Evaluation of Original and Water Stress-Incorporated Modified Weather Research and Forecasting Vegetation Photosynthesis and Respiration Model in Simulating CO₂ Flux and Concentration Variability over the Tibetan Plateau

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Original Submission

 Evaluation of Original and Water Stress-incorporated Modified Weather Research and Forecasting-vegetation Photosynthesis and Respiration Model in Simulating CO2 Flux and Concentration Variability over the Tibetan Plateau

1.1. Recommendation

Major revision

2. Comments to Author:

Overall opinion: This paper demonstrates a model application study. The authors used CO2 observations from Tibetan Plateau to improve existing WRF-VPRM model simulating carbon fluxes and CO2 airborne concentrations. I think you should focus on reporting the quantitative improvements of the model amendment by meticulously explaining the exact amendments of your model and by clearly reporting QUANTITATIVE arguments behind your statement about model improvement in Abstract, Results and Discussion. Revise the manuscript please by taking into account this recommendation and comments below.

 

Important remark (!): Please prepare an author response file with either direct quotes or exact guidelines on the lines where you applied your amendments. Regarding the main text of the manuscript, put yellow highlighted font in the places where you applied amendments. Do not leave any revision marks in the response files.

 

2.1. Comments:

Abstract: Quantitative information is completely missing in the abstract. For a journal, focused on remote sensing-oriented application studies, this is a critical oversight. Report your findings concretely.

·       Use academic language and proper formulations for a peer-review please. Experts in carbon research familiar with the standards of academic English would not say how carbon moves for instance. Ask a more experienced colleague with English to help with this aspect; do not use mysterious terms such as “the researchers” in the abstract, be concrete and brief please.

·       “The study emphasizes the importance of water 29 stress in shaping carbon movement, especially in semi-arid and semi-humid regions, providing a 30 new tool for studying this vital ecosystem component” -> Your conclusive remark is too ambitious for a local study. Where have you shown a regional analysis demonstrating the importance of water stress in semi-arid and semi-humid regions, assumingly while comparing this with… other regions? Respond below.

 

Format: Follow MDPI guidelines for formatting manuscript, namely, use  the template that editors suggest through their manuscript preparation guidelines. Note that your format is wrong in many places (see just as example, wrongly formatted title; it strikes one’s attention immediately). Equations are completely misaligned as well. Tables are not following MDPI guideline formatting requirements also.

Introduction: The role of the Tibetan Plateau in your story is underemphasized. You centered your introduction around the history on development of models establishing relationships between CO2 and water/temperature (e.g. also flux-oriented models of whatever type). If this is true, please put an EMPHASIS that the main focus of your study is a study evaluation and Tibetan Plateau is just a region you choose to test the model. By the way, explain here why you choose TP as your evaluation region. Justify this with arguments please.

Methodology: I am not sure whether you need the description of the calculus behind the simplest statistical metrics possible (Analytical Approach section). Also, please ensure that you articulate all the quantitative procedures by adhering to parameters, units and numbers; not just qualitative descriptions. There are many vague qualitative formulations that could rely on more quantitative remarks; please ensure you address all such vague formulations during the review.

 

Results, Discussion, Conclusions:

·       Results demonstrate the evaluation of GEE fluxes against ground truth in 3.1. In this section (3.1), ensure that you adhere to quantitative arguments as much as possible. Specifically, back up your qualitative descriptions like “significant”, “stronger”, “similar” etc with actual numbers. If you use words like similar, adhere to statistics. The same applies to “significance”. The model evaluation attempt is basically an application study without a truly unique scientific aim; thus, it should adhere to numerical arguments. Ensure it is the case in the submission. Also, do not use any vague terms such as “growing season” because your article is intended to a general reader; he/she is not by default familiar with growing seasons in TP. Ensure that readers are familiar wit the concept of GEE and, especially, wit the concept of GEE = 0 μmol·m-2·s-1. Avoid the words like “Tremendous” (like in 264 line), adhere to numbers and more neutral connotations.

·       The discussion is poorly structured and seems speculative by only loosely relying on any quantitative arguments, shown in the study. You just reiterate the same idea, that your model demonstrated superior results compared to previous models and that water stress has to be accounted in any carbon-related simulations in TP but then suddenly reveals that the model is actually not perfect and has deficiencies. I would recommend you to thoroughly focus on your results and exact implications of your findings. Support any claims about model improvement by numerical arguments from the results.

