the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Jan 2023
Research on the unusual spring 2020 Arctic stratospheric ozone depletion above Ny-Ålesund, Norway
Abstract. Of the severe stratospheric ozone depletion events (ODEs) reported over the Arctic, the third and most severe occurred during the spring of 2020; we analyzed the reasons for this event herein. We retrieved the critical indicator ozone vertical column density (VCD) using zenith scattered light differential optical absorption spectroscopy (ZSL-DOAS) located in Ny-Ålesund, Svalbard, Norway. The average ozone VCDs over Ny-Ålesund between March 18 and April 18, 2020, were approximately 274.8 Dobson units (DU), which was only about 64.7 % of that in normal years. The retrieved daily averages of ozone VCDs were compared with satellite observations from Global Ozone Monitoring Experiment 2 (GOME-2), a Brewer spectrophotometer, and a Système d’Analyze par Observation Zénithale (SAOZ) spectrometer at Ny-Ålesund; the resulting Pearson correlation coefficients were relatively high at 0.94, 0.86, and 0.91, with relative deviations of 2.3 %, 3.1 %, and 3.5 %, respectively. Compared with normal years, the 2020 daily peak relative ozone loss was approximately 44.3 %. During the 2020 Arctic spring ODE, the ozone VCDs and potential vorticity (PV) had a negative correlation with their fluctuations, suggesting a clear effect of the polar vortex on stratospheric ozone depletion. To better understand what caused the ozone depletion, we also considered the chemical components of this process in the Arctic winter of 2019/2020 with the specified dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM). The SD-WACCM model results indicated that both ClO and BrO concentrations peaked in late March, which was a critical factor during the ozone depletion observed in Ny-Ålesund. Chlorine activation was clearly apparent during the Arctic spring of 2020, whereas the partitioning of bromine species was different from that of chlorine. By combining observations with modeling, we provide a reliable basis for further research on global climate change due to polar ozone concentrations and the prediction of severe Arctic ozone depletion in the future.
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Status: closed
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RC1: 'Comment on acp-2022-859', Anonymous Referee #1, 13 Feb 2023
- AC1: 'Reply on RC1', Qidi Li, 18 Apr 2023
- AC2: 'Reply on RC1', Qidi Li, 18 Apr 2023
-
RC2: 'Comment on acp-2022-859', Anonymous Referee #2, 16 Feb 2023
Comments on
“Research on the unusual spring 2020 Arctic stratospheric ozone depletion above Ny-Alesund, Norway” by Li et al.
In the current manuscript, Li et al has introduced the retrieval method (ZSL-DOAS) by the ground-based instrument installed at Yellow River Station in the Arctic. Then they have validated the retrieved ozone VCD with some widely used measurements including GOME2, Bremer spectrophotometers and SAOZ, the latter uses DOAS with precise measurements of stratospheric constituents during twilight. All these show the observed ozone value is much lower in late winter/early spring in 2020 comparing with the recent five years. Then the authors have investigated the daily variability in ozone changes by calculating the 4-year mean ozone value (2017-2021 excluding the extreme year 2020) and the absolute (and the relative percentage) difference with respace to the mean (?) and have tried to link it to the dynamics (for example by looking at the temperature, PV evolutions). They have also done a model simulation (SD-WACCM) to look at the model performance and the chemical species changes. However, the paper is not well written though the message is still clear for me. There are many confusions (for example, definitions like ozone loss etc that are quite different from the community has used). It is no doubt that the current ZSL-DOAS observations give another evidence for the unusual Arctic 2020 spring ozone and the unique dataset will be of interest to the atmospheric community. There are many studies over many years show that chlorine and bromine compounds are responsible for the polar ozone depletion in winter and spring. However, the current manuscript has not provided the firm conceptual advance in our understanding of Arctic ozone depletion and there is no new insight into the underlying mechanism responsible for the Arctic ozone depletion. Therefore, the paper has to be rejected or rewritten to find something new.
Specific Comments:
- The title is too general. “Research” is quite broad.
- Line 13 in the Abstract: “Severe”, the “third and most severe” is vague. There are still larger Arctic ozone loss for other years. Do you mean the long-lasting cold polar vortex years?
- Actually, I find “event” is confusing.
- There are many “normal” in the whole text. What is the definition for the normal year? Need to be clear with it.
