Evaluation of the GPM IMERG v5 and TRMM 3B42 v7 Precipitation Products in the Yangtze River Basin, China

Round 1

Reviewer 1 Report

This is a good effort for evaluating GPM IMERG v5 and TMM 3B42 for China, but the paper in my opinion needs a great editing of English language. It is not clear to the reader. 

I would also recommend to add a methodology flow chart. It would help the reader to clarify what is the happening. Now this is difficult.

Thank you

Author Response

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Reviewer 2 Report

The authors have conducted a very good work of comparing satellite-based precipitation products (SPP) against rain gauge observations. Moving forward there would be many more SPPs developed, because there is a huge demand for spatially distributed precipitation data. And hence the need for ascertaining the uncertainty and accuracy of these SPPs. The work is well articulated and nicely written. There are many minor grammar and sentence formulation errors and suggest a review of the language before publication.  

Author Response

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Reviewer 3 Report

This manuscript describes a study to evaluate the performance of the IMERG and 3B42 through comparison against the 224 rain-gauges over Yangtze River basin. IMERG is the GPM official products for level 3 global gridded precipitation and is expected to be used widely in various applications. It is therefore of particular importance to examine its quantitative accuracy in representing precipitation and its variations and the improvements in the product quality upon previous products.

Although the work is not very innovative but could be considered for publication after major revision. However, the manuscript should by carefully grammatically check by a native English speaker, while there are many mistake and some sentences are needed to be re-write.

I have mentioned some issues and have some comments, but there are more similar issues in the manuscript that should be carefully revised.

 

Attention: There is mistake in numbering the line and pages at the PDF version of the manuscript. At page 13, the page and line number reset to one. So after page 12, I refer “Second – Line ?”, before my comments.

 

General comments

The abstract should re-write. The structure and the sentences are not well-prepared.

Line 17: “… lowest accuracy …”, I think you should write low accuracy.

Line 18: Since it is first appearance of SPP, please introduce it, instead of its abbreviation.

The same in Line 62 for “NASA” and some other places.

Line 78: This is “JAXA”.

Line 78: You have already introduce GPM.

Line 86: remove the extra GPM in the parenthesis.

Line 91-95: As it is written in GPM documentation, there are three Level products. Please carefully check it and re-write this part.

Line 98: The “final-run” products has a latency of about 3-4 months and not 18 hours.

Line 101: What are these “four consecutive monthly ground validation”?

Line 119: “… it’s accuracy”

Line 195 –196: You did not mentioned MAE, while later you used MAE as one of the statistical indicators.

Equation 3 (relative bias) should multiply 100 at the end. Please check.

Equation 7: I suggest to use another regular name for this indicator such as “frequency bias (F-bias)” to avoid misunderstanding this indicator with the normal bias.

Line242-260 (figure 2): In this scatterplot it seems the number of points are reduced for annual evaluation in compare to monthly, and monthly in compare to daily time-scale. Could you please explain why? Moreover, the error indicators (Bias, RMSE and MAE) should be lower for the daily and higher for the annual time-scale, while the precipitation magnitude is higher in annual time-scale. Why here is vice versa?

 

Page 11, second line: what was the criteria to choose this 7 thresholds? Do the stations you used can measure the precipitation amonth between 0 and 0.1 mm?

Page 11, second paragraph, second line: “For rainfall rates ≤10 mm/d …” do you mean the PDF of rainfall rate ≤10 mm or  5 mm< P ≤10 mm?

Since interpolation performance depends generally on topography, temporal resolution, station density and the spatial variability of the climate information, how did you deal with the impact elevation on the interpolation algorithm in such an area with large difference in altitude, particularly for daily time-scale?

Page 11, second paragraph: Please re-write this paragraph. Moreover, I don’t completely understand what do you mean by“… during the rainfall from 0.1~5 mm/d, GPM showed …… this threshold of precipitation.” How you can strongly conclude that this low accuracy in just because of the DPR sensors. It is better to say, “it might be due to … “.

Second - Line 8-9: again the question raised, why the annual bias and RMSE at annual time-scale should be less than daily precipitation.

Second - Line 17: do you mean stations’ altitude between 1000 m and 2000 m ?  

Second - Line 58: “… in the areas >2000 m, but …”, I think you mean the areas less than 2000 m. But to me “areas >2000” means areas greater than 2000 m. Please check the sign through the whole manuscript.

Second – Line 107: PDF has been already introduced.

Second – Line 112: Please check the whole manuscript and replace the TRMM with 3B42 product. Because as I already mention TRMM is just one satellite but the product that you used (3B42) is obtained from different satellites that TRMM is just one of them.

Second – Line 113-115: again you cannot strongly conclude that “it is due to…” the PR and DPR onboard the TRMM and GPM respectively. Please use other words such as “could be” or “might be”.

Second – Line 120-124: Please use a reference here.

Second – Line 139: “rainfall volume in four altitudes”, I think you mean “rainfall values in the four altitude categories”.

Second – Line 217: Simple interpolation can produce large errors especially over the complex terrain. Why any downscaling technique doesn’t have been mentioned such as:

https://doi.org/10.1029/2018JD028795 

https://doi.org/10.1016/j.rse.2008.10.004 

Second – Line 237: in several places you used “Two SPPs both …. “. Please remove the extra word (two or both).

 

Comments for author File: Comments.docx

Author Response

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Round 2

Reviewer 1 Report

There is a significant improvement to the paper. Many corrections have been made according to the other reviewers as well. I think that the paper is worth to be published.

Just a comment. Please avoid to use "we" ( for example lines 258, 291).

Thank you!

Author Response

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Reviewer 3 Report

The authors have revised the manuscript satisfactorily and the revised manuscript reads better. I recommend it for acceptance. However, regarding the authors' response to question number 16, I suggest that they put their explanation into the manuscript. 

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