the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Jun 2024
Classification of North Atlantic and European extratropical cyclones using multiple measures of intensity
Abstract. The question of how to quantify the intensity of extratropical cyclones does not have a simple answer. To offer some perspective on this issue, multiple measures of intensity are analyzed in this study for North Atlantic and European extratropical cyclones for the extended winter season between 1979 and 2022 using ERA5 reanalysis data. The most relevant intensity measures are identified by investigating relationships between them and by performing sparse principal component analysis on the set of measures. We show that dynamical intensity measures correlate strongly with each other, while correlations are weaker for impact-relevant measures. Based on the correlations and the sparse principal component analysis, we find that five intensity measures, namely 850 hPa relative vorticity, 850 hPa wind speed, wind footprint, precipitation, and a storm severity index, describe cyclone intensity comprehensively and non-redundantly. Using these five measures as input, we objectively classify the extratropical cyclones with a cluster analysis based on a Gaussian mixture model. The cluster analysis is able to produce four clusters between which cyclones differ in terms of their intensity, life cycle characteristics such as deepening rate and lifetime, and geographical location. A clear majority (81 %) of investigated impactful storms belong to the most intense cluster, which demonstrates the ability of the method to identify potentially damaging extratropical cyclones.
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Status: closed
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RC1: 'Comment on egusphere-2024-1749', Anonymous Referee #1, 05 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC1-supplement.pdf
- AC1: 'Reply on RC1', Joona Cornér, 11 Sep 2024
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RC2: 'Comment on egusphere-2024-1749', Anonymous Referee #2, 19 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC2-supplement.pdf
- AC2: 'Reply on RC2', Joona Cornér, 11 Sep 2024
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RC3: 'Comment on egusphere-2024-1749', Anonymous Referee #3, 28 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC3-supplement.pdf
- AC3: 'Reply on RC3', Joona Cornér, 11 Sep 2024
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RC4: 'Comment on egusphere-2024-1749', Anonymous Referee #4, 07 Aug 2024
Overview
The authors here present an interesting study where they examine variability and relationships between numerous measures of intensity of extratropical cyclones in the North Atlantic in ERA5. This is a very comprehensive study and methodical in nature and presents very interesting results. The main results of interest are on the clusters of storms, their different geographic locations and also different populations in the wider intensity distributions. Due to the methodical nature of this study, it clearly presents very worthwhile findings, my only criticism of this work is that the study is incredibly long and in some places perhaps overly so. I understand why this is as the authors have conducted a lot of analysis, however in places brevity may be an option. I have other minor comments, which i have detailed below, and once these have been addressed i think this study will be an excellent addition to this journal.
Minor comments
- L37/38 "However, in many cases, neither the minimum MSLP nor maximum VO correlates well with the impacts of a given ETC" needs a reference
- L52 - specify that you are referring to "average strength" cyclones
- L88 - typo in the statement of spectral resolution
- Section 2.2 - do you also perform the tracking using 3-hourly resolution, or use the standard 6-hourly approach? Please specify in this section
- L111 - I assume you are using VO at 850 hPa for tracking, but you do not state this initially, this needs to be done
- L161 - your baseline intensity measure is VO from the tracks. If this is the case you need to state that this is the T42 filtered vorticity, and not vorticity that you would get directly out of ERA5. Anyone trying to re-produce your results would have to do the tracking in order to get this variable
- L245 - i believe there is a brackets issue in this line
- Section 4.3 - all sections here are very long and descriptive and i feel is an area where some text can be removed and sections shortened for the benefit of future readers.
- L500-511 - you state for this paragrpah that the results of Fig 9 are the same as Fig 8, which is what you would expect as it is just the same data but presented in a different manner. If this paragraph (and Fig. 9) are not essential for your results i would consider removing.
- Figure 10 - it would be good to state the trend value (and associated uncertainty) in each panel and the associated places in the text. Also, how much are your trends associated with modes of variability such as the NAO?
Citation: https://doi.org/10.5194/egusphere-2024-1749-RC4 - AC4: 'Reply on RC4', Joona Cornér, 11 Sep 2024
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AC5: 'Comment on egusphere-2024-1749', Joona Cornér, 25 Sep 2024
Thank you again for your valuable comments on our manuscript. Based on the editor decision we have further shortened the manuscript from the version which functioned as the basis of the reviewer response. There are therefore some inconsistencies between the response and the revised manuscript. Some comments may not apply anymore if the parts have been removed completely. The largest modifications have been made in Sections 2.1, 2.2, 3.3, 4.1, and 4.3. of the manuscript. The discussion and introduction have also been shortened slightly.
