then there will only be three rows. The latitudes of the eruptions should be listed in the figure caption.
331-332 What is the reason for this oscillation, when the sulfur burden is declining everywhere else? A somewhat similar oscillation, but offset, is observed in the Northern Hemisphere. Why does the sulfur burden persist to 1994 in the Southern Hemisphere while it decays everywhere else?
341-343 This point would be a lot clearer for the reader if the ordinate scale on all plots was the same. But this statement, “Starting from 1993, the stratospheric burden south of 30 S in MAM5 begins to make up at least half of the total between 80 S and 80 N (about 0.8 Tg S out of the total of 1.7 Tg S)”, doesn’t make sense. Between 80 S and 80 N includes 30 S – 30 N, so the total sulfur burden in early 1993 for MAM5FC is ~4.1 Tg S.
349-350 Suggest rephrasing to. “The tendencies are the integrals over three-dimensions of: all longitudes, …”
Fig. 6 is problematic. There are too many rows making the figure so small that most readers have to blow it up to see it. This could be fixed by breaking it into two figures: the first containing the first 4 rows, the next containing the last 3. Another suggestion is to combine the right and left panels into a single plot with separate ordinates on the right and left. Since the left shows a rate and right shows an accumulation the lines will generally not overlap but rather complement each other. Again the ordinate labels are incorrect. They should be tendency (kg/s) for the left plots and their integrals (or cumulative) (Tg S) for the right. Include the name of the row as a label in each plot. The labels RNMxx are too tied to the inner workings of the model, “renaming”. But physically what is happening? The particles are growing to the next largest size distribution mode. If labels were added to the plots to identify them RNMaa could become Aitken->Accumulation mode and RNMasc Accumulation->Coarse mode.
Fig 6 e, f) shows the growth from Aitken to accumulation mode presumably by several processes including growth by condensation and coagulation, correct? If that is the case then why are the ordinate scales on COAG so much larger than for RNMaa? Both are showing mass loss rate and total mass lost. It seems it should be the other way around with COAG less than RNMaa. Why is this one process coagulation singled out for a special plot?
Fig 6 i – n) Condensation? Why are these processes now called condensation? Condensing from what? Weren’t these earlier called renaming, which is also not that helpful or descriptive. Isn’t this particle growth from one mode to another? Ordinate problems again. What is on the left and right ordinates? Is it again rate (kg/s) and cumulative mass (Tg S)? The reader doesn’t know and the figure caption does not help.
351-415 Again the figure discussion consists primarily of describing the figure, pointing out maximum values and dates when they occur. Relatively little is describing what can be learned from the figure which is the importance of the figure. Here and elsewhere, if these dates and amounts are particularly important organize them into a table. Then they could really be compared. It is not clear how listing them in the text helps the reader.
Figs. 4-8, 11 The plotting for these figures could be made much more intuitive, so the reader doesn’t constantly have to refer to the legend to remember which is which. It would be quite easy to do. Use one color for MAM4 and one for MAM5, then one line style (e.g. solid) for FC and another (dashed or dotted) for SC. Then each figure can be immediately understood without referring to the legend but once.
Figs 7 and 8 suffer from the same problem as Fig. 6. There are too many panels and they are too small. What are Figs. 7 and 8 adding to what we learned from Fig. 6? Are all these rows necessary? Which ones are the most informative?
420-430 In fact the discussion of Figs. 7 and 8 acknowledges that not much new is added. “The same patterns as above apply between 30 S and 30 N. Above 30 N and below 30 S the same signal from the Pinatubo is still present, though slightly delayed due to the time that it took for the aerosol to transport poleward. Signals from other eruptions (Spurr and Lascar) are also present” Then a few interesting differences are discussed. Just show the interesting panels and combine Figs 7 and 8 into one figure with the few interesting panels.
503 condensation? Same questions as above. What does this mean?
503-505 What is the reason for quoting these numbers? How will the reader use such information rather than the already stated comparison about the difference rates? Too detailed.
506 Here COAG is separated from RNMaa, but aren’t both processes doing the same thing? There is only the transition from Aitken to accumulation. Is it important how it happens? If so why isn’t that mentioned earlier?
509 deposition? Does this mean sedimentation out of the stratosphere? Generally deposition refers to losing aerosol due to contact with a surface.

