Statistical Analysis of the Spatiotemporal Distribution of Lower Atmospheric Ducts over the Seas Adjacent to China, Based on the ECMWF Reanalysis Dataset

Round 1

Reviewer 1 Report

Abstract should is very concise and should be written precisely highlighting the main results of the work provided with the conclusions.

Most of the sentences are written in present tense and however, i would recommend the authors to be written entire in past tense and use present tense wherever is required.

hence, suggesting for correction of English grammar usage throughout the paper.

the root cause or the problem with its definition is not identified properly and hence not proposed the mitigation measures for the control of ducts over the seas surrounding the china.

the significance of present work should be highlighted provided the background of research carried out in provincial, regional, national and global levels.

the objectives designed for the work are appreciable and however, i feel still there is a lot of scope for the improvement of objectives section.

the statistical data and methods presented are well given as such they are nicely helpful for the young researchers.

the figure 3 can be moved to supplementary material.

section 3 should results and discussion only

there are huge number of figures adn hence recommended to move some of figures which are of less importance in the context of title and work to the SM.

the discussions are elaborated keeping in view fo the results obtained which are well presented in all figures. however, there lacks consistency in writing part as compared to that found in figures. this shuld be corrected at several instances of writing part.

the discussion pertaining to the figures 5, 6, 7,9, and 10 should be precisely written avoding some unnecessary contradiction statements to overcome the statement of conflicts.

Author Response

We thank the reviewer for the careful examination of the manuscript and the valuable comments on the manuscript. We have modified our paper according to the reviewer’s comments and suggestions. All the modifications and changes are shown in the revised manuscript in red font. Our responses to the reviewer’s comments are listed below.

 

Response to Reviewer #1:

Abstract should be very concise and should be written precisely highlighting the main results of the work provided with the conclusions.

Reply:

We would like to thank you for giving us valuable and supportive suggestion. We have modified the Abstract to make it more concise in the revised manuscript (please see the Abstract in line 10 to line 22 in Page1) according to your helpful advice.

 

Most of the sentences are written in present tense and however, i would recommend the authors to be written entire in past tense and use present tense wherever is required.

Reply:

Thank you very much to point out the grammatical issues in our manuscript. We have checked and modified the sentences in full text according to your helpful advice.

 

The root cause or the problem with its definition is not identified properly and hence not proposed the mitigation measures for the control of ducts over the seas surrounding the china.

Reply:

Thank you for your valuable and supportive suggestions. The duct is formed as a result of temperature and humidity inversions. Three process that form temperature inversions are advection, radiation and subsidence. The most common and important

Case of advection is that of dry air above a warm land surface flowing out over a cold sea. Differences in daytime and night radiation are the causes of diurnal variation in refractivity. Clear skies and light surface winds at night result in consider able cooling of the earth, thus causing the information of temperature inversions. Subsidence is the slow settling of air from a high-pressure system. This process produces stable layers and inversions of temperature with an accompanying decrease in relative humidity. Since the air has come from a high level in the atmosphere, it is dry and may overlay a cooler, moist air mass. This type of inversion may cause the formation of an elevated super-refractive layer. [Turton and Bennets, Chapter 4, Page 132-135]

 

Atmospheric duct formation is closely related to meteorological parameters, which significantly affects radio wave propagation. At present, there are not the technology or methods to control atmospheric duct, but the negative impact of duct can be reduced through the duct prediction and detection technology. For example, atmospheric ducts can be predicted by predicting the parameters of meteorological conditions (temperature, humidity, pressure), which is helpful for the deployment and design of radar systems and communication systems.

 

Reference:

Turton J.D.; Bennets D. A.; Farmer S. F. G. An introduction to radio ducting. Meteorol Mag 1988, 117, 245–254.

 

The significance of present work should be highlighted provided the background of research carried out in provincial, regional, national and global levels.

