The Effect of Atmospheric Water Vapor on Neutron Count in the Cosmic-Ray Soil Moisture Observing System

Rosolem, Rafael; Shuttleworth, W. James; Zréda, Marek; Franz, Trenton E.; Zeng, Xubin; Kurc, S. A.

doi:10.1175/jhm-d-12-0120.1

Cited by 167 publications

(202 citation statements)

References 40 publications

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“…Since neutron counts are mainly related to the amount of hydrogen molecules in an area, raw moderated neutron counts must also be corrected for differences in atmospheric water vapour. Rosolem et al (2013) found the following correction function for atmospheric water vapour:…”

Section: Raw Moderated Neutron Correctionmentioning

confidence: 99%

Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

Sigouin

Bing

2016

The Cryosphere

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Abstract. Measuring snow water equivalent (SWE) is important for many hydrological purposes such as modelling and flood forecasting. Measurements of SWE are also crucial for agricultural production in areas where snowmelt runoff dominates spring soil water recharge. Typical methods for measuring SWE include point measurements (snow tubes) and large-scale measurements (remote sensing). We explored the potential of using the cosmic-ray soil moisture probe (CRP) to measure average SWE at a spatial scale between those provided by snow tubes and remote sensing. The CRP measures above-ground moderated neutron intensity within a radius of approximately 300 m. Using snow tubes, surveys were performed over two winters (2013/2014 and 2014/2015) in an area surrounding a CRP in an agricultural field in Saskatoon, Saskatchewan, Canada. The raw moderated neutron intensity counts were corrected for atmospheric pressure, water vapour, and temporal variability of incoming cosmic-ray flux. The mean SWE from manually measured snow surveys was adjusted for differences in soil water storage before snowfall between both winters because the CRP reading appeared to be affected by soil water below the snowpack. The SWE from the snow surveys was negatively correlated with the CRP-measured moderated neutron intensity, giving Pearson correlation coefficients of −0.90 (2013/2014) and −0. 87 (2014/2015). A linear regression performed on the manually measured SWE and moderated neutron intensity counts for 2013/2014 yielded an r 2 of 0.81. Linear regression lines from the 2013/2014 and 2014/2015 manually measured SWE and moderated neutron counts were similar; thus differences in antecedent soil water storage did not appear to affect the slope of the SWE vs. neutron relationship.The regression equation obtained from 2013/2014 was used to model SWE using the moderated neutron intensity data for 2014/2015. The CRP-estimated SWE for 2014/2015 was similar to that of the snow survey, with an root-mean-square error of 8.8 mm. The CRP-estimated SWE also compared well to estimates made using snow depths at meteorological sites near (< 10 km) the CRP. Overall, the empirical equation presented provides acceptable estimates of average SWE using moderated neutron intensity measurements. Using a CRP to monitor SWE is attractive because it delivers a continuous reading, can be installed in remote locations, requires minimal labour, and provides a landscape-scale measurement footprint.

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Section: Raw Moderated Neutron Correctionmentioning

confidence: 99%

Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

Sigouin

Bing

2016

The Cryosphere

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“…The correction of influencing factors has also received much attention. The analysis and correction of the influences of atmospheric pressure, water vapor, solar activity and aboveground biomass on the neutrons have been studied (Desilets and Zreda, 2001;Moraal et al, 2005;Rosolem et al, 2013;Coopersmith et al, 2014;McJannet et al, 2014;Baatz et al, 2015) and can improve the accuracy of the CRNS. These studies have built the foundation for the application of the CRNS method (Rivera villarreyes et al, 2011;Bogena et al, 2013;Han et al, 2014;Wang et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Application of cosmic-ray neutron sensing to monitor soil water content in an alpine meadow ecosystem on the northern Tibetan Plateau

