the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Aug 2023
In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption
Abstract. Stratospheric aerosols play important roles in Earth’s radiative budget and in heterogeneous chemistry. Volcanic eruptions modulate the stratospheric aerosol layer by injecting particles and particle precursors like sulfur dioxide (SO2) into the stratosphere. Beginning on April 9th, 2021, La Soufrière erupted injecting SO2 into the tropical upper troposphere and lower stratosphere, yielding a peak SO2 loading of 0.3–0.4 Tg. The resulting volcanic aerosol plumes dispersed predominately over the northern hemisphere (NH), as indicated by the CALIOP/CALIPSO satellite observations and model simulations. From June to August 2021 and May to July 2022, the NASA ER-2 high-altitude aircraft extensively sampled the stratospheric aerosol layer over the continental United States during the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) mission. These in situ aerosol measurements provide detailed insights into the number concentration, size distribution, and spatiotemporal variations of particles within volcanic plumes. Notably, aerosol surface area density and number density in 2021 were enhanced by a factor of 2–4 between 380–500 K potential temperature compared to the 2022 DCOTSS observations, which were minimally influenced by volcanic activity. Within the volcanic plume, the observed aerosol number density exhibited significant meridional and zonal variations while the mode and shape of aerosol size distributions did not vary. The La Soufrière eruption led to an increase in the number concentration of small particles (<400 nm), resulting in a smaller aerosol effective diameter during the summer of 2021 compared to the baseline conditions in the summer of 2022, as observed in regular ER-2 profiles over Salina, Kansas. A similar reduction in aerosol effective diameter was not observed in ER-2 profiles over Palmdale, California, possibly due to the already smaller values in that region during the limited sampling period in 2022. The La Soufrière eruption was modeled with the SOCOL-AERv2 aerosol-chemistry-climate model. The modeled aerosol enhancement aligned well with DCOTSS observations, although the direct comparison was complicated by issues related to the model’s background aerosol burden. This study indicates that the La Soufrière eruption contributed at most 0.6 % to Arctic and Antarctic ozone column depletion in both 2021 and 2022, which is well within the range of natural variability. The modeled top-of-atmosphere one-year global average radiative forcing was -0.08 W/m2 clear-sky and -0.04 W/m2 all-sky. The radiative effects were concentrated in the tropics and NH midlatitudes and diminished to near-baseline levels after one year.
-
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
(5164 KB)
-
Supplement
(4323 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5164 KB) - Metadata XML
-
Supplement
(4323 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1891', Daniele Visioni, 05 Sep 2023
Review of “In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption” by Li et al.
This paper is a really great work that looks at how the eruption of La Soufrière affected the stratospheric aerosol layer through a mix of observations and modeling, which is always a great approach! The paper is very well done, comprehensive and well written while staying terse, so I don’t have much to add, and I fully endorse publication in ACP. Just a few comments below.
L 43: I would add a “Additionally, we also modeled the eruption with…” to make it sound more like the two things are connected and follow from one another!
L 300: I think this point could be expressed better: it’s sort of misleading as of now. Quaglia et al. (2023) was about Pinatubo, which is very large, and we have numerous measurements demonstrating the increase in size distribution. This paper and Wrana et al. (2023) both point out that smaller eruptions could decrease size actually, which is interesting! But also a different ballpark compared to Pinatubo… So keep the Quaglia et al. (2023) reference, but be clearer in specifying that those are two entirely different observations and not in conflict with each other.
L 329: specify this is ERF and not IRF, as (even though it’s not exactly specified) SOCOL is run here with fixed SSTs.
L 372: a bit uncomfortable with the speculation about the fires here. Not the point of the paper, you didn’t check for it, so sounds a bit unsubstantiated.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC1 -
RC2: 'Comment on egusphere-2023-1891', J.M. Haywood, 18 Sep 2023
Review: In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption
Li et al, 2023.
The paper addresses scientific questions that are well within the scope of ACP. The aerosol data collected in the DCOTSS stratospheric aerosol flights with the ER2 combined with balloon borne ascents in unique. The comparison between the SOCOL-AERv2 model and the observations is interesting.
