2017
DOI: 10.5194/hess-21-5009-2017
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Improving calibration and validation of cosmic-ray neutron sensors in the light of spatial sensitivity

Abstract: Abstract. In the last few years the method of cosmic-ray neutron sensing (CRNS) has gained popularity among hydrologists, physicists, and land-surface modelers. The sensor provides continuous soil moisture data, averaged over several hectares and tens of decimeters in depth. However, the signal still may contain unidentified features of hydrological processes, and many calibration datasets are often required in order to find reliable relations between neutron intensity and water dynamics. Recent insights into … Show more

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Cited by 123 publications
(278 citation statements)
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“…This radius varies between 130 and 240 m depending on the site conditions, which is significantly larger than the typical spatial correlation length of soil moisture patterns (Western et al, 2004). The penetration depth of CRNP measurements varies between 15 cm for wet soils to 55 cm for dry soils (Schrön et al, 2017). Due to this large sample volume, the information content of CRNP data could potentially improve the estimation of effective SHPs for LSMs because the scale mismatch between sample volume and model resolution is much smaller.…”
mentioning
confidence: 99%
“…This radius varies between 130 and 240 m depending on the site conditions, which is significantly larger than the typical spatial correlation length of soil moisture patterns (Western et al, 2004). The penetration depth of CRNP measurements varies between 15 cm for wet soils to 55 cm for dry soils (Schrön et al, 2017). Due to this large sample volume, the information content of CRNP data could potentially improve the estimation of effective SHPs for LSMs because the scale mismatch between sample volume and model resolution is much smaller.…”
mentioning
confidence: 99%
“…To this end, different weighting approaches have been proposed for CRNP calibration, taking into account the probe's effective measuring footprint. The methods include the conventional (Franz et al, ), conventional nonlinear (Bogena et al, ), and revised (Schrön et al, ) approaches. Since points in the CRNP's footprint contribute differently to the measured neutron counts, different weights need to be assigned as functions of soil moisture, distance, and depth (Schrön et al, ).…”
Section: Methodsmentioning
confidence: 99%
“…The methods include the conventional (Franz et al, ), conventional nonlinear (Bogena et al, ), and revised (Schrön et al, ) approaches. Since points in the CRNP's footprint contribute differently to the measured neutron counts, different weights need to be assigned as functions of soil moisture, distance, and depth (Schrön et al, ). The equally weighting method has thus been replaced with the conventional and revised methods in current CRNP calibration/validation campaigns as they are based on the cosmic neutron creation and transport theory, that is, weighting is based on the contribution of fast neutron flux from different layers to the total flux over the profile (Bogena et al, ; Franz et al, ; Köhli et al, ; Schrön et al, ; Zreda et al, ).…”
Section: Methodsmentioning
confidence: 99%
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“…Bogena et al 2013;Franz et al 2015Franz et al , 2016Iwema et al 2017, among others) have shown the CRNP to have area-average measurement accuracies of less than 0.03 cm 3 cm −3 against a variety of industry standard SWC point scale probes. The calculated SWC within the measurement volume in a non-linearly weighed average with increased sensitivity near the CRNP (Schrön et al 2017). In order to provide a SWC map, first a spatial map of neutron intensity was estimated, then a calibration function was applied following details in Franz et al (2015) for agricultural fields.…”
Section: Hydrogeophysical Datasetsmentioning
confidence: 99%