Ensemble hindcasting of wind and wave conditions with WRF and WAVEWATCH III<span style="position:relative; bottom:0.5em; " class="text">®</span> driven by ERA5

Osinski, Robert Daniel; Radtke, Hagen

doi:https://doi.org/10.5194/os-16-355-2020

Articles | Volume 16, issue 2

https://doi.org/10.5194/os-16-355-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/os-16-355-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 2

Research article

|

17 Mar 2020

Research article |

| 17 Mar 2020

Ensemble hindcasting of wind and wave conditions with WRF and WAVEWATCH III® driven by ERA5

Robert Daniel Osinski and Hagen Radtke

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Final revised paper (published on 17 Mar 2020)
Supplement to the final revised paper
Preprint (discussion started on 26 Jul 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Review comment for os-2019-76', Anonymous Referee #1, 23 Aug 2019
- AC1: 'Response to reviewer #1', Robert Osinski, 13 Sep 2019
RC2: 'Referee Comment', Anonymous Referee #2, 30 Aug 2019
- AC2: 'Response to reviewer #2', Robert Osinski, 13 Sep 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Robert Osinski on behalf of the Authors (30 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Nov 2019) by Judith Wolf

RR by Anonymous Referee #2 (26 Dec 2019)

Suggestions for revision or reasons for rejection

The manuscript has considerably improved. The revised version includes reflections to most of my comments to the first version as well as a number of valuable adjustments and amendments according to the recommendations of the other referee. There are still a few concerns and several mostly minor issues that need adjustment before the manuscript can be accepted.
It is said both in Abstract and Conclusions that the event addressed in the manuscript “provoked a severe storm surge in February 2002“. Please insert the relevant information (how high surge and where was observed) or just say it was a relatively strong storm event. For example, nothing specific happened in Latvian waters.
Modelled wave heights above 11 m in some ensemble members: I agree with the explanation of the authors that (i) some realisations of wind fields contained wind speeds of 28 m/s and such winds may drive very high waves in the Baltic Sea, (ii) the use of constant roughness length over the sea surface in the wave model could unrealistically contribute to the wave energy growth, and (iii) as a result, the spread of the ensemble may be fairly large (e.g., page 11, lines 20-23). However, point (ii) in plain English means that the used model setup most likely systematically overestimates wave heights in some storms, including the analysed event. I strongly recommend to say that explicitly both in the body text and in conclusions.
Lines 4-7 of Abstract are too unspecific. Consider saying, for example: “In this study, we apply an atmospheric downscaling to (i) add regional details to the wind field, (ii) increase the temporal resolution of the wind fields, (iii) provide a more detailed representation of transient events such as storms, and (iv) generate ensembles with perturbed atmospheric conditions which allow for a spatiotemporally variable uncertainty estimation.” Also please insert the explanation of WRF already in Abstract.
Minor comments
Consider saying “in the Baltic Sea” in the title
The style of using -isa/iza- etc. should be unified. For example, there is “realisations” on page 1, line 19 but “parameterizations” on page 2, line 17.
Page 3, line 25 and in several occasions below: as the length of a degree along latitudes and along longitudes differs by a factor of ~2 in the Baltic Sea region, please make sure to the readers that the grid cells in the used models have quite large aspect ratio, the length of their sides in N-S direction roughly twice as long as in the E-W directions. Also, consider using the degree sign instead of deg in the entire manuscript.
Page 3, line 29: probably should be “and interpolated”
Page 4, line 27: use Greek $\eta$
Page 5, line 11: must be “unrealistic”
Page 7, lines 13-15: the sentence is unclear, in particular the expression “why some directions”.
Page 7, lines 18-19: The LAF ensemble not only shows a very small spread. It is obviously underdispersive (and saying that “an indication that these ensembles could be underdispersive” is probably not sufficient). And this is by no means good from the viewpoint of forecast or hindcast.
Page 7, line 20: Here and in several occasions below (page 11, line 13; page 11, line 16; page 17, lines 4, 7, and possibly in some other locations) the use of the word “comparable” is not appropriate. It is possible to compare quantities that differ by tens and hundreds of times. Please be more specific and use, whenever applicable, quantitative comparisons.
Page 8, lines 14-15: I do not recognise the point of the sentence “Comparing a ten with a thirty member ensemble is not really a fair comparison.”
Page 8, line 15: delete “number”; ‘approach 6’ is enough
Page 9, line 1: delete “of all ensemble members”
Page 9, lines 3 and 4: delete “number”; ‘approach 6’ is enough
Page 9, line 9: replace “station” by “location”
Page 11, line 2: probably “variability in (wind and) wave properties” is meant
Page 11, line 4: probably “position of wave height maxima” or similar is meant
Page 11, line 8: “is in this region with” does not make sense to me; probably “represent” is meant
Page 12, line 1: remove “the fact”
Page 13, line 10: remove the second “apply”
Page 14, line 6: please give an extended formula for the expression (500//N); I guess that most of the potential readers do not associate it with math/combinatorics.
Page 14, line 13: should be “a higher”
Page 15, line 4: remove “’numerical”, replace “can be counted in seconds” by “is less than a minute” and say “few minutes” at the end of the line
Page 15, line 8: explain SST
Page 15, line 10: should be “an erroneous”
Page 16, last sentence to the caption of Fig. 10 could be simply “The northern part of the Gulf of Bothnia is covered by sea ice”
Page 16, line 4: better say “high resolution setup”
Page 16, line 5: better remove “what explains the higher but also the lower wave heights” and say: “Wave height maxima …”
Page 17, line 16: consider saying “than the one obtained using”
Page 18, line 4: consider saying “difference in wave heights between simulations using 5 and 60”

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ED: Publish subject to minor revisions (review by editor) (09 Jan 2020) by Judith Wolf

AR by Robert Osinski on behalf of the Authors (16 Jan 2020) Author's response Manuscript

ED: Publish as is (09 Feb 2020) by Judith Wolf

AR by Robert Osinski on behalf of the Authors (13 Feb 2020)

Short summary

The idea of this study is to quantify the uncertainty in hindcasts of severe storm events by applying a state-of-the-art ensemble generation technique. Other ensemble generation techniques are tested. The atmospheric WRF model is driven by the ERA5 reanalysis. A setup of the Wavewatch III^® wave model for the Baltic Sea is used with the wind fields produced with the WRF ensemble. The effect of different spatio-temporal resolutions of the wind fields on the significant wave height is investigated.