TY - JOUR A1 - Schrön, Martin A1 - Zacharias, Steffen A1 - Womack, Gary A1 - Köhli, Markus A1 - Desilets, Darin A1 - Oswald, Sascha A1 - Bumberger, Jan A1 - Mollenhauer, Hannes A1 - Kögler, Simon A1 - Remmler, Paul A1 - Kasner, Mandy A1 - Denk, Astrid A1 - Dietrich, Peter T1 - Intercomparison of cosmic-ray neutron sensors and water balance monitoring in an urban environment JF - Geoscientific instrumentation, methods and data systems N2 - Sensor-to-sensor variability is a source of error common to all geoscientific instruments that needs to be assessed before comparative and applied research can be performed with multiple sensors. Consistency among sensor systems is especially critical when subtle features of the surrounding terrain are to be identified. Cosmic-ray neutron sensors (CRNSs) are a recent technology used to monitor hectometre-scale environmental water storages, for which a rigorous comparison study of numerous co-located sensors has not yet been performed. In this work, nine stationary CRNS probes of type "CRS1000" were installed in relative proximity on a grass patch surrounded by trees, buildings, and sealed areas. While the dynamics of the neutron count rates were found to be similar, offsets of a few percent from the absolute average neutron count rates were found. Technical adjustments of the individual detection parameters brought all instruments into good agreement. Furthermore, we found a critical integration time of 6 h above which all sensors showed consistent dynamics in the data and their RMSE fell below 1% of gravimetric water content. The residual differences between the nine signals indicated local effects of the complex urban terrain on the scale of several metres. Mobile CRNS measurements and spatial simulations with the URANOS neutron transport code in the surrounding area (25 ha) have revealed substantial sub-footprint heterogeneity to which CRNS detectors are sensitive despite their large averaging volume. The sealed and constantly dry structures in the footprint furthermore damped the dynamics of the CRNS-derived soil moisture. We developed strategies to correct for the sealed-area effect based on theoretical insights about the spatial sensitivity of the sensor. This procedure not only led to reliable soil moisture estimation during dry-out periods, it further revealed a strong signal of intercepted water that emerged over the sealed surfaces during rain events. The presented arrangement offered a unique opportunity to demonstrate the CRNS performance in complex terrain, and the results indicated great potential for further applications in urban climate research. Y1 - 2018 U6 - https://doi.org/10.5194/gi-7-83-2018 SN - 2193-0856 SN - 2193-0864 VL - 7 IS - 1 SP - 83 EP - 99 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Francke, Till A1 - Heistermann, Maik A1 - Köhli, Markus A1 - Budach, Christian A1 - Schrön, Martin A1 - Oswald, Sascha T1 - Assessing the feasibility of a directional cosmic-ray neutron sensing sensor for estimating soil moisture JF - Geoscientific Instrumentation, Methods and Data Systems N2 - Cosmic-ray neutron sensing (CRNS) is a non-invasive tool for measuring hydrogen pools such as 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 prevent neutrons from certain angles from being counted while counting neutrons entering the detector from other angles and explores its potential to gain a sharper horizontal view on the surrounding soil moisture distribution. Using the Monte Carlo code URANOS (Ultra Rapid Neutron-Only Simulation), 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 half-spaces could not lead to acceptable precision at a daily time resolution. However, the mere statistical distinction of two rates should be feasible. KW - water-balance KW - quantification KW - calibration KW - validation Y1 - 2021 U6 - https://doi.org/10.5194/gi-11-75-2022 SN - 2193-0864 SN - 2193-0856 VL - 11 SP - 75 EP - 92 PB - Copernicus Publ. CY - Göttingen ER -