Research on the Ionospheric Delay of Long-Range Short-Wave Propagation Based on a Regression Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General comment: This work presents simulations and regression analysis to identify the interrelationship of group delay time and phase advance time with frequency, critical frequency, and elevation angle in the shortwave band (3–30 MHz). In my opinion, this paper is worthy of prompt publication as it is focused on the shortwave band, and the analysis gives an important outcome of ionospheric delay dependency on elevation angle.

Authors need to incorporate/reply following queries;

Introduction:

Line 29: Ionization of O2, N2, NO and O in ionosphere is occurred due to X-ray, UV, Lyman α and EUV depending upon altitude and ionization potential. Statement should be reframed accordingly.

Line 47: What is order of maximum absolute ionospheric error? Need to mention here

Theory description:

What is author’s assumption to ignore influence of the geomagnetic field?  

Line 154: The dispersive nature of the ionosphere results in less attenuation for higher-frequency carrier waves, indicating that L1 (1575.42 MHz) is less affected than L2 (1227.60 MHz), and L2 is less affected than L5 (1176.45 MHz).

However, your statement is “As shown in Figure 1, the group time delay and percentage relative error increase with an increase in frequency for a fixed elevation angle (30⁰).” clarify this

Data Availability Statement: Author may provide (strongly encouraged) “ray tracing algorithm” as an appendix in supplementary material.  

Author Response

We would like to thank the reviewer for carefully reading our manuscript and providing constructive suggestions. Please see the attachment for detailed responses.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer comments on manuscript ID remotesensing-2835725, entitled:
"Research on the Ionospheric Delay of Long-Range Short Wave Based on the Regression Analysis"

General Comments

The manuscript addresses the study of variations of the ratio between the group delay time and phase advance time with reference to the study of L-band radio waves in the ionosphere.
The variations in this ratio are investigated with respect to the radio frequency, the critical frequency, and the ray elevation angle.
In my opinion there is a moderately interesting paper since it focuses only in find a numerical approximating function capable of describe the variations in the ratio.
The Abstract section will need some minor improvement in order to highlight the main findings of the research.  
The discussion and methodology is pretty well presented, but need some improvement because some equations relies on Chinese only papers which were not found.

The manuscript seems to be logically organized, but the English grammar needs improvement. Some grammatical errors were marked
in the annotated PDF enclosed.  Additionally, some graphs presented need to be improved for ensuring a better presentation.

Reference Section must be improved. Even the references are sufficient for this study, there are several errors and some of them, and others I was unable to check because they are in Chinese unreachable sources for me.

Particular Comments

Minor comments were marked in the annotated PDF enclosed.


Final Recommendation
I would recommend another round of revision to address the raised issues in order to have the manuscript in proper form to be published.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English language editing needs some improvement. There are some grammatical mistakes that have to be fixed. Some of them were marked in de annotated PDF enclosed.

Author Response

We would like to thank the reviewer for carefully reading our manuscript and providing constructive suggestions. Please see the attachment for detailed responses.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents a comparison between group delay and phase advance for HF radio propagation. The methodology and results appear sound, though some improvements are suggested.

If possible, the focus on the ratio of group delay and phase advance in this paper should be explained. How can this information be used and where (if anywhere) has it been studied previously?

For figures 10-12, data are treated as if they were generated in a process with stochastic noise. My understanding is that the ray tracing calculations were deterministic, though. The errors likely follow a trend with respect to the input variables. Where and why were the largest errors occurring?

For Table 1, please explain what is meant by mean squared error with respect to each of the variables? Does this represent error when each quantity is varied holding the other fixed?

L27: States that neutral components are part of the ionosphere. These are generally referred to as belonging to the thermosphere, which is overlapping but distinct from the ionosphere.

L64-65: Advantages and disadvantages of single vs dual frequency depend on application. The reference provided does not say that single-frequency is generally better.

L141-142: "and not affected by any horizontal gradient" is redundant and should be deleted.

L297: Should note that a different profile ionosphere is used.

Comments on the Quality of English Language

The quality of the English language writing in this draft is mostly good. The writing flows well and grammar is acceptable. There are some inappropriate word choices, though, which obscure or distort the meaning the authors presumably intended. Examples are included below.

L16: "for" should replace "versus"

L20: "relationship" should replace "relativity"

L50: "neglected" should replace "negligible"

L160: "expectation" should replace "cognition"

L217: "approximately" should replace "basically"

Also the following typo was found:

L151: "we" should not be captitalised.

Author Response

We would like to thank the reviewer for carefully reading our manuscript and providing constructive suggestions. Please see the attachment for detailed responses.

Author Response File: Author Response.pdf