CosmOz Newsletter, August 2013
How do we know the cosmic-ray probe gives reliable estimates?
A team in Tasmania, under the leadership of Auro Almeida (CSIRO Ecosystem Sciences) has instrumented a site in Tullochgorum to test how cosmic-ray probe (CRP) soil moisture measurements at a scale of 30 ha compare to those from a distributed network of capacitance soil moisture probes installed within the CRP footprint. The team has installed and calibrated 25 capacitance probes which measure soil moisture at half hour intervals at 5 depths between 0 to 50 cm (Figure 1).
Figure 1. Location of capacitance probes within the footprint of the cosmic-ray probe (left), capacitance probe and data- logger (middle), and calibration of capacitance probes (right) .
When the soil moisture from 25 capacitance probe measurements are averaged and corrected for measurement depth, comparison with CRP results is very impressive (Figure 2). This work demonstrates that CRP is able to effectively capture the variability in moisture seen over the whole footprint. This study is just the second full scale field test of the CRP measurements undertaken in the world and provides further evidence supporting the strength of the method.
Figure 2. Comparison of neutron count from the cosmic-ray probe and respective average soil moisture from the network of capacitance probes.
The team from Tasmania now plans to look at techniques for estimating temporal and spatial variability in soil moisture within the CRP footprint using data from the CRP combined with Neuro Fuzzy Inference System (NFIS) approaches. The results of this work is being presented in the IEEE-Sensors Conference in Baltimore in November. For further information contact Auro Almeida: Auro.Almeida@csiro.au
New papers recently published:
Franz, T. E., M. Zreda, R. Rosolem, B. K. Hornbuckle, S. L. Irvin, H. Adams, T. E. Kolb, C. Zweck, and W. J. Shuttleworth (2013), Ecosystem-scale measurements of biomass water using cosmic ray neutrons, Geophys. Res. Lett., n/a-n/a, doi: 10.1002/grl.50791. http://dx.doi.org/10.1002/grl.50791
Franz, T. E., M. Zreda, R. Rosolem, and T. P. A. Ferre (2013), A universal calibration function for determination of soil moisture with cosmic-ray neutrons, Hydrol. Earth Syst. Sci., 17(2), 453-460, doi: 10.5194/hess-17-453-2013.
Rosolem, R., W. J. Shuttleworth, M. Zreda, T. E. Franz, X. Zeng, and S. A. Kurc (2013), The Effect of Atmospheric Water Vapor on Neutron Count in the Cosmic-Ray Soil Moisture Observing System, Journal of Hydrometeorology, doi: 10.1175/jhm-d-12-0120.1. http://dx.doi.org/10.1175/JHM-D-12-0120.1
Rivera Villarreyes, C. A., G. Baroni, and S. E. Oswald (2013), Calibration approaches of cosmic-ray neutron sensing for soil moisture measurement in cropped fields, Hydrol. Earth Syst. Sci. Discuss., 10(4), 4237-4274, doi: 10.5194/hessd-10-4237-2013. http://www.hydrol-earth-syst-sci-discuss.net/10/4237/2013/