The most prominent conclusion is that the aerosol size distribution in the lower stratosphere consists of more numerous smaller (presumably) sulfuric acid particles, with larger particles overlying them. Sound conclusions are drawn. The presentation in terms of clarity is good, with good figures and captions but a few clarifications and caveats are required. Some of the clarifications are important, and the authors should address them in a revision of the manuscript.
General comments:
- Without a description of how ozone is impacted by aerosols within the SOCOL model, one cannot assess the model’s treatment of any ozone depletion – at least a basic description of e.g. heterogeneous chemistry, treatment of PSCs should be given in section 2.4.
- Any impacts on ozone from the eruption are likely to occur from a) heterogeneous chemistry, b) aerosol-induced stratospheric heating which can change the poleward transport of ozone. Given that you are using nudged simulations, the dynamically induced response is likely to be suppressed. This caveat should be included.
- In the modelling, some mention of the approximate number of model layers in the stratosphere should be mentioned together with the model top. From looking at the supplement (e.g. S5) it appears that the resolution in the stratosphere is quite limited with 5-6 layers being represented.
- Some acknowledgment of the limitations of model resolution (spatial and temporal) should be made. For example, the study of the combined eruption of Raikoke using a global model with a resolution of around 10km and 59model levels (e.g. de Leuuw et al., 2021, https://doi.org/10.5194/acp-21-10851-2021; Osborne et al., 2022; https://doi.org/10.5194/acp-22-2975-2022) does not have to make an injection into such a large area. The detailed evolution and ‘filamentary’ structure that is referred to in the text in this study is difficult to model with such a crude injection strategy and such a coarse resolution and an appropriate caveat should be made.
- There needs to be an acknowledgement that comparison between Fig 2 and Fig 4 is not a like-like comparison as Fig 2 includes the background aerosol while Figure 4 does not. This is mentioned later in the paper, but needs to be acknowledged sooner.
- In section 3.2 the statement, “As discussed in Section 3.1, the modelled plume agrees well with CALIOP/CALIPSO ……” is rather pushing it. There is one sentence in section 3.1, which does not constitute a discussion. There is no quantitative analysis that supports the ‘good agreement’ – its just done by eyeballing the two plots. Ideally the background could be removed from multi-year CALIPSO data. Then you’d be much closer to a like-like comparison and could provide quantitative numbers to back up your text.
- Do the authors think that the rapid change in the observed size distribution with diameter by the POPS (which is a nice bit of lightweight kit) at 300nm diameter is real? I know that there have been some comparisons between the POPS and other instrumentation such as the SMPS which operate quite differently in terms of physical measurements, and there seem to be some differences in the slope of the size distribution that is derived between the two instruments (e.g. Liu et al., 2021; https://doi.org/10.5194/amt-14-6101-2021). There has been some discussion with Handix as to whether the cross over in gain stages of the pre-amplifier/amplifier could have some influence. Whatever, the case, it does seem a notable feature throughout the results that are presented here.
Specific comments:
- L121 – size distribution – is this radius or diameter? Actually you can find that this is diameter (L198), but diameter should be stated here.
- The size distributions and effective diameters in Figure S6 & S7 should be the same as those in Figure 6 and 7 to aid comparison.
- The white lines and numbers in Fig 2 should be boldened.
-
RC3: 'Comment on egusphere-2023-1891', Anonymous Referee #3, 26 Sep 2023
120-150 It might be useful to include flow rates of the aerosol instruments and estimates of their minimum concentration sensitivity.
289 Are there really substantial zonal variations in number density. The profiles in Fig. 7a have the same shape and for 86-100 W the same values, with the profiles 105-110 W being only slightly higher.
293-294 This is only true above the tropopause region.
Fig. S1. With a few assumptions about index of refraction the POPC aerosol size distribution measurements could be converted to a backscatter for direct comparison with COBALD. That would be a nice addition to more realistically compare these two independent measurements, than a simple profile of backscatter and number concentration at one channel.
