A Radar-Based Methodology for Aerosol Plume Identification and Characterisation on the South African Highveld

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. We appreciate your thoughtful comments and suggestions. Based on your feedback, as well as feedback from another reviewer, we have made several revisions to the manuscript. Please refer to the detailed point-by-point responses below for specific revisions and corrections. Should you have any further concerns or questions, please do not hesitate to let us know.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

The introduction has been improved to better articulate existing data gaps and include additional relevant references. Key challenges in current monitoring methods have been highlighted.

Are all the cited references relevant to the research?

Yes

The references list has been updated to include several recent works relevant to the study, strengthening the manuscript.

Is the research design appropriate?

Yes

The research design has been clarified and justified in the context of the study’s objectives, reinforcing its appropriateness.

Are the methods adequately described?

Yes

The methodology was noted as well defined by the reviewer. No changes were necessary, as it adequately addresses the study’s requirements.

Are the results clearly presented?

Yes

The results section has been restructured for clarity.

Are the conclusions supported by the results?

Yes

The conclusion has been revised to more closely align with the key findings and outcomes presented in the results section, emphasising the implications for air quality management.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The one missed opportunity I see is the lack of discussion on Doppler radial velocity observation associated with the smoke plumes. Based on the reflectivity plots, I believe there are some high radial velocity values and comparing transport speed with observed evolution would be quite interesting. I also believe there are likely some interesting 3-D velocity characteristics within the plumes that could provide additional insight. For this work, I will not require a full radial velocity component to be added, but I would like to see at least some mention of its potential use somewhere in the discussion.

Response 1: Thank you for the comment. We agree that Doppler radial velocity observations could provide valuable additional insights, particularly in assessing the transport speed and internal dynamics of the plumes. Although the current study focuses on reflectivity data, we have now included a brief mention of the potential applications of radial velocity data in the discussion section of the revised manuscript (lines 323–332). In this addition, we acknowledge the potential for future studies to integrate radial velocity measurements to better understand plume transport, evolution, and the three-dimensional velocity characteristics that could further complement the current methodology.

Comments 2: Figure 4: There is an opportunity to reduce white space and make the figures larger. Also, the yaxes on the vertical profile plots can be reduced to something like 20 and 5 km respectively.  

Response 2: Thank you for this suggestion. We agree with the comment and have made the necessary adjustments. Specifically, we increased the size of Figure 4 and reduced the white space for better clarity. Additionally, the y-axes on the vertical profile plots have been adjusted to 20 km and 4 km, as recommended. These changes can be found in the revised manuscript on page 7.

Comments 3: Figure 6: It is not clear what the overpass time for this image is. Also, are the plotted thermal anomalies valid at this me, or are aggregated over some time window. At least to me, it seems like the latter. Please be specific in the figure caption and surrounding text.

Response 3: We agree with the reviewer’s observation regarding the clarity of Figure 6. To address this, we have coloured the dots according to the acquisition time, and the corresponding times are now shown in the legend for improved clarity. Additionally, we have updated the figure caption to specify that the plotted thermal anomalies are not aggregated over a time window, ensuring that this distinction is clear to the reader.

These changes can be found in the revised manuscript on page 8. The updated caption for Figure 6 now reads: "MODIS Aqua true-colour corrected surface reflectance and VIIRS thermal anomalies for widespread plume events on the Highveld on 29 August 2014, which were outside the maximum detectable range of the radar. The thermal anomalies are coloured according to acquisition time, with the corresponding time indicated in the legend."

The suggested change was also made for Figure 5 to improve clarity. 

Thank you for your constructive feedback, which has helped enhance the clarity of this figure.

Comments 4: Figure 8: Again, I think there is an opportunity to remove white space and make panel b larger. The dots are hard to discern as well. 

Response 4: Thank you for pointing this out. We agree with the comment and have revised Figure 8 to address these issues. Specifically, we have removed the excess white space by resizing the layout, which allows more space for panel b. Additionally, we have increased the size of the dots representing the data points, making them easier to discern. These revisions ensure that the visual elements are clearer and more readable for the audience.