Reply:

Thank you for your useful and supportive suggestions. Firstly, this work is conducive to the establishment of lower atmospheric ducts environment database in the adjacent seas around China, which provides a reference for the radio system design. Secondly, the duct parameters can be used as input for the microwave propagation model in this region. In addition, the synoptic conditions and formation mechanism of atmospheric duct are studied to provide scientific basis for analyzing, forecasting and utilizing atmospheric waveguides. We have added it in the manuscript. (please see the Abstract in Line 82- 89, Page 2).

 

The objectives designed for the work are appreciable and however, I feel still there is a lot of scope for the improvement of objectives section.

Reply:

Thank you for your valuable and helpful suggestions. The influence of atmospheric ducts on radio waves is closely related to the duct parameters. Our present works are analyzing the temporal-spatial distribution characteristics of lower atmospheric ducts in the seas adjacent to China, and studying the generation mechanisms of duct events.

The main objectives of our works are as follows: Firstly, the lower atmospheric duct parameters are counted to establish lower atmospheric duct environment database in the region, and provide reference for the design and deployment of radar and communication systems in this region. Secondly, study the synoptic conditions and formation mechanism of the atmospheric duct to provide scientific basis for analyzing, forecasting and utilizing the atmospheric ducts. Finally, it provides parameters input and reference for establishing microwave propagation model of the seas adjacent to China in our future works. (please see the Abstract in Line 82- 89, Page 2).

 

The statistical data and methods presented are well given as such they are nicely helpful for the young researchers.

Reply:

We would like to thank you for the positive evaluation on our study.

 

The figure 3 can be moved to supplementary material.

Reply:

Thank you for your valuable suggestion. We have moved the Figure 3 to supplementary material (please see supplementary material) according to your advice.

 

Section 3 should be result and discussion only.

Reply:

Thank you for your valuable suggestion. We have modified the Section 3 and moved some number of figures to the summery accordingly to your advice in the revised manuscript.

 

There are huge number of figures and hence recommended to move some of figures which are of less importance in the context of title and work to the SM.

Reply:

Thank you for your help suggestion. We have moved some number of figures to the summery and made some changes in the revised manuscript accordingly to your advice in the revised manuscript.

 

The discussions are elaborated keeping in view of the results obtained which are well presented in all figures. however, there lacks consistency in writing part as compared to that found in figures. this should be corrected at several instances of writing part.

Reply:

Thank you for your helpful and valuable suggestion. We are sorry that some statements are not clearly expressed. We have checked and modified the statements of several instances in the discussion.

 

The discussion pertaining to the figures 5, 6, 7,9, and 10 should be precisely written avoiding some unnecessary contradiction statements to overcome the statement of conflicts.

Reply:

Thank you for your useful and valuable suggestion. We have modified the statements and made they express precisely in the discussion about the Figure 5, 6, 7,9, 10 in the revised manuscript.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Many thanks, I am now happy to recommend publication.

Author Response

Response to Reviewer #2:

Many thanks, I am now happy to recommend publication.

Reply:

We thank you for the positive evaluation on our study. We hope that our manuscript can contribute to better understanding of the distribution and climatological formation mechanism of lower atmospheric ducts over the seas adjacent to China.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Response to Reviewer #3:

1. The title sounds very strange for the phrase “Investigation Statistical analysis.” Please consider a revision.

Reply:

Thank you for your suggestion. We have deleted the word of “Investigation” in the revised manuscript. (Please see the title in the manuscript, Page 1).

2. To help readers to understand the manuscript, more technical details should be provided. For example:
3. The authors should give the pressure levels of the original data and the total number of levels. Without the information, it is hard for me to understand Figure 2.

Reply:

We would like to thank you for giving us valuable and supportive suggestion. There are 14 pressure levels from 1000hPa to 600hPa used in our manuscript. They are 1000hPa,975hPa,950hPa,925hPa,900hPa,875hPa,850hPa,825hPa,800hPa,775hPa,750hPa,700hPa, 650hPa, 600hPa. We have added the information about the pressure levels in the revised manuscript according to your advice. (Please see Line 96-98, Page 3 in the manuscript).

1. What interpolation method is used? Although specific method is not important for the result, I still like to know the details.