Citation: https://doi.org/10.5194/egusphere-2024-2227-RC1
- AC1: 'Reply on RC1', Allen Hu, 26 Dec 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2227/egusphere-2024-2227-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2227-AC1
RC2:
'Comment on egusphere-2024-2227', Anonymous Referee #2, 03 Sep 2024

Overview:
This paper explores simulations of the Pinatubo eruption using different configurations of the Modal Aerosol Module (MAM) in E3SMv2. MAM is used with 4 modes and extended with a 5^th mode to better capture large stratospheric aerosol particles. Additionally, both simplified and full chemistry modes are tested. The paper is well written and structured with clear explanations of the differences for full chemistry due the importance of OH reactions and inclusion of a larger mode to more accurately capture growth and sedimentation processes. I think this paper is a good contribution to the literature on prognostic aerosol modelling in the stratosphere and I would recommend publication with minor clarifications provided it falls within the scope of ACP.
General Comment:
I think the article is well written and a nice advancement to stratospheric aerosol modeling but may be better suited in its current form for a journal such as Geoscientific Model Development. While the differences in aerosol loading due to model configuration are made clear, it is left to the reader to interpret how this improves understanding of atmospheric chemistry or physics. The authors provide in-depth discussion on the relative importance of coagulation, nucleation and renaming/growth in the model, but have little discussion on the physical processes this may help resolve. Similarly, few comparisons are made with measurements for AOD, particle size or radiative flux, with no discussion given to possible sources of disagreement, or what implications these results may have for observations (e.g. the assumptions going into the HIRS results used here). Personally, I think addressing any of these points would help expand the applicability of the paper to a more general audience.
Specific Comments:
Line 50-65: This geoengineering section seems a bit out of place to me. I'm sure this work has implications for geoengineering studies, but no indication of exactly what those may be is provided. I recommend clarifying the link to this work or removing this paragraph. Perhaps the geoengineering discussion and the link to this work would be better placed in the discussion/conclusion?
Line 415: “MAM4 also generally has stronger nucleation and coagulation processes than MAM5.” From Figure 6 it isn’t clear whether MAM4FC has greater coagulation tendencies for physical reasons or if it is just due to the increased NUCL. This is discussed in the conclusion of the paper (Line 503), but I think should be mentioned here. I would suggest rewording to something like: “MAM4 also generally has stronger nucleation than MAM5, and due to these higher concentrations, increased coagulation processes as well” Or, if there are other reasons for increased COAG then this should also be discussed.
Line 490: “large differences in both the temporal variations and the spatial distributions of sulfate concentrations” It is difficult to tell from Figures 7/8, but in Figures 9/10 there doesn’t appear to be much change in spatial distribution. Both MAM4 and MAM5 show large increase in the tropics and later transport to the NH. Some expansion on the spatial differences the authors are referring to would be welcome.
Line 521-522: If the use of full chemistry and MAM5 helped improve agreement with AVHRR, why is the TOA flux more comparable to Brown (2024) and Mills (2017) results than the MAM4 version? Is this related to the geometric standard deviation that was used?

Citation: https://doi.org/10.5194/egusphere-2024-2227-RC2
- AC2: 'Reply on RC2', Allen Hu, 26 Dec 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2227/egusphere-2024-2227-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2227-AC2

Peer review completion

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

AR by Allen Hu on behalf of the Authors (26 Dec 2024) Author's response Author's tracked changes Manuscript

