Cosmic Ray Neutron Soil Moisture Estimation Using Physically Based Site‐Specific Conversion Functions

2020 ◽  
Vol 56 (11) ◽  
Author(s):  
Mie Andreasen ◽  
Karsten H. Jensen ◽  
Heye Bogena ◽  
Darin Desilets ◽  
Marek Zreda ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Cosmic Ray ◽  
Site Specific ◽  
Physically Based ◽  
Moisture Estimation

scholarly journals Investigating temporal field sampling strategies for site-specific calibration of three soil moisture–neutron intensity parameterisation methods

2015 ◽  
Vol 19 (7) ◽  
pp. 3203-3216 ◽  
Author(s):  
J. Iwema ◽  
R. Rosolem ◽  
R. Baatz ◽  
T. Wagener ◽  
H. R. Bogena
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Satellite Remote Sensing ◽  
Cosmic Ray ◽  
Sampling Strategies ◽  
Site Specific ◽  
Neutron Intensity ◽  
Soil Wetness ◽  
Semi Arid

Abstract. The Cosmic-Ray Neutron Sensor (CRNS) can provide soil moisture information at scales relevant to hydrometeorological modelling applications. Site-specific calibration is needed to translate CRNS neutron intensities into sensor footprint average soil moisture contents. We investigated temporal sampling strategies for calibration of three CRNS parameterisations (modified N0, HMF, and COSMIC) by assessing the effects of the number of sampling days and soil wetness conditions on the performance of the calibration results while investigating actual neutron intensity measurements, for three sites with distinct climate and land use: a semi-arid site, a temperate grassland, and a temperate forest. When calibrated with 1 year of data, both COSMIC and the modified N0 method performed better than HMF. The performance of COSMIC was remarkably good at the semi-arid site in the USA, while the N0mod performed best at the two temperate sites in Germany. The successful performance of COSMIC at all three sites can be attributed to the benefits of explicitly resolving individual soil layers (which is not accounted for in the other two parameterisations). To better calibrate these parameterisations, we recommend in situ soil sampled to be collected on more than a single day. However, little improvement is observed for sampling on more than 6 days. At the semi-arid site, the N0mod method was calibrated better under site-specific average wetness conditions, whereas HMF and COSMIC were calibrated better under drier conditions. Average soil wetness condition gave better calibration results at the two humid sites. The calibration results for the HMF method were better when calibrated with combinations of days with similar soil wetness conditions, opposed to N0mod and COSMIC, which profited from using days with distinct wetness conditions. Errors in actual neutron intensities were translated to average errors specifically to each site. At the semi-arid site, these errors were below the typical measurement uncertainties from in situ point-scale sensors and satellite remote sensing products. Nevertheless, at the two humid sites, reduction in uncertainty with increasing sampling days only reached typical errors associated with satellite remote sensing products. The outcomes of this study can be used by researchers as a CRNS calibration strategy guideline.

scholarly journals Improving calibration and validation of cosmic-ray neutron sensors in the light of spatial sensitivity

2017 ◽  
Vol 21 (10) ◽  
pp. 5009-5030 ◽  
Author(s):  
Martin Schrön ◽  
Markus Köhli ◽  
Lena Scheiffele ◽  
Joost Iwema ◽  
Heye R. Bogena ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Cosmic Ray ◽  
Water Dynamics ◽  
Hydrological Processes ◽  
Spatial Sensitivity ◽  
Calibration And Validation ◽  
Physically Based ◽  
Point Data ◽  
Neutron Sensors

