the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Feb 2024
Aerosols in the central Arctic cryosphere: Satellite and model integrated insights during Arctic spring and summer
Abstract. The central Arctic cryosphere is influenced by the Arctic Amplification (AA) and is warming faster than the lower latitudes. AA affects the formation, loss and transport of aerosols. Efforts to assess the underlying processes determining aerosol variability are currently limited due to the lack of ground-based and space-borne aerosol observations with high spatial coverage in this region. This study addresses the observational gap by making use of total aerosol optical depth (AOD) data sets retrieved by the AEROSNOW algorithm over the vast cryospheric region of the central Arctic during the Arctic spring and summer. GEOS-Chem (GC) simulations combined with AEROSNOW retrieved data are used to investigate the processes controlling aerosol loading and distribution at different temporal and spatial scales. For the first time, an integrated study of AOD over the Arctic cryosphere during sunlight conditions was possible with the AEROSNOW retrieval and GC simulations. The results show that the spatial patterns observed by AEROSNOW differ from those simulated by GC. During spring, which is characterised by long-range transport of anthropogenic aerosols in the Arctic, the GC underestimates the AOD in the vicinity of Alaska. At the same time, it overestimates the AOD along the Bering Strait, Northern Europe, and the Siberian central Arctic sea ice regions, with differences of -12.3 % and 21.7 %, respectively. In contrast, the GC consistently underestimates AOD compared to AEROSNOW in summer, when transport from lower latitudes is insignificant and local natural processes are the dominant source of aerosol, especially north of 70° N. This underestimation is particularly pronounced over the central Arctic sea ice region, where it is -10.6 %. Conversely, the GC tends to overestimate AOD along the Siberian and Greenland marginal sea ice zones by 19.5 %, but underestimates AOD along the Canadian Archipelago by -9.3 %. The differences in summer AOD between AEROSNOW data products and GC simulated AOD highlight the need to integrate improved knowledge of the summer aerosol process into existing models to constrain its effects on cloud condensation nuclei, ice nucleating particles, and any effects on the radiation budget over central Arctic sea ice during the developing AA period.
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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.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-440', Anonymous Referee #1, 28 Feb 2024
The review of the manuscript of Swain et al., 2024 on the topic “Aerosols in the central Arctic cryosphere: Satellite and model integrated insights during Arctic spring and summer”.
This manuscript presents the integrated view of aerosol load over central Arctic cryospheric region. I would like to appreciate the authors for doing a difficult task of combing satellite and model simulations to study aerosol over central Arctic region, as the retrieval of AOD over highly reflective snow and ice region is very challenging.
This manuscript has been gone through a previous review (https://doi.org/10.5194/egusphere-2023- 730) and all the critical aspects raised by the previous reviewers were addressed very well in this revised version.
Further, this manuscript is bringing valuable information of spring and summer AOD distributions and the anthropogenic and natural aerosol load behind it and highlighted the need to add summer time aerosol processes in the models for the central Arctic to properly quantify Arctic warming.
In addition, this manuscript is conforming for the first time the unconfirmed prospective highlighted by a recent valuable paper (Schmale et al., 2021), that models might be missing the summer aerosol processes due to sea ice reduction and open ocean emissions by using AEROSNOW space-borne data.
This version of the manuscript has been written very well and falls within the aim and scope of the ACP journal. I would like to recommend it for publication with minor corrections. The minor corrections are listed below:
Abstract:
Line 8: Although this study is conducted for the first time over central Arctic cryospheric region, is it necessary to mention in the abstract?
Introduction:
The overall introduction has been written very well and the story is very easy to follow.
Results:
At Figure 2, please use different colors for clear read. i.e, AEROSNOW ( may be red) and AERONET (black).
Conclusion:
At line 362-365, I would recommend to remove the paragraph
“The promising results derived from the AEROSNOW approach hold significant value for both a) constraining the accuracy of AOD simulations in chemical transport models (CTMs) and b) determining the changing AOD in the Arctic sea ice regions currently experiencing AA.”.
As you are mentioning that the AEROSNOW data is valuable to access models over central Arctic at line 415-420.
In summary, I enjoyed reading the manuscript.
Reference: Schmale, J., Zieger, P., and Ekman, A. M.: Aerosols in current and future Arctic climate, Nature Climate Change, 11, 95–105, https://doi.org/10.1038/s41558-020-00969-5, 2021.
Citation: https://doi.org/10.5194/egusphere-2024-440-RC1 -
AC1: 'Reply on RC1', Basudev Swain, 04 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-440/egusphere-2024-440-AC1-supplement.pdf
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AC1: 'Reply on RC1', Basudev Swain, 04 Apr 2024
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RC2: 'Comment on egusphere-2024-440', Anonymous Referee #2, 01 Mar 2024
Some minor corrections:
- Please clarify in the abstract “During spring, which is characterized by long-range transport of anthropogenic aerosols in the Arctic, the GC underestimates the AOD in the vicinity of Alaska”. In comparison to what?