- Some results are obvious: “effect of the polar vortex on stratospheric ozone depletion”, “Chlorine activation” and “bromine compounds”
- The last sentence in the abstract. What is the main point here? Is this relevant to this work?
- Introduction is not well written. Most of them are too general and the background is well known. If you focus on Arctic winter/spring 2020, then you need to brief summary the available publications and what are the unique research questions you need to address or the methods you have applied.
- I also find it is difficult to see the purpose of this work. Are you aiming to validate your ZSL-DOAS observations using other measurements? I am not an expert in the retrieval method so it is hard for me to judge your method. What is the difference in the retrieval of ozone from ZSAL-DOAS and SAOZ because SAOZ also uses DOAS method? For the Air Mass Factor (AMF) in section 2.2, the authors have mentioned the related parameters in Table 2 and AMF will be quite different for different assumed profiles (for example Lines 121-123). So I am curious what are these profiles from. It is vague just to mention SCIATRAN without any reference there.
- SD-WACCM. This section needs some more details since the authors have carried out the simulation. It should come from CESM1 (but which version) but not sure what other changes have been made by the author. I assume this is a released version but ported and run on a different HPCx in China. However, some of the emissions and other input data have not been updated/available for year 2020. One simple example is that this version uses the prescribed stratospheric sulphur aerosol density (SAD) which is important for the ozone depletion. How the SAD used in SD-WACCM4 for this? Do you use the previous years values or fixed values? Which component you are using? It seems that the authors only mentioned MOZART3, so I am not sure if this one “pp_waccm_mozart” used or you also have MAM model in the model simulation etc.. For the SD, the author need to realize that this is not a fully nudged version, which all depends on the relaxation time etc. This needs to make clear. I have not heard “thermogenic” layer, should be use the correct term like “lower thermosphere”. It is strange to say the “parameters” in the Line 140. Please note it uses CAM4 physics. It is impropriate to say “the SD-WACCM with meteorological parameters driven by …”, note even SD-WACCM most of the temperature etc. are still from WACCM itself (driven by SST, solar etc…). How can you say “Data from MERRA-2 guaranteed the accuracy of simulated values”? Note that other processes play roles.
- Auxiliary data: Can be concise and have proper references. For example ERA5. Some sentences are not necessary at all. For example. Lines 152, 165.
- It reads to me that the authors just SHOW the results itself, rather than describe the results in a correct/proper way. For example, for Figure4, we can see large daily variability that has never mentioned. We also see the differences among these measurements but have never explained. For example, why your data ZSL-DOAS is much lower than other observations? I don’t think the gradient of “~0.92DU per day” is similar for all the “normal” years claimed. It is also not correct to say “Ozone VCD begins to decrease in March.” For Figure 5, I understand the VCD and TCO can be used but the authors need to be consistent in the whole text. The presentation for Figure 6 is not good at all. Why the authors term this “ozone loss”? How do you estimate “ozone loss”? It looks that this is just ozone difference between 2020 and the 4-year mean. For Figure 7, it seems that temperature is from ERA5, why use “measured” in Line 190? It is a reanalysis product, which is from ECMWF model simulation using the data assimilation from the measurements. Figure 8, it seems that the authors just look at one time period of ozone and PV evolution, then comes the conclusion of “PV correlates negatively with ozone VCD” etc. The authors seems not have a deep understanding their figures even they made it (for example, stratospheric warming after mid-April that made polar vortex weaker and TOC higher) etc.. Figure9, the authors said “unusual low”. This is only for 2020, have you made O3 volume mixing ration comparison with others. Why “< 0.5ppmv suggested the ozone was nearly completed depleted. “?. For the Tnat, it also depends on H2O, HNO3 and H2SO4? What is their values used for the Tnat? Figure 10, why “HNO3 changes abruptly from abnormally high values to normal values, which indicated the abundant PSC activities of the period” only applies for “Between late January and early February”? What caused the low value patches around 20-22km? Figure 11, I saw the model showed a complete HCl depletion on 21 Feb. How the modelled HCl etc chemical species compared with ACE observation for example?
- This reads like a summary from the main text. I am not sure why the last sentence is matter based on this study.
