Dual-Polarization Radar Fingerprints of Precipitation Physics: A Review
Jong-Hoon Jeong
Round 1
Reviewer 1 Report
Summary – As entitled, this manuscript reviews the use of dual-pol radar ‘fingerprints’ in the interpretation of both warm and cold precipitation processes. The fingerprints are introduced as the vertical gradients / change in the retrievals of the horizontal polarization (ZH), differential reflectivity (ZDR), specific differential phase shift (KDP), and the co-polar correlation coefficient (?h?) with a positive gradient indicating growth during descent. The primary focus is on warm precipitation processes (coalescence, break-up, evaporation on size sorting) although cold cloud physics is explored in somewhat less detail. The focus then turns to the ability to use these fingerprints to quantify process rates.
Recommendation – minor revisions
The authors are all very well placed to produce such a review. Indeed, it’s great to see the work of genuine experts in the field. They do a nice job limiting the scope of this work, focussing on microphysical processes, leaving hydrometeor classification algorithms for elsewhere. Much of the understanding comes from using a dual-pol radar simulator on model output – primarily bin microphysics schemes used in the simulation of an idealised rain shaft. Section 3 was most interesting.
Technically the writing is strong with few typos. That said, I did not find this review to be particularly easy to read, although I accept that it’s an advanced subject. As a critical comment, the first part of the manuscript felt like it came from the midst of lecture notes for a post-graduate subject rather than a review manuscript. In my opinion, this manuscript was light on details in many places, directing the reader to go back to the source material far too often. The manuscript should be written for the wider community. Not everyone who wants to read this paper will have sat through a post-graduate subject on dual-pol radars.
Specific points
1. You absolutely must define AND introduce the dual pol radar variables in a review article (line 92). You cannot delegate core knowledge to other works, no matter how trivial and redundant you may find this. This review article is presumably a standalone piece for the wider community.
2. I strongly recommend that you provide one or two actual images of real fingerprints from actual dual-pol retrievals of field observations. Don’t leave everything to idealised numerical simulations.
3. Given that so much of the theoretical development is from the idealised rain shaft simulations, you need to discuss model configuration in much greater detail, including the parameter space explored by the microphysics scheme.
4. I’d really like a statement on the (potential) sensitivity of the results to the bin microphysics scheme employed. It is a great challenge that radar retrievals are most sensitive to larger hydrometeors, where the different schemes can diverge. Some fingerprints will be quite robust, but it isn’t clear to me that all are.
5. The concluding remarks section is very light. It’s shorter than the abstract.
Lesser points – (that you’ll probably find to be annoying)
6. Line 26: (liquid, ice, etc.) – ETC? For a hydrometeor there’s just liquid and ice/glaciated. I've never seen slush classifed.
7. There is no overview of the development of this methodology, or how it is an advancement on CFADS from single pol radars.
8. Line 88: Earth should be capitalized.
9. Line 92: If you’re not going to use the co-polar correlation coefficient, then why introduce it?
10. Line 104: Why bother saying your approach differs from some other approach? This is an unnecessary digression.
11. Line 129: It would be best to explain why coalescence increases ZDR and KDP. This may not be intuitive to a wider audience. (Kind of what you did at line 339.)
12. Figure 3: It would be better to label the contours. The color of the third contour isn’t clear, given the change in the background from brown to yellow.
13. Line 195: Isn’t the cooling rate to the environment strictly a function of evaporation? Why do I need a dual-polarized radar for this?
14. Line 204: Is size-sorting ever free of evaporation?
15. Line 252: decreasing aspect ratio? Two lines earlier you say growth… with extreme aspect ratio.
16. Again, here, it would be good to inform the wider community on how growing snowflakes change ZDR and KDP.
17. Line 287: Huh? How do you go from monomer crystals to mid-latitude snowstorms?
18. Line 307: The role of temperature is critical here, but that can be said for a variety of cold precipitation processes, like the Hallett-Mossop process. This could be stated more clearly.
