Use of cosmic-ray neutron sensors for soil moisture monitoring in forests

Heidbüchel, Ingo; Güntner, Andreas; Blume, Theresa

doi:https://doi.org/10.5194/hess-20-1269-2016

Articles | Volume 20, issue 3

https://doi.org/10.5194/hess-20-1269-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-20-1269-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 20, issue 3

Research article

|

30 Mar 2016

Research article |

| 30 Mar 2016

Use of cosmic-ray neutron sensors for soil moisture monitoring in forests

Ingo Heidbüchel, Andreas Güntner, and Theresa Blume

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Final revised paper (published on 30 Mar 2016)
Supplement to the final revised paper
Preprint (discussion started on 25 Sep 2015)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C4229: 'Review of “Use of cosmic ray neutron sensors for soil moisture monitoring in forests“ by Heidbüchel et al', Heye Bogena, 13 Oct 2015
- AC C4959: 'Response to Interactive comment by H. Bogena (Referee)', Ingo Heidbüchel, 19 Nov 2015
RC C4344: 'Review comments', Anonymous Referee #2, 20 Oct 2015
- AC C4960: 'Response to Interactive comment by Anonymous Referee #2', Ingo Heidbüchel, 19 Nov 2015
RC C4347: 'Review text: HESSD 12-9813-2015', Anonymous Referee #3, 21 Oct 2015
- AC C4961: 'Response to Interactive comment by Anonymous Referee #3', Ingo Heidbüchel, 19 Nov 2015
  - RC C4962: 'answer to the question how to convert pressure to shielding depth', Anonymous Referee #3, 19 Nov 2015
    - AC C4966: 'Shielding depth will be added!', Ingo Heidbüchel, 20 Nov 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (05 Dec 2015) by Harrie-Jan Hendricks Franssen

AR by Ingo Heidbüchel on behalf of the Authors (15 Jan 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Jan 2016) by Harrie-Jan Hendricks Franssen

RR by Heye Bogena (05 Feb 2016)

Suggestions for revision or reasons for rejection

Second review of “Use of cosmic ray neutron sensors for soil moisture monitoring in forests“ by Heidbüchel et al.

I have reviewed this manuscript for the second time. The authors have improved their manuscript considering most of my earlier comments. It will be a nice contribution to the HESS. However, there are still several minor issues which need to be considered:

As mentioned in my earlier review, calibration has to be performed using the total hydrogen pool, and soil moisture is then computed by subtracting other hydrogen pools than soil moisture from the measured neutron-derived soil moisture. Also the authors have stated in their cover letter that this procedure was applied in this study but this procedure is still not clearly stated in the revised manuscript and it is also not mentioned in their “Best practice” description.

In my first review I have stated the following: “The results plotted in Fig. 12 show clearly, that only the most extreme dry and wet samplings result in an acceptable calibration result, whereas sampling at intermediate soil moisture will lead to very uncertain calibration of the modified N0-method. On the other hand, this illustrates the value of the standard N0-method that will also produce stable results in case only one sampling date is available. Please add this to the discussion.”
The authors answer was: “Fig. 9 shows that the best 2-point-calibrations are achieved with one sampling point taken under very dry conditions and another sampling point taken either under intermediate or wet conditions. In our case it is hard to see the value of the standard N0-method since it always resulted in too much soil moisture variability no matter whether the calibration was performed during wet, intermediate or dry conditions (because the standard calibration of N0 does not allow a change of the slope of the calibration function).”
Clearly the authors didn’t fully grasp my comment. The value of the standard N0-method lies in its predefined form that makes calibration using data from a single sampling date more stable than the modified N0-method. This should be added to the discussion since there might be cases where only one calibration date is available.

L47: …neutrons interact with air and soil nuclei…

L414: delete “resolution”

Figure 1: The blue dots are difficult to discern.

Figure 2: The modified schematic shown in this figure is still confusing. Why should the factors influencing the cosmic-ray intensity a ground level be symbolized a rays of different length? I find this irritating and not helpful for the understanding of the involved processes. In addition, the presented sensing depth boundaries are too numerous be discernible and the distribution is not correct. A better representation can be found in Köhli et al., 2015.Thus, in my opinion the figure should be omitted.

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RR by Anonymous Referee #2 (09 Feb 2016)

RR by Anonymous Referee #3 (18 Feb 2016)

ED: Publish subject to minor revisions (Editor review) (26 Feb 2016) by Harrie-Jan Hendricks Franssen

AR by Ingo Heidbüchel on behalf of the Authors (07 Mar 2016) Author's response Manuscript

ED: Publish subject to technical corrections (16 Mar 2016) by Harrie-Jan Hendricks Franssen

Short summary

Cosmic-ray neutron sensors bridge the gap between point-scale measurements of soil moisture and remote sensing applications. We tested four distinct methods to calibrate the sensor in a temperate forest environment using different soil moisture weighting approaches. While the variable leaf biomass of the deciduous trees had no significant influence on the calibration, it proved necessary to modify the standard calibration method to achieve the best sensor performance.