Applications of Ground-Based Infrared Cameras for Remote Sensing of Volcanic Plumes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presents a recently developed IR camera and uses data collected to illustrate its application for volcano monitoring. The instrument is based on a small and cheap IR detector that has yet to be utilized in this type application. The authors use two volcanoes to demonstrate the functioning of the device, which includes a visible light camera to obtain additional information. The paper describes how calibration was performed and demonstrate that the effects of vignetting are minimal. Importantly, a radiative transfer model was developed and is used to estimate the emissivity of an eruption cloud. This is related to he opacity of the cloud, which is what shows most structural information. A method for estimating ascent rates is presented, with a comparison between three systems installed at Stromboli.

 

The paper has been well-written and presents an important instrumental development for volcano monitoring and research. The new system potentially will provide useful information on the development of explosion columns during eruptive phases. There are a few grammatical or typographical errors, which have been indicated in the attached document.

 

Comments:

 

It would be handy to present comparisons of the specifications of other available thermal cameras. The authors mention the “high” temporal resolution at 1 Hz, however, many cameras have the capability of much higher frequencies (e.g. 30 Hz). Yes, they are far more expensive but is it a significant drawback to have only a 1 Hz sample rate. This should be discussed.

 

For the demonstrated application, determination of ascent rate and plume height, it would be useful to have some further examples of where this type of measurement has been routinely carried out. The data presented is an example, just to show the usefulness of the camera, however, further examples would be useful, e.g. the following papers:

 

Rowell, C.R., Jellinek, A.M. and Gilchrist, J.T., 2023. Tracking Eruption Column Thermal Evolution and Source Unsteadiness in Ground-Based Thermal Imagery Using Spectral-Clustering. Geochemistry, Geophysics, Geosystems, 24(11): e2022GC010845.

 

Others have presented systems to monitor eruption columns using thermal and visual images and it would be appropriate to mention them, e.g.

 

Vásconez, F., Moussallam, Y., Harris, A.J.L., Latchimy, T., Kelfoun, K., Bontemps, M., Macías, C., Hidalgo, S., Córdova, J., Battaglia, J., Mejía, J., Arrais, S., Vélez, L. and Ramos, C., 2022. VIGIA: A Thermal and Visible Imagery System to Track Volcanic Explosions. Remote Sensing, 14(14): 3355.

 

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for the helpful comments.

 

Our revision addresses all of the comments by:

1. We have added a new section titled: “Ground-based infrared sensing of volcanoes” in which we describe other systems used in a similar way to ours.  We also refer to several more papers including all of those suggested by the reviewer.
2. We have listed three papers where ascent rate measurements have been made and provided their estimates (which are in general agreement with ours).
3. The minor comments on the m/s were also addressed.
4. All of the changes/additions are highlighted in red text on the revision.

Reviewer 2 Report

Comments and Suggestions for Authors

A Review of “Applications of ground-based infrared cameras for remote sensing of volcanic plumes”

Summary

This paper presents a new camera system, the IIRc, with the paper focused on the application of these data to the study of volcanic plumes. Overall, the paper is well written, easy to read, and structured well. The camera design, calibration, and radiative transfer are well described and follow similar regimes designed for other ground and orbital instruments.

My comments overall are minor for this paper – general comments are discussed below, and specific comments are listed in the annotated manuscript. This paper requires minor revisions before it is acceptable for publication.

General Comments

There is a lack of referencing in the paper, and it would benefit from additional articles, specifically describing the use of IR cameras in volcanology, as this would be useful to see the systems that are already utilized.

Secondly, I also feel that perhaps the article should be framed specifically to the application that is being presented. The results from the camera are interesting, specifically looking at the optical flow analyses, however, it would be good to have this information described in the introduction. Furthermore, there are many examples of other plume properties being detected from thermal camera systems (e.g., Sahetapy-Engel and Harris, 2009; Valade et al., 2014; Bombrun et al., 2018) and these should be acknowledged in the manuscript.

Line Comments

Please see the attached annotated .pdf file for specific line by line comments on this article.

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for the helpful comments.

These have all been addressed in the following way:

1. We agree it was remiss not to include more detail on prior work.  To mitigate this we have added a new section titled “Ground-based thermal infrared sensing of volcanoes” where we review prior work, include references (including all of those the reviewer has suggested) and provide details on what prior research has produced (and where it differs from our work).
2. Throughout we have included references to prior work, where we had missed doing this in our original submission.  There are 11 new references.
3. To address the second comment we have added a dot-point list of the main applications we are exploring with the camera and placed this in the Introduction (at the start of the paper).
4. All (9) of the minor comments on the m/s have been addressed including improving a Figure for legibility and correcting minor errors.
5. The changes we have made are highlighted in red text on our Revision