Factors Controlling a Synthetic Aperture Radar (SAR) Derived Root-Zone Soil Moisture Product over The Seward Peninsula of Alaska
Round 1
Reviewer 1 Report
The paper entitled “Factors Controlling a Synthetic Aperture Radar (SAR) Derived Root-Zone Soil Moisture Product over the Seward Peninsula of Alaska” investigated the effects of topography, vegetation, and some meteorological factors on soil moisture at 6, 12, and 20 cm derived from P-band AirMOSS SAR data collected over the Seward Peninsula of Alaska in 2017. The random forest method was employed to determine the importance of the investigated factors. This work is interesting since the P-band derived soil moisture product is less explored compared to other soil moisture data derived from L/C/X-band observations. The paper can be published after the following issues being addressed properly.
General comments:
It is good to see the authors used the rarely explored P-band SAR-derived soil moisture data for analysis. But it is recognized that it is very difficult to estimate soil moisture under frozen soil or snow-covered areas. Thus, the soil moisture values in regions with frozen soil and snow are commonly masked in the released soil moisture products (e.g., SMAP and ESA CCI soil moisture products, see SMAP and ESA CCI ATBD). The authors said the data were collected near the maximum thaw (08/17/2017) and partially frozen (10/10/2017) time periods, and it is not clear that how the soil moisture is estimated in 10/10/2017? What is the reported accuracy of this P-band derived soil moisture product at 6, 12 and 20 cm respectively? How did you validate the soil moisture product when the soil is frozen? Why the soil depths is determined at 6, 12 and 20 cm? It is better to add some descriptions or clarification concerning these issues to benefit the RS reader.
Specific comments:
Line 18-19: impact of ... on what? Clarify.
Line 24: “environmental factors” are too general, please to be specific.
Line 162: how did you determine the penetration depth here?
Fig. 2: what do Z1 and Z2 mean?
Line 262-263: since the topography is static, does it mean the derived solar radiation and winter wind are also static? These seem not consistent with the actual situation. Have you considered the impact of these uncertainties on your results?
Line 296: why did you select R2 rather other metrics such as RMSE?
Fig. 5: it is better to explain the feature variables in the caption.
Line 365: should be “Figure 5”?
Line 382 and elsewhere: add unit for VWC.
Line 434-436 and elsewhere: add unit for RMSE.
Line 439: “Figure 9” should be changed to “Figure 8”. Please check the number of all the figures and tables carefully.
Section 4: The topic concerning the possible drivers of soil moisture has already been investigated in recent years though may be not in the Alaska. What are the similarities and differences between these previous works and your work? What is the new findings in your study? Some discussion regarding this issue will strengthen the novelty of this paper.
Section 4.1: can you explain why elevation becomes the most important variable explaining the variance of soil moisture at 12 and 20 cm?
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In the paper entitled, "Factors Controlling a Synthetic Aperture Radar (SAR) Derived Root-Zone Soil Moisture Product over the Seward Peninsula of Alaska" the authors present a method for modeling root-zone soil moisture from SAR remote sensing. The author clearly states the topic. The overall design and approach are appropriate. The manuscript is well organized and presented. The validations and results of this study are not fully explored. I suggest the authors include more details and discussions in the manuscript. A minor revision is recommended before consideration for publication.
General comments:
Line 34, Surface air temperature? Please provide a definition.
Line 215, Please provide more discussion on what is DTM, and the differences from DEM.
Line 216, “qGIS” are you referring to QGIS? Why do you need both ArcGIS and QGIS for processing the DTM? Please explain more on the steps of using these softwares.
The study uses an 80-20 split for data modeling and validation. Have you considered using ground truth, or reference remote sensing data for validation purposes?
The R squares in the result indicate there is room for improvement, please discuss why the R square is relatively low, and what can be done in future research.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript assessed the role of variation factors on root-zone soil moisture by SAR, it is interesting and valuable for us to earth science, but some opinions following need to note:
Specific comments:
1. The keywords need revise, so as to avoid repeat with title, for instance, Synthetic Aperture Radar, soil moisture.
2. In P11L383, “respectively” should be added after soil depths.
3. In conclusion, the literature is not available appear again, and the L583-593, belongs to the research advance, is not available as part of conclusion, while are more putting in introduction section. In addition, limitation of the work and further issues should provide.
4. For research article, the references are too much; the redundant need to be deleted, it commonly will be better to maintain no more than fifty references.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have addressed my previous comments and the paper has been much improved than its first version.
There are only one minor comment:
Regarding the comment “can you explain why elevation becomes the most important variable explaining the variance of soil moisture at 12 and 20 cm”, please add some literature or evidence to support your statement “This could be due to a variety of factors including increased precipitation at high elevations, higher wind speeds leading to increased redistribution of snow, and the draining of water to lower elevations.”
Author Response
Point: Regarding the comment “can you explain why elevation becomes the most important variable explaining the variance of soil moisture at 12 and 20 cm”, please add some literature or evidence to support your statement “This could be due to a variety of factors including increased precipitation at high elevations, higher wind speeds leading to increased redistribution of snow, and the draining of water to lower elevations.”
Agreed! We have updated the text to include citations for each of these points, thank you.