ED: Reconsider after major revisions (19 Feb 2025) by Matthew Toohey

Dear Authors,
I thank you for the replies you have provided and the revised manuscript. However, at this point I do not believe you have adequately addressed the referee comments in order to return the manuscript to the referees. I also would like to point out a few additional points that require attention.
1. Please include line numbers in your revised manuscripts.
2. In terms of comparisons with observations, in your reply to Referee 1, you state “Other sources of observational data are available, such as TOA radiative flux with ERBS and aerosol size comparisons with WOPC and SAGE. However, Brown et al. (2024), another study regarding the simulation of Pinatubo in E3SMv2 (the same model as we used in this work), has mostly already covered these comparisons.” I see that Brown et al. (2024) is mentioned in the introduction section, but only in passing. If the results of that work are important for validating the model used here, it is essential that those results are introduced in sufficient detail in the introduction and methodology sections so the reader is informed of those important results. It is furthermore essential that in the methodology, it is clearly explained which simulations shown here are identical to any used previously in Brown et al (2024), or to clearly point out any differences.
3. Please note that the HIRS sulfate burden observations are not of “stratospheric aerosol” as stated in your reply to Referee 1, the HIRS product is a total column burden. Even a burden anomaly can contain anomalous sulfate mass in both the stratosphere and troposphere.
4. The statement “Neither the addition of the new mode or the use of a more complex chemistry scheme is meant to significantly alter model output of TOA radiative flux, and so we do not think it is necessary to repeat such comparisons in this work” confused me, as you do show TOA flux anomalies, and these results seem to show that changes in the mode structure and chemistry may indeed affect the TOA radiative fluxes. Please clarify in your revised responses to the referee comments.
5. The addition of the comparison to the OPC data is welcome, but it seems to me that you are missing a chance to justify the addition of the course mode to the model by not including the MAM4 accumulation mode on these plots. It is also not clear to me how the results shown support the statement that “MAM5FC did better capture the coarse mode volume (or mass) of sulfate aerosol in 1992 and 1993.”
6. Concerning Referee 1’s comment “Fig. 1 What happens to particles in MAM4 when they exceed Dg_hi (0.48 μm), which is not that large for sulfate particles following Pinatubo? See e.g. Deshler et al., GRL, 1992.” It is important to point out here in the manuscript whether or not the mode structure of MAM4 is inherently ill-equipped to represent stratospheric aerosol from a large eruption like Pinatubo. One needs to be careful because capping Dg_hi to 0.48 μm doesn’t mean that is the largest size (since it’s a distribution), but some words in the manuscript coming the parameters of the mode set up with what is known about Pinatubo aerosol is needed here to address the referee’s comment.
7. Concerning the relationship between sedimentation rates and the mode structure of MAM4 and MAM5, the explanations given seem to oversimplify the issue, since it is not just the standard deviation of the mode that controls how many “very large” particles there are, but also the mode’s mean radius. Therefore, it is not readily apparent that an accumulation mode with large SD will always have more large particles than a course mode with smaller SD since the course mode can have a larger mean radius. Evidence is required here to support the arguments made. Also, the presentation should be careful to remember that most readers will automatically assume that a course mode is larger in size than an accumulation mode. Here it seems that the modes overlap strongly and that is an important things to point out and discuss, in contrast to many modal aerosol schemes where the modes are well separated.
8. In your replies you mention uncertainties in the HIRS burden outside of the tropics, but such discussion would be useful to include in the manuscript.
9. Please adjust plot axes labels according to the suggestions of referee #1.
10. You have added some information about “renaming”, but given its centrality to the results, I suggest even more description is needed, and some discussion to help differentiate it from the physical processes that make aerosols grow and move from one mode to another. Why is renaming needed if the model includes these processes that grow particles? I assume it is important to include when the modes overlap in terms of radii included with the different modes. What controls the rate of renaming? Does it only act to increase size, or does it act in both directions?
