Cosmic ray neutrons provide an innovative technique for estimating intermediate scale soil moisture

Vather, Thigesh; Everson, C. S.; Mengistu, M. G.; Franz, Trenton E.

doi:10.17159/sajs.2018/20170422

Cited by 9 publications

(20 citation statements)

References 21 publications

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“…On the other hand, the global comparison of the satellite products ( Figures 5-7) suggests that ASCAT product is as successful as the SMAP surface product in many regions. This result was also in line with the findings of recent studies [10,42]. It was also mentioned in Reference [14] that, among the other space-borne products, SMAP has greater correlation with CRNPs.…”

Section: And Unbiasedsupporting

confidence: 92%

Using Cosmic-Ray Neutron Probes in Validating Satellite Soil Moisture Products and Land Surface Models

Duygu

Akyürek

2019

Water

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Soil moisture content is one of the most important parameters of hydrological studies. Cosmic-ray neutron sensing is a promising proximal soil moisture sensing technique at intermediate scale and high temporal resolution. In this study, we validate satellite soil moisture products for the period of March 2015 and December 2018 by using several existing Cosmic Ray Neutron Probe (CRNP) stations of the COSMOS database and a CRNP station that was installed in the south part of Turkey in October 2016. Soil moisture values, which were inferred from the CRNP station in Turkey, are also validated using a time domain reflectometer (TDR) installed at the same location and soil water content values obtained from a land surface model (Noah LSM) at various depths (0.1 m, 0.3 m, 0.6 m and 1.0 m). The CRNP has a very good correlation with TDR where both measurements show consistent changes in soil moisture due to storm events. Satellite soil moisture products obtained from the Soil Moisture and Ocean Salinity (SMOS), the METOP-A/B Advanced Scatterometer (ASCAT), Soil Moisture Active Passive (SMAP), Advanced Microwave Scanning Radiometer 2 (AMSR2), Climate Change Initiative (CCI) and a global land surface model Global Land Data Assimilation System (GLDAS) are compared with the soil moisture values obtained from CRNP stations. Coefficient of determination ( r 2 ) and unbiased root mean square error (ubRMSE) are used as the statistical measures. Triple Collocation (TC) was also performed by considering soil moisture values obtained from different soil moisture products and the CRNPs. The validation results are mainly influenced by the location of the sensor and the soil moisture retrieval algorithm of satellite products. The SMAP surface product produces the highest correlations and lowest errors especially in semi-arid areas whereas the ASCAT product provides better results in vegetated areas. Both global and local land surface models’ outputs are highly compatible with the CRNP soil moisture values.

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Section: And Unbiasedsupporting

confidence: 92%

Using Cosmic-Ray Neutron Probes in Validating Satellite Soil Moisture Products and Land Surface Models

Duygu

Akyürek

2019

Water

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“…Soil water content is one of the key state variables in the soil-vegetation-atmosphere continuum, which is due to its role in the exchange of water and energy at the soil surface [1,2]. Soil water content is of great importance for several applications throughout numerous disciplines,; however, its quantification at a range of scales is challenging due to its spatial and temporal heterogeneity [3]. Accurate knowledge of the soil water content at a range of spatial scales is critical for water management, improved weather prediction, flood forecasting, and efficient irrigation scheduling [4,5].…”

Section: Introductionmentioning

confidence: 99%

The Applicability of the Cosmic Ray Neutron Sensor to Simultaneously Monitor Soil Water Content and Biomass in an Acacia mearnsii Forest

2020

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Soil water content is an important hydrological parameter, which is difficult to measure at a field scale due to its spatial and temporal heterogeneity. The Cosmic Ray Neutron Sensor (CRNS) is a novel and innovative approach to estimate area-averaged soil water content at an intermediate scale, which has been implemented across the globe. The CRNS is moderated by all hydrogen sources within its measurement footprint. In order to isolate the soil water content signal from the neutron intensity, the other sources of hydrogen need to be accounted for. The CRNS’s applications are not only limited to soil water content estimation, as it can potentially be used to monitor biomass. The Two-Streams clear-felling provided the unique opportunity to monitor the cosmic ray neutron intensities before, during, and after the clear-felling. The cadmium-difference method was used to obtain the pure thermal and epithermal neutron intensities from the bare and moderated detectors. The study concluded that the presence of biomass within the site reduced the epithermal neutron intensity by 12.43% and the N0 value by 13.8%. The use of the neutron ratio to monitor biomass was evaluated and changes in the neutron ratio coincided with biomass changes and resulted in a high correlation (R2 of 0.868) with the normalized difference vegetation index (NDVI) and (R2 of 0.817) leaf area index (LAI). The use of the CRNS to simultaneously monitor soil water content and biomass will be beneficial in providing more reliable soil water content estimates, provide biomass estimates at a field scale, and aid in understanding the dynamics between soil water content and vegetation.

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“…The other hydrogen sources include water in above-ground and below-ground biomass, lattice water, atmospheric water vapour and water in soil organic carbon. The external factors include incoming cosmic ray neutrons and barometric pressure [32,33].…”

Section: Neutron Correction Factorsmentioning

confidence: 99%

Calibration and Validation of the Cosmic Ray Neutron Rover for Soil Water Mapping within Two South African Land Classes

2019

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Knowledge of soil water at a range of spatial scales would further our understanding of the dynamic variable and its influence on numerous hydrological applications. Cosmic ray neutron technology currently consists of the Cosmic Ray Neutron Sensor (CRNS) and the Cosmic Ray Neutron Rover (CRNR). The CRNR is an innovative tool to map surface soil water across the land surface. This research assessed the calibration and validation of the CRNR at two survey sites (hygrophilous grassland and pine forest) within the Vasi area with an area of 72 and 56 ha, respectively. The assessment of the calibrations showed that consistent calibration values (N 0 ) were obtained for both survey sites. The hygrophilous grassland site had an average N 0 value of 133.441 counts per minute (cpm) and an average error of 2.034 cpm. The pine site had an average N 0 value of 132.668 cpm and an average error of 0.375 cpm between surveys. The validation of CRNR soil water estimates with interpolated hydro-sense soil water estimates showed that the CRNR can provide spatial estimates of soil water across the landscape. The hydro-sense and CRNR soil water estimates had a R 2 of 0.439 at the hygrophilous grassland site and 0.793 at the pine site.

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Cosmic ray neutrons provide an innovative technique for estimating intermediate scale soil moisture

Cited by 9 publications

References 21 publications

Using Cosmic-Ray Neutron Probes in Validating Satellite Soil Moisture Products and Land Surface Models

Using Cosmic-Ray Neutron Probes in Validating Satellite Soil Moisture Products and Land Surface Models

The Applicability of the Cosmic Ray Neutron Sensor to Simultaneously Monitor Soil Water Content and Biomass in an Acacia mearnsii Forest

Calibration and Validation of the Cosmic Ray Neutron Rover for Soil Water Mapping within Two South African Land Classes

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