Reply:

Thank you for your valuable suggestion. The interpolation method we used in our manuscript is cubic-spline interpolation. Consider an unknown function whose values are known only at points,where . interpolation involves the estimation of values of at points in the interval . The method is to construct a piecewise-cubic polynomial that interpolates the real-valued function at the points at which the values of are known. So, we construct on each interval , , as a cubic polynomial

Once we find the coefficients , we can evaluate for any point in . Our task before us, then, is to determine . The detailed method to find the coefficients can refer to

the reference of Dyer S A. And we have added the interpolation method in the revised manuscript according to your helpful suggestion. (Please see Line 145, Page 4 in the manuscript).

 

Reference:

[ Dyer S A, Dyer J S. Cubic-Spline Interpolation: Part 1[J]. IEEE Instrumentation and Measurement Magazine, 2001, 4(1):44-46]

 

3. I realized later that the authors describe the ERA5 in details in Section 2.2. I strongly suggest that the authors give the data description before the calculation of the duct (L122-149).

Reply:

We would like to thank you for giving us constructive and supportive suggestion. We have modified the manuscript that giving the ERA5 data description in Section 2.1 before the calculation of the duct in Section 2 according to your valuable suggestion. Besides, we also have made some changes in describing the ERA5 data in Section 2.1 in the revised manuscript. (Please see Line 94- 106, Page 2&3 in the manuscript).

 

4. Assuming that the authors described the ERA5 data before the M calculation (the contents between L122-149), clarification is still needed.
5. It seems that not all vertical layers are used. Then which layers are used?

Reply:

Thank you for your careful work and your valuable suggestion. The ERA5 data has a total of 37 vertical levels. Because the height of 14th layer from the ground is about 4.5km, so we just used the lower 14 vertical layers. (Please see Line 104-106, Page 3 in the manuscript).

 

1. L168-9 mentioned how to get altitude from pressure. At least for the used layers, the authors should give a table (if possible) for the corresponding pressure levels and altitudes.

Reply:

Thank you for your valuable advice. We have tried to make a table for the corresponding pressure levels and altitudes. However, since the altitude in a same pressure is different with different areas and time, we can't get a fixed altitude for each level of pressure. Therefore, we cannot provide a table for the corresponding pressure levels and altitudes. But, we have provided the pressure levels of the original data in the revised manuscript. (Please see Line 96-98, Page 3 in the manuscript).

3. Equation (4) should be with Item 3. Related to this, the authors should tell readers how many profiles are calculated and introduce the profile index i earlier.

Reply:

Thank you for your careful work and your valuable question. We have moved Equation (4) to Item 3 and given the number of the profiles are calculated in the revised manuscript according to your useful suggestion. However, Since the lowest pressure level in the ERA5 data is 1000hPa, the altitude of 1000hPa is different in different areas and time, which makes the profile index i not fixed. Therefore, we can’t give a define number of the profile index i. (Please see Line 153-154, Page 4 in the manuscript).

5. There are some inconsistences:
6. L159 and L168: The authors mentioned 137 and 37 layers, respectively. Is there a typo?

Reply:

Thank you for your careful work and your valuable suggestion. We have confirmed that there are no errors in the description. Hans Hersbach et al described the ERA5 global reanalysis data in their paper as follows: “ERA5 is the much higher temporal and spatial resolutions than those of previous global reanalysis. The hourly output, 31 km horizontal resolution and 137 levels spanning the surface of the Earth to 0.01hPa capture much finer details of atmospheric phenomena than in previous, lower-resolution, global reanalysis” [Hans Hersbach. et al. The ERA5 global reanalysis. Q.J.R Meteorological Society 2020, 146, 1999–2049.]

Overview of characteristics of ERA5 in Hans’ paper

The detailed information about the ERA5 hourly data on pressure levels can be found in the ERA5 Data Documentation Report (https://cds.climate.Copernicus.eu/).

In order not to cause confusion, we have modified the ERA5 data description. (Please see Line 94- 106, Page 2&3 in the manuscript).

