Rapid amplification of Compound Drought and Heatwave risk over India: a regime shift from arid northwest to humid southern and eastern hotspots

Bhattacharjee, Debankana; Dhanya, Chandrika Thulaseedharan

doi:10.5194/nhess-26-791-2026

Articles | Volume 26, issue 2

https://doi.org/10.5194/nhess-26-791-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/nhess-26-791-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 26, issue 2

Research article

|

13 Feb 2026

Research article |

| 13 Feb 2026

Rapid amplification of Compound Drought and Heatwave risk over India: a regime shift from arid northwest to humid southern and eastern hotspots

Debankana Bhattacharjee and Chandrika Thulaseedharan Dhanya

Download

Final revised paper (published on 13 Feb 2026)
Supplement to the final revised paper
Preprint (discussion started on 22 Jul 2025)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-1886', Anonymous Referee #1, 11 Aug 2025

Recommendation: Major Revision

Major Comments:

(1) The manuscript does not adequately acknowledge the body of research already established in the field of Compound Drought and Heatwaves (CDHW).

Several references (e.g., Lines 62–64) are generic and not directly relevant to CDHW-specific studies.

A comprehensive literature review is necessary, focusing on relevant and recent works in this domain. The current citations should be replaced or supplemented with more pertinent references that align with the topic and claims of this paper.

Most of the references are vague and are cited from a general perspective.

(2) The introduction is poorly organized. The first paragraph discussing various compound extremes is unnecessary; the authors should start directly with droughts, heatwaves, and their compound occurrences.

The literature review is fragmented, and research gaps are not clearly identified.

The claimed novelty—that CDHW evolution at intramonthly scale is unexplored—is incorrect, as there are several studies in the past 8 years addressing CDHW at weekly, biweekly, and monthly scales

Line 131: The stated hypothesis has already been demonstrated in prior literature; thus, its inclusion as a hypothesis here is unjustified. The study’s objectives and genuinely new contributions remain unclear.

(4) Lines 175–178: The manuscript states that precipitation data covers 6,995 grids, while temperature data is available at 395 stations. How was the analysis conducted with such mismatched spatial coverage and resolution? This needs to be clearly explained.

(5) Lines 196–206: It is unclear whether the heatwave definition used is adopted from existing literature or proposed by the authors. If novel, a rationale and validation are needed.

The choice of the SNEPI drought index over widely used indices such as SPI, SPEI, or PDSI is not justified. The use of an uncommon index raises concerns about comparability and acceptance in the broader literature.

The CDHW definition and framework appear ambiguous and lack physical and temporal coherence. Drought evolves at weekly to monthly scales, while heatwaves occur at daily scales—this mismatch is not adequately addressed.

The “overlapping framework” used to define CDHW is mathematically unclear and appears impractical for scaling or deployment.

(6) Poor figure quality: The quality of the presented figures is poor. Fonts are too small, making them difficult to read. Figures must be revised for clarity, resolution, and readability.

General Comments:

(1) LINE 93: The authors should be consistent when writing the key term CDHW. its compound drought and heatwave, dont write hot-dry event. Both have different meaning and different definitions and occur at different time scales. This hot-dry spell wording is repeated many places.

(2) Line 77-83: most of the references presented are not pertinent to the compound drought and heatwave study. they are rather individual extremes such as either drought or heatwave or other extreme databases. The authors should pay attention to what they are citing.

Minor Comments:

(1) Remove the bracket (CDHW) from the title.

(2) Line 17: Is it precipitation "spell" variability? The spell of precipitation could be dry/wet. Did the authors

explored these various categorical spells?

(3) Line 27: The 5th highlight is not actually potent. It should be removed.

(4) Line 42: change from compound (CDHW) to only CDHW.

(5) LINE 147: menion the sqmiles area of India.

Citation: https://doi.org/10.5194/egusphere-2025-1886-RC1
- AC1: 'Reply on RC1', C.T. Dhanya, 19 Oct 2025
  
  We sincerely thank Reviewer 1 for their thoughtful and constructive feedback on our manuscript. We greatly appreciate the time and effort dedicated to reviewing our work and providing insightful comments and suggestions. Each comment has been carefully considered, and corresponding revisions have been made to enhance the clarity, rigor, and overall quality of the manuscript. The detailed response sheet is attached herewith for your kind perusal.
  Please note that the response sheet has been uploaded as a ZIP file containing the original Word document to ensure full preservation of figure quality and formatting.
  