310-312 It would be good to include on the figures the date span of the measurements, e.g. for Palmdale June 29 – July 11. This is hardly June-July, as presently noted on the figure. The same could be done for the Salina site.
314-328 Given the clearly demonstrated impact of La Soufriere on northern hemisphere aerosol and minimal impact in the southern hemisphere, Figs. 2 and 4, does it make sense to discuss Antarctic ozone loss due to La Soufriere? What is the mechanism by which this would occur? What is the argument of Yook et al. [2022] to show an impact on southern hemisphere ozone? This all seems a big stretch.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC3 -
RC4: 'Comment on egusphere-2023-1891', Anonymous Referee #3, 26 Sep 2023
I forgot in my review to complement the authors on a clear well written paper.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC4 -
AC1: 'Comment on egusphere-2023-1891', Yaowei Li, 25 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1891/egusphere-2023-1891-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1891', Daniele Visioni, 05 Sep 2023
Review of “In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption” by Li et al.
This paper is a really great work that looks at how the eruption of La Soufrière affected the stratospheric aerosol layer through a mix of observations and modeling, which is always a great approach! The paper is very well done, comprehensive and well written while staying terse, so I don’t have much to add, and I fully endorse publication in ACP. Just a few comments below.
L 43: I would add a “Additionally, we also modeled the eruption with…” to make it sound more like the two things are connected and follow from one another!
L 300: I think this point could be expressed better: it’s sort of misleading as of now. Quaglia et al. (2023) was about Pinatubo, which is very large, and we have numerous measurements demonstrating the increase in size distribution. This paper and Wrana et al. (2023) both point out that smaller eruptions could decrease size actually, which is interesting! But also a different ballpark compared to Pinatubo… So keep the Quaglia et al. (2023) reference, but be clearer in specifying that those are two entirely different observations and not in conflict with each other.
L 329: specify this is ERF and not IRF, as (even though it’s not exactly specified) SOCOL is run here with fixed SSTs.
L 372: a bit uncomfortable with the speculation about the fires here. Not the point of the paper, you didn’t check for it, so sounds a bit unsubstantiated.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC1 -
RC2: 'Comment on egusphere-2023-1891', J.M. Haywood, 18 Sep 2023
Review: In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption
Li et al, 2023.
The paper addresses scientific questions that are well within the scope of ACP. The aerosol data collected in the DCOTSS stratospheric aerosol flights with the ER2 combined with balloon borne ascents in unique. The comparison between the SOCOL-AERv2 model and the observations is interesting.
The most prominent conclusion is that the aerosol size distribution in the lower stratosphere consists of more numerous smaller (presumably) sulfuric acid particles, with larger particles overlying them. Sound conclusions are drawn. The presentation in terms of clarity is good, with good figures and captions but a few clarifications and caveats are required. Some of the clarifications are important, and the authors should address them in a revision of the manuscript.
General comments:
- Without a description of how ozone is impacted by aerosols within the SOCOL model, one cannot assess the model’s treatment of any ozone depletion – at least a basic description of e.g. heterogeneous chemistry, treatment of PSCs should be given in section 2.4.
- Any impacts on ozone from the eruption are likely to occur from a) heterogeneous chemistry, b) aerosol-induced stratospheric heating which can change the poleward transport of ozone. Given that you are using nudged simulations, the dynamically induced response is likely to be suppressed. This caveat should be included.
- In the modelling, some mention of the approximate number of model layers in the stratosphere should be mentioned together with the model top. From looking at the supplement (e.g. S5) it appears that the resolution in the stratosphere is quite limited with 5-6 layers being represented.
- Some acknowledgment of the limitations of model resolution (spatial and temporal) should be made. For example, the study of the combined eruption of Raikoke using a global model with a resolution of around 10km and 59model levels (e.g. de Leuuw et al., 2021, https://doi.org/10.5194/acp-21-10851-2021; Osborne et al., 2022; https://doi.org/10.5194/acp-22-2975-2022) does not have to make an injection into such a large area. The detailed evolution and ‘filamentary’ structure that is referred to in the text in this study is difficult to model with such a crude injection strategy and such a coarse resolution and an appropriate caveat should be made.