·       Conclusions. Ensure that you do not reiterate anything you already said in discussion in conclusions, now these sections look like they conflict and resonate each other at the same time. They conflict each other because you said in the discussion that your model is superior, but in conclusions you toned down and started speculating on “varying degrees of simulation results” (Line 538). Harmonize these sections.

 

Also, clarify the following minor aspects:

·       Line 36 Why such attention was received? Unclear

·       Line 41 Why only satellite inversions not just satellite observations for observing CO2 sources for instance? To give examples, studies like Fu et al [https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019EF001282], Ye et al [https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JD030528] or Labzovskii et al [https://www.sciencedirect.com/science/article/abs/pii/S0034425719303785] on this regard. Check their experience and add as references here if needed.

·       Line 43 -> What is even that? “More explanatory methods” Clarify please. Moreover, you mentioned model simulations already and here you call model simulations to be “more refined method”

·       Line 47 “significant” -> In peer-review it’s a statistical term normally, rephrase

·       Line 52 “Detect” might be the wrong word choice here

·       Line 83 Not true, if you are speaking about China only, emphasize “studies about China”. You are not speaking about general or global context.

·       Line 93 Suitability in what way? Accuracy? Precision? Ability to reconstruct realistic CO2 fluxes/concentrations. Moreover, “CO2 concentration”, do you mean airborne fraction or for instance, ocean?

·       Line 103 Site?? How can you address the entire region if you are dealing with “site”-scale analysis. Please clarify.

·       Line 109, adhere to conventional format of references for MDPI. Several surname format of references is not common.

·       Line 115 Sensitivity to what?

·       Line 120. Which thresholds? Numbers and reasons behind these numbers, please.

·       Line 124 – 126 Vague description of the data gap alleviation approach. Specify please when you used each of the methods and explain why you think they were efficient in means of gap closure.

·       Line 129. Speak up what do you mean directly: parameters, units, etc.

·       Line 132 Reference and the information for reproducibility, please.

·       Line 136 Aligned? What does it mean

·       Line 138 Furnished? I am pretty sure it’s a wrong word choice here. Mention MODIS product as well, MODIS provides so many parameters (chlorophyll, water vapor, aerosol, biomass burning parameters, etc).

·       Line 264. Readers do not know r values for non-improved WRF-VPRM by hear. Stick to numbers please.

·       Line 277 Self-explanatory information about RSD, it’s a scientific journal

·       Line 280 Explain the consequences on these limitations in terms of applying statistical analysis to verify your model

·       Line 288 Remove coloring from the table, it is not common for MDPI journals from the formatting point of view.

·       Line 301 Why daily variations are challenging and hourly simulations are simple to run then?

·       Line 311 Approximated to approximately??

·       Line 314 Any quantitative arguments to prove the successful capturing? You just gave a number for readers.

·       Line 319. Explain horizontal line patterns in NEE in this figure

·       Line 322 Dubious statement here, re-read it please. Also, a line below. Are you sure WRF-VPRM responds to carbon fluxes, not reproduces them?

·       Line 326 -> Provide statistical arguments behind “Significantly” here and elsewhere.

·       Line 410 Increased respiration is a part of carbon cycle as well as airborne CO2 concentration… I am also sure that once some model reproduces CO2 concentration, there are prior biosphere-related fluxes, no?

·       Line 426 Daily variations driven by what? Can you name few examples of prominent global anomalies of CO2 concentration reported.

·       Lines 426 – 437 Add quantitative arguments behind qualitative statements here please.

·       Line 432 Which trend? Peak is not a trend from statistical point of view.

·       Line 441 Biological absorption of CO2 -> find the correct term reflecting biospheric absorption of carbon please.

·       Lines 439 – 447 Add numbers behind your qualitative statements throughout the paragraph.

·       Line 455 You did not resolve underestimation of ER, you just reported lower estimates, no? I mean in order to speculate about under and over-estimation you should rely on the intercomparison study of tools/models/methods, being compared to the ground truth. Is it your case here? Also, a reader won’t understand which amendment you mean here.