- Introduction is well written and has a good flow to it. However, there is one incomplete line
Line 70 when you talk about “To address the recently posted…and compare it to.” Compare it to what? Please complete
- It would be easier if you marked central arctic sea-ice region that you are interested in along with the AERONET sites in figure 1
- Do the optical properties used in the GOES-Chem model vary with time? Studies have shown that temporal evolution of the aerosol size distribution in models closely resemble to observations.
- Figure 2: Put Hornsund in the bottom and PEARL, OPAL and Thule on top (this gives the reader a consistency because these three sites are from CA side). Are the correlation numbers mentioned in each figure for spring and summer for all the years put together? PEARL and OPAL are close together, then why do they have different correlations of GC with AERONET and AEROSNOW? What factors do you think affect the GC simulations? Its important you mention somewhere how you derived the natural AOD (marked with white in Figure 2).
- Figure 3: Please use the same symbols for AERONET and AEROSNOW as in Figure 2 for consistency.
- Line 210: “Additionally, and on average, all three datasets show periods of haze episodes during the spring season”. Is it three or four? Its confusing because there are 4 sites mentioned in the paper
- Line 215; “We attribute these differences can largely be attributed to the fact that GOES-Chem simulates AOD independent of meteorological conditions, cloud cover and the spatial…” . Please rewrite the first part of the sentence. Also in Section 2.2, it was mentioned that GC uses MERRA 2 reanalysis for meteorological fields but Line 215 contradicts this. Please clarify.
- Line 225: “Further, during summer, the discrepancies in GOES-Chem AOD can be attributed to various factors, including limitations related to NPF and inherent effects of a relatively coarse horizontal model resolution”. In Line 215, it is mentioned that GC is independent of cloud cover. Arctic receives precipitation in summer and it is also possible, in addition to NPF and low res, that the GC doesn’t represent clouds well and because of which there are discrepancies mainly in summer!!
- Line 234: In figure 4, we present the seasonal AOD for spring and summer, averaged over the entire study period. For each station, three circles are displayed” I think there are 4 circles displayed, so please correct this.
- Line 270: there is a typo. Make it 2003 instead of 203.
- Line 282: “GOES-Chem simulations showed higher and lower AOD during spring of the year 2009 and 2007 respectively”. Are there any reasons why only these particular years were chosen? 2004, 2006, 2008 also showed higher GC-derived AOD.
- It is very interesting that this study talks about the lack of NPF in the models. During summer, the GC underestimates in some places and overestimates in others wrt AEROSNOW. And the authors say this could be due to lack of proper representation of NPF in model, which in my opinion, could be true but also I feel NPF is a common occurring in the Arctic summer. So if lack of NPF was the main issue, then it would have underestimated all throughout and not shown such discrepancies spatially! How can you explain why it overestimates AOD in some places? Lack of NPF cannot be the reason! When you measure AOD, do you also take into account cloud residuals?
- This isn’t related to this study but I think we can see interesting results when AEROSNOW algorithm will be applied to study the aerosols during Arctic winters.
Citation: https://doi.org/10.5194/egusphere-2024-440-RC2 -
AC2: 'Reply on RC2', Basudev Swain, 04 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-440/egusphere-2024-440-AC2-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-440', Anonymous Referee #1, 28 Feb 2024
The review of the manuscript of Swain et al., 2024 on the topic “Aerosols in the central Arctic cryosphere: Satellite and model integrated insights during Arctic spring and summer”.
This manuscript presents the integrated view of aerosol load over central Arctic cryospheric region. I would like to appreciate the authors for doing a difficult task of combing satellite and model simulations to study aerosol over central Arctic region, as the retrieval of AOD over highly reflective snow and ice region is very challenging.
This manuscript has been gone through a previous review (https://doi.org/10.5194/egusphere-2023- 730) and all the critical aspects raised by the previous reviewers were addressed very well in this revised version.
Further, this manuscript is bringing valuable information of spring and summer AOD distributions and the anthropogenic and natural aerosol load behind it and highlighted the need to add summer time aerosol processes in the models for the central Arctic to properly quantify Arctic warming.
In addition, this manuscript is conforming for the first time the unconfirmed prospective highlighted by a recent valuable paper (Schmale et al., 2021), that models might be missing the summer aerosol processes due to sea ice reduction and open ocean emissions by using AEROSNOW space-borne data.
This version of the manuscript has been written very well and falls within the aim and scope of the ACP journal. I would like to recommend it for publication with minor corrections. The minor corrections are listed below:
Abstract:
Line 8: Although this study is conducted for the first time over central Arctic cryospheric region, is it necessary to mention in the abstract?
Introduction:
The overall introduction has been written very well and the story is very easy to follow.