4. Response to Comments on the Quality of English Language

Point 1: The English language is fine. No issues detected.

Response 1:   Thank you for your positive feedback.

5. Additional clarifications

No additional clarifications.

Response to Reviewer 2 Comments

1. Introduction

Thank you for your detailed and thorough review of the manuscript. We have carefully considered your comments and have made substantial revisions to address the concerns raised, particularly regarding the contribution of the study to the body of knowledge.

We acknowledge that the original manuscript did not sufficiently articulate the objectives, which may have diluted the perceived contribution and significance of the research. Your feedback has been instrumental in refining the clarity and focus of the objectives, as well as improving the overall presentation of the results and conclusions.

Key revisions made include:

• Revised Objectives: The objectives are now clearly stated and linked to the research gap and the significance of using radar technology for aerosol plume monitoring.
• Results and Conclusion Refinement: We have reworked the results section to be more supportive of the objectives and included a stronger justification for the use of case studies. The conclusions have been revised to directly reflect the findings and reinforce the practical implications of the methodology for air quality management.

In addition, we were encouraged by Reviewer 1’s recognition of the potential contribution of the study, as stated:
"This study describes a methodology to modify severe weather tracking algorithms to diagnose the characteristics of wildfire smoke and debris plumes. I believe this is an excellent paper overall and am impressed by the work. In particular, the use of satellite data to classify radar returns as either clouds or smoke is novel."
This recognition from Reviewer 1 further motivated us to address the points you raised regarding the contribution of the research.

We provide a detailed point-by-point response below, with a focus on how the revisions have strengthened the study's contribution and clarity.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Must be improved

The introduction has been improved to better articulate existing data gaps and include additional relevant references. Key challenges in current monitoring methods have been highlighted.

Are all the cited references relevant to the research?

Must be improved

The references list has been updated to include several recent works relevant to the study, strengthening the manuscript.

Is the research design appropriate?

Must be improved

The research design has been clarified and justified in the context of the study’s objectives, reinforcing its appropriateness.

Are the methods adequately described?

Must be improved

The methodology was noted as well defined by the reviewer. No changes were necessary, as it adequately addresses the study’s requirements.

Are the results clearly presented?

Must be improved

The results section has been restructured for clarity.

Are the conclusions supported by the results?

Must be improved

The conclusion has been revised to more closely align with the key findings and outcomes presented in the results section, emphasising the implications for air quality management.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: I suggest the authors avoid using personal nouns such as we, our, etc.

Response 1: Thank you for your suggestion. We have revised the manuscript to remove personal pronouns such as "we" and "our" in accordance with your recommendation. The text has been adjusted to ensure a more formal and objective tone throughout.

Comments 2: In the abstract, I insist the authors to present some brief highlights of work which deal as the main results rather than presenting the entire portion as in general format.

Response 2: We have revised the abstract to focus on presenting brief highlights of the main results of the study rather than providing a general overview. The revised abstract now clearly outlines the key findings, including the results from validating the radar's ability to distinguish aerosol plumes from meteorological phenomena, the tracking of plumes spatially and temporally, and the utility of radar for assessing plume impacts on regional air quality. This focused approach enhances the clarity of the abstract.

Comments 3: The existing data gap and knowledge is not focussed in the introduction section.

Response 3: We agree with the reviewer’s suggestion that the existing data gap and knowledge should be more clearly focused in the introduction. We have revised the introduction to better emphasise this gap, specifically highlighting the limitations of current monitoring methods and the need for alternative approaches, such as the integration of radar technology for aerosol plume monitoring. Changes made:

• In the new introduction, we have clearly articulated the challenges of monitoring particulate matter (PM) concentrations due to their spatial and temporal variability, especially for transboundary and fugitive sources such as biomass burning aerosols (lines 27-37).
• We further stressed the limitations of satellite-based remote sensing methods, such as their inability to capture low-level sources and their limited temporal resolution due to satellite overpass times (lines 59-69). This supports the need for ground-based measurements, including radar, as an alternative method.
• We specifically introduced the idea that weather radar provides a powerful alternative for real-time aerosol plume monitoring, addressing the data gaps in both satellite and ground-based systems (lines 70-105). This section supports the motivation for the proposed radar-based methodology.

