Articles | Volume 18, issue 18
https://doi.org/10.5194/amt-18-4839-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.A hybrid algorithm for ship clutter identification in pulse compression polarimetric radar observations
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- Final revised paper (published on 26 Sep 2025)
- Supplement to the final revised paper
- Preprint (discussion started on 13 Jan 2025)
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
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RC1: 'Comment on amt-2024-194', Anonymous Referee #1, 07 Apr 2025
- AC1: 'Reply on RC1', Shuai Zhang, 27 Apr 2025
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RC2: 'Comment on amt-2024-194', Anonymous Referee #2, 11 Apr 2025
- AC2: 'Reply on RC2', Shuai Zhang, 27 Apr 2025
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Shuai Zhang on behalf of the Authors (28 Apr 2025)
Author's response
Author's tracked changes
Manuscript
EF by Polina Shvedko (28 Apr 2025)
Supplement
ED: Referee Nomination & Report Request started (04 May 2025) by Gianfranco Vulpiani
RR by Anonymous Referee #1 (05 May 2025)

ED: Reconsider after major revisions (22 Jun 2025) by Gianfranco Vulpiani

AR by Shuai Zhang on behalf of the Authors (08 Jul 2025)
Author's response
Author's tracked changes
Manuscript
ED: Referee Nomination & Report Request started (09 Jul 2025) by Gianfranco Vulpiani
RR by Anonymous Referee #1 (09 Jul 2025)

ED: Publish subject to minor revisions (review by editor) (17 Jul 2025) by Gianfranco Vulpiani

AR by Shuai Zhang on behalf of the Authors (22 Jul 2025)
Author's response
Author's tracked changes
Manuscript
ED: Publish as is (22 Jul 2025) by Gianfranco Vulpiani
AR by Shuai Zhang on behalf of the Authors (23 Jul 2025)
General Comments
This manuscript presents a Hybrid Ship Clutter Identification (HSCI) algorithm aimed at improving data quality in pulse compression polarimetric radar observations. The problem is timely and operationally relevant, especially as solid-state transmitters and long-pulse waveforms become more common in weather radar networks.
The algorithm is structured in two stages: (1) machine-learning-based mainlobe detection using a random forest classifier, and (2) heuristic sidelobe identification based on empirical analysis of pulse compression and antenna patterns. The authors evaluate the method using C-band radar data from the Kumpula radar and show promising qualitative and statistical performance.
While the contribution is promising, several aspects require major clarification and strengthening before this work can be considered for publication in AMT. The current form lacks sufficient quantitative validation, generalizability testing, and clear discussion of algorithm limitations. These issues must be addressed to ensure scientific rigor and reproducibility.
Major Concerns
Lack of Rigorous Validation Metrics
The model evaluation focuses on overall accuracy and a small overlap percentage in histograms. However, these metrics are insufficient for a classification task with imbalanced classes (e.g., 400 vs. 2,500 gates in the test set). The manuscript should report precision, recall, and F1-score, especially for ship clutter, as false negatives can lead to significant data quality issues, and false positives can unnecessarily degrade precipitation data.
Limited Generalization and Dataset Diversity
The random forest model is trained and tested on data derived from the same radar (Kumpula), location (Gulf of Finland), waveform (LFM), and limited events. There is no evidence that the algorithm generalizes to other waveform types (e.g., NLFM), elevation angles, or environmental conditions (e.g., high sea clutter, near-shore echoes, different clutter types). The authors must either test the model on independent cases or clearly state the generalization limitations.
Overreliance on Manual Labeling
Both the ship clutter and precipitation echo datasets are manually labeled, and the methodology for doing so is not sufficiently described. This introduces potential biases. What criteria were used to define clutter? Were multiple annotators involved? Was any inter-annotator agreement measured? These questions should be addressed or acknowledged as limitations.
Sidelobe Suppression Logic May Be Overly Aggressive
The PSD definition and filtering logic—especially the combination of velocity and SNR thresholds—may lead to over-removal of precipitation echoes, particularly in overlap regions. While some case studies suggest selective filtering is achieved, the possibility of precipitation loss is real and must be quantified. For example, is there a statistical estimate of how many precipitation gates were removed in mixed scenes?
No Independent Test Dataset or Cross-validation
The authors should demonstrate model robustness through k-fold cross-validation or by holding out an entire day or event as an independent test case. Without this, it is difficult to assess whether the model is overfitting or merely capturing spatiotemporal autocorrelation patterns.
Lack of Code or Reproducibility Path
For a method combining machine learning and empirical filtering, reproducibility is essential. At a minimum, a flowchart covering the entire algorithmic sequence, and pseudocode or a link to a repository, should be provided. Currently, implementation details are scattered and would be difficult for others to reproduce.
Minor Comments
Typographic Fixes: