Seasonal Dynamics of Flux Footprint for a Measuring Tower in Southern Taiga via Modeling and Experimental Data Analysis

Round 1

Reviewer 1 Report

The manuscript presents a well-structured study of flux footprints and extension of the fetch comparing different methods and data sources. The methodology is neat, results are precisely described proven concepts from the literature, and data-driven explanations; conclusions are well supported by the results. Some minor shortcomings are listed in the following, but there is a major issue is of primary importance:

2-     The complete failure of consideration for the roughness layer at the top of the canopy. This layer is almost always present at the top of the canopy with or instead of a shear layer. Within this layer, the log-law of the wind speed is not necessarily holding, and its validity must be proven, and use justified.

I therefore recommend a major revision of this manuscript. Please find my comments and suggestions below.

 

Specific comments

Line 97: How is the “crosswind-integrated flux footprint” defined and how does it differ from the footprint in Eq. 4? Are those the same? If so, why differentiate between footprint and crosswind-integrated flux footprint?

Figure 1D, 1E, and 1F: Are those variables coming from satellite measurements or are those results of some numerical simulations?

Lines 156-158: How is this uniformity of the upwind area considered in the footprint computation? What would be different with a non-uniform area? Also, it is unclear to me if the soil properties are considered uniform or the atmospheric thermodynamics.

Line 178: Why did you choose 25 m as the canopy height instead of the mean canopy height?

Line 237: The assumption of a log-law profile above the forest must be better justified. Typically, at the canopy top, a shear layer or a roughness layer can develop, and the wind speed solution would not be logarithmic anymore (Raupach et al. 1996). For a forest of similar geometric characteristics and similar measurement types and levels within and above the canopy, Cintolesi et al. 2023 found that the roughness layer was indeed reaching the utmost measuring point and that a different analytic solution was needed (such as Rannik et al. 2003). The use of a measurement point outside the forest or the use of a database for the class of land use would serve the purpose of calculating z_0 to than calculate d according to Rannik et al. 2003. The are also recursive methods that allow the computation of z_0 and d from a single measuring point (Martano, 2000). Please revise the computation of z_0 and d.

Eq. 7: same problem as my previous comment

Lines 246-247: The assumption of uniform fluxes holds if the canopy is homogeneous (which is partially true), the distance from the forest edge (close to the edge, turbulence is not uniform), and if you consider a single homogeneous vertical layer (not defined here). Please clarify.

Eq. 9: What is the final range of values you obtained for alpha using this equation? Is it in line with values from the literature for similar forests?

 

References

Raupach, M.R., Finnigan, J.J., Brunei, Y., 1996. Coherent eddies and turbulence in vegetation canopies: The mixing-layer analogy. Bound.-Lay. Meteorol. 78, 351—382. http://dx.doi.org/10.1007/BF00120941.

Cintolesi, C., Barbano, F., Trudu, P. L., Finco, A., Gerosa, G., & Di Sabatino, S. (2023). Characterisation of flow dynamics within and around an isolated forest, through measurements and numerical simulations. Agricultural and Forest Meteorology, 339, 109557.

 

Martano, P. (2000). Estimation of surface roughness length and displacement height from single-level sonic anemometer data. Journal of Applied Meteorology, 39(5), 708-715.

The writing is sometimes lengthy and the manuscript is hard to read. Some sentences (see the examples below) are hard to understand and the general meaning needs to be extrapolated from the context. I suggest a deep rewriting, particularly of the first two sections which now and then are hard to follow.

 

Some unclear sentences to be rephrased:

Line 15: “… were used for footprint estimation for sources inside the canopy.” Did you mean the footprint of different sources inside the canopy?

Lines 24-25: “The FFP tool fails to evaluate the fetch of the cumulative flux of 80% against other methods; its value is approximately 3-5 fewer values of other methods (e.g. 200 m against 600-1100 m, which is circa 7h vs 25-40h).”

Lines: 76-77: “Reviewing data from Ameriflux Network, they found several order magnitude differences in the extents and areas of the footprint climatologies”. I understand that the authors found a difference of several orders of magnitude but not on what.

Line 90: “… as the actual area affected sensor …” Do you mean the actual area affecting the measurement of the sensor?

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors.

I am grateful for the opportunity to review the article "Seasonal dynamics of flux footprint for a measuring tower in Southern taiga via modeling and experimental data analysis". The article is devoted to an interesting and relevant topic.

There are several points that need improvement:

1. Line 18. Citations should be issued [].

2. The article completely lacks the "Discussion" section.

3. In Figure 7, the two seasons are indicated by the letter "S". How to distinguish them? Similarly with the letter "W". Give more detailed comments.

4. In section 1, specify the structure of the work by chapters and their brief description.

5. In section 1, specify the goals and objectives of the study.

6. Specify the limitations of the study.

7. In general, it seemed to me that the article is quite difficult to understand and I recommend the authors to improve the style of presentation of the material.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have made a good effort for improving the manuscript. Both language and scientific issues raised by this reviewer were satisfactorily addressed and I can recommend this paper for publication. Here you find few very minor comments or typos.

Lines 248-250: I am not fully convinced by the fact that averaging would cancel out the roughness layer effect because this might be a site specificity. Since you cited Fig 3 for this scope I would rather refer to it to explain how the agrrement you see there is sufficient for your scopes and you can avoid accounting for the roughness layer.

Line 267: this might be a typo but I cannot see a ratio in this sentence

Line 343: This should be referenced to section 2.3

 

Language issues has been addressed. Very minor correct could be possible but the quality is more than acceptable

Author Response

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Reviewer 2 Report

Esteemed Authors,

 

I am content with the responses provided to my inquiries. I would like to propose refinements for further enhancing the manuscript:

 

1. Improve the image quality. It has come to my attention that the clarity of the illustrations appears to have diminished compared to the initial manuscript version.

 

2. In lines 15 and 19, kindly refrain from specifying the year and, instead, employ square brackets [] for author citations.

Author Response

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Author Response File: Author Response.docx