the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Mar 2025
The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24
Abstract. The winter 2023/24 exhibited remarkable stratospheric dynamics with multiple sudden stratospheric warmings (SSWs). Based on the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) polar-cap averaged 10 hPa zonal wind, three major SSWs are identified – an extremely rare occurrence in a single winter. Two of three SSWs were short-lived, lasting under 7 days. In this study, we give an overview of the three SSWs that occurred in winter 2023/24 and focus on the impact of tropospheric forcing on their duration. Blocking high-pressure systems are shown to modulate wave activity flux into the stratosphere through interactions with tropospheric planetary waves, depending on their location. The rapid termination of the first SSW (14–19 January 2024) is linked to a developing high-pressure system over the North Pacific. The second SSW (16–22 February 2024) terminated quickly due to more contributing factors, one of which was a high-pressure system developed over the Far East. The third SSW (3–28 March 2024) was a long-duration canonical event extending to levels below 100 hPa. In contrast to two short-lived SSWs in winter 2023/24, the tropospheric forcing was sustained around the SSW onset in March 2024, allowing a long event to develop. We also note that conditions for these SSWs were particularly favorable due to external factors, including an Easterly Quasi-Biennial Oscillation (QBO), the presence of El Niño conditions of the ENSO cycle, and the proximity to the solar maximum.
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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
(3494 KB)
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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-2025-976', Anonymous Referee #1, 05 Apr 2025
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AC2: 'Reply on RC1', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC2-supplement.pdf
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AC2: 'Reply on RC1', Ekaterina Vorobeva, 16 Jun 2025
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RC2: 'Comment on egusphere-2025-976', Anonymous Referee #2, 20 Apr 2025
Comments on “The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24” by Vorobeva and Orsolini
Summary
Using the reanalysis, this study analyzed the successive SSWs in the 2023/24 winter, which has been reported in a series of recent studies (Rao et al. 2025AR; Lee et al. 2025 Weather; Lu Qian et al. 2024). Especially, the study analyzed the linear interference of climatological waves and synoptic waves in the eddy heat flux. The blocking highs are emphasized. This paper is well written and I only have several minor questions.
Specific comments
- The decomposition of the eddy heat flux into different terms is necessary to better understand the wave driving. However, the anomalous eddy heat flux might be problematic. See the derivation below:
(v’T’)c = (v’cT’c+v’aT’c+v’cT’a+v’aT’a)c = v’cT’c+(v’aT’a)c
(v’T’)a = v’T’ - (v’T’)c = v’aT’c+v’cT’a+ [v’aT’a - (v’aT’a)c]
This paper did not consider the contribution of (v’aT’a)c for the climatological eddy heat flux, and place this term in the total nonlinear term, which might lead to wrong conclusions.
- L22-23: This sentence is partially true for a few SSWs that the easterlies begin to appear in the upper stratosphere. I am not sure if this statement is true for other SSWs, since the wave forcing for SSWs is primarily from the troposphere and lower stratosphere. Please insert references.
- L26-27: The SSW occurs 6-7 times every decade. Please update the SSW frequency using the modern reanalysis. Further, models also produce a frequency 6-7 every 10 years. See Rao and Garfinkel 2021 (ERL, doi: 10.1088/1748-9326/abd4fe). Baldwin et al. 2021.
- L31: Liang et al. also discussed the global impact of the SSW using model simulations (doi: 10.1007/s00382-022-06293-2).
- L40-41: There are too many studies emphasizing the impact of the high blocking on the SSWs. Refer to Rao et al. 2018 (doi: 10.1029/2018JD028908) if necessary.
- L54: This SSW is reported in several recent studies that should be considered. Add Qian et al. 2024; Rao et al. 2025 (doi: 10.1016/j.atmosres.2024.107882); Lee et al. 2024 (doi: 10.1002/wea.7656).
