Review/comments on Brief Communication: A new drought monitoring network in the state of Brandenburg (Germany) using cosmic-ray neutron sensing by Altdorff et al.

General comments

The Authors present a very relevant and interesting initiative to establish an operational ground-based long-term soil moisture monitoring based on cosmic-ray neutron sensors (CRNS). Nine locations and around six months of data are presented. Comparisons with the soil moisture simulated by the agro-hydrological model SWAP are also reported. The manuscript reads well and clear. The preliminary results are meaningful and the discussion fair.

Personally, I believe that the main contribution of this initiative is (L39) to bring together a consortium of research institutions and state agencies for establishing a long-term monitoring. And I would congratulate with the Authors for such an effort in moving CRNS research activities towards long term operational monitoring. But back to the manuscript, it reads like an internal report of current status of the initiative and I’m not convinced that is worth a publication.

I admit that this bold statement starts from the wish to read novelty in scientific papers and to not consider pure tech-transfer project innovative. In questioning my self-position, I made two actions. First, I look at the description of Brief communications, as it could have provided me with the right angle for judging the manuscript. The description is reported below. In addition, I looked at other published papers with similar vision (to my knowledge). Some of the papers are listed below.

Brief communications are timely, peer-reviewed, and short (2–4 journal pages). These may be used to (a) report new developments, significant advances, and novel aspects of experimental and theoretical methods and techniques which are relevant for scientific investigations within the journal scope; (b) report/discuss significant matters of policy and perspective related to the science of the journal, including "personal" commentary; (c) disseminate information and data on topical events of significant scientific and/or social interest within the scope of the journal. Brief communications have a maximum of three figures and/or tables, maximum 20 references, and an abstract length not exceeding 100 words. The manuscript title must start with "Brief communication:".

Benninga, Harm-Jan F., Coleen D. U. Carranza, Michiel Pezij, Pim van Santen, Martine J. van der Ploeg, Denie C. M. Augustijn, and Rogier van der Velde. ‘The Raam Regional Soil Moisture Monitoring Network in the Netherlands’. Earth System Science Data 10, no. 1 (11 January 2018): 61–79. https://doi.org/10.5194/essd-10-61-2018.

Cosh, Michael H., Todd G. Caldwell, C. Bruce Baker, John D. Bolten, Nathan Edwards, Peter Goble, Heather Hofman, et al. ‘Developing a Strategy for the National Coordinated Soil Moisture Monitoring Network’. Vadose Zone Journal 20, no. 4 (July 2021): e20139. https://doi.org/10.1002/vzj2.20139.

Well, as for the Brief Communications, I leave to the Handling Editor to decide. Anyway, I highlight how the number of pages of the manuscript is way too much. Moreover, its scope might be (c) even if information and data do not seem to be properly disseminated.

By looking at other published papers on similar topic (examples above), I have seen much more information in describing the issues and the effort, e.g., to establish such a network, to standardize the observations, to integrate the new data in current platforms, in defining accessibility to end users.

Overall, while I’m currently not in favour of the publication of the present manuscript, by considering previous published papers, it might be considered if the Authors put much more effort and they succeed in improving the manuscript, e.g., by sharing their experiences in establishing, maintaining, and managing a fixed environmental sensor network that could be of utility to the community for avoiding mistakes and reproducing good practices. Improving metadata (e.g., how was the calibration performed?), transparency (how data have been processed) and data accessibility (e.g., by API-type) should also justify the publication.

In this Brief Communication, the authors present a new initiative in Germany to establish an operational, long-term soil moisture monitoring system based on cosmic-ray neutron sensors (CRNS) for the state of Brandenburg. In general, this is a very positive development, as CRNS has established itself as a new standard method for the continuous determination of soil moisture at the field scale and the widespread deployment of these sensors is very helpful and highly welcome both for environmental research and for the support of water management.

In terms of content, this article presents the status of the project as well as a comparison of the measured soil moisture with simulations of the agrohydrological model SWAP.

The manuscript is well written; however, I have to agree with reviewer #1 that the paper reads more like a project report and does not fulfil the NHESS requirements for short communications, especially in terms of the length of the paper.

Also, it may be beneficial to complete the installation and subsequently measure soil moisture over a longer period of time. Once this has been achieved, the authors could publish the results as a data paper. Finally, we don’t learn much from the case study and the context of the comparison of CRNS data with simulation is unclear (see also specific comment further below).

Specific comments:

L38: Why mention only national networks?

L44: Such an initiative is not unique in Germany, see e.g. Ney et al. (2021).

Figure 1: The small maps are hardly recognizable and the situation at the measuring stations is not readable. Also, this this information is already available in table 1. Therefore, I suggest removing the small maps.

L54-71: This sounds very much like an interim report.

L116-119: It is not clear to me how this comparison is to be analysed in this project. What are the consequences if there are discrepancies? Do you then not trust the measurement data, even though the model certainly may have a much higher uncertainty?

L126-129: Describing commitments should not be part of a scientific publication. It would make more sense to present the concrete implementation of a real-time data platform.

L139-140: Formulations such as “some validity” and “some transferability” are too vague.

L142-145: This seems to be rather an alternative measurement approach instead of an upscaling approach for the presented CRNS network.

References

Ney, P., Köhli, M., Bogena, H., & Goergen, K. (2021). CRNS-based monitoring technologies for a weather and climate-resilient agriculture: Realization by the ADAPTER project. In 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor) (pp. 203-208). IEEE.