Risks of seasonal extreme rainfall events in Bangladesh under 1.5 and 2.0&thinsp;°C warmer worlds – how anthropogenic aerosols change the story

Rimi, Ruksana H.; Haustein, Karsten; Barbour, Emily J.; Sparrow, Sarah N.; Li, Sihan; Wallom, David C. H.; Allen, Myles R.

doi:https://doi.org/10.5194/hess-26-5737-2022

Articles | Volume 26, issue 22

https://doi.org/10.5194/hess-26-5737-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-26-5737-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 26, issue 22

Research article

|

15 Nov 2022

Research article |

| 15 Nov 2022

Risks of seasonal extreme rainfall events in Bangladesh under 1.5 and 2.0 °C warmer worlds – how anthropogenic aerosols change the story

Ruksana H. Rimi, Karsten Haustein, Emily J. Barbour, Sarah N. Sparrow, Sihan Li, David C. H. Wallom, and Myles R. Allen

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Final revised paper (published on 15 Nov 2022)
Supplement to the final revised paper
Preprint (discussion started on 10 Sep 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Referee comments', Anonymous Referee #1, 01 Dec 2018
- AC1: 'Author Reply to Reviewer 1', Ruksana Rimi, 02 Jul 2019
RC2: 'Review of "Rimi et al., 2018"', Anonymous Referee #2, 14 Dec 2018
- AC2: 'Author Reply to Reviewer 2', Ruksana Rimi, 02 Jul 2019
RC3: 'Review of “Risks of seasonal extreme rainfall events in Bangladesh under 1.5 and 2.0 degress’ warmer worlds – How anthropogenic aerosols change the story” by Rimi et al.', Anonymous Referee #3, 19 Dec 2018
- AC3: 'Author Reply to Reviewer 3', Ruksana Rimi, 02 Jul 2019
AC1: 'Author Reply to Reviewer 1', Ruksana Rimi, 02 Jul 2019
AC4: 'Author Response - potential edits to manuscript', Ruksana Rimi, 07 Jul 2019

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (15 Jul 2019) by Theresa Blume

AR by Ruksana Rimi on behalf of the Authors (26 Aug 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (25 Sep 2019) by Theresa Blume

RR by Anonymous Referee #3 (29 Sep 2019)

Suggestions for revision or reasons for rejection

In this revision, Rimi and co-authors have improved their manuscript and properly accounted for most of my previous comments. I think the presentation of the results is now clearer, and the paper is almost ready for publication. I only have a few minor remarks for the authors to consider when preparing the final version of the manuscript.

Just as a note: the page/line numbering in the response document is not consistent with the revised paper (at least in my pdf). For instance, the term “might partially” (page 37 in the response document) appears on page 10, line 9 in my pdf, instead of page 9 line 40 as indicated by the authors.

I appreciate the effort made by the authors to update the version of the APHRODITE dataset, which has a positive effect on the results, and to include an additional model intercomparison analysis. I just think that describing the results of the latter in the conclusions section is somewhat uncommon. You may consider moving this paragraph to the results section.

Two reviewers commented on the use of the term “linear”. The authors note that “By linear response, we meant steady and gradual increase…”. However, this is not the original meaning of this term, which, in my opinion, leads to confusion (a linear response is more than just steady and gradual). I’d suggest to replace “linear” with “monotonic”.

My comment on page 7, line 14 in the original manuscript referred to the text on Figs. 4/5 (not 2/3; “yet the relative change is smaller”, page 9, line 11 in the revised version). Maybe it would improve the readability if the relative changes were specified more explicitly (add a few numbers in the main text).

I’m still slightly confused by Fig. 2. Does panel a show NAT relative to ACT (as stated in the heading) or ACT relative to NAT (as stated in the caption)? In addition: Why do some of the patterns seem to differ between upper and lower row (e.g., panel a vs. e in the southern part)?

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RR by Anonymous Referee #2 (06 Nov 2019)

Suggestions for revision or reasons for rejection

I thank the authors for the revised version of the manuscript. The “Results and Discussion” section and the figure quality has substantially improved. However, the Introduction and “Data and Method” parts are not yet appropriate. Currently, I can not recommend publication.

Main Comment
============
* The text (mainly the Introduction and Data and Methods) really need to improve. There is a large number of mistakes and inconsistencies that can be corrected and improvements that can be made. Most of them are small but they add up. I ask all co-authors to work on the text such that it can reach publication-quality.

