General Comments:
You can tell from the authors’ response and the revised manuscript that they really made an effort to take on the suggested changes from the reviews. That is very much appreciated.
The structure of the manuscript has improved considerably. It is much clearer now and the results are explained in a more comprehensible way than before. Also, the authors added more details and explanations of their findings.
Within the text there is still a frustrating amount of spelling, syntax and style errors. Given the amount of co-authors well capable of detecting and correcting these errors, this fact is surprising. It feels like they left these errors for the reviewers to point out and correct.
The story of the abstract could be improved for better readability and the use of the word ‘sensitivity’ should be checked carefully at each occurrence.
For these reasons I recommend this manuscript for publication pending some more revisions.
Specific Comments:
Abstract: The abstract could tell a better story by giving some more information and connecting the individual statements better. You write for example: ‘This method has been used for measuring soil moisture but several other hydrogen pools affect the signal.’
-Which method?
-The ‘but’ does not fit in this sentence
-Why is it a problem that other pools affect the signal?
Maybe it would be better to write something along the lines of ‘Relating cosmic ray neutron counts to the presence of (more or fewer) water molecules within the footprint of the sensor is used for quantifying/measuring the hydrogen content of soil moisture. This is, however, complicated by the fact that several other hydrogen pools affect the signal.’
It would be much easier for the reader to follow.
You should state your intentions early in the abstract: Why have you done this study? You tell us what you have done but with little explanation on your actual goals.
Appropriate would be something like: ‘In order to shed light on the influence of several other hydrogen pools on the measured signal we performed a sensitivity analysis using a neutron transport model with various representations of…’.
Maybe add a concluding statement to the end. ‘While biomass affects … considerably, we found canopy interception to be of minor importance…’.
Page 2, Line 28: ‘…at intermediate spatial scales…’
Page 3, Line 12: ‘For the preparation of cosmic-ray neutron data THE correction for changes in atmospheric water vapor is A STANDARD PROCEDURE along with corrections for temporal variations in barometric pressure and incoming cosmic radiation…’
The native English speakers amongst your co-authors could have done a better job in correcting some of the language and style. Maybe they can carefully read the whole paper one more time.
Page 3, Line 20: What about studies that call for a modification of the calibration function itself (e.g. Iwema et al. 2015, Heidbüchel et al. 2016)? They argue that the function must be adapted to the local environment (more biomass vs. less biomass, higher variability in soil properties with depth vs. lower variability, etc.).
Page 5, Line 5-6: Thermal and epithermal neutron intensities are considered in order to explore the possibilities they offer when observed at the same time (not because they are characterized by very different physical properties – that is the prerequisite for using them in combination).
Page 5, Line 15: What exactly is the ‘environmental effect’?
Page 5: Line 29-31: No dots after ‘eV’.
Page 6, Line 3: ‘…are sensitive…’.
Page 6, Line 22: Better write: ‘Nonetheless, still a large proportion originates from below 0.5 eV (approximately…’.
Page 6, Line 30: Any clues on why you believe that?
Page 7, Line 14: Potential problems could arise here. If you use a model to correct/infer pure thermal and pure epithermal neutron intensities, the observed differences can always be explained by this correction model and all the assumptions you made when setting it up.
Page 8, Line 11: ‘…the Danish…’.
Page 9, Line 17: Maybe add some units (m³ m-³)?
Page 11, Line 27: You should definitely add some units (m³ m-³).
Page 11, Line 32: You don’t have to repeat the whole ‘The Gludstedt Plantation reference model’. The second time, just say ‘It’.
Page 13, Line 10: You ‘…rely mostly on the time series measurements…’ for what purpose exactly?
Page 13, Line 13-14: Did you specify this theory anywhere? For example, why does the thermal neutron intensity theoretically decrease with height?
Page 13, Line 14: considerably
Page 14, Line 1: What do you mean by ‘Here’.
Page 14, Line 1: performED
Page 14, Line 1: What do you mean by ‘occasionally’?
Page 14, Line 12-13: Please rearrange the sentence. This way it is confusing.
Page 14, Line 18-20: The two sentences contradict each other (similar vs. more sensitive).
Page 14, Line 20: sensitive
Page 15, Line 5: Additionally, SINCE(?) a considerable range of (what kind of?) values is measured within the footprint of the neutron detector the sensitivity OF NEUTRON INTENSITY to litter and mineral soils dry bulk density is examined…
Carefully check your language again, often the sentences are in the wrong order and therefore very hard to understand.
Page 15, Line 7: What is a ‘higher’ litter layer?
Page 15, Line 9-12: Any ideas on why this is observed?
Page 15, Line 27: ‘we chose’
Page 16, Line 1: So is this change in t/e ratio larger than the noise/measurement uncertainty?
Page 16, Line 4-5: Maybe ‘relation’ is a more appropriate word than ‘sensitivity’. Not only here but throughout the manuscript you should review the use of ‘sensitivity’ which describes in my view the responsiveness of one variable to the change of a certain parameter (mostly used in a modeling context).
Then you could write: The relation of thermal and epithermal neutron intensity to the amount of forest biomass using the forest canopy conceptualization of… is presented…
Page 16, Line 29: ‘provide’
Page 17, Line 15: Are the bi-weekly averages of measurements really much wider? They should be the same, no?
Page 17, Line 27: The area average soil moisture derived from field sampling (and oven-drying)?
Page 17, Line 28: You do have that data to look at. I mean you have the soil moisture profile from the field sampling and the soil moisture content of the litter layer, no? You could mention the observed differences more explicitly.
Page 17, Line 31: ‘AdditionalLY’
Page 18, Line 12: ‘The sensitivity OF neutron…’. Again, this should be picked up by native English speakers.
Page 18, Line 13: ‘Contrary to Gludsted Plantation, the sensitivity of thermal and epithermal neutron intensity profiles to soil chemistry was…’
Page 18, Line 16-26: This is an excellent example of how to discuss and interpret your findings. Very clear and comprehensible.
Page 19, Line 3: See Page 18, Line 12.
Page 20, Line 26: ‘…using the simplest…’.
Page 20, Line 27: ‘…the forest’s…’.
Page 20, Line 31: You should use only one tense in a sentence (or better, in the whole section) not both past and present mixed.
Page 20, Line 32: ‘…half-hourLY…’.
Page 21, Line 2: ‘…more sensitive…’.
Page 21, Line 9: ‘…were found…’.
Figure 1: It looks as if something is wrong with this figure. You should make the background of the small map of Denmark nontransparent.
Figure 6: Better write the caption this way: ‘Sensitivity to (A.) litter layer thickness using Model Tree trunk, Foliage, Air, (B.) canopy interception using Model Tree trunk, Foliage, Air, biomass using (C.) Model Tree trunk, Foliage, Air and (D.) Model Foliage, respectively…’
References:
Iwema, J., Rosolem, R., Baatz, R., Wagener, T., and Bogena, H. R.: Investigating temporal field sampling strategies for site-specific calibration of three soil moisture–neutron intensity parameterisation methods, Hydrol. Earth Syst. Sci., 19, 3203-3216, 10.5194/hess-19-3203-2015, 2015.
Heidbüchel, I., Güntner, A., and Blume, T.: Use of cosmic-ray neutron sensors for soil moisture monitoring in forests, Hydrol. Earth Syst. Sci., 20, 1269-1288, 10.5194/hess-20-1269-2016, 2016. |