Global Monitoring of the Vegetation Dynamics from the Vegetation Optical Depth (VOD): A Review
, Jean-Pierre Wigneron 2, Xiaojun Li 2, Xiangzhuo Liu 2, Amen Al-Yaari 3, Lei Fan 4, Mengjia Wang 2,5, Christophe Moisy 2, Erwan Le Masson 2, Zacharie Aoulad Lafkih 2, Clément Vallé 2, Bertrand Ygorra 2,6 and Nicolas Baghdadi 7Round 1
Reviewer 1 Report
A very comprehensive review of the Vegetation Optical Depth (VOD) describing methods (passive/active sensors), applications, datasets, advantages, and drawbacks.
Minor issues.
L63: more properly than "were used" is "have been used"
L76: remove "the" from "the between."
Figure 1: lines could be of different colors or shapes to ease figure interpretation. Why roman and Arabic numbers?
L122-L123: change the point for "x", e.g., 6.62607015.10−34 J by 6.62607015 x 10−34 122 J
L127: use the greek letter epsilon for emissivity
Table 1: what about Sentinel-1? as shown in [140]
L493-506: letter size change regarding the rest of the manuscript.
L675-676: caption of the figure is on a different page from the plot.
L175: "NDI" is "NDVI"
Author Response
Please find our responses to your comments.
Kind regards,
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper “Global monitoring of the vegetation dynamics from the Vegetation Optical Depth (VOD): a review” presented a good summary of previous studies on VOD. This article will have a wide range of readers. I have some suggestions to improve the manuscript. The comments are written briefly. Sorry about it.
- Line 31, ….a wide range of ecological vegetation variables. Could you give some examples of the vegetation variables here? For example, …ecological vegetation variables (e.g. XX, XX ….).
- Line 81, … the spatial resolution increases with the frequency. Please clarify how the frequency changes like frequency increase or decrease?
- Line 93-94, … the extinction effects due to the vegetation ….. In this sentence, the extinction effects were not described clearly. Please rehearse this sentence with more detailed information.
- Line 96, …are available at different frequency bands and ….. What are the widely used frequency? Please give some examples.
- Line 97, there are many vegetation features. Please list some specific features here.
- Line 110, a short sentence to describe the meaning of figure 1 was put at the beginning of the caption, which will be better for readers to understand.
- Line 177, could you give more information about the results obtained in [72]?
- Line 205, there are tleaf and tstalk in the equations. Please double-check it is tleaf or tstalk.
- Line 207, How to determine the model parameters of αleaf and αstalk?
- Part 2.3 Global long-term VOD products: Readers could want to use these products in their studies. Could you give some information about the availability of these products? If they are public, could you provide the download links?
- Line 407, part 3.1 Experimental and theoretical studies: Could you make a figure to summarize the critical results of empirical and semi-empirical relationships in previous studies. Thus, it is easy for readers to get knowledge without check the references one by one.
- Line 435-436, lower biomass and higher biomass levels are vague. Could you give some numbers to show the ranges of biomass that are defined as lower or higher biomass?
- Line 443, what are the land cover types in this study?
- Line 453, …obtained over sparse vegetation areas in central Australia ….
What is the coverage of the vegetation? How to define the sparse?
- Line 469-471, what are the land cover types, e.g. forest, crop or grasslands?
- Line 612-613, This time-lag …light availability. Please give more descriptions about this phenomenon to explain why the adaptation decreased the time-lags between LAI and VOD?
Author Response
Please find our responses to your comments.
Kind regards,
Author Response File: Author Response.docx