11. Figure 7: please confirm, are the quantities here still in terms of mass sulfur?
12. Figure 7: please address referee comments about the size of panels. There is a lot of information on these plots, and what is worth showing should be related to the conclusions one draws from the results. There is some lack of clarity in what exactly are the important conclusions a reader is supposed to draw from these plots, aside from that there are differences between the models.
13. The word “deposition” is still found at the end of page 23 and should be changed as stated in the replies to referee #1.
14. Concerning the “geoengineering” focus of lines 50-65, while I agree that geoengineering is a motivation for studying volcanic eruptions, the issue here is that the references in this paragraph do not actually support the first sentence, which states that “Previous studies have shown that the impacts of volcanic aerosol injections on climate are dependent on the latitude, aerosol type, and season of the injection of volcanic aerosols.” While the geoengineering studies cited are not irrelevant, there are other more relevant studies which specifically look at the impact of latitude, aerosol type and season on aerosol from eruptions like Pinatubo. It is essential that the introduction of this work do a better job of summarizing the existing literature on modeling of Pinatubo and Pinatubo-like eruptions. The review paper of Marshall et al. (2022) and references therein should provide a base upon which to build a more comprehensive literature review.
15. Concerning “large differences in both the temporal variations and the spatial distributions of sulfate concentrations”, please edit the sentence to make it clearer you are referring to the vertical distribution of aerosol.
16. Revised manuscript: end of paragraph 1. Please note, Kremser et al. (2016) states stratospheric aerosol is removed “through sedimentation and in air traversing the extratropical tropopause”, so this citation is misleading. Both are important, it is not only sedimentation that removes aerosol. In fact, other studies (e.g., Hamill et al., 1997) argue that cross tropopause air mixing is much more important than sedimentation for the removal of stratospheric aerosol.
17. Paragraph 2 quote a range for SO2 for Pinatubo of 15-18 Tg SO2, then on page 10 we are told simulations are run with 10 Tg SO2 injection. This is a significant difference and requires justification. Also, the uncertainty in the SO2 injection is a very important issue for discussion of the results and their implications.
18. A major novelty of this work appears to be the OH replenishment mechanism. It would be useful to have more discussion of this—have other modeling studies included this mechanism? How confident are we of the chemistry? If there is confidence that replenishment occurs, what do the results here tell us about the importance of this process?
19. Figure 4: Prior studies (e.g., Clyne et al., 2021) have suggested that OH depletion slows the rate of aerosol growth, leading to smaller particle size and therefore a longer lasting aerosol burden. The results shown here do not seem consistent with this theory. Discussion is warranted.
20. Sect. 3.4, subtracting the climatology from 1989 produces an anomaly: this is not a normalization. Text here and labels on figure 8 must be corrected.
21. Page 21: here it is stated “The e-folding time, calculated as the time between the maximum and the 1/e value, was 13 months in AVHRR and 23 months in GloSSAC.” Looking at Figure 9 b, these times appear to actually be the time between the eruption and the crossing of the 1/e line, not the time from the peak value to the crossing of 1/e. The difference is quite important, see e.g., Toohey et al., (2024).
22. Page 22, you could here compare the rough magnitude of the global mean TOA radiative flux changes with those shown from observations in Fig 11 of Hansen et al. (2005).
23. The conclusion section includes a summary of results shown, and some discussion of possible caveats to the results, but lacks discussion of the implications of the results with reference to prior studies. This is an essential ingredient for papers in ACP (see https://www.atmospheric-chemistry-and-physics.net/policies/guidelines_for_authors.html) and should be improved.
24. Referee #2 points out that the subject matter of the paper is technical in nature. A reminder that research articles in ACP “must include substantial advances and general implications for the scientific understanding of atmospheric chemistry and physics.” Given the results and conclusion of the paper focus on the representation of aerosol in models, and not general scientific understanding, I strongly suggest the manuscript type be changed to technical note. https://www.atmospheric-chemistry-and-physics.net/about/manuscript_types.html