Major Comments
==============
* It would be very helpful to include a figure (or a table) summarising the global mean temperature and aerosol levels over South Asia for each experiment.
* The aerosol levels are “0” (NAT, GHG-ONLY), “1/3" (H1.5, H2.0), and “1” (ACT). Thus, in all comparisons between experiments (except ACT - CO2-ONLY) there is a change in global mean temperature and aerosols. This makes it very hard to disentangle (in my head) the contributions of global mean temperature and aerosols. One way around this (assuming additivity of the responses) would be to conduct a linear regression: (mean) rainfall as a function of global mean temperature and aerosol levels for each season and region. (I think this could be very insightful but I also understand if you deem it beyond the scope of the paper).
* Is my summary of your results correct?: “In general, higher global mean temperatures lead to higher rainfall and higher aerosols to lower rainfall, however, the relative importance of the two varies between the regions”? If so, it would be good to add such a sentence at the beginning of the results as it would help to understand the rest of the paper.
* I still don’t find the notion of a “linear response” fitting. Linear can be defined as “arranged in or extending along a straight or nearly straight line”. Given the change in aerosols you would not expect a linear response between the experiments (unless the aerosols do not play a role). I would say “monotonic” or maybe “gradual” would be more appropriate words here.
* You still mention results in the figure captions. Remove them.

Minor comments
==============
* Is there a reason the regions are called “sub-regions”? I’d recommend just calling them “regions”.
* P4 L37-L42: “representing the current decade” has a strange ring to it, as it basically is a pre-industrial simulation. Can you reformulate.
* In Figure 2 and Figure 3 (also Section 2.3) you compare e.g. “ACT to NAT” - I had more trouble than necessary figuring out which way round this actually is - it would be so much easier if you wrote this as “ACT - NAT”. (NOTE: in the supplementary you write this as “ACT relative to NAT”, i.e. the other way round).
* You can delete Table S1, all information is contained in the text (once you mention the one missing resolution).
* P11 L9-L22: This section belongs to the results.
* The boxes indicating the regions in Figure 2 e got lost.
* The abbreviation SA (in the figure captions) is not defined.
* P7 L29: I don’t think this is a confidence interval. I would call that “range”.
P7 L37: I am still not happy with this formulation: you do not know whether the bias is present in all scenarios - you assume so (and it is fine to assume this), but you do not know.
* Not all colors in the figure captions are correct.
* You mix red and green in the figures, which is not colorblind-friendly. Can you make one of them magenta?

Text
====
Note: I did not add any comments on the introduction
P3 L35: The -> Two
P3 L35: delete “that” and “include”
P3 L37: high resolution -> 0.5°
P3 L39: present -> 2016 (according to Table S1)
P3 L40: Basic facts...: Delete this sentence and Table S1.
P4 L2: “similar and comparable” -> “the same” (else the regridding would not really make sense?)
P4 L5: delete “The”
P4 L5: is able -> targets
P4 L7: 50 km is not high resolution for an RCM
P4 L8: region: delete
P4 L8: model of weather@home system -> model.
P4 L8: and is -> Both are
P4 L11: Recent -> The recent
P4 L11: v5a -> (v5a)
P4 L28-L34: This paragraph can be left out.
P4 L33: Please cite the Chapter of the IPCC by the name of the Coordinating Lead Author.
P5 L5: Really?
P5 L12: different two -> two different
P5 L12: delete “from pre-industrial” and “current” (also major comment above)
P5 L19: landslide -> landslides
P5 L19: eventually -> potentially
P5 L24: remove “during” and “season”
P5 L27-L28: We use sub-regions 1-4 located at -> We analyse four regions in Bangladesh, located in the ... of the country.
P5 L28: are the rainier part -> are located in the rainier part
P5 L29: remove “other”, “of” and “up to 100 years”.
P5 L30: periods are -> periods of up to 100 years are
P5 L30: these -> the
P5 L35-L39: This does not belong to the methods. Please delete.
P6 L1: remove “events”
P6 L5-L7: please reformulate these sentences
P6 L9: occuring. On the contrary, the rarest event is -> occuring, while
P6 L10: with -> has
P6 L12: delete “method”
P6 L40: Please mention the four climate models here.
P7 L1: pertubations however; -> pertubations. However,
P7 L32: regions. -> region.
P7 L33: remove “based”
P9 L9: forcing to another forcing scenario. -> forcing scenario to another.
P10 L31: remove “associated”
P10 L36: shows -> show
P10 L38: is that mm/day?
P11 L28: hike -> spike
P11 L31: Finding -> The findings
P11 L31: remove “relevant”

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ED: Publish subject to revisions (further review by editor and referees) (14 Nov 2019) by Theresa Blume

AR by Ruksana Rimi on behalf of the Authors (20 Jan 2022) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (25 Jan 2022) by Theresa Blume

RR by Anonymous Referee #2 (02 Feb 2022)

Suggestions for revision or reasons for rejection

I thank the authors for the third version of the manuscript and the open discussion of the reasons for the delay. I am looking forward to seeing the article published! I do unfortunately still have some minor comments on the text but hope they are straightforward to fix.

