On the Spectral and Polarimetric Signatures of a Bright Scatterer before and after Hardware Replacement
Round 1
Reviewer 1 Report
General remarks
This technical note on the effects of a hardware change from a weather radar is well prepared and contains sufficient information on the technical aspects of the radar. In general, the manuscript is longish and contains several repetitions. It could be shortened considerable. It also contains parts (e.g. lines 231 - 261) which can be found in every text book about meteorological radars and do not needed to be repeated here.
My personal feeling is that the author should wait with the submission of the paper until they found (together with the manufacturer) the reason for the discrepancy. Currently it has the subliminal feeling of blaming the manufacturer not finding a solution after more than 1 year of trouble-shooting, or ignoring your findings.
Nevertheless, the manuscript deserves publication as a technical note after some minor modifications.
Specific remarks
Line52: a detailed study with a polarimetric radar was also performed by Friedrich, Germann, Tabary JTECH 2009(2)
Line 90: … obviously HAS a huge …
Line 153: is the tower in the center of the 1° sampling interval, or is it seen in more than one sampling interval?
Line 177: what is the resolution of DN in terms of radial speed? It is in [18] but would help to understand the considerations
Line 200: how important is the rotation speed on rhoHV for the tower? For each pulse you see a different section of the scene with probably different properties in H and V polarization.
Line 231 to 265: this is text book content.
Following the review of Smith JTECH 2010(3) lower case z should be used for the reflectivity FACTOR (!) if used in linear mm^6/m^3 units and upper-case Z for logarithmic reflectivity factor. The unit should be dBz, not dBZ.
Line 272: section 2.3.2
Line 282: surplus text “3. Results”
Line 416: missing “was installed” after (LNAs)
Lines 421 to 427: what is the idea behind this point of view? Do you expect temporal variations in the impedance (Line 420)? Maybe caused by temperature fluctuations in the calibration unit?
Line 473: Is there any chance to see some relevant signatures in the days before and after the exchange in summer 2019. A drop of 6 to 9 dB should be obvious, even when the weather is not favorable for detailed studies as outlined in the manuscript.
Line 476: extra “is”
Lines 495 to 503: I can not follow the argumentation about depolarization ratio (DR). Can we assume that the depolarization of H (or V) waves by the tower has not changed at all between January 2019 and 2020? And, obviously nothing else than the calibration unit was exchanged at the radar. The method proposed by Matrosov describes how to estimate DR for a radar operating in STAR mode. If, for any reason, the observed rhoHV and zH or zV have changed by other errors, then of course DR will be different. But, I do not see not how this can help in identifying the cause for the discrepancy between the measurements in 2019 and 2020.
Line 501: … as LARGE as -12.7 dB …
Author Response
Please see the file in attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper is very much radar hardware oriented and I'm not sure if this is
suitable for publication in MDPI Remote Sensing. It sounds more like a 'Report to the manufacturer', and does not seem to contain much 'science'. However, if it is found suitable, then the following comments need to be considered:
- Mention C-band in the abstract
- Line 82 .. in detail
- Line 184 ... copolar correlation coefficient is often denoted as
rho_hv (where hv is subscript and not superscript). The same applies to rho_co - Line 220: Psi subscipt 0
- Line 229: psi subscript
- Line 248: Power
- line 252: so-called
- line 276: Zh and Zv were as large as 81.49 and 80.27 dBZ. Very large indeed! Is this expected?
- line 287: we expect a random scattering pattern that is characterized by rapid short-term fluctuations - would help to specify the cause of the fluctuations
- line 306: "unfortunately, they sounds like warnings for the polarimetric
signatures that will be analyzed in the the following Sections.
Finally, it is nice to see that all WBN samples have the usual 0.1 dB value (DN=1)" - this needs to be written in a better way. - Line 429: from 8 UTC to 18 UTC on January 22 .. is this 2020?
- line 470: a daily average differential reflectivity between 0.7 dB and 1.9 dB; How does this compare with Zdr from other previous studies using BS?
- There are too many 'on the other hand' and 'on the contrary' statements.
- Also 'what concerns' needs to be modified.
- Title: what is the purpose of the word 'peculiar'?
Author Response
Please see the file in attachment
Author Response File: Author Response.docx
Reviewer 3 Report
The technical note is interesting and I don't see any major problem impeding the paper to be accepted. It is an honest account of a series of measurements whose consequences can have an impact on the community. The manuscript is informative and the results intriguing. There are some typos that require attention before publication:
l 248. Typo: poiwer.
l 282. saturation.3. Results
l 341. Font type in the table is different.
Author Response
Please see the file in attachment
Round 2
Reviewer 2 Report
There is nothing peculiar about the 'average rhoHV being close to 1 with very small dispersion', since the tower is a single stationary target/scatterer. On the other hand, I do agree with the statement 'aim at reporting not only to the manufacturer, but also to other national weather services that are running operationally dual-pol weather radars'. Overall, the paper has been improved, and am glad that the word 'peculiar' in the title has been changed. The paper can be accepted for publication in MDPI-Remote Sensing.
