Testing a novel sensor design to jointly measure cosmic-ray neutrons, muons and gamma rays for non-invasive soil moisture estimation
Abstract. Cosmic-ray neutron sensing (CRNS) has emerged as a reliable method for soil moisture and snow estimation. However, the applicability of this method beyond research has been limited due to, among others, the use of relatively large and expensive sensors. This paper presents the tests conducted to a new scintillator-based sensor especially designed to jointly measure neutron counts, total gamma-rays, and muons. The neutron signal is firstly compared against two conventional gas-tube-based CRNS sensors at two locations (Austria and Germany). The estimated soil moisture is further assessed at four agricultural sites in Italy based on gravimetric soil moisture collected within the sensor footprint. The results show that the signal detected by the new scintillator-based CRNS sensor is well in agreement with the conventional CRNS sensors and with the gravimetric soil moisture measurements. In addition, the muons and the total gamma-rays simultaneously detected by the sensor show promising features for a better correction of the incoming variability and for discriminating irrigation and precipitation events, respectively. Further experiments and analyses should be conducted, however, to better understand the added value of these additional data for soil moisture estimation. Overall, the new scintillator design shows to be a valid and compact alternative to conventional CRNS sensors for non-invasive soil moisture monitoring that can open the path to a wide range of applications.
Stefano Gianessi et al.
Status: final response (author comments only)
- RC1: 'Comment on gi-2022-20', Anonymous Referee #1, 02 Nov 2022
- CC1: 'Comment on gi-2022-20', Daniel Rasche, 10 Feb 2023
- RC2: 'Comment on gi-2022-20', Anonymous Referee #2, 14 Feb 2023
Stefano Gianessi et al.
Data in support to the manuscript: Testing a novel sensor design to jointly measure cosmic-ray neutrons, muons and gamma rays for non-invasive soil moisture estimation by Gianessi et al. https://zenodo.org/record/7261534
Model code and software
Spreadsheets for soil samples and CRNS data processing https://zenodo.org/record/7156607
Stefano Gianessi et al.
Viewed (geographical distribution)
The authors present a novel set of experiments using a new sensor to simultaneously measure neutrons, muons, and gammas. The new sensor is compared to conventional sensors with satisfactory results for longer time periods of integration (i.e. 6 hrs for neutrons). The technology is lighter and potentially a lower cost, which will open up doors for more applications in science and in practical applications. The manuscript is well written and appropriate for the journal. I have a few suggestions that should be addressed prior to publication. Some instances of English grammar and word choice will need to be addressed.
L33: “Runoff generation”
L 40: “More recently, attention”
L 44: “has shown”
Figure 1: Are events outside of the blue and red ovals not included in the analysis?
L165: For the gammas are there any corrections needed for pressure or air temperature/humidity variations?
L247: I would use the SG filter on the neutron/gamma count time series, not the soil moisture time series that have been transformed by the calibration function.
L 302-305: This sentence is confusing and long. Please rewrite.
Figure 7. Will be interesting to compare the Muon detection with the correction factor being proposed by McJannet and Desilets using cutoff rigidity and atmospheric depth with the NMDB historical data. Unfortunately, that work is in the review process still.
Figure 8. So the soil moisture data is from FINAPP and not depth weighted following the Schron method? If you did have gravimetric surveys how would you depth weight them for the gamma sensitivity? From my understanding they would have a similar sensitivity with depth as the neutrons but be a little shallower (10-15cm?)?
Table 1. Iwema et al. 2015 recommends 3 calibrations for estimating N0. From the variability here I would do at least 3 to estimate some uncertainty on N0. I agree additional gravimetric studies are needed, particularly for establishing the gamma to soil moisture dependence, especially when used in cropping systems with significant temporal variations in vegetation biomass. Unfortunately, for CRNS and GRS studies all roads don’t lead to Rome but to more gravimetric sampling :).
Iwema, J., Rosolem, R., Baatz, R., Wagener, T., & Bogena, H. (2015). Investigating temporal field sampling strategies for site-specific calibration of three soil moisture–neutron intensity parameterisation methods. HESS, 19, 3203–3216. https://doi.org/10.5194/hess-19-3203-2015