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 environmental neutrons accurately described the spatial sensitivity of the sensor and thus allowed one to quantify the contribution of individual sample locations to the CRNS signal. Consequently, data points of calibration and validation datasets are suggested to be averaged using a more physically based weighting approach. In this work, a revised sensitivity function is used to calculate weighted averages of point data. The function is different from the simple exponential convention by the extraordinary sensitivity to the first few meters around the probe, and by dependencies on air pressure, air humidity, soil moisture, and vegetation. The approach is extensively tested at six distinct monitoring sites: two sites with multiple calibration datasets and four sites with continuous time series datasets. In all cases, the revised averaging method improved the performance of the CRNS products. The revised approach further helped to reveal hidden hydrological processes which otherwise remained unexplained in the data or were lost in the process of overcalibration. The presented weighting approach increases the overall accuracy of CRNS products and will have an impact on all their applications in agriculture, hydrology, and modeling.

scholarly journals Investigating temporal field sampling strategies for site-specific calibration of three soil moisture – neutron intensity parameterisation methods

2015 ◽  
Vol 12 (2) ◽  
pp. 2349-2389 ◽  
Author(s):  
J. Iwema ◽  
R. Rosolem ◽  
R. Baatz ◽  
T. Wagener ◽  
H. R. Bogena
Keyword(s):  
Soil Moisture ◽  
Cosmic Ray ◽  
Strong Increase ◽  
Sampling Strategies ◽  
Work Effort ◽  
Site Specific ◽  
Temporal Sampling ◽  
Soil Wetness ◽  
Temporal Field ◽  
Semi Arid

Abstract. The Cosmic-Ray Neutron Sensor (CRNS) can provide soil moisture information at scales relevant to hydrometeorological modeling applications. Site-specific calibration is needed to translate CRNS neutron intensities into sensor footprint average soil moisture contents. We investigated temporal sampling strategies for calibration of three CRNS parameterisations (modified N0, HMF, and COSMIC) by assessing the effects of the number of sampling days and soil wetness conditions on the performance of the calibration results, for three sites with distinct climate and land use: a semi-arid site, a temperate grassland and a temperate forest. When calibrated with a year of data, COSMIC performed relatively good at all three sites, and the modified N0 method performed best at the two humid sites. It is advisable to collect soil moisture samples on more than a single day regardless of which parameterisation is used. In any case, sampling on more than ten days would, despite the strong increase in work effort, improve calibration results only little. COSMIC needed the least number of days at each site. At the semi-arid site, the N0mod method was calibrated better under average wetness conditions, whereas HMF and COSMIC were calibrated better under drier conditions. Average soil wetness condition gave better calibration results at the two humid sites. The calibration results for the HMF method were better when calibrated with combinations of days with similar soil wetness conditions, opposed to N0mod and COSMIC, which profited from using days with distinct wetness conditions. The outcomes of this study can be used by researchers as a CRNS calibration strategy guideline.

scholarly journals Status and Perspectives on the Cosmic-Ray Neutron Method for Soil Moisture Estimation and Other Environmental Science Applications

2017 ◽  
Vol 16 (8) ◽  
pp. vzj2017.04.0086 ◽  
Author(s):  
Mie Andreasen ◽  
Karsten H. Jensen ◽  
Darin Desilets ◽  
Trenton E. Franz ◽  
Marek Zreda ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Environmental Science ◽  
Cosmic Ray ◽  
Neutron Method ◽  
Moisture Estimation

scholarly journals Accuracy and precision of the cosmic‐ray neutron sensor for soil moisture estimation at humid environments

2021 ◽  
Author(s):  
Joost Iwema ◽  
Martin Schrӧn ◽  
Juliana Koltermann Da Silva ◽  
Rodolfo Schweiser De Paiva Lopes ◽  
Rafael Rosolem
Keyword(s):  
Soil Moisture ◽  
Cosmic Ray ◽  
Accuracy And Precision ◽  
Moisture Estimation

scholarly journals A Novel Cosmic-Ray Neutron Sensor for Soil Moisture Estimation over Large Areas

Agriculture ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 202 ◽  
Author(s):  
Luca Stevanato ◽  
Gabriele Baroni ◽  
Yafit Cohen ◽  
Cristiano Lino Fontana ◽  
Simone Gatto ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Moisture Content ◽  
Cosmic Ray ◽  
Soil Heterogeneity ◽  
Robust Solution ◽  
Drought Prediction ◽  
New Instrument ◽  
Agricultural Applications ◽  
Water Accounting ◽  
Moisture Estimation