  Citation: https://doi.org/10.5194/egusphere-2025-1886-AC1
RC2:
'Comment on egusphere-2025-1886', Anonymous Referee #2, 10 Sep 2025

Apologies for the delay in reviewing the manuscript. I have now read the manuscript; my initial assessment is that the findings are important, but I am concerned about the novelty of the work, and the authors need to perform more work to make the work suitable for this journal:
1. The first question I have is whether the co-occurrences of drought and heatwave are due to any specific co-founders, or is it because of general increases in both events, resulting in more co-occurrences. This is the fundamental question the authors need to address, and I request the authors to please consider this.
2. My second question is what are the joint impacts of the co-occurrences, can they evaluate the impacts to a specific sector from observed data? Can they use historical agricultural yield to show how the co-occurrence impacts?
3. The physics component is fully missing in this work, and that is my biggest concern. The physical explanation is needed. For example, do heatwaves impact SM and then lead to land-atmosphere feedback, and then rainfall, or does rainfall impact SM and then lead to heatwaves through feedback? These are questions that need to be addressed. Claiming them to be out of scope will not make the present study novel.
4. The writing is loosely done, for example, the last few lines of the abstract, where terms like "mitigation", "adaptation" are a bit randomly used. the authors have to be careful.

Citation: https://doi.org/10.5194/egusphere-2025-1886-RC2
- AC2: 'Reply on RC2', C.T. Dhanya, 19 Oct 2025
  
  We sincerely thank Reviewer 2 for their thoughtful and constructive feedback on our manuscript. We greatly appreciate the time and effort dedicated to reviewing our work and providing insightful comments and suggestions. Each comment has been carefully considered, and corresponding revisions have been made to enhance the clarity, rigor, and overall quality of the manuscript. The detailed response sheet is attached herewith for your kind perusal.
  Please note that the response sheet has been uploaded as a ZIP file containing the original Word document to ensure full preservation of figure quality and formatting.
  
  Citation: https://doi.org/10.5194/egusphere-2025-1886-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (13 Nov 2025) by Philip Ward

AR by C.T. Dhanya on behalf of the Authors (18 Nov 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (27 Nov 2025) by Philip Ward

RR by Anonymous Referee #2 (27 Nov 2025)

RR by Anonymous Referee #1 (16 Dec 2025)

ED: Reconsider after major revisions (further review by editor and referees) (18 Dec 2025) by Philip Ward

AR by C.T. Dhanya on behalf of the Authors (28 Dec 2025) Author's response Author's tracked changes Manuscript

ED: Reconsider after major revisions (further review by editor and referees) (04 Jan 2026) by Philip Ward

ED: Referee Nomination & Report Request started (05 Jan 2026) by Philip Ward

RR by Anonymous Referee #3 (05 Jan 2026)

RR by Anonymous Referee #1 (12 Jan 2026)

ED: Reconsider after major revisions (further review by editor and referees) (14 Jan 2026) by Philip Ward

Dear authors,

Thank you for the submission of your revised manuscript “Rapid Amplification of Compound Drought and Heatwave Risk over India: A Regime Shift from Arid Northwest to Humid Southern and Eastern Hotspots” to NHESS.

As you know, in total three reviewers have provided detailed reviews and comments over three different review rounds.

In the first round, two reviewers suggested major revisions. Based on these comments, you provided a revised manuscript.

In the second round, the same two reviewers assessed the paper. One of them felt that all comments had been addressed adequately. The other reviewer acknowledged large improvements and felt that some of their points had been addressed, but felt that there were still methodological issues that warranted further major revisions.

In the third round, the reviewer from the previous round assessed that their previous concerns had been meticulously addressed, and indicate that they also recommended to accept the paper. During this round, I also received a third review. As you can see, this reviewer suggested to reject the paper, for several reasons:
1. lack of rigorous statistical testing on the spatial maps
2. manuscript’s structure and length hinder clarity.

Based on these comments, I have also re-read the paper. In terms of the second comment, I found the manuscript to be well structured and of a length relevant to the findings, and therefore concur with the first two reviewer that the paper has an adequate quality on these grounds. With regards to the first comment, I would like to give you the opportunity to reply to this comment, and submit a revised version of the manuscript based on your reply.

Depending on the answer, I may take a decision based on my own review if I have enough knowledge and information to be able to make an informed decision. However, I reserve the right to request further reviews in case I deem this necessary, and as such I have selected “Reconsider after major revisions (further review by editor and referees)” in the system.

Best regards

Philip Ward

NHESS Editor
Professor of Global Water Risk Dynamics, VU University Amsterdam

Hide

AR by C.T. Dhanya on behalf of the Authors (18 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (21 Jan 2026) by Philip Ward

AR by C.T. Dhanya on behalf of the Authors (26 Jan 2026) Author's response Manuscript

Download

Article (10213 KB)
Full-text XML

Short summary

India has been increasingly facing simultaneous drought and heatwave events over the past six decades. Using a spell-sensitive index to capture variability in precipitation spells, the spread and intensification of the compound events is tracked toward historically safe humid regions. These events are becoming more frequent, severe, and harder to mitigate, even with short wet spells, highlighting the urgent need to rethink climate preparedness across both traditionally dry and wet regions.

Rapid amplification of Compound Drought and Heatwave risk over India: a regime shift from arid northwest to humid southern and eastern hotspots

Download

Interactive discussion

Peer review completion

Suggestions for revision or reasons for rejection

Suggestions for revision or reasons for rejection

Suggestions for revision or reasons for rejection