Deriving the Vertical Variations in the Diffuse Attenuation Coefficient of Photosynthetically Available Radiation in the North Pacific Ocean from Remote Sensing
Round 1
Reviewer 1 Report (Previous Reviewer 3)
The author has responded to my comments.
A minor suggestion: In validation of Aqua results, is the satellite data collected according to all the in-situ data listed in Table 1? The main matching criteria is suggested to be provided briefly with the supporting reference [38].
Author Response
Yes, the match-up satellite data were collected according to all in situ data listed in Table 1. A brief description on the matching criteria has been provided in the revised manuscript (Lines 365-368).
Reviewer 2 Report (New Reviewer)
Please see the attached file, thank you
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report (New Reviewer)
Thanks for your responses and clarifications.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The authors develop an empirical model to relate the remotely sensed PAR attenuation coefficient (MODIS KPAR), which is a depth averaged product, to the depth resolved KPAR. They have incorporated a large in-situ data set, and further test their model on a portion of the set with good results.
Overall this is a succinct, well presented, well written paper. There are a few small spelling/diction errors but nothing that impedes the reader. I cannot comment on the novelty of the research. I have no major concerns at this time, and the study should be of interest to the community.
Line 118: The method used to assess chlorophyll content here is flourometry. While this is a useful and expedient technique, it produces "relative" values of chlorophyll (and therefore biomass/carbon fixation) due to the phsyiology of different plankton groups, nutrient/health state, packaging effects, etc. That is as opposed to a more absolute value like that determined from HPLC. That is not to invalidate the authors data set, but they should note this as a source of uncertainty.
Line 55: argument should be augment
Figure 3: I would like to see profiles for more stations, perhaps as supplemental materials. Averages for certain subregions such as those presented in section 3.1 would be interesting.
The conclusions section is a bit sparse. One of the more significant things to come from this study (as shown in Figure 3) is the underestimation of euphotic zone depth using remotely sensed data, relative to the new model. What could be the significance of this to global/regional models of productivity, carbon export, etc.?
Reviewer 2 Report
The manuscript is based on a two-step algorithm to infer vertical variations in the diffuse attenuation coefficient of PAR specifically tuned for the North Pacific Ocean.
The article is well structured and the topic falls within the scope of the Journal. The introduction is very much focused on PAR decrease with depth, estimated from empirical equations, perhaps it might be helpful for readers to include a few sentences related to the general dynamics of PAR in the investigation area.
A short sentence describing the content of each section is missing at the end of the Introduction.
Some minor observations:
line 38: I suggest to use "on the water column" instead of "depth"
line 103: I suggest deleting the reference to Figure 1.
line 113: What formula do the authors use to calculate the MLD?
line 161: Reference to Figure 1 and Table 1 is redundant
Figure 3: indications (a) and (b) are missing from the two panels.
Figure 7 Caption: Changing 'corresponding' to 'associated'
Figure 9: postpone after the quote in the text., i.e. lines 365-366
line 352: change "verse vice" to "vice versa".
Reviewer 3 Report
This paper presents a method to estimate the Kpar at different depth from Rrs using in-situ data in North Pacific. It is useful in deriving the underwater PAR information in satellite remote sensing. Some specific comments are listed below.
1. The definition of Kpar^rs should be given in the main body. The average Kpar within one optical depth at which PAR is reduced to about 37% of its surface value?
2. The paper orgnization is suggested to be adjusted. The content of the research area in 3.1 and 3.2 is suggested to move to section 2 , and simplified reasonably, providing relavent background information.
3. The data in Apr.-May 2017 should use the same name throuthout the paper, Pac_2017, April-May 2017 cruise? The relavent refence indicating the data source of April-May 2017 cruise should be given.
4. In principle, the in-situ data processing and screening method in preparing the model construction&validation dataset should be the same. If there is difference, i.e. Line164-166 ' To reduce....were excluded', the reason should be given.
5. Section 2.3 is suggested to be combined with section 3.5 as a demostration of the model application in satallite data.
6. Does 'uncertainly' used in this paper mean the relative difference in percentage? It is suggested to replace uncertainly with a more specific definition.
7. The main point of this paper is the construction&validation of the Kpar^z using Rrs. Section 2.4 is suggested to be combined in this part. The regression information of (7a) and (7b) such as R2 should be given.
8. It is suggested to provide the site distribution of Table 1.
9. It is suggested to provide validation result of Aqua-derived Kpar and EZD to verify the real application performance.
10. The model is obtained using data in North Pacific. The presented result can not well support the conclusion of 'may be a good representative to the global oceans'.
Reviewer 4 Report
Dear authors,
The authors need to improve the scientific quality of the manuscript rather than purely algorithmic descriptions, and the authors need to be careful to understand that a small number of sites is not enough to describe the dynamic marine environment. In the current manuscript, there appears to be no potential readership to cite this result.
1. Introduction strongly suggests the need to reorganize. At present, only the estimation of vertical distributions is mentioned. The literature review is almost all about the calculation of optical parameters. However, there is little inkling on scientific issues, but it is clear that such parameters have been used by many scientists. To observe the marine environment, it is necessary to review where the parameters calculated in this manuscript can be used or what kind of marine environment monitoring results can be improved.
2. The detailed dates mentioned in Table 1 should be placed in the appendix.
3. Can the data inverted by only a few stations in Fig. 1 represent the optical characteristics of the entire North Pacific Ocean (Fig. 9)? Although the stations contain several important ocean current systems, the detailed features are still insufficient, especially for each Inshore locations and marginal seas at land-sea boundaries. Section 3.5 seems to be just a description and speculation of storytelling.
4. The conclusion seems to be written too positively. The author himself also used "may be". Obviously, the analysis of the global seas through the stations of several oceans is not enough, and even the North Pacific Ocean has not been analyzed yet. When the vertical movement of sea water in some sea areas is large, this algorithm will not be accurate.