The revised introduction, particularly in paragraphs 2-6 (lines 27-105), directly addresses the knowledge gap by discussing both the limitations of existing methods and the potential for radar to fill these gaps.

Comments 4: The objectives are not very motivating. I recommend authors provide clear objectives for the authors' intent to conduct this work.

Response 4: We agree with the reviewer that the objectives in the original manuscript were not clearly stated. In the revised introduction, we have refined the objectives to make them more explicit and motivating by better articulating the need for this work, its scientific relevance, and the benefits of the proposed radar-based methodology for aerosol plume monitoring.

Changes made:

1. In the old introduction, the objectives were implicit, as we primarily discussed the limitations of current methods for monitoring air quality and aerosol plumes but did not clearly articulate how our work addresses these limitations.
2. In the new introduction, we now explicitly state that the aim of this study is to develop a radar-based methodology for identifying and characterising aerosol plumes from non-industrial sources, such as biomass burning. The objectives of the study are to (1) demonstrate the effectiveness of the methodology in detecting and discerning aerosol plumes from meteorological events, (2) evaluate the utility of the derived spatial and temporal characteristics, and (3) assess the practical application of the methodology for air quality management. This structured presentation can be found on page 1, lines 97-106.
3. We have introduced a clearer scientific motivation for the study, highlighting the potential of radar technology to provide real-time monitoring and improve understanding of the spatial and temporal dynamics of aerosol plumes. This understanding is particularly important for air quality management and policy development (lines 98-102).
4. Furthermore, we discuss the limitations of existing methods (satellite and ground-based systems), reinforcing the importance of our approach in addressing these gaps (lines 66-69, 79-81).
5. The revised results section validates the radar-based methodology developed to detect and characterise aerosol plumes from non-industrial sources, specifically biomass burning. The objectives of this analysis are to (1) demonstrate the effectiveness of the adapted TITAN algorithm in distinguishing aerosol plumes from meteorological storm echoes, (2) evaluate the utility of the derived spatial and temporal characteristics of aerosol plumes, and (3) compare radar-detected plume events with surface air quality data to evaluate the practical application of the methodology (lines 217-223).

These changes collectively provide a stronger rationale for conducting this research and clarify how the radar-based methodology can contribute to improving air quality assessments and management strategies.

Comments 5: Methodology is well defined.

Response 5: We appreciate the reviewer’s positive feedback regarding the methodology. No changes were necessary, as the methodology was already well defined in the original manuscript.

Comments 6: In figure 4, the discussion went based on the analysis conducted rather than scientifically. At several instance the discussion is not consistent with that observed.

Response 6: We appreciate this feedback. The discussion related to Figure 4 has been revised to ensure it is more scientifically rigorous and directly aligned with the observations made (lines 229 - 238). The revised text now focuses on the radar's ability to distinguish between aerosol plumes and meteorological phenomena and provides a more detailed analysis of the plume dynamics observed.

Comments 7: The entire results section went like a case study rather than with some specified objectives.

Response 7: We agree with the reviewer’s comment. The results section has been revised to include clearly defined objectives at the beginning, outlining the purpose of the analysis. This restructuring helps to clarify the intent of each result and moves the section away from a case study format, making it more focused on achieving the study's objectives.

Comments 8: I recommened the authors to rework in conducting supportive analysis from the observed datasets.

Response 8: We appreciate the reviewer's suggestion regarding the need for supportive analysis from the observed datasets. While we did not rework the analysis extensively in this revision, we have restructured the results section to clearly validate the radar-based methodology for detecting and characterising aerosol plumes.