References

Clyne, M., Lamarque, J. F., Mills, M. J., Khodri, M., Ball, W., Bekki, S., Dhomse, S. S., Lebas, N., Mann, G., Marshall, L., Niemeier, U., Poulain, V., Robock, A., Rozanov, E., Schmidt, A., Stenke, A., Sukhodolov, T., Timmreck, C., Toohey, M., Tummon, F., Zanchettin, D., Zhu, Y., and Toon, O. B.: Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble, Atmos. Chem. Phys., 21, 3317–3343, https://doi.org/10.5194/ACP-21-3317-2021, 2021.

Hamill, P., Jensen, E. J., Russell, P. B., and Bauman, J. J.: The Life Cycle of Stratospheric Aerosol Particles., Bull. Am. Meteorol. Soc., 78, https://doi.org/10.1175/1520-0477(1997)078<1395:TLCOSA>2.0.CO;2, 1997.

Hansen, J., Sato, M., Ruedy, R., Nazarenko, L., Lacis, A., Schmidt, G. A., Russell, G., Aleinov, I., Bauer, M., Bauer, S., Bell, N., Cairns, B., Canuto, V., Chandler, M., Cheng, Y., Genio, A. Del, Faluvegi, G., Fleming, E., Friend, A., Hall, T., Jackman, C., Kelley, M., Kiang, N., Koch, D., Lean, J., Lerner, J., Lo, K., Menon, S., Miller, R., Minnis, P., Novakov, T., Oinas, V., Perlwitz, J. J., Perlwitz, J. J., Rind, D., Romanou, A., Shindell, D., Stone, P., Sun, S., Tausnev, N., Thresher, D., Wielicki, B., Wong, T., Yao, M., and Zhang, S.: Efficacy of climate forcings, J. Geophys. Res., 110, D18104, https://doi.org/10.1029/2005JD005776, 2005.

Kremser, S., Thomason, L. W., von Hobe, M., Hermann, M., Deshler, T., Timmreck, C., Toohey, M., Stenke, A., Schwarz, J. P., Weigel, R., Fueglistaler, S., Prata, F. J., Vernier, J.-P., Schlager, H., Barnes, J. E., Antuña-Marrero, J.-C., Fairlie, D., Palm, M., Mahieu, E., Notholt, J., Rex, M., Bingen, C., Vanhellemont, F., Bourassa, A., Plane, J. M. C., Klocke, D., Carn, S. A., Clarisse, L., Trickl, T., Neely, R., James, A. D., Rieger, L., Wilson, J. C., and Meland, B.: Stratospheric aerosol - Observations, processes, and impact on climate, Rev. Geophys., 54, https://doi.org/10.1002/2015RG000511, 2016.

Marshall, L. R., Maters, E. C., Schmidt, A., Timmreck, C., Robock, A., and Toohey, M.: Volcanic effects on climate: recent advances and future avenues, Bull. Volcanol. 2022 845, 84, 1–14, https://doi.org/10.1007/S00445-022-01559-3, 2022.

Toohey, M., Jia, Y., Khanal, S., and Tegtmeier, S.: Stratospheric residence time and the lifetime of volcanic stratospheric aerosols, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-2400, 2024.

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AR by Allen Hu on behalf of the Authors (02 Apr 2025)

EF by Mario Ebel (04 Apr 2025) Manuscript

EF by Mario Ebel (04 Apr 2025) Author's response

EF by Mario Ebel (04 Apr 2025) Author's tracked changes

ED: Referee Nomination & Report Request started (23 Apr 2025) by Matthew Toohey

RR by Anonymous Referee #1 (23 May 2025)

Suggestions for revision or reasons for rejection

This paper compares four simulations of the Dept. of Energy’s Earth system model: two chemistry modes and two modal aerosol configurations. The bulk of the paper discusses plots produced to compare the impact on stratospheric sulfate of these four scenarios. Comparison with observations is limited to one satellite, AVHRR.

The paper is of most interest to other modelers, much less so for those of us concerned with how well a model reproduces observations. Those modelers may find Figs. 6, 7, 8 interesting, as well as the quantities quoted to three significant figures, of interest, but the rest of the community will find these figures difficult to see, understand, and perhaps even misleading. Fig. 5 also falls into this latter category.

Aside from these important details the biggest deficiency in this paper for the community is the lack of comparison with observations! Yes, at the peak of the Pinatubo impact on the stratosphere AVHRR was one of the few satellite sensors not saturated. But the model results here extend through 1993. By 1992 most of the saturated satellite sensors had recovered, and in any case had always provided higher latitude observations. Meanwhile there are a significant number of ground based and in situ measurements of the Pinatubo aerosol. As the authors point out, “Mt. Pinatubo was the first major eruption to be observed with modern instruments.” That is correct, so why don’t the authors take advantage of this rich data set to compare their model runs with a wide set of observations, and thereby describe the strengths and weaknesses of the model runs in hand? Such an exercise would make this paper of much broader interest to the stratospheric aerosol science community.