1. L165 mentioned “below 5km” but the contents in Figure 2 is up to 3km only. I know the information above 3km may not important. However, the authors should say something about that.

Reply:

Thank you for your careful work and your precious suggestion. We have modified the altitude up to 5km in Figure 2 according to your useful advice in the revised manuscript.

In order not to cause confusion, we have modified the ERA5 data description. (Please see Figure 2, Line 175-176, Page 5 in the manuscript).

6. Figure 3 is not mentioned in the main text. Although it is an easy fix, mishandling such an easy issue makes me concern the quality of the work and the manuscript. The same applies to Figure 13.

Reply:

Thank you very much to point out the issues in our manuscript. We have corrected this mistake according to your comment. And we have moved the Figure 3 to supplementary material.

7. There are many grammatical issues, and I gave up to identify all of them after a while. I strongly suggest that authors carefully proofread the manuscript.

Reply:

Thank you very much to point out the grammatical issues in our manuscript. Thank you again for your hard work and your valuable suggestions. We have carefully proofread and corrected the grammatical issues in the revised manuscript.

8. It is better to give an estimate on the total number of vertical profiles, best before the details starting at Line 122 (mentioned in 4c above). I believe the authors include all grids in the given region (Figure 3), and for all hours in the covered period (unclear to me, or 1/2008 to 9/2020 according to the Abstract only). It is easy to estimate the total profile number based on the information above. I raised this issue because 1) I think the information will make the description complete; 2) it will help readers to understand the numbers in Figure 6.

Reply:

Thank you for your valuable question and precious suggestion. There are profiles calculated in total. We have added the total number of vertical profiles in the revised manuscript according to your helpful comment. (Please see Line 154, Page 4 in the manuscript).

9. Figure 7: Since the longitude coverage is more than 15 degrees, local time will be different for certain areas. I did not see any mentioning of the handling of the local time difference, and like to know the details.

Reply:

Thank you very much to point out the issue in our manuscript. We have added the handling of the local time difference in the revised manuscript according to your useful comment.

The formula for calculating local time is:

LT = UTC+

Where, LT is the local time, UTC is the Universal Time Coordinated. long is the longitude (deg) of M profiles, where the east longitude is positive and the west longitude is negative. (Please see Figure 2, Line 171-175, Page 5 in the manuscript).

10. L263-4: Please tell readers which height(s) is taken for the composite ducts, the top one or all of them?

Reply:

Thank you for your valuable question and helpful suggestion. The composite duct altitude is & in Figure 1d. We have modified it in the revised manuscript according to your useful advice. (Please see Figure 2, Line 262, Page 9 in the manuscript).

11. L319 (&312): The caption and the label in the figure are not consistent. Thickness or intensity?

Reply:

We are sorry for mistaking the duct intensity as the duct thickness in Figure 11 carelessly. Thank you for your careful work. We have corrected it in the revised manuscript according to your helpful advice. (Please see Figure 2, Line 318-320, Page 13 in the manuscript).

12. L363: The word “shows” is too strong here. Although the authors gave reasons for the spatio-temporal variation of ducting, all of them are plausible, and the authors did not put any efforts to really show the reason is the reason.

Reply:

Thank you for your helpful suggestion. We have changed the word “shows” to the word “indicates” in the revised manuscript according to your useful advice (Please see Figure 2, Line 369, Page 5 in the manuscript).

 

Minor Comments:
• I do not think it is necessary to capitalize “s” in word, “statistical,” in the title and keywords list.

Reply:

Thank you very much to point out the grammatical issue in our manuscript. We have corrected it in the manuscript according to your useful advice.

• L82: Please change “We” to “we.”

Reply:

Thank you very much to point out the grammatical issues in our manuscript. We have corrected it in the manuscript according to your useful advice.

• Equation (2): Please tell readers what are q, epsilon, and even p (if different from pressure, P).

Reply:

Thank you for your careful work and precious suggestion. We have corrected the Equation (2) and explained the parameter in Equation (2) according to your useful advice in the revised manuscript.