Citation: https://doi.org/10.5194/acp-2022-859-RC2 - AC3: 'Reply on RC2', Qidi Li, 18 Apr 2023
-
EC1: 'Comment on acp-2022-859', Jens-Uwe Grooß, 08 Mar 2023
Publisher’s note: this comment was edited on 21 March 2023. The following text is not identical to the original comment, but the adjustments were minor without effect on the scientific meaning.
Dear Li Qidi et al.,
normally, ACP encourages the authors at this stage to prepare an
answer to the reviewers and revised version of the manuscript.However, it seems that you have not convinced the reviewers, that your
manuscript contains new scientific findings. While some points of the
reviewers can likely be solved easily, as the detailed description of
the measurements as well as the description of the model runs, the
lack of new scientific findings is a strong argument.I see two options to continue this project. Either you try to
formulate clearly the novelty of this study or you could switch the
focus and re-write it as a measurement report, in which only the
measurements are reported and the consistency with other studies and
measurements are shown.Citation: https://doi.org/10.5194/acp-2022-859-EC1 - AC4: 'Reply on EC1', Qidi Li, 18 Apr 2023
Status: closed
-
RC1: 'Comment on acp-2022-859', Anonymous Referee #1, 13 Feb 2023
- AC1: 'Reply on RC1', Qidi Li, 18 Apr 2023
- AC2: 'Reply on RC1', Qidi Li, 18 Apr 2023
-
RC2: 'Comment on acp-2022-859', Anonymous Referee #2, 16 Feb 2023
Comments on
“Research on the unusual spring 2020 Arctic stratospheric ozone depletion above Ny-Alesund, Norway” by Li et al.
In the current manuscript, Li et al has introduced the retrieval method (ZSL-DOAS) by the ground-based instrument installed at Yellow River Station in the Arctic. Then they have validated the retrieved ozone VCD with some widely used measurements including GOME2, Bremer spectrophotometers and SAOZ, the latter uses DOAS with precise measurements of stratospheric constituents during twilight. All these show the observed ozone value is much lower in late winter/early spring in 2020 comparing with the recent five years. Then the authors have investigated the daily variability in ozone changes by calculating the 4-year mean ozone value (2017-2021 excluding the extreme year 2020) and the absolute (and the relative percentage) difference with respace to the mean (?) and have tried to link it to the dynamics (for example by looking at the temperature, PV evolutions). They have also done a model simulation (SD-WACCM) to look at the model performance and the chemical species changes. However, the paper is not well written though the message is still clear for me. There are many confusions (for example, definitions like ozone loss etc that are quite different from the community has used). It is no doubt that the current ZSL-DOAS observations give another evidence for the unusual Arctic 2020 spring ozone and the unique dataset will be of interest to the atmospheric community. There are many studies over many years show that chlorine and bromine compounds are responsible for the polar ozone depletion in winter and spring. However, the current manuscript has not provided the firm conceptual advance in our understanding of Arctic ozone depletion and there is no new insight into the underlying mechanism responsible for the Arctic ozone depletion. Therefore, the paper has to be rejected or rewritten to find something new.
Specific Comments:
- The title is too general. “Research” is quite broad.
- Line 13 in the Abstract: “Severe”, the “third and most severe” is vague. There are still larger Arctic ozone loss for other years. Do you mean the long-lasting cold polar vortex years?
- Actually, I find “event” is confusing.
- There are many “normal” in the whole text. What is the definition for the normal year? Need to be clear with it.
- Some results are obvious: “effect of the polar vortex on stratospheric ozone depletion”, “Chlorine activation” and “bromine compounds”
- The last sentence in the abstract. What is the main point here? Is this relevant to this work?
- Introduction is not well written. Most of them are too general and the background is well known. If you focus on Arctic winter/spring 2020, then you need to brief summary the available publications and what are the unique research questions you need to address or the methods you have applied.
- I also find it is difficult to see the purpose of this work. Are you aiming to validate your ZSL-DOAS observations using other measurements? I am not an expert in the retrieval method so it is hard for me to judge your method. What is the difference in the retrieval of ozone from ZSAL-DOAS and SAOZ because SAOZ also uses DOAS method? For the Air Mass Factor (AMF) in section 2.2, the authors have mentioned the related parameters in Table 2 and AMF will be quite different for different assumed profiles (for example Lines 121-123). So I am curious what are these profiles from. It is vague just to mention SCIATRAN without any reference there.