In its present form I do not recommend this paper for publication. It needs major changes to the figures as outlined below, and most importantly a significantly expanded section on comparison with observations. In its current version there are only 2 figures out of 11 where observations are presented. A suitably modified submission then may be considered for publication.

Here follows a mix of major and minor comments organized by line number.

166-167 What is the difference between R1 and R2? Why is R1 included?

169-171 It seems intermediate steps are left out in this chemistry? Or why don’t the equations balance, e.g. R4, R6. R7?

Fig. 2 What is the explanation of the widespread aerosol in the mid SH for both runs using MAM5? There is some evidence of this in MAM4 but much weaker and confined near the equator.

Fig. 4. Why switch the order in which the chemistry models are listed? In Figs. 2 and 3 the order was SC then FC for both MAMs. Now its FC then SC. This order then persists until Fig. 11 when it is back to SC then FC. For the readers sake it would be helpful to always use the same order of presentation.

Fig. 5 The vertical line for the Lascar eruption (in yellow?) is hardly visible. This should be fixed here and everywhere it is used.

Fig. 5 is inherently misleading because of the scale changes from NH (0-2) to equator (0-4) to SH (0-0.1) with no warning to the reader either in the text or figure caption. To really put these regions into the proper perspective the scales should stay the same across any row of the figure. Yes this wastes space, but better that, than wasting the reader’s time as they only slowly begin to recognize this deficiency. Thereby struggling to understand the text describing the figure. Without this change it is very tedious to try and check the authors description of the figure on page 14, and this reader has given up trying to do so.

345 “In order” The authors use this throw away phrase too much. It is almost never necessary.

Fig. 6 has numerous problems: 1) It has too many rows, making it very difficult to see the whole figure on a single page once it is blown up far enough to read the axes numbers and the legends. 2) The y-axis is mis-labeled with the title of the figure. It should be labeled with the quantity and units that are plotted. 3) The scale is changing all over the place, sometimes by a lot sometimes by a little, again making it tiresome to compare the processes, particularly when you can’t read the scale if the figure is reduced in size to fit all on one page. 4) There is some kind of mistake in the caption, “COAG represents Aitken mode mass loss due to coagulation into the accumulation mode, RNMaa represents Aitken mode mass loss due to renaming into the accumulation mode.” So COAG and RNMaa represent the same process? And indeed the figures look quite comparable. 5) Splitting the figure by moving the bottom three rows to another figure would make sense. 6) The line representing Lascar is invisible.

The limitations in reading Fig. 6 makes checking the authors’ description of the figure difficult. But it is surprising to see them quoting mass rates and percentages to three significant figures. Quite exact for a model that can’t be compared to anything at this point. Isn’t the important thing a general description of how the SC and FC schemes and the MAM4/5 models differ rather than these exact numbers?

364-365 How important are these differences? Fig. 6 (b) is misleading. The integrated tendency shown and quoted in the text does not persist because of coagulation. So the real integrated tendency in the NUCL mode has to be coupled with the loss to coagulation before one can discuss the long term amount in NUCL. Fig. 6 (b) suggests this amount just persists the same after Oct. 1991. In fact this is the conclusion for all the right hand figures. As soon as the gain or loss process is over, which all occurs by the end of 1991, nothing changes unless another volcano erupts. Yet surely by 1993 aerosol was being lost to the atmosphere through the usual sedimentation processes if nothing else. It is quite difficult to understand the point of Fig. 6 as currently presented. This seems to be something only a modeler may find useful.