• L102: I am afraid that the sentence is grammatically incorrect. Please check it.

Reply:

Thank you for your careful work and precious suggestion. We have checked and modified the sentence in the revised manuscript according to your helpful advice.

• L115: The second part of the sentence (after “that”) sounds very strange. Please check it.

Reply:

Thank you to point out the grammatical issue in the manuscript. We have checked and modified it in the manuscript according to your useful advice.

• L125-6: The sentence sounds very strange. Please check it.

Reply:

Thank you to point out the grammatical issue in the manuscript. We have checked and modified it in the manuscript according to your useful advice.

• L157: Please add “of” after “is.”

Reply:

Thank you to point out the grammatical issue in the manuscript. We have added “of” after “is” in the manuscript according to your useful advice.

• L205-6: The sentence sounds very strange. Please check it.

Reply:

Thank you to point out the grammatical issue. We have checked and modified it in the manuscript according to your useful advice.

• L236: Please change “suspended” to “elevated.” Although the meaning is clear, I do not like to see the change of special terms without any warning.

Reply:

Thank you for your careful work and precious suggestion. We have checked and modified it in the revised manuscript according to your helpful advice.

• L296: I think it is “in Figure 1a&b” instead of “in Figure 1a” only.

Reply:

Thank you for your helpful suggestion. We have modified it in the revised manuscript according to your useful advice.

 

 

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I appreciate the authors for providing revised manuscript in which all the amendments are shown as per the recommendations or suggestions of reviewers. With this revised version of paper, the current format of  paper is encouraged and recommended for publication with my acceptance.

Author Response

We thank the reviewer for the careful examination of the manuscript and the valuable comments on the manuscript. We have checked and modified our manuscript according to your comments and suggestions. All the modifications and changes are shown in the revised manuscript in red font. Thank you very much, again.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Response to Reviewer #3:

Thank the authors for their efforts on the revision of the manuscript. I have problem to follow the line number information in the response related to the revised version. I am afraid that the authors used different version (instead of the current revised version) for line numbers.

We thank the reviewer for the careful examination of the manuscript and the valuable comments on the manuscript. With your help, our manuscript has been greatly improved. Thank you very much, again. All the modifications and changes are shown in the revised manuscript in red font.

 

Major Comments:

1. (old 4c, in last version of the comments): Thank you for the efforts in the revision. I am afraid that I did not make myself clear. Here, I am not asking for any change but just tell you the confusion I have when reading this part.
2. In my understanding, a profile is a whole curve along the vertical direction such as those displayed in Figure 2. In Equation (5), the index i is used for a vertical location. I do not think each vertical point (including three vertical points for calculating the derivative at the middle point) is a profile defined by the authors. This caused the confusion. To me, index i is for a horizontal point. One potential version is to use two indices, one for horizontal location (may be two indices for lat/lon), and the other for vertical position.

Reply:

Thank you for your hard work and helpful comment. We are sorry for our description is not accurate. The i in Equation (5) is the vertical point index of each profile instead of the profile index. We have modified our description to make it clearly in the revised manuscript. (Please see Line 154, Page 4 in the revised manuscript)  

1. I suppose that the authors do the M profile calculations for all 0.25oX0.25o grids in the selected area. If that is true, why do we need step 6 to put them into 1X1 grid. If not true, then what? (I am sorry for not clearly pointed out this. When I asked author to say how many profiles at beginning, I implied to say at each original grid, a profile is calculated although I am not sure if this was true).

Reply:

Thank you for your careful work and valuable question. We calculated the M profile in all  grids in the selected area. Firstly, we calculated the duct parameters of each M profile. And then, the duct parameters of each M profile were put into the corresponding  grid according to the latitude and longitude. Finally, we calculated the mean of duct parameters in each grid. We did this for two reasons. One is to ensure that there is enough data in each grid to reduce abnormal values. The other is that the duct changes significantly mainly in the vertical direction, but not much in the horizontal direction in short distance.