- There needs to be an acknowledgement that comparison between Fig 2 and Fig 4 is not a like-like comparison as Fig 2 includes the background aerosol while Figure 4 does not. This is mentioned later in the paper, but needs to be acknowledged sooner.
- In section 3.2 the statement, “As discussed in Section 3.1, the modelled plume agrees well with CALIOP/CALIPSO ……” is rather pushing it. There is one sentence in section 3.1, which does not constitute a discussion. There is no quantitative analysis that supports the ‘good agreement’ – its just done by eyeballing the two plots. Ideally the background could be removed from multi-year CALIPSO data. Then you’d be much closer to a like-like comparison and could provide quantitative numbers to back up your text.
- Do the authors think that the rapid change in the observed size distribution with diameter by the POPS (which is a nice bit of lightweight kit) at 300nm diameter is real? I know that there have been some comparisons between the POPS and other instrumentation such as the SMPS which operate quite differently in terms of physical measurements, and there seem to be some differences in the slope of the size distribution that is derived between the two instruments (e.g. Liu et al., 2021; https://doi.org/10.5194/amt-14-6101-2021). There has been some discussion with Handix as to whether the cross over in gain stages of the pre-amplifier/amplifier could have some influence. Whatever, the case, it does seem a notable feature throughout the results that are presented here.
Specific comments:
- L121 – size distribution – is this radius or diameter? Actually you can find that this is diameter (L198), but diameter should be stated here.
- The size distributions and effective diameters in Figure S6 & S7 should be the same as those in Figure 6 and 7 to aid comparison.
- The white lines and numbers in Fig 2 should be boldened.
-
RC3: 'Comment on egusphere-2023-1891', Anonymous Referee #3, 26 Sep 2023
120-150 It might be useful to include flow rates of the aerosol instruments and estimates of their minimum concentration sensitivity.
289 Are there really substantial zonal variations in number density. The profiles in Fig. 7a have the same shape and for 86-100 W the same values, with the profiles 105-110 W being only slightly higher.
293-294 This is only true above the tropopause region.
Fig. S1. With a few assumptions about index of refraction the POPC aerosol size distribution measurements could be converted to a backscatter for direct comparison with COBALD. That would be a nice addition to more realistically compare these two independent measurements, than a simple profile of backscatter and number concentration at one channel.
310-312 It would be good to include on the figures the date span of the measurements, e.g. for Palmdale June 29 – July 11. This is hardly June-July, as presently noted on the figure. The same could be done for the Salina site.
314-328 Given the clearly demonstrated impact of La Soufriere on northern hemisphere aerosol and minimal impact in the southern hemisphere, Figs. 2 and 4, does it make sense to discuss Antarctic ozone loss due to La Soufriere? What is the mechanism by which this would occur? What is the argument of Yook et al. [2022] to show an impact on southern hemisphere ozone? This all seems a big stretch.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC3 -
RC4: 'Comment on egusphere-2023-1891', Anonymous Referee #3, 26 Sep 2023
I forgot in my review to complement the authors on a clear well written paper.
Citation: https://doi.org/10.5194/egusphere-2023-1891-RC4 -
AC1: 'Comment on egusphere-2023-1891', Yaowei Li, 25 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1891/egusphere-2023-1891-AC1-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 460 | 206 | 21 | 687 | 38 | 9 | 11 |
- HTML: 460
- PDF: 206
- XML: 21
- Total: 687
- Supplement: 38
- BibTeX: 9
- EndNote: 11
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Corey Pedersen
John Dykema
Jean-Paul Vernier
Sandro Vattioni
Amit Kumar Pandit
Andrea Stenke
Elizabeth Asher
Troy Thornberry
Michael A. Todt
Thao Paul Bui
Jonathan Dean-Day
Frank N. Keutsch
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5164 KB) - Metadata XML
-
Supplement
(4323 KB) - BibTeX
- EndNote
- Final revised paper