- SD-WACCM. This section needs some more details since the authors have carried out the simulation. It should come from CESM1 (but which version) but not sure what other changes have been made by the author. I assume this is a released version but ported and run on a different HPCx in China. However, some of the emissions and other input data have not been updated/available for year 2020. One simple example is that this version uses the prescribed stratospheric sulphur aerosol density (SAD) which is important for the ozone depletion. How the SAD used in SD-WACCM4 for this? Do you use the previous years values or fixed values? Which component you are using? It seems that the authors only mentioned MOZART3, so I am not sure if this one “pp_waccm_mozart” used or you also have MAM model in the model simulation etc.. For the SD, the author need to realize that this is not a fully nudged version, which all depends on the relaxation time etc. This needs to make clear. I have not heard “thermogenic” layer, should be use the correct term like “lower thermosphere”. It is strange to say the “parameters” in the Line 140. Please note it uses CAM4 physics. It is impropriate to say “the SD-WACCM with meteorological parameters driven by …”, note even SD-WACCM most of the temperature etc. are still from WACCM itself (driven by SST, solar etc…). How can you say “Data from MERRA-2 guaranteed the accuracy of simulated values”? Note that other processes play roles.
- Auxiliary data: Can be concise and have proper references. For example ERA5. Some sentences are not necessary at all. For example. Lines 152, 165.
- It reads to me that the authors just SHOW the results itself, rather than describe the results in a correct/proper way. For example, for Figure4, we can see large daily variability that has never mentioned. We also see the differences among these measurements but have never explained. For example, why your data ZSL-DOAS is much lower than other observations? I don’t think the gradient of “~0.92DU per day” is similar for all the “normal” years claimed. It is also not correct to say “Ozone VCD begins to decrease in March.” For Figure 5, I understand the VCD and TCO can be used but the authors need to be consistent in the whole text. The presentation for Figure 6 is not good at all. Why the authors term this “ozone loss”? How do you estimate “ozone loss”? It looks that this is just ozone difference between 2020 and the 4-year mean. For Figure 7, it seems that temperature is from ERA5, why use “measured” in Line 190? It is a reanalysis product, which is from ECMWF model simulation using the data assimilation from the measurements. Figure 8, it seems that the authors just look at one time period of ozone and PV evolution, then comes the conclusion of “PV correlates negatively with ozone VCD” etc. The authors seems not have a deep understanding their figures even they made it (for example, stratospheric warming after mid-April that made polar vortex weaker and TOC higher) etc.. Figure9, the authors said “unusual low”. This is only for 2020, have you made O3 volume mixing ration comparison with others. Why “< 0.5ppmv suggested the ozone was nearly completed depleted. “?. For the Tnat, it also depends on H2O, HNO3 and H2SO4? What is their values used for the Tnat? Figure 10, why “HNO3 changes abruptly from abnormally high values to normal values, which indicated the abundant PSC activities of the period” only applies for “Between late January and early February”? What caused the low value patches around 20-22km? Figure 11, I saw the model showed a complete HCl depletion on 21 Feb. How the modelled HCl etc chemical species compared with ACE observation for example?
- This reads like a summary from the main text. I am not sure why the last sentence is matter based on this study.
Citation: https://doi.org/10.5194/acp-2022-859-RC2 - AC3: 'Reply on RC2', Qidi Li, 18 Apr 2023
-
EC1: 'Comment on acp-2022-859', Jens-Uwe Grooß, 08 Mar 2023
Publisher’s note: this comment was edited on 21 March 2023. The following text is not identical to the original comment, but the adjustments were minor without effect on the scientific meaning.
Dear Li Qidi et al.,
normally, ACP encourages the authors at this stage to prepare an
answer to the reviewers and revised version of the manuscript.However, it seems that you have not convinced the reviewers, that your
manuscript contains new scientific findings. While some points of the
reviewers can likely be solved easily, as the detailed description of
the measurements as well as the description of the model runs, the
lack of new scientific findings is a strong argument.I see two options to continue this project. Either you try to
formulate clearly the novelty of this study or you could switch the
focus and re-write it as a measurement report, in which only the
measurements are reported and the consistency with other studies and
measurements are shown.Citation: https://doi.org/10.5194/acp-2022-859-EC1 - AC4: 'Reply on EC1', Qidi Li, 18 Apr 2023
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