Round 1

Reviewer 1 Report

This paper presents a study for monitoring of floating Tonga-Fiji pumice rafts using satellite ocean color products. Various ocean color level 2 products were used for automatic detection of pumice rafts and discolored water areas. The results and methodology presented are interesting, however some description in method section require clarifications before publishing.

Specific comments:

L153 - L158. Figure 1.  It would be more interesting to display the spectra of different water types (pumice raft, discolored water, ocean water) in a single figure for better presenting their spectral behavior. The image of rhos_443 is not very relevant to the text. Idem for Figure 2 (L185 – L192).

L182. “Error! Reference source not found…”, check for citation errors.

L183 – L184. Specify bbp_giop at what band (center wavelength)?

L207. In Table 2, is the “Pumice Raft” class is identical to “consolidated pumice raft” in section 2.2.1?

L5 in update.pdf. Figure 3. “QC L2 flags”, what does QC mean?

L27 in update.pdf. “Chla>0.1”  instead of “>0.1”

L30 in update.pdf Figure 5. Pixel percentage of the discolored waters on 08 Aug 19 is 0, but the area is well presented in Figure 4, why?

L30 in update.pdf. Figure 5. Axis label is not plotted in English

Author Response

"Please see the attachment".

Author Response File: Author Response.docx

Reviewer 2 Report

This study focus on the illustration of ocean color change by retrieving data from MODIS-Aqua, OCLI-Sentinel-3, and VIIRS-Suomi NPP satellites sensors. The study tested the scope of the pumice raft area by using SST and ocean color thresholds. The result indicates volcanic pumice induced the increase of SST, and to some extent the mesotropic condition of water body by supplying phytoplankton-need but limited micro-nutrient iron to increase of chlorophyll concentration. At present, a few comments are being considered to improve the quality of the manuscript. 

1 The evidence is missing that the increased chlorophyll concentration could be as a result of cyclonic or anti-cyclonic eddies. Necessary references should be cited and sufficient reasonable discussion should be added. In addition, the mechanism impact of a cyclonic eddy or an anti-cyclonic eddy on phytoplankton is different, or even opposite. Thus please specify which one is being concerned to impact the increased chlorophyll concentration here.

2 In line 134, the rho seems to be one of those key parameters in succeeding text, but the current interpretation of this physical parameter is insufficient. Besides citing references, it is suggested to state or even reiterate the physical definition, the scope of the usage of this parameter, and how it was calculated in MODIS algorithm. 

3 With regards to the fourth row of Figure 3, would it be better to use SST threshold instead of the SST value to illustrate the pumice area? It is because the SST threshold method was proposed in the methodology section. 

4 For Figure 4, (1)please divide it into two separate panels, i.e. one is for pumice raft, the other is for discolored water, for a much better clarity. (2) please select a gradually changed color map (e.g. gradual red, or rainbow, etc...) to better reflect the daily change. 

Author Response

Please see the attachment.

Reviewer 3 Report

Summary: In this paper the authors focus on detection of the pumice rafts by optical satellite instruments with moderate spatial resolution (MODIS, VIIRS, and OLCI). They analyze pumice rafts during one month from their formation in the beginning of August 2019 till the moment they reached Fiji in the beginning of September. The authors determine procedures to detect pumice rafts and “discolored waters” which accompanied pumice rafts using SST and satellite reflectance data. Also the authors analyzed influence of pumice rafts on satellite Chl-a concentrations in the surrounding waters.

The topic addressed in this manuscript is of certain scientific and practical interest, the results are well supported by analysis of satellite data. Therefore, I think that his article is worth to be published in Remote Sensing.

Minor comments:

Please check indication of month in Figure 5.

Author Response

Response to Reviewer 3 Comments

Point 1: Please check indication of month in Figure 5 (now Figure 6).

Response 1: Thank you for your comment. The month is now displayed in English with the caption in Figure 5 further stating, “Pixel percentage of the observed area for the dates studied in the month of August 2019 ………….” (L358-L359).

Author Response File: Author Response.docx