Zhu

Shao

Zeng

et al. 2016

Journal of Hydrology

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Keywords: CRNS Soil moisture Alpine meadow Tibetan Plateau s u m m a r y Cosmic-ray neutron sensing (CRNS) is a new method for continuously monitoring mean soil water content (SWC) on a hectometer scale. To evaluate the application and accuracy of the method for SWC observation in an alpine meadow ecosystem (AME), we installed the CRNS in a flat meadow near the Naqu prefecture on the northern Tibetan Plateau. We collecting soil samples and applying the system by the oven-drying method. A weather station was also installed near the CRNS for monitoring basic meteorological variables and the soil temperature and water content at various depths. Three Em-50 instruments for monitoring SWC and soil temperature were buried in three sub-quadrats northwest, northeast and southeast of the CRNS at distances of 460, 370 and 373 m, respectively, to observe the variation of SWC at the various depths. The footprint of the CRNS for SWC observation in the meadow was about 580 m, and the mean measuring depth was about 31 cm according to the general calculation equations. The reference neutron flux for dry soil (N 0 ) had a mean and coefficient of variation of 8686 and 3%, respectively, and remained substantially invariant throughout the measuring period. The five SWCs from the independent field samples almost passed through the SWC trend of the CRNS, the root mean square error (RMSE) was 0.011 m 3 m À3 for the CRNS and oven-drying method. The time series of SWC measured by the CRNS agreed well with the mean SWC series to a depth of 20 cm measured by the weather station. The trend of SWC measured by the Em-50s generally agreed with the trend of SWC measured by the CRNS, but some values and variations of SWC differed between the Em-50s and CRNS data. Because of the good agreement between the CRNS and independent field samples, we suspect that this disagreement is due to an insufficient representativeness of point observations and the distances of the points from the CRNS. The diurnal variation of hourly SWC from the CRNS was sinusoidal during a dry period, peaking at 11:00 and was minimum at 18:00 (Beijing time), with a range of 1%. Overall, the CRNS measured SWC in the AME with an acceptable accuracy, providing a scientific basis for the promotion and application of the CRNS in high, cold ecosystems.

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“…[17] investigated the effect of atmospheric water on low-energy neutrons with Monte-Carlo simulations. Knowing the absolute humidity of air near the surface, h, the correction is then given by:…”

Section: Barometric Effect and Water Vapormentioning

confidence: 99%

Monitoring Environmental Water with Ground Albedo Neutrons from Cosmic Rays

Schrön¹,

Zacharias²,

Köhli³

et al. 2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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Neutron monitors on the Earth's surface are usually used to track the dynamics of incoming cosmic-ray neutrons of high energy under the assumption that local environmental conditions do not influence the highly shielded flux. Oppositely, in a recently established research field the local dynamics of environmental water is monitored by detecting low-energy cosmic-ray neutrons. Water in soil, air, snow and vegetation determines the amount of ground albedo neutrons in the sensitive energy range from 1 eV to 100 keV. Plenty of small neutron detectors have been installed on natural or agricultural sites all around the world Climate research, hydrologic models and irrigation management rely on these measurements, which represent area-average water content within tens of hectares due to the fast diffusion of neutrons in air. A major issue is the modulation of the neutron flux by the dynamics of incoming cosmic-ray neutrons. Conventionally, independent data from neutron monitors are consulted to serve as a reference for the correction of the local detectors. However, the performance of this comparative correction approach is unreliable, because it does not account for geographical displacement, different energy windows of the detectors, or potential influence of atmospheric conditions on the referenced neutron monitor. In addition, neutron monitor stations are sparse on Earth, and occasionally signals from different locations appear to be significantly inconsistent. The presentation shows how ground albedo neutrons from cosmic-rays are used in environmental research and emphasizes the need for a reliable correction for the incoming flux.

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The Effect of Atmospheric Water Vapor on Neutron Count in the Cosmic-Ray Soil Moisture Observing System

Cited by 167 publications

References 40 publications

Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

Application of cosmic-ray neutron sensing to monitor soil water content in an alpine meadow ecosystem on the northern Tibetan Plateau

Monitoring Environmental Water with Ground Albedo Neutrons from Cosmic Rays

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