Extreme wind return periods from tropical cyclones  in Bangladesh: insights from a high-resolution convection-permitting numerical model

Steptoe, Hamish; Economou, Theodoros

doi:https://doi.org/10.5194/nhess-21-1313-2021

Articles | Volume 21, issue 4

https://doi.org/10.5194/nhess-21-1313-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/nhess-21-1313-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 4

Research article

|

29 Apr 2021

Research article |

| 29 Apr 2021

Extreme wind return periods from tropical cyclones in Bangladesh: insights from a high-resolution convection-permitting numerical model

Hamish Steptoe and Theodoros Economou

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Final revised paper (published on 29 Apr 2021)
Preprint (discussion started on 12 Oct 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review', Anonymous Referee #1, 05 Nov 2020
- AC1: 'Reply to RC1: ‘Review’ of nhess-2020-299', Hamish Steptoe, 18 Nov 2020
RC2: 'Review of manuscript', Anonymous Referee #2, 17 Nov 2020
- AC2: 'Reply to RC2: 'Review of manuscript' of nhess-2020-299', Hamish Steptoe, 20 Nov 2020

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (30 Nov 2020) by Animesh Gain

AR by Hamish Steptoe on behalf of the Authors (14 Dec 2020) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (31 Dec 2020) by Animesh Gain

RR by Anonymous Referee #1 (06 Jan 2021)

Suggestions for revision or reasons for rejection

General comments

I appreciate all of the work that has gone into addressing both reviewers’ comments and this has improved the manuscript. I reiterate my comments from the first review, in that the paper is well written and addresses an interesting scientific question with robust techniques.

Reviewer 2 expressed concerns about the fundamental aims of this work and the reply from the authors goes into detail to answer these questions. The authors have made modifications to highlight the limitations of the observational dataset in the manuscript, and clarify that ‘Interpretation is strongly conditioned by the loss function and the accuracy of the gust speed information, but our aim here is demonstrate a proof-of-concept transparent workflow that clearly translates hazards into actions’. I think that these are important additions to the manuscript.

Specific comments

I have a comment on the response and paper edits from Reviewer 2 comment 3 about wind speed discrepancy.

Manuscript extract:
“In general, median peak gust speeds from the RAL2 model ensemble are found to be 22 to 43 m s-1 faster compared to ERA5, but it is known that extreme gusts associated with vigorous convection in ERA5 are generally under-estimated, sometimes by a factor of two (Owens and Hewson, 2018).”

My two questions are:
1. Can you add another comment about the implication of this bias? Are you suggesting that the bias is only in ERA5 and the RAL2 winds are correct, or might they also have errors associated with them.
2. Can you comment on the difference between IBTrACS and RAL2? If they are more similar than RAL2 and ERA5, this would help to justify ERA5 errors in wind gusts. Originally the statement was that this 22-43 m/s error was in ERA5 and IBTrACS, but was this incorrect?

Line 82: Is the model called RA2 or RAL2?

Technical corrections:

Line 197: Missing ‘to’

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RR by Anonymous Referee #2 (31 Jan 2021)

ED: Reconsider after major revisions (further review by editor and referees) (03 Feb 2021) by Animesh Gain

AR by Hamish Steptoe on behalf of the Authors (10 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (25 Feb 2021) by Animesh Gain

RR by Anonymous Referee #1 (10 Mar 2021)

ED: Publish as is (28 Mar 2021) by Animesh Gain

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Short summary

We use high-resolution computer simulations of tropical cyclones to investigate extreme wind speeds over Bangladesh. We show that some northern provinces, up to 200 km inland, may experience conditions equal to or exceeding a very severe cyclonic storm event with a likelihood equal to coastal regions less than 50 km inland. We hope that these kilometre-scale hazard maps facilitate one part of the risk assessment chain to improve local ability to make effective risk management decisions.