Dripping Rainfall Simulators for Soil Research—Design Review

Round 1

Reviewer 1 Report

Content was put together pretty well. A few comments and edit suggestions provided.

I wish there was more analysis, substance, pros/cons of the different types.  There was not much discussion about the different types of emitters that might help the reviewer better understand how the industry has progressed and why.  I would have also liked a discussion between pressurized and drop emitting simulators as well as discussions on height and terminal velocity requirements along with drawbacks of not knowing drop formation sizes, fall heights, and kinetic energy creation from these simulators.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear editor,

This is a well conceived and documented manuscript.  I appreciated the efforts to present the material on a logical (by simulator element) basis. It is clearly a well done article of great general interest to your readership. That being said, I have some narrative recommendations to improve the overall document:

1) the authors stop short of recommending the optimal simulator design.  Despite making this an objective (line 60) and suggesting this was a conclusion (line 507), the non-specificity of the text for the preferred design makes it uncertain what scientists should be using in the future.

2) The authors do a good job of characterizing the different construction components, but do not describe the effect these differences may make in results.  Given this may be a significant metadata job unto itself, even a description of potential bias from different simulator designs would be helpful.

3) the authors stop short of saying how comparable the results are from historical data.  I particularly liked figure 13, noting changes over time.  Is there a cutoff in time for which data should not be considered?

4) The statistical analysis (line 502) in the conclusions was a bit of an oversell - the statistical analysis was rather limited.  I recommend deleting this conclusion.

5) I personally would have liked to see a brief description of how rainfall simulators for soil erosion differs from (or are similar to) rainfall simulators for other applications such as agricultural irrigation or urban runoff.  This could be in the introduction or discussion, but would help scientists in tangentially related applications.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for addressing comments.  I personally feel that some of these comments could have been addressed better.  For instance, the discussion regarding drip versus pressurized rainfall simulators could have been discussed in generalizations and not long specifics. 

For instance:  "Drip emitters have very little head pressure associated with their creation and gravity is the main force for its acceleration.  Whereas pressurized rainfall systems use pressure heads and nozzles to create raindrops and typically throw the drops outwards upwards or downwards, creating nonlinear drop paths.  In order to adequately assess the forces that the drops are placing on the surface they are falling to, drop velocity is an important component to understand.  Previous research has shown that drops of certain size require certain fall distances to reach terminal velocity.  This velocity is known and therefore can be accounted for as long as the drop emitters are installed at a sufficient enough height.  For pressurized systems, the drops are likely emitted at speeds greater than terminal velocity and likely require enough time to slow to terminal and create a vertical fall path.  If fall height for either of these cannot be met, then a means for velocity detection would be needed and these papers (x, y, z) demonstrate the process.  One other major limitation factor for raindrop emitters is the repetitive nature of the drops hitting the same spot since their fall paths are usually linearly vertical.  However, some oscillating emitters have overcome this drawback."

This type of brief discussion that acknowledges other very important components of this sector of the industry but isn't necessarily a major research component would greatly benefit the reader and acknowledge your understanding of rainfall simulation in general.

Author Response

Please see the attachment.

Author Response File: Author Response.docx