A correct soil moisture estimation is a fundamental prerequisite for many applications: agriculture, meteorological forecast, flood and drought prediction, and, in general, water accounting and management. Traditional methods typically provide point-like measurements, but suffer from soil heterogeneity, which can produce significant misinterpretation of the hydrological scenarios. In the last decade, cosmic-ray neutron sensing (CRNS) has emerged as a promising approach for the detection of soil moisture content. CRNS can average soil moisture over a large volume (up to tens of hectares) of terrain with only one probe, thus overcoming limitations arising from the heterogeneity of the soil. The present paper introduces the development of a new CRNS instrument designed for agricultural applications and based on an innovative neutron detector. The new instrument was applied and tested in two experimental fields located in Potsdam (DE, Germany) and Lagosanto (IT, Italy). The results highlight how the new detector could be a valid alternative and robust solution for the application of the CRNS technique for soil moisture measurements in agriculture.

Bulk soil moisture estimation using CosmOz cosmic ray sensor and ANFIS

2012 ◽  
Author(s):  
Ritaban Dutta ◽  
Andrew Terhorst ◽  
Aaron Hawdon ◽  
Bill Cotching
Keyword(s):  
Soil Moisture ◽  
Cosmic Ray ◽  
Bulk Soil ◽  
Moisture Estimation

scholarly journals Cosmic-ray neutron transport at a forest field site: the sensitivity to various environmental conditions with focus on biomass and canopy interception

2017 ◽  
Vol 21 (4) ◽  
pp. 1875-1894 ◽  
Author(s):  
Mie Andreasen ◽  
Karsten H. Jensen ◽  
Darin Desilets ◽  
Marek Zreda ◽  
Heye R. Bogena ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Epithermal Neutron ◽  
Neutron Transport ◽  
Estimation Method ◽  
Cosmic Ray ◽  
Ground Level ◽  
Field Site ◽  
Canopy Interception ◽  
Neutron Intensity ◽  
Moisture Estimation

Abstract. Cosmic-ray neutron intensity is inversely correlated to all hydrogen present in the upper decimeters of the subsurface and the first few hectometers of the atmosphere above the ground surface. This correlation forms the base of the cosmic-ray neutron soil moisture estimation method. The method is, however, complicated by the fact that several hydrogen pools other than soil moisture affect the neutron intensity. In order to improve the cosmic-ray neutron soil moisture estimation method and explore the potential for additional applications, knowledge about the environmental effect on cosmic-ray neutron intensity is essential (e.g., the effect of vegetation, litter layer and soil type). In this study the environmental effect is examined by performing a sensitivity analysis using neutron transport modeling. We use a neutron transport model with various representations of the forest and different parameters describing the subsurface to match measured height profiles and time series of thermal and epithermal neutron intensities at a field site in Denmark. Overall, modeled thermal and epithermal neutron intensities are in satisfactory agreement with measurements; however, the choice of forest canopy conceptualization is found to be significant. Modeling results show that the effect of canopy interception, soil chemistry and dry bulk density of litter and mineral soil on neutron intensity is small. On the other hand, the neutron intensity decreases significantly with added litter-layer thickness, especially for epithermal neutron energies. Forest biomass also has a significant influence on the neutron intensity height profiles at the examined field site, altering both the shape of the profiles and the ground-level thermal-to-epithermal neutron ratio. This ratio increases with increasing amounts of biomass, and was confirmed by measurements from three sites representing agricultural, heathland and forest land cover. A much smaller effect of canopy interception on the ground-level thermal-to-epithermal neutron ratio was modeled. Overall, the results suggest a potential to use ground-level thermal-to-epithermal neutron ratios to discriminate the effect of different hydrogen contributions on the neutron signal.

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