Results:
At Figure 2, please use different colors for clear read. i.e, AEROSNOW ( may be red) and AERONET (black).
Conclusion:
At line 362-365, I would recommend to remove the paragraph
“The promising results derived from the AEROSNOW approach hold significant value for both a) constraining the accuracy of AOD simulations in chemical transport models (CTMs) and b) determining the changing AOD in the Arctic sea ice regions currently experiencing AA.”.
As you are mentioning that the AEROSNOW data is valuable to access models over central Arctic at line 415-420.
In summary, I enjoyed reading the manuscript.
Reference: Schmale, J., Zieger, P., and Ekman, A. M.: Aerosols in current and future Arctic climate, Nature Climate Change, 11, 95–105, https://doi.org/10.1038/s41558-020-00969-5, 2021.
Citation: https://doi.org/10.5194/egusphere-2024-440-RC1 -
AC1: 'Reply on RC1', Basudev Swain, 04 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-440/egusphere-2024-440-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Basudev Swain, 04 Apr 2024
-
RC2: 'Comment on egusphere-2024-440', Anonymous Referee #2, 01 Mar 2024
Some minor corrections:
- Please clarify in the abstract “During spring, which is characterized by long-range transport of anthropogenic aerosols in the Arctic, the GC underestimates the AOD in the vicinity of Alaska”. In comparison to what?
- Introduction is well written and has a good flow to it. However, there is one incomplete line
Line 70 when you talk about “To address the recently posted…and compare it to.” Compare it to what? Please complete
- It would be easier if you marked central arctic sea-ice region that you are interested in along with the AERONET sites in figure 1
- Do the optical properties used in the GOES-Chem model vary with time? Studies have shown that temporal evolution of the aerosol size distribution in models closely resemble to observations.
- Figure 2: Put Hornsund in the bottom and PEARL, OPAL and Thule on top (this gives the reader a consistency because these three sites are from CA side). Are the correlation numbers mentioned in each figure for spring and summer for all the years put together? PEARL and OPAL are close together, then why do they have different correlations of GC with AERONET and AEROSNOW? What factors do you think affect the GC simulations? Its important you mention somewhere how you derived the natural AOD (marked with white in Figure 2).
- Figure 3: Please use the same symbols for AERONET and AEROSNOW as in Figure 2 for consistency.
- Line 210: “Additionally, and on average, all three datasets show periods of haze episodes during the spring season”. Is it three or four? Its confusing because there are 4 sites mentioned in the paper
- Line 215; “We attribute these differences can largely be attributed to the fact that GOES-Chem simulates AOD independent of meteorological conditions, cloud cover and the spatial…” . Please rewrite the first part of the sentence. Also in Section 2.2, it was mentioned that GC uses MERRA 2 reanalysis for meteorological fields but Line 215 contradicts this. Please clarify.
- Line 225: “Further, during summer, the discrepancies in GOES-Chem AOD can be attributed to various factors, including limitations related to NPF and inherent effects of a relatively coarse horizontal model resolution”. In Line 215, it is mentioned that GC is independent of cloud cover. Arctic receives precipitation in summer and it is also possible, in addition to NPF and low res, that the GC doesn’t represent clouds well and because of which there are discrepancies mainly in summer!!
- Line 234: In figure 4, we present the seasonal AOD for spring and summer, averaged over the entire study period. For each station, three circles are displayed” I think there are 4 circles displayed, so please correct this.
- Line 270: there is a typo. Make it 2003 instead of 203.
- Line 282: “GOES-Chem simulations showed higher and lower AOD during spring of the year 2009 and 2007 respectively”. Are there any reasons why only these particular years were chosen? 2004, 2006, 2008 also showed higher GC-derived AOD.
- It is very interesting that this study talks about the lack of NPF in the models. During summer, the GC underestimates in some places and overestimates in others wrt AEROSNOW. And the authors say this could be due to lack of proper representation of NPF in model, which in my opinion, could be true but also I feel NPF is a common occurring in the Arctic summer. So if lack of NPF was the main issue, then it would have underestimated all throughout and not shown such discrepancies spatially! How can you explain why it overestimates AOD in some places? Lack of NPF cannot be the reason! When you measure AOD, do you also take into account cloud residuals?
- This isn’t related to this study but I think we can see interesting results when AEROSNOW algorithm will be applied to study the aerosols during Arctic winters.
Citation: https://doi.org/10.5194/egusphere-2024-440-RC2 -
AC2: 'Reply on RC2', Basudev Swain, 04 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-440/egusphere-2024-440-AC2-supplement.pdf
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Basudev Swain
Marco Vountas
Aishwarya Singh
Nidhi L. Anchan
Adrien Deroubaix
Luca Lelli
Yanick Ziegler
Sachin S. Gunthe
Hartmut Bösch
John P. Burrows
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(18061 KB) - Metadata XML