Uncertainty of Tipping-Bucket Data May Hamper Detection and Analysis of Secular Changes in Short-Term Rainfall Rates

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

A good article has been written on one of the most important topics related to atmospheric data and data recording errors, which is interesting. However, there are minor flaws in the article, which will enrich the article by correcting them. The issues that need to be corrected are: 1- The introduction is too long and should be written more concisely. 2- The quality of the figures is poor and the images are illegible, and this problem should be fixed. 3- The conclusion, unlike the introduction, is too short and should be explained a little more. 4- I am not a native English speaker, and a native speaker should comment on the English writing of the text. Of course, I did not notice any problems with the text or grammar.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

General comments

 

 

This study presents an interesting approach for analyzing measurement errors associated with tipping bucket rain gauges.

Although the topic is of interest, in my opinion, the study is not articulated in a sufficiently comprehensive way to represent significant innovations in the field. Most notably, the presentation of the data used is highly lacking, including the description of the type of measurements, the location of the events, and the length of the analyzed period, to the point that it seems the data were not actually used at all.

More specifically, I believe that the introduction would greatly benefit from a more comprehensive and detailed analysis of the different instruments available for rainfall measurement. Currently, the discussion appears limited, and it would be helpful to contextualize the performance of Tipping Bucket Rain Gauges (TBRG) within the broader spectrum of measurement technologies. It is widely recognized that TBRGs are not suitable for capturing very short-duration or instantaneous rainfall events, due to their inherent measurement mechanism based on the collection of discrete volumes of water that are then converted into rainfall values. This introduces limitations in terms of both temporal resolution and accuracy, especially during high-intensity or rapidly varying events.

For the purpose of instantaneous rainfall measurements, a variety of alternative instruments should be considered and briefly described. These include, but are not limited to, disdrometers (which measure drop size distribution and velocity), vertically pointing radars (capable of high temporal resolution observations), impact sensors, and weighing rain gauges, which offer higher accuracy for both short and long accumulation periods. A short comparative overview of these instruments, including their respective strengths and weaknesses, would strengthen the introduction and help justify methodological choices made in the study.

Furthermore, potential sources of error associated with TBRG measurements should be discussed explicitly. These include, for example, underestimation during intense rain due to bucket overflow, wind effects, mechanical delays, and evaporation losses. Ignoring these sources of uncertainty may lead to misleading interpretations of the data, particularly when high temporal accuracy is required.

The rationale behind using averaged rainfall rates should also be clarified. While averaging may simplify analysis, it can obscure important short-term variability and peak intensities, which are often critical in hydrological and meteorological applications.

Regarding the mathematical treatment, it is essential to ensure uniformity and clarity throughout the text. All equations should be presented using proper formatting tools such as equation editors or LaTeX, to ensure that the mathematical content is readable, standardized, and accessible. In its current form, the text lacks this consistency, and some formulas are difficult to interpret. A complete rewriting of the mathematical sections is strongly recommended, with detailed explanations that connect the formulas to the physical meaning of the parameters involved.

Additionally, no reference to actual data is provided in the text, which limits the empirical foundation of the study. The inclusion of at least one dataset—whether from field measurements, a case study, or simulated data—would significantly enhance the robustness and credibility of the analysis.

Moreover, the study proposes a classification of rainfall rates, referring to the American Meteorological Society (AMS). However, upon querying the AMS website with the term “heavy rain,” the result is a general definition: “Rain with a rate of accumulation exceeding a specific value that is geographically dependent.” This highlights the need to justify the selected classification scheme more rigorously. How were the threshold values chosen? Are they supported by literature or empirical observations? Furthermore, given that real rain rate values are continuous and not discretized into six predefined classes, the applicability and operational usefulness of this classification should be clearly explained.

In summary, a more thorough methodological justification, improved mathematical clarity, and the inclusion of real or simulated data would significantly enhance the scientific value and readability of the work.

 

 

Specific comments

 

Lines 87-88: The sources of errors in TBRG are not obvious and are very relevant for this work and they should be considered in the analysis.

Lines from 87 to 112: The in TBRG of correctly identifying the moment of the onset of precipitation and of identifying at any moment whether precipitation is in progress or not, becomes even more crucial in the cases of light precipitation and intermittent precipitation.

