A global high-resolution dataset of snowmelt runoff onset timing from Sentinel-1 SAR, 2015–2024

Gagliano, Eric; Shean, David; Henderson, Scott

doi:10.5194/essd-18-5871-2026

Articles | Volume 18, issue 8

https://doi.org/10.5194/essd-18-5871-2026

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

https://doi.org/10.5194/essd-18-5871-2026

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

Articles | Volume 18, issue 8

Data description article

| Highlight paper

|

14 Aug 2026

Data description article | Highlight paper |

| 14 Aug 2026

A global high-resolution dataset of snowmelt runoff onset timing from Sentinel-1 SAR, 2015–2024

Eric Gagliano, David Shean, and Scott Henderson

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Final revised paper (published on 14 Aug 2026)
Preprint (discussion started on 28 Apr 2026)

Interactive discussion

Status: closed

RC1: 'Comment on essd-2026-216', Anonymous Referee #1, 01 Jun 2026

Please refer to the attached file.

Citation: https://doi.org/10.5194/essd-2026-216-RC1
CC1: 'Comment on essd-2026-216', Sara Darychuk, 11 Jun 2026

The authors provide an interesting and important contribution through the development of a global snowmelt runoff onset dataset from Sentinel-1 observations. Readers may also be interested in Darychuk et al. (2025), which explored the use of MODIS observations to improve Sentinel-1 snowmelt onset estimates in British Columbia. In this study, optical timing constraints reduced snowmelt onset estimation errors by more than 50% in some years relative to unconstrained approaches, providing additional evidence for the utility of optical observations in SAR-based snowmelt timing workflows.
https://doi.org/10.1016/j.rse.2025.114863

Citation: https://doi.org/10.5194/essd-2026-216-CC1
RC2: 'Comment on essd-2026-216', Anonymous Referee #2, 13 Jun 2026

Gagliano et al. provide the global snowmelt onset timing dataset for the 10-year period spanning 2015-2024. which is first of its kind. The authors created the dataset by using time series of Sentinel-1 C-band SAR images, with detection constrained by a custom MODIS-derived snow phenology dataset. The generated dataset is validated using in situ snow pillow estimates of runoff onset from 735 automated weather stations in the Western United States. I am highly impressed by the depth and quality of discussion and explanation provided in this study. Overall, the manuscript provides a thorough and well-structured analysis supported by excellent figures and datasets. However, authors can include some of the minor comments.
The introduction is nicely written and provides a good background, but it is somewhat lengthy and could be shortened to improve readability and focus.
Line 95-100: The criteria for selection of just VV scenes for this study are just based on literature or have the authors also explored the applicability of VV and VH images?
Figure 1: The resolution of Sentinel-1 SAR time series, MODIS snow cover and forest cover fraction are different. How authors have merged these in the overall methodology to generate the outputs is not very clear in the manuscript. It would be more helpful for readers to have the information.
Line 225: “To aid in the interpretation of the annual snowmelt runoff onset products, we created three additional composite products for pixels with at least three years of valid annual data.” This statement is not clear. Most of the statements in the entire manuscript are written like this. I would prefer “We created three additional composite products for pixels with at least three years of valid annual data to aid the interpretation of the annual snowmelt runoff onset products.”

Citation: https://doi.org/10.5194/essd-2026-216-RC2
AC1: 'Author response to RC1, RC2, and CC1', Eric Gagliano, 13 Jul 2026

Dear Editor, Referees, and Community Commenter,
We thank both anonymous referees and the community commenter for their careful and constructive engagement with our manuscript. Their feedback prompted substantial improvements, including an expansion of our evaluation network, an independent test of the transferability of our empirically-derived quality thresholds, clearer framing of the physical interpretation of our runoff onset estimates, and stronger justifications for methodological choices.
Please find attached a PDF containing point-by-point responses to all comments (RC1, RC2, and CC1).
Thank you for your time, and we look forward to any further feedback.
Sincerely,
Eric Gagliano, on behalf of all authors

Citation: https://doi.org/10.5194/essd-2026-216-AC1

Peer review completion

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

AR by Eric Gagliano on behalf of the Authors (14 Jul 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (16 Jul 2026) by Alexander Fraser

RR by Anonymous Referee #1 (31 Jul 2026)

Suggestions for revision or reasons for rejection

General Assessment
The authors have provided an exemplary response to the review process. They addressed all major and minor concerns with remarkable thoroughness, transparency, and scientific rigor. The revised manuscript is substantially stronger than the original, and the additional analyses, particularly the expansion of the validation network and the independent testing of threshold transferability, have significantly increased my confidence in the dataset's robustness and global relevance.
I commend the authors for their willingness to engage critically with the conceptual and methodological challenges raised, and for revising both the framing and the presentation to better reflect the empirical nature of their product. The manuscript now presents a clearer, more cautious, and more useful description of a valuable global dataset.

Remaining Comments:
1. Acknowledge validation imbalance across snow classes more explicitly
The expanded network covers all Sturm-Liston snow classes, but the station level validation is still heavily weighted toward Montane Forest environments, with fewer stations in Tundra and Prairie classes. Although the pixel wise analysis suggests the derived relationships hold across classes, I recommend adding a single sentence in Section 5.3 or 5.4 to state this explicitly.
2. Provide clearer user guidance on interpreting the quality information
The authors have done well to distinguish the MAD composite (interannual variability) from retrieval uncertainty. However, the practical guidance in Section 5.4, while useful, still requires users to have independent SWE data, which may not be available to all. More importantly, there is a risk that users will misinterpret the binned MAD values in Fig. 4 as per pixel error bars. I suggest adding a brief, explicit statement in the Data Usage Guidance section or in the Data Availability statement.

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ED: Publish subject to technical corrections (31 Jul 2026) by Alexander Fraser

AR by Eric Gagliano on behalf of the Authors (07 Aug 2026) Manuscript

Editorial statement

This paper presents a global, high-resolution dataset of snowmelt runoff onset spanning a decade of Sentinel-1 observations. Its combination of global coverage, fine spatial resolution, comprehensive documentation, and broad applicability makes it a valuable resource for hydrology, cryosphere research, and water resource management.