- L75: that clause => which …
- L93: Here you should discuss the possible impact of the SSW definition on the conclusion. Using the polar cap U, you find three SSWs. But if you use CP SSW definition, you might only pick up two SSWs. Rao et al. 2025 use three stratospheric disturbances to call those SSWs. It is not a big problem.
- L99: Please add sone discussion that similar figures have been shown in Lu Qian et al. 2024; Rao et al. 2025, Lee et al. 2024.
- L110-111: Add a reference e.g., Rao et al. 2025.
- L131-132: This sentence is true. Is the SSW persistency of easterlies also discussed for other two SSWs. Since the first two and especially the second SSW provide a precondition for the major SSW in March 2024, the precondition of the last SSW should be discussed.
- Figure 2: 45N is still too far from the polar region. Will the conclusion change if the latitude is changed to 75N.
- L138: What kind of forcing is persistent and what is not? Do you have any results stating?
- L140: Please state what aspects are consistent and what are not.
- L168: Not sure if it is true. Might also indicate that the upward propagation of waves are weakened.
- L187: Eq. 1 is right but the anomalous eddy heat flux definition might be problematic.
- L196: Please clarify where the trough is situated.
- Figure 3: The climatological waves shown in black contours are not very consistent in g-i. Please check if an error exists in the plotting script. The high over 0E is not consistent, for example. The anomalous eddy heat flux is not right as I say above.
- L208: Where are those blockings?
- L211: Far East? DO you mean East Asian trough?
- L222, 226: The Alaskan blocking is not persistent at all. It weakened during the second period and reformed during the third period.
- L236, Figure 4: Figure 4 is too noisy and boring. I am not sure if there is necessity of showing figure 4.
- Figure 5: You did not remove the contribution from the climatology of nonlinear term. Please test if this will affect the conclusion.
- L262: Also see Chwat et al. 2022 doi: 10.1029/2022JD037521. All the external forcings are discussed in Chwat et al. 2022 and Rao et al. 2019.
- L273: See Rao et al. 2025AR for a review on the favorable conditions for past SSWs in last decades.
- L301: If necessary, please add the funding information. Further, the dataset availability should be shown with feasible hyperlink address.
Citation: https://doi.org/10.5194/egusphere-2025-976-RC2 -
AC3: 'Reply on RC2', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC3-supplement.pdf
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EC1: 'Comment on egusphere-2025-976', Amy Butler, 09 Jun 2025
I wanted to add a minor comment regarding the use of the polar cap averaged zonal winds to detect SSWs. I think the authors provide justification for using a different definition than what is standard/most common. However, using this other definition will change how rare the occurrence of 3 SSWs actually is. As a note, the Ineson et al. 2024 paper that is cited also uses the Charlton & Polvani 2007 definition, so those statistics are not comparable to the analysis done here. Also note that Butler et al. (2015) Fig 2 shows a large increase (about 25%) in detected SSW events when using the polar-cap averaged definition. Therefore, please be careful when making statements such as "three major SSWs are identified - an extremely rare occurrence in a single winter." If you change your definition, the statistics change too, and 3 SSWs is likely not so rare when using this definition.
Citation: https://doi.org/10.5194/egusphere-2025-976-EC1 -
AC1: 'Reply on EC1', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC1-supplement.pdf
-
AC1: 'Reply on EC1', Ekaterina Vorobeva, 16 Jun 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-976', Anonymous Referee #1, 05 Apr 2025
Comments on the manuscript entitled “The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24” by Ekaterina Vorobeva and Yvan Orsolini, submitted to Weather Climate Dynamics.
This research utilizes the ERA5 reanalysis data and defines the Sudden Stratospheric Warming (SSW) based on the polar-region-averaged wind field. In-depth analyses are conducted on the three major SSW events identified. The authors correctly note that the first two SSW events have relatively short durations, in contrast to the last SSW event, which persists for a substantially longer period. Additionally, they draw inferences about the relationship between the three SSW events and the tropospheric blocking pattern. The overall writing of the manuscript is commendably fluent. However, before recommending this manuscript for publication, I have several concerns that require attention.