19. Line 423: BOSS isn’t defined until line 472
20. Figure 7: the values are normalised from 0.5 to -0.5, not 0 to 1.
21. Line 436: Please explain the MCMC model in a bit more detail.
22. Line 472: The same can be said of the BOSS model.
23. Figure 8: When in Q3 (collison), evaporation was greatest when the point was closer to Q2… BUT it was even stronger when you moved further from the origin on a given line.
Author Response
We thank Reviewer #1 for their time and effort spent on reviewing this manuscript, as well as for their very helpful comments and suggestions to improve it! Please see the attachment for an itemized response to the comments.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This manuscript reviews how precipitation microphysics processes are observed in dual-polarization radar observations. It is a topic of interest to the researchers in the related areas. However, I personally think that the manuscript needs some necessary improvement before acceptance for publication. My detailed comments are as follows:
(1) This manuscript concentrates on the response of the dual-polarization radar variables to multiple physical processes of precipitation. However, there is no more in-depth review of how dual-polarization radar variables can be used to exactly identify (e.g., algorithms development) the size, spatial distribution, and phase of precipitation particle.
(2) In Section 3, the authors argued that they explored the cutting-edge use of dual-polarization radar data to estimate important microphysical information quantitatively. However, based on my personal knowledge and the references cited, I do not think so this is enough to represent the emerging research with microphysical fingerprints of precipitation.
(3) In the abstract, the authors stated that they concluded with an outlook of potentially fruitful future research directions. Other than lines 610-613, I found nothing else, or the authors failed to highlight it.
(4) How did the authors get the information in lines 269-271? Is it allowed to cite or explain the unpublished results in this way? The authors should confirm this under the journal requirements.
Author Response
We thank Reviewer #2 for their time and effort spent on reviewing this manuscript, as well as for their very helpful comments and suggestions to improve it! Please see the attachment for an itemized response to the comments.
Author Response File: Author Response.docx
Reviewer 3 Report
This manuscript reviews the studies using dual-polarization radar observations for the investigation of the precipitation process. Specifically, this manuscript first revisited the qualitative studies focusing on the microphysics of the precipitation process from the viewpoint of dual-polarization radar measurements. Then, studies focusing on the quantitative study of microphysics fingerprints in dual-polarization radar measurements were reviewed. Conclusions were provided.
This manuscript is valuable for providing a systematic review of using dual-polarization radar measurements for studying the precipitation process. The discussion is comprehensive. The expression is clear. It is suggested to be published after a minor revision:
The figure styles need to be unified (e.g., white background) if possible.
Author Response
We thank Reviewer #3 for their time and effort spent on reviewing this manuscript, as well as for their very helpful comments and suggestions to improve it! Please see the attachment for an itemized response to the comments.
Author Response File: Author Response.docx
Reviewer 4 Report
Recommendation: Accept in present form
General Comments: The authors provide a thorough overview of precipitation microphysics processes from dual-polarization radar observation. They explain nicely with “fingerprints” of the precipitation microphysics processes. Also, this manuscript well presents emerging research with BOSS outputs. This very well-written manuscript is sorely needed in our community, and as such, it is extremely informative and enjoyable to read. Overall, I have no—what I would consider—major suggested edits or requests. I think the manuscript will be in publishable form. I only have two questions as below, it might not consider for publication.
Questions:
1. As the author mentioned, the co-polar correlation coefficient is a useful polarimetric variable. This paper is only used this variable in the melting process. Can this variable help to identify the other microphysics processes?
2. As the author mentioned in Line 152–156, we wouldn’t explain one process in nature. Thus, the fingerprint can help to identify the dominant process. How can we determine the dominant process when the variables are small changes? For example, ZDR is useful information to determine the processes between breakup and evaporation. However, it seems ZDR is not a clear signature during rain evaporation. Also, it would have difficulties between aggregation and riming since they are very similar sign. We might also consider the observation uncertainties and errors.
3. Line 472, ‘Bayesian Observationally constrained Statistical-physical Scheme’ should move to Line 423.
Author Response
We thank Reviewer #4 for their time and effort spent on reviewing this manuscript, as well as for their very helpful comments and suggestions to improve it! Please see the attachment for an itemized response to the comments.
Author Response File: Author Response.docx
