the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Oct 2023
Brief communication: Implications of outstanding solitons for the occurrence of rogue waves at two additional sites in the North Sea
Ralf Weisse
Sander Wahls
Abstract. We investigate rogue waves in buoy and radar measurement data from shallow depths in the southern North Sea. We analyse the role of solitons for the occurrence of rogue waves by computing discrete soliton spectra using the nonlinear Fourier transform for the Korteweg-de Vries equation with vanishing boundary conditions. In a previous study, data from a single measurement site were considered. The comparison of soliton spectra from time series with and without rogue waves suggested a connection between the shape of the soliton spectrum and the occurrence of rogue waves. In this study, results for two additional sites are reported.
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Ina Teutsch et al.
Status: final response (author comments only)
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RC1: 'Comment on nhess-2023-174', Anonymous Referee #1, 01 Nov 2023
The text presents the study which is identical to the previous full-length publication in this journal (Teutsch et al., 2023) but is based on another dataset: two more measuring points are considered. One point corresponds to buoy measurements (similar to the previous study); a radar device with higher frequency was measuring waves at the other. The authors report that the main conclusion of the previous work, that ‘outstanding solitons’ seem to correspond to situations of rogue waves, holds in application to the new data. The distributions of different cases (very large wave height, very large crest, etc.) in the new measuring sites are very similar between each other and compared to the previous work, though the measurements by radar seem to demonstrate some noticeable difference, which the authors relate to the higher acquisition frequency of the device. (By the way, the location AWG is characterized by significantly smaller depth. May be, this is the real clue for the observed difference with other locations?)
Honestly speaking, I do not see a reason why this communication should be published. There is no novelty in either approach or conclusion compared to the preceding paper. In the previous (quite recent) paper by Teutsch et al. (2023) the authors considered just one measuring site from a number of available ones. The wave data from those locations were analyzed by standard methods in another former publication in this journal (Teutsch et al., 2020). In Teutsch et al. (2023) the authors explained the choice of the particular location by the fact that it was “characterized by a higher frequency of rogue wave occurrences than expected”. No arguments presented, why the two new locations (but not others) deserve consideration. The abstract concludes that “In this study, results for two additional sites are reported.” Thus, the result of this work is just the fact that the work has been done. I cannot recommend publication of this communication.
Citation: https://doi.org/10.5194/nhess-2023-174-RC1 -
RC2: 'Comment on nhess-2023-174', Anonymous Referee #2, 12 Nov 2023
The main objective of the submitted manuscript is to confirm that a conclusion drawn from a previous study of the authors, i.e., Teutsch et al. (2023), is not site specific. The paper is well written and easy to understand.
The conclusion from Teutsch et al. (2023), states that a large outstanding soliton is more correlated with a time series in the presence of rogue wave events than that in the absence. According to the submitted manuscript, the so-called ‘outstanding soliton’ is related to the amplitude ratio of the second and first largest soliton within discrete soliton spectra of time series. When this ratio (i.e., the so-called A2/A1) is small compared to the unity, it will be more likely to occur in time series with a rogue wave. It will be certainly so if the amplitude of the second-largest soliton is larger or similar to the significant wave height of the time series. It is consistent with a typical definition of a rogue wave event: it is referred to as one where the ratio of the largest crest amplitude over the significant wave height is larger than a critical value, e.g., 1.25.
It is not straightforward to the reviewer why A2/A1 was chosen for defining an outstanding soliton but not A1/Hs? The reason is that the significant height is a more representative statistic parameter than A2 which does not have much to do with the statistical properties of waves. Imagine a particular case where both the largest and second-largest soliton within a time series can represent rogue wave events (e.g., an individual amplitude is larger than 1.25 times significant height) but their amplitudes are very close; evidently, A2/A1 will close to 1 which does not correspond to an outstanding soliton. How should we understand such a case compared with these with an outstanding soliton as both may indicate the occurrence of rogue waves?
The reviewer believes there are clarifications that can be made. Firstly, the physical meaning of the definition of the outstanding soliton from a stochastic point of view. If this physical meaning can be explained in a way that would be positively correlated with a rogue wave event, this manuscript will not be necessary as it won’t be site-specific. If not, it would be good to re-think why we need a concept which does not bear a clear physical meaning. Second, if we have already had a sufficiently long time series, why do we need solitons to relate them to rogue wave events? Because we can directly analyze rogue wave events.
Citation: https://doi.org/10.5194/nhess-2023-174-RC2
Ina Teutsch et al.
Ina Teutsch et al.
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