Minor comment
=============

* It’s unfortunate that you cannot include the table summarizing the global mean temperature and aerosol levels of the experiments but I can accept your explanation. However, I would encourage you to mention the aerosol levels for the 1.5°C and 2.0°C experiments if possible in the experiment description on page 4 (e.g. mention that they are about one third of the ones in ACT, or “between ACT and NAT”).
* You mention (P5 L6): “The ‘return time’ of an event, also referred to as the ‘return period’ is the likelihood of an event occurring during a given period of time.” -> The return time of a “1 in 10 year event” is “10 years” so the return time is the inverse of the likelihood.
* There are many mentions of something happening “at region X” - I think it’s “in region X” (but I am not a native speaker).
* Can I suggest you add % signs for ranges (5-95% -> 5%-95%) and the “E” and “N” all latitudes and longitudes.

Text
====
P1 L3: increase risk -> increase the risk
P2 L19: in the recent -> in recent
P2 L18: In June 2017, at southeastern parts of Bangladesh heavy rainfall caused devastating -> In June 2017, heavy rainfall in southeastern parts of Bangladesh caused devastating (I think)
P2 L27: flood floods -> floods
P2 L36: to global -> to a global
P2 L37: rainfall respectively -> rainfall, respectively
P2 L39: in the very -> in very
P2 L40: during monsoon season -> during the monsoon season
P2 L40: According to -> According to the
P2 L41: the north-eastern -> north-eastern
P3 L1: part or whole -> part or the whole of
P3 L2: RCM to -> RCM simulations to
P3 L8: to aerosols pollution -> to aerosol pollution
P3 L10: 1.5 -> 1.5°C
P3 L10: ‘Paris Agreement’ -> Paris Agreement
P3 L11: runs -> simulations
P3 L14: for a counterfactual -> for counterfactual
P3 L18: ‘Paris Agreement’ -> Paris Agreement
P5 L6: black -> red
P5 L20: Please ensure the $^-1$ is properly formatted for the final paper.
P5 L26: spanning for 30 days -> spanning 30 days (?)
P5 L36: additional four -> four additional (?)
P5 L39: at Supplementary -> in Supplementary
P5 L41: event -> events
P5 L2: In case -> In the case
P6 L11: under five -> under all five
P6 L11: Switch order of sentence and mention the obs products first?
P6 L13: for ACT -> for the ACT
P6 L17: sub-regions -> sub region
P6 L19: over Indian -> over the Indian
P7 L40: 1-2mm -> 1mm - 2 mm
P8 L12: over sea -> over the sea
P8 L30: as -> because
P8 L39: that noticeable -> that a noticeable
P8 L39: are -> is
P9 L5: 2,the -> 2, the
P9 L39: 1 and 2 shows -> 1 and 2 show
P10 L5: aerosols -> aerosol
P10 L12: point -> points

Figure 1. L5: APHRODITE (dark purple) -> APHRODITE (light purple)
Figure 2. L3: of the South Asia -> of South Asia
Figure 4: L5: y-scale range -> y-scale

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RR by Anonymous Referee #3 (24 Feb 2022)

ED: Publish subject to minor revisions (review by editor) (09 Mar 2022) by Theresa Blume

AR by Ruksana Rimi on behalf of the Authors (19 Apr 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (27 Apr 2022) by Theresa Blume

AR by Ruksana Rimi on behalf of the Authors (09 Sep 2022) Manuscript

Short summary

Extreme rainfall events are major concerns in Bangladesh. Heavy downpours can cause flash floods and damage nearly harvestable crops in pre-monsoon season. While in monsoon season, the impacts can range from widespread agricultural loss, huge property damage, to loss of lives and livelihoods. This paper assesses the role of anthropogenic climate change drivers in changing risks of extreme rainfall events during pre-monsoon and monsoon seasons at local sub-regional-scale within Bangladesh.