Major issues
- The authors ascribe the rapid termination of the first SSW event to the westward-propagating Blocking High (BH) in the North Pacific (Lines 205-207). In reality, as evident from Figures 3b and 3c, the decline in V’T’ is not solely observed in the North Pacific region; rather, the changes over the Atlantic Ocean are quite conspicuous. The authors should consider the causes of this weakening in a more comprehensive fashion and quantitatively present the contribution ratios of each BH.
- Regarding the third SSW event, the authors indicate that the circulation after the outbreak is favorable for the upward propagation of planetary waves. Nevertheless, this conclusion is merely based on the average results for the 5–8 days following the outbreak and cannot represent the situation that may endure for up to one month.
Minor issues
- As can be seen from Figures 2 and 5, the intensities of planetary waves at 100 hPa one month after the occurrences of the second and third SSW events show minimal differences. Yet, one is a short-lived SSW event while the other is a long-lived one. What accounts for this?
- In Figure 5, it is observable that Va’Tc’ is negative during the weakening phase of each SSW event. The authors need to elucidate what factors give rise to this situation.
- The rapid weakening of the upward propagation of planetary waves is a necessary condition for the short duration of the SSW. I opine that quantitatively characterizing this feature could be an important research avenue.
Citation: https://doi.org/10.5194/egusphere-2025-976-RC1 -
AC2: 'Reply on RC1', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC2-supplement.pdf
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RC2: 'Comment on egusphere-2025-976', Anonymous Referee #2, 20 Apr 2025
Comments on “The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24” by Vorobeva and Orsolini
Summary
Using the reanalysis, this study analyzed the successive SSWs in the 2023/24 winter, which has been reported in a series of recent studies (Rao et al. 2025AR; Lee et al. 2025 Weather; Lu Qian et al. 2024). Especially, the study analyzed the linear interference of climatological waves and synoptic waves in the eddy heat flux. The blocking highs are emphasized. This paper is well written and I only have several minor questions.
Specific comments
- The decomposition of the eddy heat flux into different terms is necessary to better understand the wave driving. However, the anomalous eddy heat flux might be problematic. See the derivation below:
(v’T’)c = (v’cT’c+v’aT’c+v’cT’a+v’aT’a)c = v’cT’c+(v’aT’a)c
(v’T’)a = v’T’ - (v’T’)c = v’aT’c+v’cT’a+ [v’aT’a - (v’aT’a)c]
This paper did not consider the contribution of (v’aT’a)c for the climatological eddy heat flux, and place this term in the total nonlinear term, which might lead to wrong conclusions.
- L22-23: This sentence is partially true for a few SSWs that the easterlies begin to appear in the upper stratosphere. I am not sure if this statement is true for other SSWs, since the wave forcing for SSWs is primarily from the troposphere and lower stratosphere. Please insert references.
- L26-27: The SSW occurs 6-7 times every decade. Please update the SSW frequency using the modern reanalysis. Further, models also produce a frequency 6-7 every 10 years. See Rao and Garfinkel 2021 (ERL, doi: 10.1088/1748-9326/abd4fe). Baldwin et al. 2021.
- L31: Liang et al. also discussed the global impact of the SSW using model simulations (doi: 10.1007/s00382-022-06293-2).
- L40-41: There are too many studies emphasizing the impact of the high blocking on the SSWs. Refer to Rao et al. 2018 (doi: 10.1029/2018JD028908) if necessary.
- L54: This SSW is reported in several recent studies that should be considered. Add Qian et al. 2024; Rao et al. 2025 (doi: 10.1016/j.atmosres.2024.107882); Lee et al. 2024 (doi: 10.1002/wea.7656).
- L75: that clause => which …
- L93: Here you should discuss the possible impact of the SSW definition on the conclusion. Using the polar cap U, you find three SSWs. But if you use CP SSW definition, you might only pick up two SSWs. Rao et al. 2025 use three stratospheric disturbances to call those SSWs. It is not a big problem.