Page 17 is further detailed, as above, descriptions of the figures with rates and dates, but it is not clear who will use such exact dates and amounts. Are they to be compared to something, perhaps something physical? Aren’t the more important points to look at the figures overall from which one can conclude that, whether it is mass gain or loss, FC exceeds SC, and that MAM4 exceeds MAM5. The reasons for this have probably already been explained but could be reiterated here. This is not the case in 6 (l) and (n), and this should lead to an explanation of this difference. Such a broader description would probably be of more interest to the general reader, e.g. lines 410-414.

Figs. 7 and 8 have the same problems as Fig. 6 and the scale changes even worse, leaving only the dedicated reader with the energy to find a meaning in the figure. At face value at the scale most readers will see this figure it appears that the processes are quite similar from NH to EQ to SH. The authors need to make some decisions about which of these figures are most critical to compare the two models and two chemistry schemes, presumably leading to a conclusion about which is better, and hopefully back that up with comparisons to measurements. One cannot just publish all the figures a model produces.

Fig. 9 Why are the model AODs limited to the AVHRR footprint. Presumably the model covers the entire latitude time space. Would including that detract from the comparison?

Fig. 10 It seems odd that in each polar summer there is no impact of the Pinatubo aerosol even though, in the previous polar winter / spring there is evidence of Pinatubo all the way to the pole. Why is that? It seems this is worth a comment.

Fig. 11 It would be worth pointing out again here why the SC models estimate more cooling in both MAM4/5 than the FC models.

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RR by Anonymous Referee #2 (11 Jun 2025)

ED: Publish subject to minor revisions (review by editor) (08 Jul 2025) by Matthew Toohey

Dear authors,

Thank you for your revisions to the paper and replies to the referees’ comments. I believe you have addressed most of the concerns raised, and the manuscript has measurably improved. However, there are a few issues which should be further addressed before acceptance for publication.

It appears that Referee 1’s second round of comments refer to the originally submitted manuscript and not the revised version. I have assessed whether your revision addresses all comments from both rounds, and include below a couple of mostly minor comments raised which are still relevant. I have translated line and figure numbers to the revised manuscript version, specifically to the version with tracked changes.

Following those comments from Referee 1 are a few editorial comments from me. Again, all line numbers are from the tracked-changes version of the revised manuscript. I hope that you will be able to address these comments in a revised version that I will review before possible acceptance for publication.

Referee 1 comments:
L251ff: What is the difference between R1 and R2? Why is R1 included?
L254ff: It seems intermediate steps are left out in this chemistry? Or why don’t the equations balance, e.g. R4, R6. R7?
Fig 5 caption: please include a warning of different scales on vertical axes
L481: “In order” The authors use this throw away phrase too much. It is almost never necessary.
Figs 7,8, and 9, please include warnings of different scales on vertical axes
Fig 13: It would be worth pointing out again here why the SC models estimate more cooling in both MAM4/5 than the FC models.

Editor comments:
L208: this text and the bullet list that follows refers to “processes”, but the list includes both physical processes and the technical/computational process of renaming. This writing style can be confusing to readers who may not be familiar with the material. Please reorganize slightly (i.e., remove renaming from the list of physical processes) and be more explicit about the difference between the models’ representation of physical processes versus technical steps.
L232: symbols used in the figure should be defined in the figure caption.
L282: Is this justification for the smaller SO2 emission for Pinatubo compared to observations something that is established, or more speculated? There is also evidence that the stratospheric injection by Pinatubo is actually much smaller than the total observed emission, see Ukhov et al. (2023).
L330: please point out here and in figure caption the figure displays tropical sulfate concentrations
L366: “A smaller geometric standard deviation for stratospheric coarse mode in MAM5-PSA means that there are fewer super-coarse aerosols within the population. “ Although counterintuitive (adding a larger mode leads to smaller size distribution), this mechanism does seem like a possibility. But, there is no evidence shown to support this claim. Also, later (l393) it is pointed out that in MAM5, certain growth processes are not operational in the stratospheric course mode. At line 399, both processes are referenced as reasons for the sulfate having a longer lifespan in MAM5-PSA than MAM4. Again, both reasons seem possible, but is their evidence to support the idea that they are important?
L376: Yes, Baran and Foote have subtracted a baseline value away from the sulfate mass loadings they compute for Pinatubo. This does not mean their values are stratospheric burdens, and they do not use that language. This is because the tropospheric burden after the Pinatubo eruption can and likely is elevated compared to its background state.
Fig 10: Please update panel titles in figure to remove word “normalized”
Fig 11 and related text: it is important to be clear that AVHRR is a total AOD anomaly, while GloSSAC reports a stratospheric AOD. Similar to the HIRS data, AVHRR’s AOD likely includes some tropospheric anomaly component in the first months after the eruption.
L690: What results are you citing here, observations, models, etc? If models, what kind of models are they? The range of model results in that study appears to be 8-23 months, but that is for the decay of sulfate burden, not AOD. The two can be different as the size distribution changes with time.
L699ff: please be clear through this section whether you are comparing SW fluxes or SW+LW total fluxes. The discussion starts with reference to solar (i.e., SW) fluxes, but the comparison to results from Hansen et al. (2005) refers to their total (SW+LW) flux anomaly values, with a peak of about -3.0 W/m^2.