1. Related to above and old Major Comment 9: Thank authors to give the total profile numbers. What I was looking for is the something like xxx hours (or may be yearsX365X24) X grid numbers (may be Delta (lon)/0.25(?) X Delta(lat)/0.25). I do hope that I made myself clear. In other words, I do not like to see a total number, 6.8141 × 109 only. I also like to see the hints for the number. So that, readers can understand what the authors did without guessing.

Reply:

Thank you for your valuable and useful suggestion. We have modified the description of the number of M profiles we calculated in the revised manuscript to make readers understand clear according to your helpful advice. The total number of M profiles we calculated is. The number 4657 is days. We are sorry for the error in calculating the total number of M profiles previously. (Please see Line 154-155, Page 4 in the revised manuscript)

2. L182-3: I strongly suggest the authors to modify this sentence:
3. Literately, “occurrence” and “occurrence rate” are quite different concepts. Please use those terms carefully.
4. “observation events.” What events? I think an event is simply one observation (profile).

Reply:

Thank you very much for pointing out the problem in the sentence. We have modified the sentence to” The atmospheric duct occurrence rate is defined as the number of M profiles where duct occurred divided by the total number of M profiles in each grid.” Besides, we have checked “occurrence” and “occurrence rate” in full text and made some changes in the revised manuscript. (Please see Line 182-183, Page 6 in the revised manuscript)

3. L240-2: I may miss something but the two sentences give contradict description, March vs. July.

Reply:

We thank you for your valuable comment. The two sentences described in the manuscript are “The elevated ducts appeared most frequently in March” and “and the largest number of composite ducts occurred in July”. Elevated ducts and composite ducts are different duct types.

4. L390-4: Please tell your readers that you are talking about the monthly statistics here.

Reply:

Thank you for your helpful and valuable suggestion. We have modified the sentence to tell readers that we are talking about the monthly statistics in the revised manuscript. (Please see Line 390-391, Page16 in the revised manuscript)

 

5. L396: It is simply not true. You define winter as DJF (L170) and the values for January and February are much higher than those in October and November (Figure 5).

Reply:

Thank you for your serious work and valuable suggestion. The description in Line 395-397 is inaccuracy. We have checked and modified it to “In summer, composite ducts were more likely to appear, especially in July, while the number of composite ducting events was fewer from October to December.” (Please see Line 395-397, Page 16 in the revised manuscript)

Minor Comments:

• I suppose that the editorial office will edit the manuscript before publication. Therefore, I did not point out all apparent errors in the manuscript such as

o Cases: The “where clause” after an equation is part of the sentence unless the equation is ended with a period;

o Inconsistent citation style with multiple citations together, with comma or no comma between them;

o Space issue in many locations;

o Period after a short caption.

Reply:

Thank you for your careful work and useful suggestions. We have checked full text and tried our best to modify the errors according to your helpful advice in the revised manuscript.

• L142-3: Please revise the sentence.

Reply:

Thank you for your valuable suggestion. We have revised the sentence to ”And then, eliminating the profiles greater (less) than four standard deviations from the mean” in the modified manuscript. (Please see Line 142-143, Page 4)

• L163: Remove the “the” before “Figure.”

Reply:

Thank you for your serious work and helpful suggestion. We have modified it according to your advice in the revised manuscript. (Please see Line 164, Page 5)

• L179: Please clearly say 19:00 local time or UTC.

Reply:

Thank you for your useful suggestion. We have added “UTC” before “19:00” in the revised manuscript (Please see Line 179, Page 5)

• L211: Remove the dash sign, “-“.

Reply:

Thank you for your carefully work and useful suggestion. We have Removed the “-” in revised manuscript. (Please see Line 211, Page 7)

• L293: Figure 1d instead of 1a?

Reply:

We are sorry for the mistake. Thank you for your carful work. We have modified it in the revised manuscript. (Please see Line 293, Page 11)

• L341: Change “was” to “were.”

Reply:

Thank you to point out the grammatical issue in our manuscript. We have changed “was” to “were” according to your helpful advice in the revised manuscript. (Please see Line 341, Page 14)

 

 

 

Author Response File: Author Response.docx