 

Lines 172-174: I’m not so conviced by this statement. The rain gauge data processing must be performed using a fixed AT. This kind of errors occurs when rain gauge data are processed to extrapolate indications of instantaneous rainfall rates. Finally there is a typo as the rainfall rate was 6 mm h^-1 (see line 162) and consequently the over-estimate is 33% (2 mm h^-1  over 6 mm h^-1).

 

Line 180: 60% should be corrected accordingly to the previous point.

 

Lines 220 -229: I think this paragraph is not clear and should be rearranged.

 

Lines 236-237: Accordingly, to lines 231-233, R_T is the true correct rainfall amount, but it is not clear what R_R is.

 

Lines 238-245: Please carefully check for multiple definitions of quantities, sometimes not congruent.

 

Line 240: The equation should be rearranged following the equation at line 235. Ru, defined in (1) is positive and is the difference between R_U= R_T-R_L.

 

Line 251: Equation (3) should be explained in the text, or a reference should be provided. I suggest to introduce the filling time T_F as the quantity that can be derived from:

 

i.e:

 

Perhaps it is not very clear to me how the AT can influence the filling time.

 

 

Line 272: Equation2?

 

Line 273: Where does the value 0.17 come from? More information is needed.

 

Table 2: In the text the table is far from its header. A unit measurement should be provided

 

Line 322: th error percentage for rainfall rate is 1

 

Line 327: I is the error percentage for rainfall rate

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript provides novel insight on the potential error of tipping bucket rain gauges based on its ability to measure rainfall rates and accumulations based on the capacity of the tipping bucket itself, especially at shorter time scales. The work presented is solid, yet can use some clarifications to bolster the results and discussions presented in how much potential uncertainty there is. The reviewer will provide specific comments/recommendations below that, if utilized, will help with the body of work and help the reader follow the work presented in the results. Beyond that, the work is presented well and has good readability. The judgment of this reviewer is for minor revisions. Specific notes are presented below:

 

Line 43: The author should clarify that the “intensification in urban areas” is the intensification of rainfall rates from (what the reviewer assumes here) is urban heat island effects.

 

Line 174: The author mentions that the true rainfall rate in the conceptualized example presented was 5 mm h^-1, but based on what was stated on Line 162, the idealized example was 6 mm h^-1. If this is the case, then the overestimation error in the rainfall rate should be 33% and not 60%. If this is not the case, this would need to be explained why there is a difference in the rainfall rates presented.

 

Lines 230-242: The variable R_T is presented with two different definitions in this section. R_T is presented on Lines 231 and 241 as the true rainfall depth (accumulation; mm), yet R_T is presented on Line 236 as the constant rainfall rate (mm h^-1). This has to be changed to where the accumulation and rate are represented by two different variables. And more so, the two rainfall rates defined on Line 236 should be better differentiated. It is also recommended to take the two equations listed on Lines 235-236 and denote them as the other equations are in the manuscript.

 

Tables 2, 4: The reviewer assumes the end of the table is cut off in the peer-review version of the manuscript, since the 60-min apparent AT data is not visible. Also, the Table 2 caption is separate from the Table 2 itself in the peer-review version of the manuscript.

 

Lines 292-297: The author mentions the error rates at the 60-min accumulation period. Given what was mentioned, these values are higher than the error rates at the 50-min accumulation period. How is this possible? Please elaborate.

 

Table 2: The author should elaborate why the error rate with the 5 min accumulation and 5 mm h^-1 rain rate is 2300%. Moreover, it might be meaningful to show what the actual calculated rates were that resulted in the error values presented in Table 2.

 

Results Section: For readers to better follow the work here, the author should explicitly relate back to each equation and variable from the Materials and Methods section, especially since there are multiple rainfall rates and accumulations defined.

 

Figure 1: While the author notes that these are on different scales, the author should make an effort to put them on the same scale to better visualize the difference between the rates. One idea is to plot all three lines/points on the same graph.

 

Discussion Section: The reviewer found the discussion section as enlightening as well as thorough. The one point that the reviewer had thoughts on was the idea that two buckets were missing in the calculations. The consideration that one bucket can be missed is absolutely valid with the ending of an event. The reviewer wonders that it might be more appropriate to account for here the time delta between the event onset and when the accumulation point of the bucket is reached to garner a recorded tip.

Author Response

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Author Response File: Author Response.pdf