The results presented primarily serve to demonstrate the use and effectiveness of the methodology, and an adapted TITAN algorithm, in distinguishing aerosol plumes from meteorological events, rather than providing a comprehensive assessment of all plume dynamics across the Highveld. We recognise that conducting a more thorough analysis of the datasets could further enrich our findings, and we intend to explore this in future research. Thank you for your valuable input, which will inform our ongoing efforts.

Comments 9: I feel still there is a lot of room in improving the results section and it is not supportive and not convincing with the results obtained to publish this work in good impact factor journals like in Atmosphere journal.

Response 9: We acknowledge the need for improvement in the results section and have significantly restructured it. The revised section now includes a clearer presentation of the objectives, improved analysis with supportive data, and a more comprehensive discussion of the findings. These revisions aim to provide a stronger, more convincing narrative aligned with the expectations of high-impact journals like Atmosphere.

Comments 10: The discussion should be happened separately at the end as a separate section considering the results and the results should be improved further.

Response 10: We agree with the reviewer's suggestion. The discussion has been moved to a separate section, and the results section has been improved to focus on presenting the findings more clearly and in alignment with the study's objectives. The discussion now synthesises these results, addressing the broader implications and aligning with the overall objectives of the research.

Comments 11: considering revising the concluding remarks based on the obtained results.

Response 11: The conclusion has been revised to align more closely with the key findings of the study. It now clearly reflects the outcomes presented in the results section, emphasising the successful validation of the radar-based methodology, the integration of radar and satellite data, and the implications for air quality management.

Comments 12: the references list should be updated with several recent works.

Response 12: The references list has been reviewed and updated to include several recent works relevant to our study. This includes key publications from the last few years that enhance the context and support our findings. We believe that these additions strengthen the manuscript and provide a more comprehensive overview of the current research landscape. The updated references can be found on pages 12-13 of the revised manuscript.

4. Response to Comments on the Quality of English Language

Point 1: Minor editing is required

Response 1:  We have carefully reviewed the text for clarity and coherence, implementing minor edits as needed.

5. Additional clarifications

Thank you once again for your feedback on the manuscript. In addition to the changes already implemented, we would like to offer some further clarifications and insights to ensure our work meets the expectations for publication.

Results section improvements: We appreciate your comments regarding the structure and scientific rigour of the results section. Based on your feedback, we have restructured the results to align more closely with the objectives of the study. Each key result is now explicitly tied to the overarching goal of validating the radar-based methodology for aerosol plume detection. This includes providing more detailed analysis on plume dynamics and improving the presentation of figures, such as Figures 4-8, to highlight the radar's performance. Additionally, we have separated the results and discussion into distinct sections, as per your suggestion, and expanded our supportive analysis of the observed datasets.

Clarifications in the Discussion section: We acknowledge that in some areas, the discussion previously lacked alignment with the observed results. We have revised this section to focus more on interpreting the results scientifically and ensuring that the conclusions drawn are consistent with the data presented. Key improvements include elaborating on how radar reflectivity values distinguish aerosol plumes from meteorological echoes and how radar-detected plumes correspond with satellite and AQMS data.

Improved case study presentation: We have addressed your concern that the results resembled a case study rather than presenting a more generalised methodology. In the revised manuscript, we emphasise that while specific events (e.g., the plume events of 2013 and 2016) are used to illustrate the methodology, the approach itself is adaptable to other regions and atmospheric conditions. We now provide a clearer explanation of how the methodology can be applied broadly, supporting its utility for air quality monitoring beyond the case study presented.

Enhanced conclusion and future directions: In response to your suggestion to revise the concluding remarks based on the obtained results, we have refined our conclusion to more directly reflect the findings of our study. The conclusion now better emphasises the significance of radar for real-time plume detection and its potential for air quality management. We have also added a more detailed discussion on future research directions, including refining radar algorithms and integrating multi-platform data, as well as exploring the application of this methodology in diverse geographic regions and for different types of aerosols.

We believe these revisions address the key concerns raised in your review, and we are confident that the improved clarity and structure will strengthen the manuscript's overall impact.