The Use of High-Speed Cameras as a Tool for the Characterization of Raindrops in Splash Laboratory Studies

Round 1

Reviewer 1 Report

The paper introduces a novel method for the characterization of droplets size. It uses two high speed camerass. Concept of the article is not a new approach to the problem, but due to the combination of calibration phase and field research, it makes a significant contribution to development of this technics.

The paper is well structured. The state-of-the-art is well documented and in accordance with the objectives.

- Question : why the calibration was not performed on common rainfall intensities (<10mm/h) but on storm-like intensities (>30mm/h)?

- Remarks :

• The paragraph 2.2.5 does not seem to be useful/important
• Figure 9 is not cited.
• There is a need to standardise figures for which authors should use international standards of units.
• For figures 8 to 10, the use of double lines is confusing. Please use single lines / dots.
• The figure 10 is absolutly not clear. The authors must change the plot. May be (not sure) it would be more readable with bargraphs rathan than stepgraphs
• There is a typo on ref. 33 (line 521)

The reviewer advises the authors to carefully read the guidelines of the journal.

Author Response

Dear reviewer

Here are our answers to your questions. Thank you very much for your time and advices. We have followed your suggestions.

The team

Author Response File: Author Response.doc

Reviewer 2 Report

1. Overall perspective:

Nature of the problem is related with fields with growing interest, thus being a relevant study to develop tools for simulation. The outcomes of the study have interest to the development of this field. There’s a good contribution to the development of experimental setups and its analysis by applying this alternative method. It was expected to have a stronger discussion about the errors sources and its impact in measurement, considering that there are alternative methods that can be applied and, therefore, a comparison with the accuracy of those methods would require this information. The use of a ruler as “standard” is a very weak method to provide traceability to geometric measurements, being recommended to use a more robust way to perform it.

2. Nature of the problem is related with fields with growing interest, thus being a relevant study to develop tools for simulation.

3. Line 66: according to SI, quantities should be written in italic form (e.g. D=a*S*b) as well as their description.

4. Line 81: correct “speeds” to “speed” or “velocity”

5. Line 93: “speed and size”

6. Line 102: “speed”

7. Line 111: use the term “velocities”, should be corrected to “velocity” and should be consistent with other parts of the paper where “speed” is used.

8. Line 149 – 151: recommended to clarify the phrase, e.g. “… since at part of its ability to be able to …”

9. Chapter 2 (starting at line 152): Analysis of the metrological performance of cameras, considering the need to evaluate the effect of distortion, focal length and other features in the image to be processed. Also, would be expected a more robust method regarding the validation of the measurement method of the drops shapes and diameters (Fig. 1), considering that it is surely affected by the resolution accuracy of the optical system. The use of a ruler with resolution of cm presented looks weak to assure a proper traceability of the measurement. The Authors should develop a more accurate method for traceability using proper standards. In general, is seems that the chapter dedicated to experimental design miss information regarding the calibration and accuracy of the optical part and of the processing software, both critical to assure the quality of the results.

10. Blur effect on images are not considered as possible limitation of the method

11. Table 1: should have the quantities in italic. Surface is not a quantity – maybe surface area ?. Correct the terminology of (x: mm) and (A: mm2) to (x in mm) or (x / mm)

12. Line 306: correct “d2y/dt2” according with SI  

13. Correlation between velocities obtained experimentally and the real situation with much higher heights from clouds. Impact of influence quantities that affect the process during the fall of droplets.

14. The introduction proposes two main outcomes:

This calibration will evaluate their resemblance to reality, calculate the real kinetic energy of the rain they produce and see if they can be used to model events in nature.

Aiming to calibrate a rain drop simulator.

In both cases, information is not given in the results and discussion, thus being suggested a revision of the introduction or of the results and conclusion chapters to be consistent with the proposed title, which looks fine for me regarding the content of the paper.

Author Response

Dear reviewer

Here is the document with the answers to your suggestions. Thank you very much for your time.

The team

Author Response File: Author Response.docx