References:
Hansen, J., Sato, M., Ruedy, R., Nazarenko, L., Lacis, A., Schmidt, G. A., Russell, G., Aleinov, I., Bauer, M., Bauer, S., Bell, N., Cairns, B., Canuto, V., Chandler, M., Cheng, Y., Genio, A. Del, Faluvegi, G., Fleming, E., Friend, A., Hall, T., Jackman, C., Kelley, M., Kiang, N., Koch, D., Lean, J., Lerner, J., Lo, K., Menon, S., Miller, R., Minnis, P., Novakov, T., Oinas, V., Perlwitz, J. J., Perlwitz, J. J., Rind, D., Romanou, A., Shindell, D., Stone, P., Sun, S., Tausnev, N., Thresher, D., Wielicki, B., Wong, T., Yao, M., and Zhang, S.: Efficacy of climate forcings, J. Geophys. Res., 110, D18104, https://doi.org/10.1029/2005JD005776, 2005.

Ukhov, A., Stenchikov, G., Osipov, S., Krotkov, N., Gorkavyi, N., Li, C., Dubovik, O., and Lopatin, A.: Inverse Modeling of the Initial Stage of the 1991 Pinatubo Volcanic Cloud Accounting for Radiative Feedback of Volcanic Ash, J. Geophys. Res. Atmos., 128, e2022JD038446, https://doi.org/10.1029/2022JD038446, 2023.

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AR by Allen Hu on behalf of the Authors (18 Jul 2025) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (10 Aug 2025) by Matthew Toohey

AR by Allen Hu on behalf of the Authors (11 Aug 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (12 Aug 2025) by Matthew Toohey

AR by Allen Hu on behalf of the Authors (13 Aug 2025) Author's response Manuscript

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07 Oct 2025

Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

Allen Hu, Ziming Ke, Xiaohong Liu, Benjamin Wagman, Hunter Brown, Zheng Lu, Mingxuan Wu, Hailong Wang, Qi Tang, Diana Bull, Kara Peterson, and Shaocheng Xie

Atmos. Chem. Phys., 25, 12137–12157, https://doi.org/10.5194/acp-25-12137-2025,https://doi.org/10.5194/acp-25-12137-2025, 2025

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Allen Hu, Xiaohong Liu, Ziming Ke, Benjamin Wagman, Hunter Brown, Zheng Lu, Diana Bull, and Kara Peterson

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Allen Hu, Xiaohong Liu, Ziming Ke, Benjamin Wagman, Hunter Brown, Zheng Lu, Diana Bull, and Kara Peterson

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Volcanic eruptions have a major effect on temperature throughout the atmosphere and can be studied as a proxy for geo-engineering. The aerosol module in the Energy Exascale Earth System Model (E3SM) was originally intended for simulation of tropospheric aerosols and has problems handling stratospheric sulfate aerosols due to volcanic eruptions. We have made alterations to the aerosol module to overcome these problems, with simulation results more closely reproducing observations.


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Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

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