Utö Observatory for Analysing Atmospheric Ducting Events over Baltic Coastal and Marine Waters

Round 1

Reviewer 1 Report

The manuscript uses data collected by marine research facilities developed/available at Utö to observe and analyze ducting in the Baltic Sea.
The investigated period of four weeks is too short and the proposed empirical channel index, widely used in the study, will provide different
results depending on the radar frequency; this makes it difficult to generalize the results. However, for Baltic Sea area very few studies on
anomalous propagation have been published and this research helps to fill this gap. The following remarks may help improve the manuscript:

1) The phrase, lines 39-41, is somewhat unclear.

2) Page 7, lines 181-182 read: “It can be used beyond the normal radar horizon as a relative measure of ducting strength”; formula (7) could indicate duct appearance/presence rather than duct strength…

3) Page 9, lines 230-232: Under grazing angles the high sea waves would provoke shadowing of the microwave signal, not increase of the signal…

4) P. 14, lines 328-44: An attempt is made to determine the physical mechanisms responsible for the duct formation and the LLJ is chosen as a likely mechanism; the authors of "Surface atmospheric duct over Svalbard, Arctic, related to atmospheric and ocean conditions in winter", 2022, Doi: 10.1080/15230430.2022.2072052, found that surface ducts in this northern area are mainly due to temperature inversion and much less are due to a humidity gradient. Could you please comment on whether you have noticed such a dependency in your observations?

5) A very recent paper "Observations of anomalous propagation over waters near Sweden", 2023, DOI: 10.5194/amt-16-1789-2023, provides weather radars observation of ducts formation in a very close area to that in the manuscript. Could you comment/compare to this paper?

6) The Discussion Section repeats things already said in the text.

7) The abbreviations should be inserted in the text when they first appear.

8) The Appendix is interesting but it should be removed.

9) The Title needs refinement.

 

Author Response

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Reviewer 2 Report

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Reviewer 3 Report

In this paper, the weather conditions for the formation of evaporation ducts are studied by using the data of Utö observatory for four weeks. Three kinds of weather conditions are found: subsidence due to the prevailing high pressure system, horizontal advection of warm and dry air and/or LLJ related processes. And the authours think that the strong wind and low level jet have great influence on the evaporation duct. The data used in this paper is relatively new, but there also is a lot of improvement. It is suggested to return for major repair.

1.The title of the paper mentions a seasonally ice-covered archipelago, while the paper did not analyze the effect of ice sheet on evaporation ducts.

2.In the author profile, the author's email address is not accurate.

3.In the abstract, the observation conclusions/results are not given. It is suggested to be revised.

4.In line 28 - line 32, the authors propose that there are two types of atmosphere ducts, surface and elevated ducts. In fact, the atmosphere duct are generally divided into three categories: evaporation ducts, surface ducts and elevated ducts. Therefore, the author's classification needs modification. Moreover, the introduction does not clearly explain the relationship between the evaporation ducts and the other ducts, and what type of atmosphere duct is studied in this paper.

5.In line 56, "The latter" makes me confusing. Which one does it refer to?

6.The text in these figures is small, so it is suggested to increase font size.

7.In line 102, the sentence, “However, it is possible.....”, seems to having a grammatical problem.

8.The signal sum is mentioned in Figure 4, but the specific calculation method is not given in the paper.

9.In line 221, the author put forward that the wave height was significantly less than 1m from 12th of March to 26th of March. In fact, on 18th of March, the wave height was higher than 1m, which was not explained by the authors. And what is the effect of wave height on the formation or dissipation of atmosphere ducts?

10.In line 227, in the absence of the ducts, the wind speed varies by 8-12 m s−1. However, in the presence of the ducts, the wind speed also fluctuates within this range.

11.In line 286, "out of the 424 time steps", here, the time step is not defined in the previous passage.

12.In Figure 8, there seems to be a typo in "Note that that the values".

13.Is the assumption of 100 % humidity over the sea surface reasonable?

14.In line 296-line 297, does the difference in wind speed between upper and lower layers influence the formation of ducts? Is there any data or papers to prove it?

15.In line336-line340, Liang et al's paper is quoted in the paper. However, the ducts in the paper should be elevated ducts, whether it is reasonable to cite the point of view of the paper to demonstrate authours’ views?

16.Appendix A. Auxiliary observations at Utö have format problems.

• The language needs further polishing.

Author Response

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Round 2

Reviewer 1 Report

The article has been significantly improved.

Thanks to the authors for clarifications on the Appendix.

The article could be published as is.

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Reviewer 2 Report

Thanks for the revision as the previous comments. At the same time, these minor items need to be revised or explained.

(1) Line 284, 294,303, 308, 356, The M should be italic when it is a variable. Please carefully check!!!!

(2) The NAVSLaM (also known as NPS) code can be accessed in the reference I have given before.

Author Response

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Reviewer 3 Report

• We agree to publish it in its present form.

Minor editing of English language required

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