Seasonal Variation in Land and Sea Surface Backscatter Coefficients at High Frequencies
Round 1
Reviewer 1 Report
I recommend this paper for publication as is. It is well written, clear, and relevant to the Remote Sensing Journal. I found no errors. The paper reports results of a study where modeled OTH radar backscatter soundings are compared to long-term measurements of the same to infer changes in the scattering coefficient of the earth’s surface. The weakness in the methodology is that the modeled ionosphere and HF skywave propagation are imperfect, so that the inferred earth-surface scattering coefficient estimates are imperfect. The authors acknowledge this, especially for the longer ranges from the radar. However, the long-duration database and multiple radar analysis still provides convincing evidence of the authors’ conclusions that seasonal variations are observed from ocean backscatter, but that terrain backscatter remains fairly constant with season. This paper is the third in what could be considered a series by these authors on the use of JORN soundings as a remote sensing capability to infer backscatter scattering coefficients and nicely caps off their previous work. The opportunity to see long-term statistical behaviors using this JORN database is a definite boon for the OTHR research community.
Not required for the publication of this paper, but as something for the authors to consider for this or future publications, would be to include some evidence of the accuracy of their ionospheric models, especially as a function of range from the radar. I would suggest a comparison of synthetic and measured ionograms and some statistical measure of the models’ ability to match the measurements.
Reviewer 2 Report
I recommend to include a short description how "group range" is defined. This is very special for the sky wave application and not widely used in the radar community.
At the beginning of chapter 2.2 a few more words about the "surface backscatter coefficients" would be helpful for the reader.
Reviewer 3 Report
Dear Authors,
I've found your work very interesting. I do not have any remark about your paper. Best Regards,