- L99: Please add sone discussion that similar figures have been shown in Lu Qian et al. 2024; Rao et al. 2025, Lee et al. 2024.
- L110-111: Add a reference e.g., Rao et al. 2025.
- L131-132: This sentence is true. Is the SSW persistency of easterlies also discussed for other two SSWs. Since the first two and especially the second SSW provide a precondition for the major SSW in March 2024, the precondition of the last SSW should be discussed.
- Figure 2: 45N is still too far from the polar region. Will the conclusion change if the latitude is changed to 75N.
- L138: What kind of forcing is persistent and what is not? Do you have any results stating?
- L140: Please state what aspects are consistent and what are not.
- L168: Not sure if it is true. Might also indicate that the upward propagation of waves are weakened.
- L187: Eq. 1 is right but the anomalous eddy heat flux definition might be problematic.
- L196: Please clarify where the trough is situated.
- Figure 3: The climatological waves shown in black contours are not very consistent in g-i. Please check if an error exists in the plotting script. The high over 0E is not consistent, for example. The anomalous eddy heat flux is not right as I say above.
- L208: Where are those blockings?
- L211: Far East? DO you mean East Asian trough?
- L222, 226: The Alaskan blocking is not persistent at all. It weakened during the second period and reformed during the third period.
- L236, Figure 4: Figure 4 is too noisy and boring. I am not sure if there is necessity of showing figure 4.
- Figure 5: You did not remove the contribution from the climatology of nonlinear term. Please test if this will affect the conclusion.
- L262: Also see Chwat et al. 2022 doi: 10.1029/2022JD037521. All the external forcings are discussed in Chwat et al. 2022 and Rao et al. 2019.
- L273: See Rao et al. 2025AR for a review on the favorable conditions for past SSWs in last decades.
- L301: If necessary, please add the funding information. Further, the dataset availability should be shown with feasible hyperlink address.
Citation: https://doi.org/10.5194/egusphere-2025-976-RC2 -
AC3: 'Reply on RC2', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC3-supplement.pdf
-
EC1: 'Comment on egusphere-2025-976', Amy Butler, 09 Jun 2025
I wanted to add a minor comment regarding the use of the polar cap averaged zonal winds to detect SSWs. I think the authors provide justification for using a different definition than what is standard/most common. However, using this other definition will change how rare the occurrence of 3 SSWs actually is. As a note, the Ineson et al. 2024 paper that is cited also uses the Charlton & Polvani 2007 definition, so those statistics are not comparable to the analysis done here. Also note that Butler et al. (2015) Fig 2 shows a large increase (about 25%) in detected SSW events when using the polar-cap averaged definition. Therefore, please be careful when making statements such as "three major SSWs are identified - an extremely rare occurrence in a single winter." If you change your definition, the statistics change too, and 3 SSWs is likely not so rare when using this definition.
Citation: https://doi.org/10.5194/egusphere-2025-976-EC1 -
AC1: 'Reply on EC1', Ekaterina Vorobeva, 16 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-976/egusphere-2025-976-AC1-supplement.pdf
-
AC1: 'Reply on EC1', Ekaterina Vorobeva, 16 Jun 2025
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Yvan Orsolini
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3494 KB) - Metadata XML
Comments on the manuscript entitled “The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24” by Ekaterina Vorobeva and Yvan Orsolini, submitted to Weather Climate Dynamics.
This research utilizes the ERA5 reanalysis data and defines the Sudden Stratospheric Warming (SSW) based on the polar-region-averaged wind field. In-depth analyses are conducted on the three major SSW events identified. The authors correctly note that the first two SSW events have relatively short durations, in contrast to the last SSW event, which persists for a substantially longer period. Additionally, they draw inferences about the relationship between the three SSW events and the tropospheric blocking pattern. The overall writing of the manuscript is commendably fluent. However, before recommending this manuscript for publication, I have several concerns that require attention.
Major issues
Minor issues