On behalf of the authors,
Joona Cornér
Citation: https://doi.org/10.5194/egusphere-2024-1749-AC5
Status: closed
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RC1: 'Comment on egusphere-2024-1749', Anonymous Referee #1, 05 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC1-supplement.pdf
- AC1: 'Reply on RC1', Joona Cornér, 11 Sep 2024
-
RC2: 'Comment on egusphere-2024-1749', Anonymous Referee #2, 19 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC2-supplement.pdf
- AC2: 'Reply on RC2', Joona Cornér, 11 Sep 2024
-
RC3: 'Comment on egusphere-2024-1749', Anonymous Referee #3, 28 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1749/egusphere-2024-1749-RC3-supplement.pdf
- AC3: 'Reply on RC3', Joona Cornér, 11 Sep 2024
-
RC4: 'Comment on egusphere-2024-1749', Anonymous Referee #4, 07 Aug 2024
Overview
The authors here present an interesting study where they examine variability and relationships between numerous measures of intensity of extratropical cyclones in the North Atlantic in ERA5. This is a very comprehensive study and methodical in nature and presents very interesting results. The main results of interest are on the clusters of storms, their different geographic locations and also different populations in the wider intensity distributions. Due to the methodical nature of this study, it clearly presents very worthwhile findings, my only criticism of this work is that the study is incredibly long and in some places perhaps overly so. I understand why this is as the authors have conducted a lot of analysis, however in places brevity may be an option. I have other minor comments, which i have detailed below, and once these have been addressed i think this study will be an excellent addition to this journal.
Minor comments
- L37/38 "However, in many cases, neither the minimum MSLP nor maximum VO correlates well with the impacts of a given ETC" needs a reference
- L52 - specify that you are referring to "average strength" cyclones
- L88 - typo in the statement of spectral resolution
- Section 2.2 - do you also perform the tracking using 3-hourly resolution, or use the standard 6-hourly approach? Please specify in this section
- L111 - I assume you are using VO at 850 hPa for tracking, but you do not state this initially, this needs to be done
- L161 - your baseline intensity measure is VO from the tracks. If this is the case you need to state that this is the T42 filtered vorticity, and not vorticity that you would get directly out of ERA5. Anyone trying to re-produce your results would have to do the tracking in order to get this variable
- L245 - i believe there is a brackets issue in this line
- Section 4.3 - all sections here are very long and descriptive and i feel is an area where some text can be removed and sections shortened for the benefit of future readers.
- L500-511 - you state for this paragrpah that the results of Fig 9 are the same as Fig 8, which is what you would expect as it is just the same data but presented in a different manner. If this paragraph (and Fig. 9) are not essential for your results i would consider removing.
- Figure 10 - it would be good to state the trend value (and associated uncertainty) in each panel and the associated places in the text. Also, how much are your trends associated with modes of variability such as the NAO?
Citation: https://doi.org/10.5194/egusphere-2024-1749-RC4 - AC4: 'Reply on RC4', Joona Cornér, 11 Sep 2024
-
AC5: 'Comment on egusphere-2024-1749', Joona Cornér, 25 Sep 2024
Thank you again for your valuable comments on our manuscript. Based on the editor decision we have further shortened the manuscript from the version which functioned as the basis of the reviewer response. There are therefore some inconsistencies between the response and the revised manuscript. Some comments may not apply anymore if the parts have been removed completely. The largest modifications have been made in Sections 2.1, 2.2, 3.3, 4.1, and 4.3. of the manuscript. The discussion and introduction have also been shortened slightly.
On behalf of the authors,
Joona Cornér
Citation: https://doi.org/10.5194/egusphere-2024-1749-AC5
Data sets
Classification of extratropical cyclones using multiple measures of intensity: Data and Python code Joona Cornér et al. https://doi.org/10.5281/zenodo.11384418
Model code and software
Classification of extratropical cyclones using multiple measures of intensity: Data and Python code Joona Cornér et al. https://doi.org/10.5281/zenodo.11384418
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