Preprints
https://doi.org/10.5194/gi-2021-18
https://doi.org/10.5194/gi-2021-18

  15 Jun 2021

15 Jun 2021

Review status: this preprint is currently under review for the journal GI.

Assessing the feasibility of a directional CRNS-sensor for estimating soil moisture

Till Francke1, Maik Heistermann1, Markus Köhli3,4, Christian Budach1, Martin Schrön2, and Sascha E. Oswald1 Till Francke et al.
  • 1Institute of Environmental Science and Geography, University of Potsdam, Karl-Liebknecht-Straße 24–25, 14476 Potsdam, Germany
  • 2UFZ – Helmholtz Centre for Environmental Research GmbH, Dep. Monitoring and Exploration Technologies, Permoserstr. 15, 04318, Leipzig, Germany
  • 3Physikalisches Institut, Heidelberg University, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
  • 4Physikalisches Institut, University of Bonn, Nussallee 12, 53115 Bonn, Germany

Abstract. Cosmic Ray Neutron Sensing (CRNS) is a non-invasive tool for measuring hydrogen pools like soil moisture, snow, or vegetation. The intrinsic integration over a radial hectare-scale footprint is a clear advantage for averaging out small-scale heterogeneity, but on the other hand the data may become hard to interpret in complex terrain with patchy land use.

This study presents a directional shielding approach to block neutrons from certain directions and explores its potential to gain a sharper view on the surrounding soil moisture distribution.

Using the Mont-Carlo code URANOS, we modelled the effect of additional polyethylene shields on the horizontal field of view and assessed its impact on the epithermal count rate, propagated uncertainties, and aggregation time.

The results demonstrate that directional CRNS measurements are strongly dominated by isotropic neutron transport, which dilutes the signal of the targeted direction especially from the far field. For typical count rates of customary CRNS stations, directional shielding of halfspaces could not lead to acceptable precision at a daily time resolution. However, the mere statistical distinction of two rates should be feasible.

Till Francke et al.

Status: open (until 27 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Till Francke et al.

Till Francke et al.

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Short summary
Cosmic Ray Neutron Sensing (CRNS) is a non-invasive tool for measuring hydrogen pools like soil moisture, snow, or vegetation. This study presents a directional shielding approach, aiming to measure in specific directions only. The results show that non-directional neutron transport blurs the signal of the targeted direction. For typical instruments, this does not allow acceptable precision at a daily time resolution. However, the mere statistical distinction of two rates is feasible.