·       Line 456 Reiterate the arguments here that demonstrated that you actually found independent causal link between water stress, vegetation without relying on the model where these processes are considered to influence each other by the model setting, no? Perhaps, the wording is a problem here so ensure you nail down this argument during the revision process.

·       Line 461 Considering CO2 concentration in carbon flux analyses is an advice? It sounds weird because carbon flux analysis implies that one can capture the actual exchange between the atmosphere and biosphere in terms of carbon cycle. Remove all such trivial statements that demonstrate some gaps in your knowledge about CO2/carbon measurement state-of-the art practices.

·       Line 462 Which adjustment?

·       Line 469 You mentioned several factors, so “single” is non-sensical here. Perhaps, “few” is the word?

·       Line 472 Point out the arguments demonstrating this superiority below (quantitative arguments from your study).

·       Line 484 You should boldly state in the beginning of the introduction that the amendment you are talking about is the inclusion of water stress into parametrization (right?)

·       Line 494 So, the model is not then superior to statistical approaches if it can introduce certain previously non-existing bias, right? It improved just SOME aspects.

·       Line 498 Specify the role of satellite data, totally unclear here.

·       Line 502 Why one needs new figures in discussion, not in the results? Just a curiosity question.

·       Line 505 TP is called water tower of Asia by reason, no? I mean it’s not your finding pointing out this phenomenon. Tone down the implications to the actual scale of your findings, please. Namely, to the improvement of the modelling ability of the amended WRF_VPRM to simulate carbon fluxes in TP.

·       Line 515 I think you meant “parameterization” but never spelled it here.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The carbon cycle in the alpine grassland of the Tibetan Plateau is receiving much attention. This manuscript evaluated the performance of a modified WRF-VPRM model by adding water stress parameters in simulating the carbon fluxes in the Tibetan Plateau. It is valuable and meaningful. However, I have some concerns as following:

 

1) Why did the authors choose WRF-VPRM model to simulate carbon fluxes? Does this model have advantages over other mechanism model such as ORCHIDEE, BIOME-BGC? What is the contribution of the authors to the model?

 

2) The abstract was too simple and no data was presented to support the conclusions.

 

3) L49-50, EVI is calculated by using reflectances of NIR, Red and Blue bands.

 

4) L55-56, Use FPAR to calculate EVI?

 

5) L60-61, How to validate EVI?

 

6) L63, results?

 

7) L83-84, I don’t think studies on carbon fluxes of the TP was few.

 

8) Li, Zhang?

 

9) L89, Was the improved model proposed only by Hu and Gourdji? The correct format should be “first author et al.,”. This problem was common throughout the manuscript.

 

10) L89-90, This sentence has no link with the above content.

 

11) L105, There are six sites in Table 1.

 

12) L119-121, Please give a more specific description of growing season and non-growing season. How to set the temperature thresholds?

 

13) L150, RE, ER?

 

14) L174, add the abbreviation of land surface water index.

 

15) L176-178, How to obtain Topt, Tmax, Tmin?

 

16) L205, In section 3.1, there were some contents relating to hourly variation in carbon fluxes.

 

17) Tables 2-4, There were no units for Bias, RMSE, RSD.

 

18) Figures 11-13, were the spatial maps of CO₂ concentration simulated by the improved WRF-VPRM model?

 

19) Most of the cited references were published too early. The authors should follow up the recent researches.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

This effort can be accepted with minor changes

- Give one implication sentence in the introduction explaining why your results are important

- Remove the word 'verify' or replace it with 'evaluate' in conclusions. You cannot verify the model using the analysis like yours

- Do not write 'Bias' if this word does not start a sentence; 'bias' -> correct version

- Conclusions -> "depicted" should be "reproduced"

- Conclusions -> Add everywhere, in every strong sentence that you are talking about TP

- Conclusions -> Do not use the word "significant" without statistical arguments; remove, rephrase or add such arguments

- Conclusions -> Implication sentence should be talored only to TP, not global scales, do not mislead readers.

Comments on the Quality of English Language

Ensure that English is OK before resubmitting, MDPI does not provide rigorous language check so any mistakes you overlook in the manuscript can end up in the final version, thereby ridiculing your effort from the point of view of future readers. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have improved the manuscript much and the issues I mentioned last time have been solved.

Author Response

Thank you for your comments, which were critical to the publication of this work and significantly improved manuscript quality and readability.