the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Nov 2025
Linking large-scale climate oscillations to local wave climate and storm surge: insights from a weather typing approach
Abstract. Understanding temporal variations in nearshore sea states is crucial, as they affect shoreline evolution and coastal hazard potential. Local sea state conditions are influenced by daily synoptic weather patterns and by large-scale climate oscillations. Although the underlying mechanisms remain not fully understood, numerous studies have established the links between interannual climate patterns and local sea state variability. While most existing research has relied on correlation analyses or other statistical methods, this study explores the possibility of using a weather typing approach to relate climate oscillation patterns to local wave climate and storm surge. The analysis was conducted at Hartlepool, UK, where 36 weather types were previously developed to assess the exposure to coastal hazards for a local nuclear power station. Six climate indices were examined, and we found that the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAND) have significant correlations with local wave and storm surge variables. The weather type analysis reveals that, in response to the phases of NAO or SCAND, storm surge distributions exhibit changes in the mean and standard deviation, peak wave period distributions shift between bimodal and near-unimodal shapes, and wind waves and swell show different dominant directions. These response patterns are attributable to the impacts of atmospheric pressure, wind forcing, and extratropical storm frequency, which are modulated by large-scale climate dynamics associated with NAO and SCAND. This research demonstrates the potential of weather types to offer new perspectives into the impact of climate oscillations on local sea states.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-5400', Anonymous Referee #1, 08 Dec 2025
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RC2: 'Comment on egusphere-2025-5400', Anonymous Referee #2, 11 May 2026
"Linking large-scale climate oscillations to local wave climate and storm surge: insights from a weather typing approach" by Zhong et al. describes the relationships between wave and storm surge properties and climate oscillations near Hartlepool, UK, and how these can be tied to specific weather regimes. This paper is technically sound and uses appropriate data and analysis techniques. Rather than how the chosen analysis method has been implemented, my main question is why that analysis method was chosen. Whilst I don't believe it was the intention of the authors, the paper reads like the purpose was to use a specific analysis method, rather than answering a specific question and using the most appropriate method to do that.
After reading the paper, I was not convinced of the need to use weather types as in intermediary for explaining the relationship between climate oscillations and surges/waves. I was expecting to see strong statements like (for example) "NAO- is associated with larger period waves because the more common WTs associated with it are where storms are further offshore, and hence, waves have larger fetch" (Figure 4) and "NAO+ is associated with larger storm surges because the more common WTs associated with it are where storms are closer to shore, and hence, there is lower pressure and stronger winds at Hartlepool" (Figure 7). To me, this is why you would use weather types to explain the relationship between climate drivers and wave/surge, rather than present two separate analyses – one that looks at weather types and wave/surge response and one that looks at climate oscillations and wave/surge response.
I have a few suggestions for how these changes could be implemented in a revised manuscript:
- Follow the logic set out in the final sentence of the introduction. First, talk about climate oscillations which have a significant/important/notable relationship to wave/surge. Second, describe what the wave/surge response is. Third, explain how WTs can explain why oscillations elicit the responses that they do. I would consider combining methods and results for these sub-sections to make it clear that WTs are only relevant for the third part. This includes re-doing figures.
- Be clear about why you want to investigate climate oscillations. Presumably it is around the multi-year predictability of NAO that just doesn't exist in synoptic timescales. This paper and the references therein may be helpful (https://www.nature.com/articles/s41612-025-01027-7), although I note I am not as familiar the UK context as you likely are being based in the UK.
- Be clear about all relationships being probabilistic rather than deterministic: a specific WT may load the dice towards a specific hazardous wave and surge condition occurring, and specific climatic condition may load the dice towards a specific WT occurring. I would discourage the use of phrases that imply there is a deterministic relationship (e.g., "For WTs associated with NAO+" – Line 240). Therefore, the main value in considering WTs is why the observed relationship between oscillations and wave/surge exist, not as a means of identifying the relationship (there would be a stronger signal if one simply looked at the relationship directly).
- Consider tides and how this impacts risk of extreme water levels at the Hartlepool Power Station. For example, Whitby has a tidal range of ~ 5 metres. Hence, whether a storm surge or large wave event occurs at a spring tide or neap tide is critically important. At a minimum I think the following question should be answered and its implications discussed: Are the times of year when climate oscillations most likely to lead to high waves and large surges also the times of year when tides are highest?
Citation: https://doi.org/10.5194/egusphere-2025-5400-RC2
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This is a well written manuscript that investigates the relationship between surge/wave climate conditions and climate indices at a location (UK, North Sea). In comparison to previous studies covering the same subject, this study provides added insights by investigating a set of wave parameters (including sea and swell decomposition) with a well-stablished weather typing approach. This provides a better understanding of whether, and how, climate modes can impact waves and surges. While the study is applied to a single location, it seems that a similar approach could be followed for other locations, leading to improved understanding of these links for other areas as well.
I do not have major comments and thus recommend the publication of the paper. However, I have a few suggestions that I encourage the authors to address or consider that can potentially help to improve the manuscript.
While I think the weather typing approach provides additional insights, in my opinion a fair portion of the additional insights derived in this study come also from the fact of analyzing the wave climate using a multivariate field and sea/swell partitions, which is not commonly done in previous similar studies. I suggest the authors state that, as not all the added value comes from the weather typing approach alone. In other words, some of the conclusions derived in this study could also be derived by just looking at the entire time series of events associated to each variable without dividing into weather patterns. The division of weather patterns surely provides additional information, but it is not the only key element.
It could be informative to add Figure 4 as obtained from the mean wave period for the sea/swell partitions. Looking at Tp only can still mask some wind/swell events if the wind sea (or swell) partition is consistently the most energetic for certain weather types. Similarly, it would also be informative to see the same type of figure for Hs, with and without sea/swell separation (perhaps in the SM).
Finally, considering that the authors analyze both waves and surges, it could be interesting to investigate the impact of climate indices to compound surge-wave events. I understand that a comprehensive analysis in this regard might be out of the scope of this study, but they could provide some preliminary results, such as the correlation between surge and waves associated to different weather types and climate indices. This could increase the added value of the paper, especially in the relevance of nowadays' compound analysis frameworks.